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
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
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 does not 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;
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_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
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