Tk_CanvasTextInfo(3) Tk Library Procedures Tk_CanvasTextInfo(3)
NAME
Tk_CanvasTextInfo - additional information for managing text items in
canvases
SYNOPSIS
#include <tk.h>
Tk_CanvasTextInfo *
Tk_CanvasGetTextInfo(canvas)
ARGUMENTS
A token that identifies a particular canvas widget.
DESCRIPTION
Textual canvas items are somewhat more complicated to manage than other
items, due to things like the selection and the input focus. Tk_Can-
vasGetTextInfo may be invoked by a type manager to obtain additional
information needed for items that display text. The return value from
Tk_CanvasGetTextInfo is a pointer to a structure that is shared between
Tk and all the items that display text. The structure has the follow-
ing form: typedef struct Tk_CanvasTextInfo {
Tk_3DBorder selBorder;
int selBorderWidth;
XColor *selFgColorPtr;
Tk_Item *selItemPtr;
int selectFirst;
int selectLast;
Tk_Item *anchorItemPtr;
int selectAnchor;
Tk_3DBorder insertBorder;
int insertWidth;
int insertBorderWidth;
Tk_Item *focusItemPtr;
int gotFocus;
int cursorOn; } Tk_CanvasTextInfo; The selBorder field identifies a
Tk_3DBorder that should be used for drawing the background under
selected text. selBorderWidth gives the width of the raised border
around selected text, in pixels. selFgColorPtr points to an XColor
that describes the foreground color to be used when drawing selected
text. selItemPtr points to the item that is currently selected, or
NULL if there is no item selected or if the canvas does not have the
selection. selectFirst and selectLast give the indices of the first
and last selected characters in selItemPtr, as returned by the index-
Proc for that item. anchorItemPtr points to the item that currently
has the selection anchor; this is not necessarily the same as
selItemPtr. selectAnchor is an index that identifies the anchor posi-
tion within anchorItemPtr. insertBorder contains a Tk_3DBorder to use
when drawing the insertion cursor; insertWidth gives the total width
of the insertion cursor in pixels, and insertBorderWidth gives the
width of the raised border around the insertion cursor. focusItemPtr
identifies the item that currently has the input focus, or NULL if
there is no such item. gotFocus is 1 if the canvas widget has the
input focus and 0 otherwise. cursorOn is 1 if the insertion cursor
should be drawn in focusItemPtr and 0 if it should not be drawn; this
field is toggled on and off by Tk to make the cursor blink.
The structure returned by Tk_CanvasGetTextInfo is shared between Tk and
the type managers; typically the type manager calls Tk_CanvasGetTex-
tInfo 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 configure widget command might change the selBorder
field, or a select widget command might change the selectFirst field,
or Tk might change cursorOn in order to make the insertion cursor flash
on and off during successive redisplays.
Type managers should treat all of the fields of the Tk_CanvasTextInfo
structure as read-only, except for selItemPtr, selectFirst, selectLast,
and selectAnchor. Type managers may change selectFirst, selectLast,
and selectAnchor 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 selItemPtr or anchorItemPtr). If all of the selected
text in the item is deleted, the item should set selItemPtr to NULL to
indicate that there is no longer a selection.
KEYWORDS
canvas, focus, insertion cursor, selection, selection anchor, text
Tk 4.0 Tk_CanvasTextInfo(3)
CanvTxtInfo 8.5.4 - Generated Sat Aug 23 05:42:38 CDT 2008