path: root/libXaw/spec/List

.\" $Xorg: List,v 1.3 2000/08/17 19:42:27 cpqbld Exp $
.NH 2
List Widget
.LP
.XS
	List Widget
.XE
.IN "List widget" "" "@DEF@"
.Ds 0
.TA 2.0i
.ta 2.0i
.sp
Application header file	<X11/Xaw/List.h>
.IN "List.h" ""
Class header file	<X11/Xaw/ListP.h>
.IN "ListP.h" ""
Class	listWidgetClass
.IN "listWidgetClass" ""
Class Name	List
.IN "List widget" "class name"
Superclass	Simple
.sp
.De
.LP

The List widget contains a list of strings formatted into rows and
columns. When one of the strings is selected, it is highlighted, and the
List widget's \fBNotify\fP action is invoked, calling all routines on
its callback list.  Only one string may be selected at a time.
.NH 3
Resources
.LP
When creating a List widget instance, the following resources are
retrieved from the argument list or from the resource database:
.LP
.IN "List widget" "resources"
.TS H
expand;
lw(1i) lw(1i) lw(1i) lw(.5i) lw(2i).
_
.sp 3p
.TB
Name	Class	Type	Notes	Default Value
.sp 3p
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.TH
.R
.sp 3p
accelerators	Accelerators	AcceleratorTable		NULL
ancestorSensitive	AncestorSensitive	Boolean	D	True
background	Background	Pixel		XtDefaultBackground
backgroundPixmap	Pixmap	Pixmap		XtUnspecifiedPixmap
borderColor	BorderColor	Pixel		XtDefaultForeground
borderPixmap	Pixmap	Pixmap		XtUnspecifiedPixmap
borderWidth	BorderWidth	Dimension		1
callback	Callback	Callback		NULL
colormap	Colormap	Colormap		Parent's Colormap
columnSpacing	Spacing	Dimension		6
cursor	Cursor	Cursor		XC_left_ptr
cursorName	Cursor	String		NULL
defaultColumns	Columns	int		2
depth	Depth	int	C	Parent's Depth
destroyCallback	Callback	XtCallbackList		NULL
font	Font	FontStruct		XtDefaultFont
fontSet	FontSet	XFontSet		XtDefaultFontSet
forceColumns	Columns	Boolean		False
foreground	Foreground	Pixel		XtDefaultForeground
height	Height	Dimension	A	Enough space to contain the list
insensitiveBorder	Insensitive	Pixmap		GreyPixmap
internalHeight	Height	Dimension		2
internalWidth	Width	Dimension		4
international	International	Boolean	C	False
list	List	Pointer		name of widget
longest	Longest	int	A	0
mappedWhenManaged	MappedWhenManaged	Boolean		True
numberStrings	NumberStrings	int	A	computed for NULL terminated list
pasteBuffer	Boolean	Boolean		False
pointerColor	Foreground	Pixel		XtDefaultForeground
pointerColorBackground	Background	Pixel		XtDefaultBackground
rowSpacing	Spacing	Dimension		2
screen	Screen	Screen	R	Parent's Screen
sensitive	Sensitive	Boolean		True
translations	Translations	TranslationTable		See below
verticalList	Boolean	Boolean		False
width	Width	Dimension	A	Enough space to contain the list
x	Position	Position		0
y	Position	Position		0
.sp 3p
_
.TE
.Ac
.As
.Bg
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.Bc
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.Bw
.IP \fBcallback\fP 1.5i
All functions on this list are called whenever the \fBnotify\fP action is
invoked.  The \fIcall_data\fP argument contains information about the element
selected and is described in detail in the \fBList Callbacks\fP section.
.Cm
.IP \fBcolumnSpacing\fP 1.5i
.br
.ns
.IP \fBrowSpacing\fP 1.5i
The amount of space, in pixels, between each of the rows and columns
in the list.
.Cu
.Cn
.IP \fBdefaultColumns\fP 1.5i
The default number of columns.  This value is used when neither the
width nor the height of the List widget is specified or when
\fBforceColumns\fP is \fBTrue\fP.
.Dp
.Dc
.IP \fBfont\fP
The text font to use when displaying the \fBlist\fP, when the
\fBinternational\fP resource is \fBfalse\fP.
.IP \fBfontSet\fP
The text font set to use when displaying the \fBlist\fP, when the
\fBinternational\fP resource is \fBtrue\fP.
.IP \fBforceColumns\fP
Forces the default number of columns to be used regardless of the
List widget's current size.
.IP \fBforeground\fP 1.5i
A pixel value which indexes the widget's colormap to derive the color
used to paint the text of the list elements.
.Hw
.Ib
.IP \fPinternalHeight\fP 1.5i
.br
.ns
.IP \fPinternalWidth\fP 1.5i
The margin, in pixels, between the edges of the list and the
corresponding edge of the List widget's window.
.IP \fBlist\fP 1.5i
An array of text strings displayed in the List widget.  If
\fBnumberStrings\fP is zero (the default) then the \fBlist\fP must be
NULL terminated.  If a value is not specified for the \fBlist\fP, then
\fBnumberStrings\fP is set to 1, and the name of the widget is used as
the \fBlist\fP, and \fBlongest\fP is set to the length of the name of the
widget.  The \fBlist\fP is used in place, and must be available
to the List widget for the lifetime of this widget, or until it is
changed with \fBXtSetValues\fP or \fBXawListChange\fP.
.In
.IP \fBlongest\fP
Specifies the width, in pixels, of the longest string in the current
list.  The List widget will compute this value if zero (the default)
is specified.  If this resource is set by hand, entries longer than this
will be clipped to fit.
.Mm
.IP \fBnumberStrings\fP 1.5i
The number of strings in the current list.  If a value of zero (the
default) is specified, the List widget will compute it.  When computing
the number of strings the List widget assumes that the \fBlist\fP is NULL
terminated.
.IP \fBpasteBuffer\fP 1.5i
If this resource is set to \fBTrue\fP then the name of the currently
selected list element will be put into \fBCUT_BUFFER_0\fP.
.Pf
.Pb
.Sc
.Se
.Tr
.IP \fBverticalList\fP 1.5i
If this resource is set to \fBTrue\fP then the list elements will be
presented in column major order.
.Xy
.NH 3
List Actions
.IN "List widget" "actions"
.LP
The List widget supports the following actions:
.IP \(bu 5
Highlighting and unhighlighting the list element under the
pointer with \fBSet\fP and \fBUnset\fP
.IP \(bu 5
Processing application callbacks with \fBNotify\fP
.LP
The following is the default translation table used by the List Widget:
.IN "List widget" "default translation table"
.LP
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.TA .5i 2.25i
.ta .5i 2.25i
<Btn1Down>,<Btn1Up>:	Set(\|) Notify(\|)
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.LP
The full list of actions supported by List widget is:
.IP \fBSet\fP(\|) 1.5i
\fISets\fP the list element that is currently under the pointer.  To
inform the user that this element is currently set, it is drawn with
foreground and background colors reversed.  If this action is called when
there is no list element under the cursor, the currently \fIset\fP
element will be \fIunset\fP.
.IP \fBUnset\fP(\|) 1.5i
Cancels the \fIset\fP state of the element under the pointer,
and redraws it with normal foreground and background colors.
.IP \fBNotify\fP(\|) 1.5i
Calls all callbacks on the List widget's callback list.  Information
about the currently selected list element is passed in the
\fIcall_data\fP argument (see \fBList Callbacks\fP below).
.NH 3
List Callbacks
.IN "List widget" "callbacks"
.LP
All procedures on the List widget's callback list will have a
\fBXawListReturnStruct\fP passed to them as \fIcall_data\fP.  The
structure is defined in the List widget's application header file.
.LP
.Ds 0
.TA .5i 2.25i
.ta .5i 2.25i
.IN "XawListReturnStruct" "" "@DEF@"
typedef struct _XawListReturnStruct {
	String string;	/* string shown in the list. */
	int list_index;	/* index of the item selected. */
} XawListReturnStruct;
.IN "XawListReturnStruct" ""
.NT
The \fIlist_index\fP item used to be called simply \fIindex\fP.
Unfortunately, this name collided with a global name defined on some
operating systems, and had to be changed.
.NE
.De
.NH 3
Changing the List
.LP
To change the list that is displayed, use
.PN XawListChange .
.IN "XawListChange" "" "@DEF@"
.FD 0
void XawListChange(\fIw\fP, \fIlist\fP, \fInitems\fP, \fIlongest\fP, \fIresize\fP)
.br
     Widget \fIw\fP;
.br
     String * \fIlist\fP;
.br
     int \fInitems\fP, \fIlongest\fP;
.br
     Boolean \fIresize\fP;
.FN
.IP \fIw\fP 1i
Specifies the List widget.
.IP \fIlist\fP 1i
Specifies the new list for the List widget to display.
.IP \fInitems\fP 1i
Specifies the number of items in the \fIlist\fP.  If a value less than 1
is specified, \fIlist\fP must be NULL terminated, and the number of
items will be calculated by the List widget.
.IP \fIlongest\fP 1i
Specifies the length of the longest item in the \fIlist\fP in pixels.
If a value less than 1 is specified, the List widget will calculate the
value.
.IP \fIresize\fP 1i
Specifies a Boolean value that if \fBTrue\fP indicates that the
List widget should try to resize itself after making the change.
The constraints of the List widget's parent are always enforced,
regardless of the value specified here.
.LP
.PN XawListChange
will \fIunset\fP all list elements that are currently \fBset\fP before
the list is actually changed.  The \fIlist\fP is used in place, and must
remain usable for the lifetime of the List widget, or until \fIlist\fP
has been changed again with this function or with \fBXtSetValues\fP.
.NH 3
Highlighting an Item
.LP
To highlight an item in the list, use
.PN XawListHighlight .
.IN "XawListHighlight" "" "@DEF@"
.FD 0
void XawListHighlight(\fIw\fP, \fIitem\fP)
.br
     Widget \fIw\fP;
.br
     int \fIitem\fP;
.FN
.IP \fIw\fP 1i
Specifies the List widget.
.IP \fIitem\fP 1i
Specifies an index into the current list that indicates the item to be
highlighted.
.LP
Only one item can be highlighted at a time.
If an item is already highlighted when
.PN XawListHighlight
is called,
the highlighted item is unhighlighted before the new item is highlighted.
.NH 3
Unhighlighting an Item
.LP
To unhighlight the currently highlighted item in the list, use
.PN XawListUnhighlight .
.IN "XawListUnhighlight" "" "@DEF@"
.FD 0
void XawListUnhighlight(\fIw\fP)
.br
     Widget \fIw\fP;
.FN
.IP \fIw\fP 1i
Specifies the List widget.
.NH 3
Retrieving the Currently Selected Item
.LP
To retrieve the list element that is currently \fIset\fP, use
.PN XawListShowCurrent .
.IN "XawListShowCurrent" "" "@DEF@"
.FD 0
XawListReturnStruct *XawListShowCurrent(\fIw\fP)
.br
     Widget \fIw\fP;
.FN
.IP \fIw\fP 1i
Specifies the List widget.
.LP
.PN XawListShowCurrent
returns a pointer to an
.PN XawListReturnStruct
structure,
containing the currently highlighted item.
If the value of the index member is XAW_LIST_NONE,
.IN "XAW_LIST_NONE"
the string member is undefined, and no item is currently selected.
.NH 3
Restrictions
.LP
Many programmers create a ``scrolled list'' by putting a List
widget with many entries as a child of a Viewport widget.  The
List continues to create a window as big as its contents, but
that big window is only visible where it intersects the parent
Viewport's window.  (I.e., it is ``clipped.'')
.LP
While this is a useful technique, there is a serious drawback.
X does not support windows above 32,767 pixels in width or
height, but this height limit will be exceeded by a List's
window when the List has many entries (i.e., with a 12 point
font, about 3000 entries would be too many.)
.LP