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-

-

-                          XAA.HOWTO

-

-  This file describes how to add basic XAA support to a chipset driver.

-

-0)  What is XAA

-1)  XAA Initialization and Shutdown

-2)  The Primitives

-  2.0  Generic Flags

-  2.1  Screen to Screen Copies

-  2.2  Solid Fills

-  2.3  Solid Lines

-  2.4  Dashed Lines

-  2.5  Color Expand Fills

-    2.5.1 Screen to Screen Color Expansion

-    2.5.2 CPU to Screen Color Expansion

-      2.5.2.1 The Direct Method

-      2.5.2.2 The Indirect Method

-  2.6  8x8 Mono Pattern Fills

-  2.7  8x8 Color Pattern Fills

-  2.8  Image Writes

-    2.8.1 The Direct Method

-    2.8.2 The Indirect Method

-  2.9 Clipping

-3)  The Pixmap Cache

-4)  Offscreen Pixmaps

-

-/********************************************************************/

-

-0) WHAT IS XAA

-	

-   XAA (the XFree86 Acceleration Architecture) is a device dependent

-layer that encapsulates the unaccelerated framebuffer rendering layer,

-intercepting rendering commands sent to it from higher levels of the

-server.  For rendering tasks where hardware acceleration is not 

-possible, XAA allows the requests to proceed to the software rendering

-code.  Otherwise, XAA breaks the sometimes complicated X primitives

-into simpler primitives more suitable for hardware acceleration and

-will use accelerated functions exported by the chipset driver to 

-render these.

-

-   XAA provides a simple, easy to use driver interface that allows

-the driver to communicate its acceleration capabilities and restrictions

-back to XAA.  XAA will use the information provided by the driver

-to determine whether or not acceleration will be possible for a

-particular X primitive.

-

-

-

-1) XAA INITIALIZATION AND SHUTDOWN

-

-   All relevant prototypes and defines are in xaa.h.

-

-   To Initialize the XAA layer, the driver should allocate an XAAInfoRec

-via XAACreateInfoRec(), fill it out as described in this document

-and pass it to XAAInit().  XAAInit() must be called _after_ the 

-framebuffer initialization (usually cfb?ScreenInit or similar) since 

-it is "wrapping" that layer.  XAAInit() should be called _before_ the 

-cursor initialization (usually miDCInitialize) since the cursor

-layer needs to "wrap" all the rendering code including XAA.

-

-   When shutting down, the driver should free the XAAInfoRec

-structure in its CloseScreen function via XAADestroyInfoRec().

-The prototypes for the functions mentioned above are as follows:

-

-   XAAInfoRecPtr XAACreateInfoRec(void);

-   Bool XAAInit(ScreenPtr, XAAInfoRecPtr);

-   void XAADestroyInfoRec(XAAInfoRec);

-

-   The driver informs XAA of it's acceleration capablities by

-filling out an XAAInfoRec structure and passing it to XAAInit().

-The XAAInfoRec structure contains many fields, most of which are

-function pointers and flags.  Each primitive will typically have

-two functions and a set of flags associated with it, but it may

-have more.  These two functions are the "SetupFor" and "Subsequent" 

-functions.  The "SetupFor" function tells the driver that the 

-hardware should be initialized for a particular type of graphics 

-operation.  After the "SetupFor" function, one or more calls to the 

-"Subsequent" function will be made to indicate that an instance

-of the particular primitive should be rendered by the hardware.

-The details of each instance (width, height, etc...) are given

-with each "Subsequent" function.   The set of flags associated

-with each primitive lets the driver tell XAA what its hardware

-limitations are (eg. It doesn't support a planemask, it can only

-do one of the raster-ops, etc...).

-

-  Of the XAAInfoRec fields, one is required.  This is the

-Sync function.  XAA initialization will fail if this function

-is not provided.

-

-void Sync(ScrnInfoPtr pScrn)			/* Required */

-

-   Sync will be called when XAA needs to be certain that all

-   graphics coprocessor operations are finished, such as when

-   the framebuffer must be written to or read from directly

-   and it must be certain that the accelerator will not be

-   overwriting the area of interest.

-

-   One needs to make certain that the Sync function not only

-   waits for the accelerator fifo to empty, but that it waits for

-   the rendering of that last operation to complete.

-

-   It is guaranteed that no direct framebuffer access will

-   occur after a "SetupFor" or "Subsequent" function without

-   the Sync function being called first.

-

-

-

-2)  THE PRIMITIVES

-

-2.0  Generic Flags

-

-  Each primitive type has a set of flags associated with it which

-allow the driver to tell XAA what the hardware limitations are.

-The common ones are as follows:

-

-/* Foreground, Background, rop and planemask restrictions */

-

-   GXCOPY_ONLY

-

-     This indicates that the accelerator only supports GXcopy

-     for the particular primitive.

-

-   ROP_NEEDS_SOURCE

-

-     This indicates that the accelerator doesn't supports a

-     particular primitive with rops that don't involve the source.

-     These rops are GXclear, GXnoop, GXinvert and GXset. If neither

-     this flag nor GXCOPY_ONLY is defined, it is assumed that the

-     accelerator supports all 16 raster operations (rops) for that

-     primitive.

-

-   NO_PLANEMASK

-

-     This indicates that the accelerator does not support a hardware

-     write planemask for the particular primitive.

-

-   RGB_EQUAL

-

-     This indicates that the particular primitive requires the red, 

-     green and blue bytes of the foreground color (and background color,

-     if applicable) to be equal. This is useful for 24bpp when a graphics

-     coprocessor is used in 8bpp mode, which is not uncommon in older

-     hardware since some have no support for or only limited support for 

-     acceleration at 24bpp. This way, many operations will be accelerated 

-     for the common case of "grayscale" colors.  This flag should only

-     be used in 24bpp.

-

-  In addition to the common ones listed above which are possible for

-nearly all primitives, each primitive may have its own flags specific

-to that primitive.  If such flags exist they are documented in the

-descriptions of those primitives below.

- 

-

-

-

-2.1  Screen to Screen Copies

-

-   The SetupFor and Subsequent ScreenToScreenCopy functions provide

-   an interface for copying rectangular areas from video memory to

-   video memory.  To accelerate this primitive the driver should

-   provide both the SetupFor and Subsequent functions and indicate

-   the hardware restrictions via the ScreenToScreenCopyFlags.  The

-   NO_PLANEMASK, GXCOPY_ONLY and ROP_NEEDS_SOURCE flags as described

-   in Section 2.0 are valid as well as the following:

-

-    NO_TRANSPARENCY

-     

-      This indicates that the accelerator does not support skipping

-      of color keyed pixels when copying from the source to the destination.

-

-    TRANSPARENCY_GXCOPY_ONLY

-

-      This indicates that the accelerator supports skipping of color keyed

-      pixels only when the rop is GXcopy.

-

-    ONLY_LEFT_TO_RIGHT_BITBLT

-

-      This indicates that the hardware only accepts blitting when the

-      x direction is positive.

-

-    ONLY_TWO_BITBLT_DIRECTIONS

-

-      This indicates that the hardware can only cope with blitting when

-      the direction of x is the same as the direction in y.

-

-

-void SetupForScreenToScreenCopy( ScrnInfoPtr pScrn,

-			int xdir, int ydir,

-			int rop,

-			unsigned int planemask,

-			int trans_color )

-

-    When this is called, SubsequentScreenToScreenCopy will be called

-    one or more times directly after.  If ydir is 1, then the accelerator

-    should copy starting from the top (minimum y) of the source and

-    proceed downward.  If ydir is -1, then the accelerator should copy

-    starting from the bottom of the source (maximum y) and proceed

-    upward.  If xdir is 1, then the accelerator should copy each

-    y scanline starting from the leftmost pixel of the source.  If

-    xdir is -1, it should start from the rightmost pixel.  

-       If trans_color is not -1 then trans_color indicates that the

-    accelerator should not copy pixels with the color trans_color

-    from the source to the destination, but should skip them. 

-    Trans_color is always -1 if the NO_TRANSPARENCY flag is set.

- 

-

-void SubsequentScreenToScreenCopy(ScrnInfoPtr pScrn,

-			int x1, int y1,

-			int x2, int y2,

-			int width, int height)

-

-    Copy a rectangle "width" x "height" from the source (x1,y1) to the 

-    destination (x2,y2) using the parameters passed by the last

-    SetupForScreenToScreenCopy call. (x1,y1) and (x2,y2) always denote 

-    the upper left hand corners of the source and destination regardless 

-    of which xdir and ydir values are given by SetupForScreenToScreenCopy.  

-

-

-

-2.2 Solid Fills

-

-   The SetupFor and Subsequent SolidFill(Rect/Trap) functions provide

-   an interface for filling rectangular areas of the screen with a

-   foreground color.  To accelerate this primitive the driver should

-   provide both the SetupForSolidFill and SubsequentSolidFillRect 

-   functions and indicate the hardware restrictions via the SolidFillFlags.

-   The driver may optionally provide a SubsequentSolidFillTrap if

-   it is capable of rendering the primitive correctly.  

-   The GXCOPY_ONLY, ROP_NEEDS_SOURCE, NO_PLANEMASK and RGB_EQUAL flags

-   as described in Section 2.0 are valid.

-

-  

-void SetupForSolidFill(ScrnInfoPtr pScrn, 

-                       int color, int rop, unsigned int planemask)

-

-    SetupForSolidFill indicates that any combination of the following 

-    may follow it.

-

-	SubsequentSolidFillRect

-	SubsequentSolidFillTrap

-

-

- 

-void SubsequentSolidFillRect(ScrnInfoPtr pScrn, int x, int y, int w, int h)

-

-     Fill a rectangle of dimensions "w" by "h" with origin at (x,y) 

-     using the color, rop and planemask given by the last 

-     SetupForSolidFill call.

-

-void SubsequentSolidFillTrap(ScrnInfoPtr pScrn, int y, int h, 

-	int left, int dxL, int dyL, int eL,

-	int right, int dxR, int dyR, int eR)

-

-     These parameters describe a trapezoid via a version of

-     Bresenham's parameters. "y" is the top line. "h" is the

-     number of spans to be filled in the positive Y direction.

-     "left" and "right" indicate the starting X values of the

-     left and right edges.  dy/dx describes the edge slope.

-     These are not the deltas between the beginning and ending

-     points on an edge.  They merely describe the slope. "e" is

-     the initial error term.  It's the relationships between dx,

-     dy and e that define the edge.

-	If your engine does not do bresenham trapezoids or does

-     not allow the programmer to specify the error term then

-     you are not expected to be able to accelerate them.

-

-

-2.3  Solid Lines

-

-    XAA provides an interface for drawing thin lines.  In order to

-    draw X lines correctly a high degree of accuracy is required.

-    This usually limits line acceleration to hardware which has a

-    Bresenham line engine, though depending on the algorithm used,

-    other line engines may come close if they accept 16 bit line 

-    deltas.  XAA has both a Bresenham line interface and a two-point

-    line interface for drawing lines of arbitrary orientation.  

-    Additionally there is a SubsequentSolidHorVertLine which will

-    be used for all horizontal and vertical lines.  Horizontal and

-    vertical lines are handled separately since hardware that doesn't

-    have a line engine (or has one that is unusable due to precision

-    problems) can usually draw these lines by some other method such

-    as drawing them as thin rectangles.  Even for hardware that can

-    draw arbitrary lines via the Bresenham or two-point interfaces,

-    the SubsequentSolidHorVertLine is used for horizontal and vertical

-    lines since most hardware is able to render the horizontal lines

-    and sometimes the vertical lines faster by other methods (Hint:

-    try rendering horizontal lines as flattened rectangles).  If you have 

-    not provided a SubsequentSolidHorVertLine but you have provided 

-    Bresenham or two-point lines, a SubsequentSolidHorVertLine function 

-    will be supplied for you.

-

-    The flags field associated with Solid Lines is SolidLineFlags and 

-    the GXCOPY_ONLY, ROP_NEEDS_SOURCE, NO_PLANEMASK and RGB_EQUAL flags as

-    described in Section 2.0 are valid restrictions.  

-

-    Some line engines have line biases hardcoded to comply with

-    Microsoft line biasing rules.  A tell-tale sign of this is the

-    hardware lines not matching the software lines in the zeroth and

-    fourth octants.  The driver can set the flag:

-	

-	MICROSOFT_ZERO_LINE_BIAS

-

-    in the AccelInfoRec.Flags field to adjust the software lines to

-    match the hardware lines.   This is in the generic flags field

-    rather than the SolidLineFlags since this flag applies to all

-    software zero-width lines on the screen and not just the solid ones.

-

-

-void SetupForSolidLine(ScrnInfoPtr pScrn, 

-                       int color, int rop, unsigned int planemask)

-

-    SetupForSolidLine indicates that any combination of the following 

-    may follow it.

-

-	SubsequentSolidBresenhamLine

-	SubsequentSolidTwoPointLine

-        SubsequentSolidHorVertLine 	

-

-

-void SubsequentSolidHorVertLine( ScrnInfoPtr pScrn,

-        			int x, int y, int len, int dir )

-

-    All vertical and horizontal solid thin lines are rendered with

-    this function.  The line starts at coordinate (x,y) and extends

-    "len" pixels inclusive.  In the direction indicated by "dir."

-    The direction is either DEGREES_O or DEGREES_270.  That is, it

-    always extends to the right or down.

-

-

-

-void SubsequentSolidTwoPointLine(ScrnInfoPtr pScrn,

-        	int x1, int y1, int x2, int y2, int flags)

-

-    Draw a line from (x1,y1) to (x2,y2).  If the flags field contains

-    the flag OMIT_LAST, the last pixel should not be drawn.  Otherwise,

-    the pixel at (x2,y2) should be drawn.

-

-    If you use the TwoPoint line interface there is a good possibility

-    that your line engine has hard-coded line biases that do not match

-    the default X zero-width lines.  If so, you may need to set the

-    MICROSOFT_ZERO_LINE_BIAS flag described above.  Note that since

-    any vertex in the 16-bit signed coordinate system is valid, your

-    line engine is expected to handle 16-bit values if you have hardware

-    line clipping enabled.  If your engine cannot handle 16-bit values,

-    you should not use hardware line clipping.

-

-

-void SubsequentSolidBresenhamLine(ScrnInfoPtr pScrn,

-        int x, int y, int major, int minor, int err, int len, int octant)

-

-    "X" and "y" are the starting point of the line.  "Major" and "minor" 

-    are the major and minor step constants.  "Err" is the initial error

-    term.  "Len" is the number of pixels to be drawn (inclusive). "Octant"

-    can be any combination of the following flags OR'd together:

-

-      Y_MAJOR		Y is the major axis (X otherwise)

-      X_DECREASING	The line is drawn from right to left

-      Y_DECREASING	The line is drawn from bottom to top

-	  

-    The major, minor and err terms are the "raw" Bresenham parameters

-    consistent with a line engine that does:

-

-	e = err;

-	while(len--) {

-	   DRAW_POINT(x,y);

-	   e += minor;

-	   if(e >= 0) {

-		e -= major;

-		TAKE_ONE_STEP_ALONG_MINOR_AXIS;

-	   }

-	   TAKE_ONE_STEP_ALONG_MAJOR_AXIS;

-	}

-

-    IBM 8514 style Bresenham line interfaces require their parameters

-    modified in the following way:

-

-	Axial = minor;

-	Diagonal = minor - major;

-	Error = minor + err;

-

-SolidBresenhamLineErrorTermBits

-

-    This field allows the driver to tell XAA how many bits large its

-    Bresenham parameter registers are.  Many engines have registers that

-    only accept 12 or 13 bit Bresenham parameters, and the parameters

-    for clipped lines may overflow these if they are not scaled down.

-    If this field is not set, XAA will assume the engine can accomodate

-    16 bit parameters, otherwise, it will scale the parameters to the

-    size specified.

-

-

-2.4  Dashed Lines

-

-    The same degree of accuracy required by the solid lines is required

-    for drawing dashed lines as well.  The dash pattern itself is a

-    buffer of binary data where ones are expanded into the foreground

-    color and zeros either correspond to the background color or

-    indicate transparency depending on whether or not DoubleDash or

-    OnOffDashes are being drawn.  

-

-    The flags field associated with dashed Lines is DashedLineFlags and 

-    the GXCOPY_ONLY, ROP_NEEDS_SOURCE, NO_PLANEMASK and RGB_EQUAL flags as

-    described in Section 2.0 are valid restrictions.  Additionally, the

-    following flags are valid:

-

-      NO_TRANSPARENCY

-

-	This indicates that the driver cannot support dashed lines

-	with transparent backgrounds (OnOffDashes).

-

-      TRANSPARENCY_ONLY

-

-	This indicates that the driver cannot support dashes with

-	both a foreground and background color (DoubleDashes).

-

-      LINE_PATTERN_POWER_OF_2_ONLY

-

-	This indicates that only patterns with a power of 2 length

-	can be accelerated.

-

-      LINE_PATTERN_LSBFIRST_MSBJUSTIFIED

-      LINE_PATTERN_LSBFIRST_LSBJUSTIFIED

-      LINE_PATTERN_MSBFIRST_MSBJUSTIFIED

-      LINE_PATTERN_MSBFIRST_LSBJUSTIFIED

-

-	These describe how the line pattern should be packed.

-	The pattern buffer is DWORD padded.  LSBFIRST indicates

-	that the pattern runs from the LSB end to the MSB end.

-	MSBFIRST indicates that the pattern runs from the MSB end

-	to the LSB end.  When the pattern does not completely fill

-	the DWORD padded buffer, the pattern will be justified 

-	towards the MSB or LSB end based on the flags above.

-

-

-    The following field indicates the maximum length dash pattern that

-    should be accelerated.

-

-	int DashPatternMaxLength

-

-

-void SetupForDashedLine(ScrnInfoPtr pScrn,

-		int fg, int bg, int rop, unsigned int planemask,

-        	int length, unsigned char *pattern)

-

-    

-    SetupForDashedLine indicates that any combination of the following 

-    may follow it.

-

-	SubsequentDashedBresenhamLine

-	SubsequentDashedTwoPointLine

-

-    If "bg" is -1, then the background (pixels corresponding to clear

-    bits in the pattern) should remain unmodified. "Bg" indicates the

-    background color otherwise.  "Length" indicates the length of

-    the pattern in bits and "pattern" points to the DWORD padded buffer

-    holding the pattern which has been packed according to the flags

-    set above.  

-

-    

-void SubsequentDashedTwoPointLine( ScrnInfoPtr pScrn,

-        int x1, int y1, int x2, int y2, int flags, int phase)

-

-void SubsequentDashedBresenhamLine(ScrnInfoPtr pScrn,

-        int x1, int y1, int major, int minor, int err, int len, int octant,

-        int phase)

-  

-    These are the same as the SubsequentSolidTwoPointLine and

-    SubsequentBresenhamLine functions except for the addition

-    of the "phase" field which indicates the offset into the dash 

-    pattern that the pixel at (x1,y1) corresponds to.

-

-    As with the SubsequentBresenhamLine, there is an

- 

-	int DashedBresenhamLineErrorTermBits 

-   

-    field which indicates the size of the error term registers

-    used with dashed lines.  This is usually the same value as

-    the field for the solid lines (because it's usually the same

-    register).

-       

-      

-

-2.5   Color Expansion Fills

-

-    When filling a color expansion rectangle, the accelerator

-    paints each pixel depending on whether or not a bit in a

-    corresponding bitmap is set or clear. Opaque expansions are 

-    when a set bit corresponds to the foreground color and a clear 

-    bit corresponds to the background color.  A transparent expansion

-    is when a set bit corresponds to the foreground color and a

-    clear bit indicates that the pixel should remain unmodified.

-   

-    The graphics accelerator usually has access to the source 

-    bitmap in one of two ways: 1) the bitmap data is sent serially

-    to the accelerator by the CPU through some memory mapped aperture

-    or 2) the accelerator reads the source bitmap out of offscreen

-    video memory.  Some types of primitives are better suited towards 

-    one method or the other.  Type 2 is useful for reusable patterns

-    such as stipples which can be cached in offscreen memory.  The

-    aperature method can be used for stippling but the CPU must pass

-    the data across the bus each time a stippled fill is to be performed.  

-    For expanding 1bpp client pixmaps or text strings to the screen,

-    the aperature method is usually superior because the intermediate

-    copy in offscreen memory needed by the second method would only be 

-    used once.  Unfortunately, many accelerators can only do one of these

-    methods and not both.  

-

-    XAA provides both ScreenToScreen and CPUToScreen color expansion 

-    interfaces for doing color expansion fills.  The ScreenToScreen

-    functions can only be used with hardware that supports reading

-    of source bitmaps from offscreen video memory, and these are only

-    used for cacheable patterns such as stipples.  There are two

-    variants of the CPUToScreen routines - a direct method intended

-    for hardware that has a transfer aperature, and an indirect method

-    intended for hardware without transfer aperatures or hardware

-    with unusual transfer requirements.  Hardware that can only expand

-    bitmaps from video memory should supply ScreenToScreen routines

-    but also ScanlineCPUToScreen (indirect) routines to optimize transfers 

-    of non-cacheable data.  Hardware that can only accept source bitmaps

-    through an aperature should supply CPUToScreen (or ScanlineCPUToScreen) 

-    routines. Hardware that can do both should provide both ScreenToScreen 

-    and CPUToScreen routines.

-

-    For both ScreenToScreen and CPUToScreen interfaces, the GXCOPY_ONLY,

-    ROP_NEEDS_SOURCE, NO_PLANEMASK and RGB_EQUAL flags described in

-    Section 2.0 are valid as well as the following:

-

-    /* bit order requirements (one of these must be set) */

-   

-    BIT_ORDER_IN_BYTE_LSBFIRST

-

-      This indicates that least significant bit in each byte of the source

-      data corresponds to the leftmost of that block of 8 pixels.  This

-      is the prefered format.

-

-    BIT_ORDER_IN_BYTE_MSBFIRST    

-

-      This indicates that most significant bit in each byte of the source

-      data corresponds to the leftmost of that block of 8 pixels.

-

-    /* transparency restrictions */

-

-    NO_TRANSPARENCY

-

-      This indicates that the accelerator cannot do a transparent expansion.

-

-    TRANSPARENCY_ONLY

-

-      This indicates that the accelerator cannot do an opaque expansion.

-      In cases where where the background needs to be filled, XAA will

-      render the primitive in two passes when using the CPUToScreen

-      interface, but will not do so with the ScreenToScreen interface 

-      since that would require caching of two patterns.  Some 

-      ScreenToScreen hardware may be able to render two passes at the

-      driver level and remove the TRANSPARENCY_ONLY restriction if

-      it can render pixels corresponding to the zero bits.

-

-

-

-2.5.1  Screen To Screen Color Expansion

-

-    The ScreenToScreenColorExpandFill routines provide an interface

-    for doing expansion blits from source patterns stored in offscreen

-    video memory.

-

-    void SetupForScreenToScreenColorExpandFill (ScrnInfoPtr pScrn,

-        			int fg, int bg, 

-				int rop, unsigned int planemask)

-

-

-    Ones in the source bitmap will correspond to the fg color.

-    Zeros in the source bitmap will correspond to the bg color

-    unless bg = -1.  In that case the pixels corresponding to the

-    zeros in the bitmap shall be left unmodified by the accelerator.

-

-    For hardware that doesn't allow an easy implementation of skipleft, the

-    driver can replace CacheMonoStipple function with one that stores multiple

-    rotated copies of the stipple and select between them. In this case the

-    driver should set CacheColorExpandDensity to tell XAA how many copies of

-    the pattern are stored in the width of a cache slot. For instance if the

-    hardware can specify the starting address in bytes, then 8 rotated copies

-    of the stipple are needed and CacheColorExpandDensity should be set to 8.

-

-    void SubsequentScreenToScreenColorExpandFill( ScrnInfoPtr pScrn,

-				int x, int y, int w, int h,

-				int srcx, int srcy, int offset )

-

-   

-    Fill a rectangle "w" x "h" at location (x,y).  The source pitch

-    between scanlines is the framebuffer pitch (pScrn->displayWidth

-    pixels) and srcx and srcy indicate the start of the source pattern 

-    in units of framebuffer pixels. "Offset" indicates the bit offset

-    into the pattern that corresponds to the pixel being painted at

-    "x" on the screen.  Some hardware accepts source coordinates in

-    units of bits which makes implementation of the offset trivial.

-    In that case, the bit address of the source bit corresponding to

-    the pixel painted at (x,y) would be:

-	

-     (srcy * pScrn->displayWidth + srcx) * pScrn->bitsPerPixel + offset

-

-    It should be noted that the offset assumes LSBFIRST hardware.  

-    For MSBFIRST hardware, the driver may need to implement the 

-    offset by bliting only from byte boundaries and hardware clipping.

-

-

-

-2.5.2  CPU To Screen Color Expansion

-

-

-    The CPUToScreenColorExpandFill routines provide an interface for 

-    doing expansion blits from source patterns stored in system memory.

-    There are two varieties of this primitive, a CPUToScreenColorExpandFill

-    and a ScanlineCPUToScreenColorExpandFill.  With the 

-    CPUToScreenColorExpandFill method, the source data is sent serially

-    through a memory mapped aperature.  With the Scanline version, the

-    data is rendered scanline at a time into intermediate buffers with

-    a call to SubsequentColorExpandScanline following each scanline.

-

-    These two methods have separate flags fields, the

-    CPUToScreenColorExpandFillFlags and ScanlineCPUToScreenColorExpandFillFlags

-    respectively.  Flags specific to one method or the other are described 

-    in sections 2.5.2.1 and 2.5.2.2 but for both cases the bit order and

-    transparency restrictions listed at the beginning of section 2.5 are 

-    valid as well as the following:

-    

-    /* clipping  (optional) */

-    

-    LEFT_EDGE_CLIPPING

- 

-      This indicates that the accelerator supports omission of up to

-      31 pixels on the left edge of the rectangle to be filled.  This

-      is beneficial since it allows transfer of the source bitmap to

-      always occur from DWORD boundaries. 

-

-    LEFT_EDGE_CLIPPING_NEGATIVE_X

-

-      This flag indicates that the accelerator can render color expansion

-      rectangles even if the value of x origin is negative (off of

-      the screen on the left edge).

-

-    /* misc */

-

-    TRIPLE_BITS_24BPP

-

-      When enabled (must be in 24bpp mode), color expansion functions

-      are expected to require three times the amount of bits to be

-      transferred so that 24bpp grayscale colors can be used with color

-      expansion in 8bpp coprocessor mode. Each bit is expanded to 3

-      bits when writing the monochrome data.

-

-

- 2.5.1 The Direct Method 

-

-

-    Using the direct method of color expansion XAA will send all

-    bitmap data to the accelerator serially through an memory mapped

-    transfer window defined by the following two fields:

-

-      unsigned char *ColorExpandBase

-

-        This indicates the memory address of the beginning of the aperture.

-

-      int ColorExpandRange

-

-        This indicates the size in bytes of the aperture.

-

-    The driver should specify how the transfered data should be padded.

-    There are options for both the padding of each Y scanline and for the

-    total transfer to the aperature.

-    One of the following two flags must be set:

-

-      CPU_TRANSFER_PAD_DWORD

-

-        This indicates that the total transfer (sum of all scanlines) sent

-        to the aperature must be DWORD padded.  This is the default behavior.

-

-      CPU_TRANSFER_PAD_QWORD 

-

-	This indicates that the total transfer (sum of all scanlines) sent

-	to the aperature must be QWORD padded.  With this set, XAA will send

-        an extra DWORD to the aperature when needed to ensure that only

-        an even number of DWORDs are sent.

-

-    And then there are the flags for padding of each scanline:

-

-      SCANLINE_PAD_DWORD

-

-	This indicates that each Y scanline should be DWORD padded.

-        This is the only option available and is the default.

-

-    Finally, there is the CPU_TRANSFER_BASE_FIXED flag which indicates

-    that the aperture is a single register rather than a range of

-    registers, and XAA should write all of the data to the first DWORD.

-    If the ColorExpandRange is not large enough to accomodate scanlines

-    the width of the screen, this option will be forced. That is, the

-    ColorExpandRange must be:

-

-        ((virtualX + 31)/32) * 4   bytes or more.

-

-        ((virtualX + 62)/32 * 4) if LEFT_EDGE_CLIPPING_NEGATIVE_X is set.

-  

-    If the TRIPLE_BITS_24BPP flag is set, the required area should be 

-    multiplied by three.

-     

-    

-void SetupForCPUToScreenColorExpandFill(ScrnInfoPtr pScrn,

-        		int fg, int bg,

-			int rop,

-			unsigned int planemask)

-

-  

- 

-     Ones in the source bitmap will correspond to the fg color.

-     Zeros in the source bitmap will correspond to the bg color

-     unless bg = -1.  In that case the pixels corresponding to the

-     zeros in the bitmap shall be left unmodified by the accelerator.

-

-

-void SubsequentCPUToScreenColorExpandFill(ScrnInfoPtr pScrn,

-			int x, int y, int w, int h,

-			int skipleft )

-

-     When this function is called, the accelerator should be setup

-     to fill a rectangle of dimension "w" by "h" with origin at (x,y)

-     in the fill style prescribed by the last call to 

-     SetupForCPUToScreenColorExpandFill.  XAA will pass the data to 

-     the aperture immediately after this function is called.  If the 

-     skipleft is non-zero (and LEFT_EDGE_CLIPPING has been enabled), then 

-     the accelerator _should_not_ render skipleft pixels on the leftmost

-     edge of the rectangle.  Some engines have an alignment feature

-     like this built in, some others can do this using a clipping

-     window.

-

-     It can be arranged for XAA to call Sync() after it is through 

-     calling the Subsequent function by setting SYNC_AFTER_COLOR_EXPAND 

-     in the  CPUToScreenColorExpandFillFlags.  This can provide the driver 

-     with an oportunity to reset a clipping window if needed.

-

-    

-2.5.2  The Indirect Method 

-

-     Using the indirect method, XAA will render the bitmap data scanline

-     at a time to one or more buffers.  These buffers may be memory

-     mapped apertures or just intermediate storage.

-

-     int NumScanlineColorExpandBuffers

-

-       This indicates the number of buffers available.

-

-     unsigned char **ScanlineColorExpandBuffers

-

-       This is an array of pointers to the memory locations of each buffer.

-       Each buffer is expected to be large enough to accommodate scanlines

-       the width of the screen.  That is:

-

-        ((virtualX + 31)/32) * 4   bytes or more.

-

-        ((virtualX + 62)/32 * 4) if LEFT_EDGE_CLIPPING_NEGATIVE_X is set.

-  

-     Scanlines are always DWORD padded.

-     If the TRIPLE_BITS_24BPP flag is set, the required area should be 

-     multiplied by three.

-

-

-void SetupForScanlineCPUToScreenColorExpandFill(ScrnInfoPtr pScrn,

-        		int fg, int bg,

-			int rop,

-			unsigned int planemask)

- 

-     Ones in the source bitmap will correspond to the fg color.

-     Zeros in the source bitmap will correspond to the bg color

-     unless bg = -1.  In that case the pixels corresponding to the

-     zeros in the bitmap shall be left unmodified by the accelerator.

-

-     

-void SubsequentScanlineCPUToScreenColorExpandFill(ScrnInfoPtr pScrn,

-			int x, int y, int w, int h,

-			int skipleft )

-

-void SubsequentColorExpandScanline(ScrnInfoPtr pScrn, int bufno)

-

-

-    When SubsequentScanlineCPUToScreenColorExpandFill is called, XAA 

-    will begin transfering the source data scanline at a time, calling  

-    SubsequentColorExpandScanline after each scanline.  If more than

-    one buffer is available, XAA will cycle through the buffers.

-    Subsequent scanlines will use the next buffer and go back to the

-    buffer 0 again when the last buffer is reached.  The index into

-    the ScanlineColorExpandBuffers array is presented as "bufno"

-    with each SubsequentColorExpandScanline call.

-

-    The skipleft field is the same as for the direct method.

-

-    The indirect method can be use to send the source data directly 

-    to a memory mapped aperture represented by a single color expand

-    buffer, scanline at a time, but more commonly it is used to place 

-    the data into offscreen video memory so that the accelerator can 

-    blit it to the visible screen from there.  In the case where the

-    accelerator permits rendering into offscreen video memory while

-    the accelerator is active, several buffers can be used so that

-    XAA can be placing source data into the next buffer while the

-    accelerator is blitting the current buffer.  For cases where

-    the accelerator requires some special manipulation of the source

-    data first, the buffers can be in system memory.  The CPU can

-    manipulate these buffers and then send the data to the accelerator.

-

-

-

-2.6   8x8 Mono Pattern Fills

-

-    XAA provides support for two types of 8x8 hardware patterns -

-    "Mono" patterns and "Color" patterns.  Mono pattern data is

-    64 bits of color expansion data with ones indicating the

-    foreground color and zeros indicating the background color.

-    The source bitmaps for the 8x8 mono patterns can be presented

-    to the graphics accelerator in one of two ways.  They can be

-    passed as two DWORDS to the 8x8 mono pattern functions or

-    they can be cached in offscreen memory and their locations

-    passed to the 8x8 mono pattern functions.  In addition to the

-    GXCOPY_ONLY, ROP_NEEDS_SOURCE, NO_PLANEMASK and RGB_EQUAL flags

-    defined in Section 2.0, the following are defined for the

-    Mono8x8PatternFillFlags:

-

-    HARDWARE_PATTERN_PROGRAMMED_BITS

-

-      This indicates that the 8x8 patterns should be packed into two

-      DWORDS and passed to the 8x8 mono pattern functions.  The default

-      behavior is to cache the patterns in offscreen video memory and

-      pass the locations of these patterns to the functions instead.

-      The pixmap cache must be enabled for the default behavior (8x8 

-      pattern caching) to work.  See Section 3 for how to enable the

-      pixmap cache. The pixmap cache is not necessary for 

-      HARDWARE_PATTERN_PROGRAMMED_BITS.

-

-    HARDWARE_PATTERN_PROGRAMMED_ORIGIN

-

-      If the hardware supports programmable pattern offsets then

-      this option should be set. See the table below for further

-      infomation.

-

-    HARDWARE_PATTERN_SCREEN_ORIGIN

-

-      Some hardware wants the pattern offset specified with respect to the

-      upper left-hand corner of the primitive being drawn.  Other hardware 

-      needs the option HARDWARE_PATTERN_SCREEN_ORIGIN set to indicate that 

-      all pattern offsets should be referenced to the upper left-hand 

-      corner of the screen.  HARDWARE_PATTERN_SCREEN_ORIGIN is preferable 

-      since this is more natural for the X-Window system and offsets will 

-      have to be recalculated for each Subsequent function otherwise.

-

-    BIT_ORDER_IN_BYTE_MSBFIRST

-    BIT_ORDER_IN_BYTE_LSBFIRST

-

-      As with other color expansion routines this indicates whether the

-      most or the least significant bit in each byte from the pattern is 

-      the leftmost on the screen.

-

-    TRANSPARENCY_ONLY

-    NO_TRANSPARENCY

-

-      This means the same thing as for the color expansion rect routines

-      except that for TRANSPARENCY_ONLY XAA will not render the primitive

-      in two passes since this is more easily handled by the driver.

-      It is recommended that TRANSPARENCY_ONLY hardware handle rendering

-      of opaque patterns in two passes (the background can be filled as

-      a rectangle in GXcopy) in the Subsequent function so that the

-      TRANSPARENCY_ONLY restriction can be removed. 

-

-

-

-    Additional information about cached patterns...

-    For the case where HARDWARE_PATTERN_PROGRAMMED_BITS is not set and 

-    the pattern must be cached in offscreen memory, the first pattern

-    starts at the cache slot boundary which is set by the 

-    CachePixelGranularity field used to configure the pixmap cache.

-    One should ensure that the CachePixelGranularity reflects any 

-    alignment restrictions that the accelerator may put on 8x8 pattern 

-    storage locations.  When HARDWARE_PATTERN_PROGRAMMED_ORIGIN is set 

-    there is only one pattern stored.  When this flag is not set,

-    all 64 pre-rotated copies of the pattern are cached in offscreen memory.

-    The MonoPatternPitch field can be used to specify the X position pixel

-    granularity that each of these patterns must align on.  If the

-    MonoPatternPitch is not supplied, the patterns will be densely packed

-    within the cache slot.  The behavior of the default XAA 8x8 pattern

-    caching mechanism to store all 8x8 patterns linearly in video memory.

-    If the accelerator needs the patterns stored in a more unusual fashion,

-    the driver will need to provide its own 8x8 mono pattern caching 

-    routines for XAA to use. 

-

-    The following table describes the meanings of the "patx" and "paty"

-    fields in both the SetupFor and Subsequent functions.

-

-    With HARDWARE_PATTERN_SCREEN_ORIGIN

-    -----------------------------------

-

-    HARDWARE_PATTERN_PROGRAMMED_BITS and HARDWARE_PATTERN_PROGRAMMED_ORIGIN

-

-	SetupFor: patx and paty are the first and second DWORDS of the

-		  8x8 mono pattern.

-

-	Subsequent: patx and paty are the x,y offset into that pattern.

-		    All Subsequent calls will have the same offset in 

-		    the case of HARDWARE_PATTERN_SCREEN_ORIGIN so only

-		    the offset specified by the first Subsequent call 

-		    after a SetupFor call will need to be observed.

-

-    HARDWARE_PATTERN_PROGRAMMED_BITS only

-

-	SetupFor: patx and paty hold the first and second DWORDS of

-		  the 8x8 mono pattern pre-rotated to match the desired

-		  offset.

-

-	Subsequent: These just hold the same patterns and can be ignored.

-

-    HARDWARE_PATTERN_PROGRAMMED_ORIGIN only

-

-	SetupFor: patx and paty hold the x,y coordinates of the offscreen

-		  memory location where the 8x8 pattern is stored.  The

-		  bits are stored linearly in memory at that location.

-

-	Subsequent: patx and paty hold the offset into the pattern.

-		    All Subsequent calls will have the same offset in 

-		    the case of HARDWARE_PATTERN_SCREEN_ORIGIN so only

-		    the offset specified by the first Subsequent call 

-		    after a SetupFor call will need to be observed.

-

-    Neither programmed bits or origin

-

-	SetupFor: patx and paty hold the x,y coordinates of the offscreen 	

-		  memory location where the pre-rotated 8x8 pattern is

-		  stored.

-

-	Subsequent: patx and paty are the same as in the SetupFor function

-		    and can be ignored.

-		  

-

-    Without HARDWARE_PATTERN_SCREEN_ORIGIN

-    -------------------------------------- 

-

-    HARDWARE_PATTERN_PROGRAMMED_BITS and HARDWARE_PATTERN_PROGRAMMED_ORIGIN

-

-	SetupFor: patx and paty are the first and second DWORDS of the

-		  8x8 mono pattern.

-

-	Subsequent: patx and paty are the x,y offset into that pattern.

-

-    HARDWARE_PATTERN_PROGRAMMED_BITS only

-

-	SetupFor: patx and paty holds the first and second DWORDS of

-		  the unrotated 8x8 mono pattern.  This can be ignored. 

-

-	Subsequent: patx and paty hold the rotated 8x8 pattern to be 

-		    rendered.

-

-    HARDWARE_PATTERN_PROGRAMMED_ORIGIN only

-

-	SetupFor: patx and paty hold the x,y coordinates of the offscreen

-		  memory location where the 8x8 pattern is stored.  The

-		  bits are stored linearly in memory at that location.

-

-	Subsequent: patx and paty hold the offset into the pattern.

-

-    Neither programmed bits or origin

-

-	SetupFor: patx and paty hold the x,y coordinates of the offscreen 	

-		  memory location where the unrotated 8x8 pattern is

-		  stored.  This can be ignored.

-

-	Subsequent: patx and paty hold the x,y coordinates of the

-		    rotated 8x8 pattern to be rendered.

-

-

-

-void SetupForMono8x8PatternFill(ScrnInfoPtr pScrn, int patx, int paty,

-        int fg, int bg, int rop, unsigned int planemask)

-

-    SetupForMono8x8PatternFill indicates that any combination of the 

-    following  may follow it.

-

-	SubsequentMono8x8PatternFillRect

-	SubsequentMono8x8PatternFillTrap

-

-    The fg, bg, rop and planemask fields have the same meaning as the

-    ones used for the other color expansion routines.  Patx's and paty's

-    meaning can be determined from the table above.

-

- 

-void SubsequentMono8x8PatternFillRect( ScrnInfoPtr pScrn,

-        	int patx, int paty, int x, int y, int w, int h)

-

-     Fill a rectangle of dimensions "w" by "h" with origin at (x,y) 

-     using the parameters give by the last SetupForMono8x8PatternFill

-     call.  The meanings of patx and paty can be determined by the

-     table above.

-

-void SubsequentMono8x8PatternFillTrap( ScrnInfoPtr pScrn,

-     			   int patx, int paty, int y, int h, 

-     			   int left, int dxL, int dyL, int eL,

-     			   int right, int dxR, int dyR, int eR )

-

-     The meanings of patx and paty can be determined by the table above.

-     The rest of the fields have the same meanings as those in the 

-     SubsequentSolidFillTrap function. 

-

-

-

-2.7   8x8 Color Pattern Fills

-  

-    8x8 color pattern data is 64 pixels of full color data that

-    is stored linearly in offscreen video memory.  8x8 color patterns 

-    are useful as a substitute for 8x8 mono patterns when tiling,

-    doing opaque stipples, or in the case where transperency is

-    supported, regular stipples.  8x8 color pattern fills also have

-    the additional benefit of being able to tile full color 8x8

-    patterns instead of just 2 color ones like the mono patterns.

-    However, full color 8x8 patterns aren't used very often in the

-    X Window system so you might consider passing this primitive

-    by if you already can do mono patterns, especially if they 

-    require alot of cache area.  Color8x8PatternFillFlags is

-    the flags field for this primitive and the GXCOPY_ONLY,

-    ROP_NEEDS_SOURCE and NO_PLANEMASK flags as described in

-    Section 2.0 are valid as well as the following:

-

-

-    HARDWARE_PATTERN_PROGRAMMED_ORIGIN

-

-      If the hardware supports programmable pattern offsets then

-      this option should be set.  

-

-    HARDWARE_PATTERN_SCREEN_ORIGIN

-

-      Some hardware wants the pattern offset specified with respect to the

-      upper left-hand corner of the primitive being drawn.  Other hardware 

-      needs the option HARDWARE_PATTERN_SCREEN_ORIGIN set to indicate that 

-      all pattern offsets should be referenced to the upper left-hand 

-      corner of the screen.  HARDWARE_PATTERN_SCREEN_ORIGIN is preferable 

-      since this is more natural for the X-Window system and offsets will 

-      have to be recalculated for each Subsequent function otherwise.

-

-    NO_TRANSPARENCY

-    TRANSPARENCY_GXCOPY_ONLY

-

-      These mean the same as for the ScreenToScreenCopy functions.

-

-

-    The following table describes the meanings of patx and paty passed

-    to the SetupFor and Subsequent fields:

-

-    HARDWARE_PATTERN_PROGRAMMED_ORIGIN && HARDWARE_PATTERN_SCREEN_ORIGIN

-	

-	SetupFor: patx and paty hold the x,y location of the unrotated 

-		  pattern.

-

-	Subsequent: patx and paty hold the pattern offset.  For the case

-		    of HARDWARE_PATTERN_SCREEN_ORIGIN all Subsequent calls

-		    have the same offset so only the first call will need

-		    to be observed.

-

-    

-    HARDWARE_PATTERN_PROGRAMMED_ORIGIN only

-

-	SetupFor: patx and paty hold the x,y location of the unrotated

-		  pattern.

-

-	Subsequent: patx and paty hold the pattern offset. 

-

-    HARDWARE_PATTERN_SCREEN_ORIGIN

-

-	SetupFor: patx and paty hold the x,y location of the rotated pattern.

-

-	Subsequent: patx and paty hold the same location as the SetupFor

-		    function so these can be ignored.

-

-    neither flag

-

-	SetupFor: patx and paty hold the x,y location of the unrotated

-		  pattern.  This can be ignored.

-

-	Subsequent: patx and paty hold the x,y location of the rotated

-		    pattern.

-

-    Additional information about cached patterns...

-    All 8x8 color patterns are cached in offscreen video memory so

-    the pixmap cache must be enabled to use them. The first pattern

-    starts at the cache slot boundary which is set by the 

-    CachePixelGranularity field used to configure the pixmap cache.

-    One should ensure that the CachePixelGranularity reflects any 

-    alignment restrictions that the accelerator may put on 8x8 pattern 

-    storage locations.  When HARDWARE_PATTERN_PROGRAMMED_ORIGIN is set 

-    there is only one pattern stored.  When this flag is not set,

-    all 64 rotations off the pattern are accessible but it is assumed

-    that the accelerator is capable of accessing data stored on 8

-    pixel boundaries.  If the accelerator has stricter alignment 

-    requirements than this the dirver will need to provide its own 

-    8x8 color pattern caching routines. 

-

-

-void SetupForColor8x8PatternFill(ScrnInfoPtr pScrn, int patx, int paty,

-        	int rop, unsigned int planemask, int trans_color)

-

-    SetupForColor8x8PatternFill indicates that any combination of the 

-    following  may follow it.

-

-	SubsequentColor8x8PatternFillRect

-	SubsequentColor8x8PatternFillTrap	(not implemented yet)

-

-    For the meanings of patx and paty, see the table above.  Trans_color

-    means the same as for the ScreenToScreenCopy functions.

-

-

- 

-void SubsequentColor8x8PatternFillRect( ScrnInfoPtr pScrn,

-        	int patx, int paty, int x, int y, int w, int h)

-

-     Fill a rectangle of dimensions "w" by "h" with origin at (x,y) 

-     using the parameters give by the last SetupForColor8x8PatternFill

-     call.  The meanings of patx and paty can be determined by the

-     table above.

-

-void SubsequentColor8x8PatternFillTrap( ScrnInfoPtr pScrn,

-     			   int patx, int paty, int y, int h, 

-     			   int left, int dxL, int dyL, int eL,

-     			   int right, int dxR, int dyR, int eR )

-

-    For the meanings of patx and paty, see the table above. 

-    The rest of the fields have the same meanings as those in the 

-    SubsequentSolidFillTrap function. 

-

-

-

-2.8  Image Writes

-

-    XAA provides a mechanism for transfering full color pixel data from

-    system memory to video memory through the accelerator.  This is 

-    useful for dealing with alignment issues and performing raster ops

-    on the data when writing it to the framebuffer.  As with color

-    expansion rectangles, there is a direct and indirect method.  The

-    direct method sends all data through a memory mapped aperature.

-    The indirect method sends the data to an intermediated buffer scanline 

-    at a time.

-

-    The direct and indirect methods have separate flags fields, the

-    ImageWriteFlags and ScanlineImageWriteFlags respectively.

-    Flags specific to one method or the other are described in sections 

-    2.8.1 and 2.8.2 but for both cases the GXCOPY_ONLY, ROP_NEEDS_SOURCE

-    and NO_PLANEMASK flags described in Section 2.0 are valid as well as

-    the following:

-

-    NO_GXCOPY

-

-      In order to have accelerated image transfers faster than the 

-      software versions for GXcopy, the engine needs to support clipping,

-      be using the direct method and have a large enough image transfer

-      range so that CPU_TRANSFER_BASE_FIXED doesn't need to be set.

-      If these are not supported, then it is unlikely that transfering

-      the data through the accelerator will be of any advantage for the

-      simple case of GXcopy.  In fact, it may be much slower.  For such

-      cases it's probably best to set the NO_GXCOPY flag so that 

-      Image writes will only be used for the more complicated rops.

-

-    /* transparency restrictions */

-

-    NO_TRANSPARENCY

-     

-      This indicates that the accelerator does not support skipping

-      of color keyed pixels when copying from the source to the destination.

-

-    TRANSPARENCY_GXCOPY_ONLY

-

-      This indicates that the accelerator supports skipping of color keyed

-      pixels only when the rop is GXcopy.

-

-    /* clipping  (optional) */

-    

-    LEFT_EDGE_CLIPPING

- 

-      This indicates that the accelerator supports omission of up to

-      3 pixels on the left edge of the rectangle to be filled.  This

-      is beneficial since it allows transfer from the source pixmap to

-      always occur from DWORD boundaries. 

-

-    LEFT_EDGE_CLIPPING_NEGATIVE_X

-

-      This flag indicates that the accelerator can fill areas with

-      image write data even if the value of x origin is negative (off of

-      the screen on the left edge).

-

-

-2.8.1 The Direct Method

-

-    Using the direct method of ImageWrite XAA will send all

-    bitmap data to the accelerator serially through an memory mapped

-    transfer window defined by the following two fields:

-

-      unsigned char *ImageWriteBase

-

-        This indicates the memory address of the beginning of the aperture.

-

-      int ImageWriteRange

-

-        This indicates the size in bytes of the aperture.

-

-    The driver should specify how the transfered data should be padded.

-    There are options for both the padding of each Y scanline and for the

-    total transfer to the aperature.

-    One of the following two flags must be set:

-

-      CPU_TRANSFER_PAD_DWORD

-

-        This indicates that the total transfer (sum of all scanlines) sent

-        to the aperature must be DWORD padded.  This is the default behavior.

-

-      CPU_TRANSFER_PAD_QWORD 

-

-	This indicates that the total transfer (sum of all scanlines) sent

-	to the aperature must be QWORD padded.  With this set, XAA will send

-        an extra DWORD to the aperature when needed to ensure that only

-        an even number of DWORDs are sent.

-

-    And then there are the flags for padding of each scanline:

-

-      SCANLINE_PAD_DWORD

-

-	This indicates that each Y scanline should be DWORD padded.

-        This is the only option available and is the default.

-

-    Finally, there is the CPU_TRANSFER_BASE_FIXED flag which indicates

-    that the aperture is a single register rather than a range of

-    registers, and XAA should write all of the data to the first DWORD.

-    XAA will automatically select CPU_TRANSFER_BASE_FIXED if the 

-    ImageWriteRange is not large enough to accomodate an entire scanline.   

-

-

-void SetupForImageWrite(ScrnInfoPtr pScrn, int rop, unsigned int planemask,

-        			int trans_color, int bpp, int depth)

-

-     If trans_color is not -1 then trans_color indicates the transparency

-     color key and pixels with color trans_color passed through the 

-     aperature should not be transfered to the screen but should be 

-     skipped.  Bpp and depth indicate the bits per pixel and depth of

-     the source pixmap.  Trans_color is always -1 if the NO_TRANSPARENCY

-     flag is set.

-

-

-void SubsequentImageWriteRect(ScrnInfoPtr pScrn, 

-				int x, int y, int w, int h, int skipleft)

-

-     

-     Data passed through the aperature should be copied to a rectangle

-     of width "w" and height "h" with origin (x,y).  If LEFT_EDGE_CLIPPING

-     has been enabled, skipleft will correspond to the number of pixels

-     on the left edge that should not be drawn.  Skipleft is zero 

-     otherwise.

-

-     It can be arranged for XAA to call Sync() after it is through 

-     calling the Subsequent functions by setting SYNC_AFTER_IMAGE_WRITE 

-     in the  ImageWriteFlags.  This can provide the driver with an

-     oportunity to reset a clipping window if needed.

-

-2.8.2  The Indirect Method

-

-     Using the indirect method, XAA will render the pixel data scanline

-     at a time to one or more buffers.  These buffers may be memory

-     mapped apertures or just intermediate storage.

-

-     int NumScanlineImageWriteBuffers

-

-       This indicates the number of buffers available.

-

-     unsigned char **ScanlineImageWriteBuffers

-

-       This is an array of pointers to the memory locations of each buffer.

-       Each buffer is expected to be large enough to accommodate scanlines

-       the width of the screen.  That is:

-

-         pScrn->VirtualX * pScreen->bitsPerPixel/8   bytes or more.

-

-       If LEFT_EDGE_CLIPPING_NEGATIVE_X is set, add an additional 4

-       bytes to that requirement in 8 and 16bpp, 12 bytes in 24bpp.

-  

-     Scanlines are always DWORD padded.

-

-void SetupForScanlineImageWrite(ScrnInfoPtr pScrn, int rop, 

-				unsigned int planemask, int trans_color, 

-				int bpp, int depth)

-

-     If trans_color is not -1 then trans_color indicates the transparency

-     color key and pixels with color trans_color in the buffer should not 

-     be transfered to the screen but should be skipped.  Bpp and depth 

-     indicate the bits per pixel and depth of the source bitmap.  

-     Trans_color is always -1 if the NO_TRANSPARENCY flag is set.

-

-

-void SubsequentImageWriteRect(ScrnInfoPtr pScrn, 

-				int x, int y, int w, int h, int skipleft)

-

-     

-void SubsequentImageWriteScanline(ScrnInfoPtr pScrn, int bufno)

-

-

-    When SubsequentImageWriteRect is called, XAA will begin

-    transfering the source data scanline at a time, calling  

-    SubsequentImageWriteScanline after each scanline.  If more than

-    one buffer is available, XAA will cycle through the buffers.

-    Subsequent scanlines will use the next buffer and go back to the

-    buffer 0 again when the last buffer is reached.  The index into

-    the ScanlineImageWriteBuffers array is presented as "bufno"

-    with each SubsequentImageWriteScanline call.

-

-    The skipleft field is the same as for the direct method.

-

-    The indirect method can be use to send the source data directly 

-    to a memory mapped aperture represented by a single image write

-    buffer, scanline at a time, but more commonly it is used to place 

-    the data into offscreen video memory so that the accelerator can 

-    blit it to the visible screen from there.  In the case where the

-    accelerator permits rendering into offscreen video memory while

-    the accelerator is active, several buffers can be used so that

-    XAA can be placing source data into the next buffer while the

-    accelerator is blitting the current buffer.  For cases where

-    the accelerator requires some special manipulation of the source

-    data first, the buffers can be in system memory.  The CPU can

-    manipulate these buffers and then send the data to the accelerator.

-

-

-2.9 Clipping

-

-    XAA supports hardware clipping rectangles.  To use clipping

-    in this way it is expected that the graphics accelerator can

-    clip primitives with verticies anywhere in the 16 bit signed 

-    coordinate system. 

-

-void SetClippingRectangle ( ScrnInfoPtr pScrn,

-        		int left, int top, int right, int bottom)

-

-void DisableClipping (ScrnInfoPtr pScrn)

-

-    When SetClippingRectangle is called, all hardware rendering

-    following it should be clipped to the rectangle specified

-    until DisableClipping is called.

-

-    The ClippingFlags field indicates which operations this sort

-    of Set/Disable pairing can be used with.  Any of the following

-    flags may be OR'd together.

-

-	HARDWARE_CLIP_SCREEN_TO_SCREEN_COLOR_EXPAND

-	HARDWARE_CLIP_SCREEN_TO_SCREEN_COPY

-	HARDWARE_CLIP_MONO_8x8_FILL

-	HARDWARE_CLIP_COLOR_8x8_FILL

-	HARDWARE_CLIP_SOLID_FILL

-	HARDWARE_CLIP_DASHED_LINE

-	HARDWARE_CLIP_SOLID_LINE

-

-

-

-3)  XAA PIXMAP CACHE

-

-   /* NOTE:  XAA has no knowledge of framebuffer particulars so until

-	the framebuffer is able to render into offscreen memory, usage

-	of the pixmap cache requires that the driver provide ImageWrite

-	routines or a WritePixmap or WritePixmapToCache replacement so

-	that patterns can even be placed in the cache.

-

-      ADDENDUM: XAA can now load the pixmap cache without requiring

-	that the driver supply an ImageWrite function, but this can

-	only be done on linear framebuffers.  If you have a linear

-	framebuffer, set LINEAR_FRAMEBUFFER in the XAAInfoRec.Flags

-	field and XAA will then be able to upload pixmaps into the

-	cache without the driver providing functions to do so.

-   */

-

-

-   The XAA pixmap cache provides a mechanism for caching of patterns

-   in offscreen video memory so that tiled fills and in some cases

-   stippling can be done by blitting the source patterns from offscreen

-   video memory. The pixmap cache also provides the mechanism for caching 

-   of 8x8 color and mono hardware patterns.  Any unused offscreen video

-   memory gets used for the pixmap cache and that information is 

-   provided by the XFree86 Offscreen Memory Manager. XAA registers a 

-   callback with the manager so that it can be informed of any changes 

-   in the offscreen memory configuration.  The driver writer does not 

-   need to deal with any of this since it is all automatic.  The driver 

-   merely needs to initialize the Offscreen Memory Manager as described 

-   in the DESIGN document and set the PIXMAP_CACHE flag in the 

-   XAAInfoRec.Flags field.  The Offscreen Memory Manager initialization 

-   must occur before XAA is initialized or else pixmap cache 

-   initialization will fail.  

-

-   PixmapCacheFlags is an XAAInfoRec field which allows the driver to

-   control pixmap cache behavior to some extent.  Currently only one

-   flag is defined:

-

-   DO_NOT_BLIT_STIPPLES

-

-     This indicates that the stippling should not be done by blitting

-     from the pixmap cache.  This does not apply to 8x8 pattern fills. 

-

-

-   CachePixelGranularity is an optional field.  If the hardware requires

-   that a 8x8 patterns have some particular pixel alignment it should

-   be reflected in this field.  Ignoring this field or setting it to

-   zero or one means there are no alignment issues.

-

-

-4)  OFFSCREEN PIXMAPS

-

-   XAA has the ability to store pixmap drawables in offscreen video 

-   memory and render into them with full hardware acceleration.  Placement

-   of pixmaps in the cache is done automatically on a first-come basis and 

-   only if there is room.  To enable this feature, set the OFFSCREEN_PIXMAPS

-   flag in the XAAInfoRec.Flags field.  This is only available when a

-   ScreenToScreenCopy function is provided, when the Offscreen memory 

-   manager has been initialized and when the LINEAR_FRAMEBUFFER flag is

-   also set.

-

-   int maxOffPixWidth

-   int maxOffPixHeight

-

-       These two fields allow the driver to limit the maximum dimensions

-     of an offscreen pixmap.  If one of these is not set, it is assumed

-     that there is no limit on that dimension.  Note that if an offscreen

-     pixmap with a particular dimension is allowed, then your driver will be

-     expected to render primitives as large as that pixmap.  

-

-$XFree86: xc/programs/Xserver/hw/xfree86/xaa/XAA.HOWTO,v 1.12 2000/04/12 14:44:42 tsi Exp $