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; 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.