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diff --git a/xorg-server/hw/xfree86/xaa/XAA.HOWTO b/xorg-server/hw/xfree86/xaa/XAA.HOWTO new file mode 100644 index 000000000..cbd71c138 --- /dev/null +++ b/xorg-server/hw/xfree86/xaa/XAA.HOWTO @@ -0,0 +1,1427 @@ + + + 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 $ |