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
Tk_Canvas canvas (in) 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_CanvasGetTextInfo may be invoked by a type manager to obtain addi-tional additional
tional 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 struc-ture structure
ture has the following 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 doesn't have the selection. selectFirst and selectLast give the indices of
the first and last selected characters in selItemPtr, as returned by the indexProc 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 position within
anchorItemPtr. insertBorder contains a Tk_3DBorder to use when drawing the insertion cursor; inser-tWidth insertWidth
tWidth 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_CanvasGetTextInfo 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 select-First selectFirst
First field, or Tk might change cursorOn in order to make the insertion cursor flash on and off dur-ing during
ing 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)
|