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'\"
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" RCS: @(#) $Id: CanvTxtInfo.3,v 1.3 2004/09/19 16:05:36 dkf Exp $
'\"
.so man.macros
.TH Tk_CanvasTextInfo 3 4.0 Tk "Tk Library Procedures"
.BS
.SH NAME
Tk_CanvasTextInfo \- additional information for managing text items in canvases
.SH SYNOPSIS
.nf
\fB#include <tk.h>\fR
.sp
Tk_CanvasTextInfo *
\fBTk_CanvasGetTextInfo\fR(\fIcanvas\fR)
.SH ARGUMENTS
.AS Tk_Canvas canvas
.AP Tk_Canvas canvas in
A token that identifies a particular canvas widget.
.BE
.SH DESCRIPTION
.PP
Textual canvas items are somewhat more complicated to manage than
other items, due to things like the selection and the input focus.
\fBTk_CanvasGetTextInfo\fR may be invoked by a type manager
to obtain additional information needed for items that display text.
The return value from \fBTk_CanvasGetTextInfo\fR is a pointer to
a structure that is shared between Tk and all the items that display
text.
The structure has the following form:
.CS
typedef struct Tk_CanvasTextInfo {
Tk_3DBorder \fIselBorder\fR;
int \fIselBorderWidth\fR;
XColor *\fIselFgColorPtr\fR;
Tk_Item *\fIselItemPtr\fR;
int \fIselectFirst\fR;
int \fIselectLast\fR;
Tk_Item *\fIanchorItemPtr\fR;
int \fIselectAnchor\fR;
Tk_3DBorder \fIinsertBorder\fR;
int \fIinsertWidth\fR;
int \fIinsertBorderWidth\fR;
Tk_Item *\fIfocusItemPtr\fR;
int \fIgotFocus\fR;
int \fIcursorOn\fR;
} Tk_CanvasTextInfo;
.CE
The \fBselBorder\fR field identifies a Tk_3DBorder that should be
used for drawing the background under selected text.
\fIselBorderWidth\fR gives the width of the raised border around
selected text, in pixels.
\fIselFgColorPtr\fR points to an XColor that describes the foreground
color to be used when drawing selected text.
\fIselItemPtr\fR points to the item that is currently selected, or
NULL if there is no item selected or if the canvas doesn't have the
selection.
\fIselectFirst\fR and \fIselectLast\fR give the indices of the first
and last selected characters in \fIselItemPtr\fR, as returned by the
\fIindexProc\fR for that item.
\fIanchorItemPtr\fR points to the item that currently has the selection
anchor; this is not necessarily the same as \fIselItemPtr\fR.
\fIselectAnchor\fR is an index that identifies the anchor position
within \fIanchorItemPtr\fR.
\fIinsertBorder\fR contains a Tk_3DBorder to use when drawing the
insertion cursor; \fIinsertWidth\fR gives the total width of the
insertion cursor in pixels, and \fIinsertBorderWidth\fR gives the
width of the raised border around the insertion cursor.
\fIfocusItemPtr\fR identifies the item that currently has the input
focus, or NULL if there is no such item.
\fIgotFocus\fR is 1 if the canvas widget has the input focus and
0 otherwise.
\fIcursorOn\fR is 1 if the insertion cursor should be drawn in
\fIfocusItemPtr\fR and 0 if it should not be drawn; this field
is toggled on and off by Tk to make the cursor blink.
.PP
The structure returned by \fBTk_CanvasGetTextInfo\fR
is shared between Tk and the type managers; typically the type manager
calls \fBTk_CanvasGetTextInfo\fR once when an item is created and
then saves the pointer in the item's record.
Tk will update information in the Tk_CanvasTextInfo; for example,
a \fBconfigure\fR widget command might change the \fIselBorder\fR
field, or a \fBselect\fR widget command might change the \fIselectFirst\fR
field, or Tk might change \fIcursorOn\fR in order to make the insertion
cursor flash on and off during successive redisplays.
.PP
Type managers should treat all of the fields of the Tk_CanvasTextInfo
structure as read-only, except for \fIselItemPtr\fR, \fIselectFirst\fR,
\fIselectLast\fR, and \fIselectAnchor\fR.
Type managers may change \fIselectFirst\fR, \fIselectLast\fR, and
\fIselectAnchor\fR to adjust for insertions and deletions in the
item (but only if the item is the current owner of the selection or
anchor, as determined by \fIselItemPtr\fR or \fIanchorItemPtr\fR).
If all of the selected text in the item is deleted, the item should
set \fIselItemPtr\fR to NULL to indicate that there is no longer a
selection.
.SH KEYWORDS
canvas, focus, insertion cursor, selection, selection anchor, text
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