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.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 \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

\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