1Tk_CanvasTextInfo(3)         Tk Library Procedures        Tk_CanvasTextInfo(3)
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NAME

8       Tk_CanvasTextInfo  -  additional information for managing text items in
9       canvases
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SYNOPSIS

12       #include <tk.h>
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14       Tk_CanvasTextInfo *
15       Tk_CanvasGetTextInfo(canvas)
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ARGUMENTS

18       Tk_Canvas canvas (in)          A token  that  identifies  a  particular
19                                      canvas widget.
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DESCRIPTION

24       Textual canvas items are somewhat more complicated to manage than other
25       items, due to things like the selection and the input  focus.   Tk_Can‐
26       vasGetTextInfo  may  be  invoked by a type manager to obtain additional
27       information needed for items that display text.  The return value  from
28       Tk_CanvasGetTextInfo is a pointer to a structure that is shared between
29       Tk and all the items that display text.  The structure has the  follow‐
30       ing form:
31              typedef struct Tk_CanvasTextInfo {
32                  Tk_3DBorder selBorder;
33                  int selBorderWidth;
34                  XColor *selFgColorPtr;
35                  Tk_Item *selItemPtr;
36                  int selectFirst;
37                  int selectLast;
38                  Tk_Item *anchorItemPtr;
39                  int selectAnchor;
40                  Tk_3DBorder insertBorder;
41                  int insertWidth;
42                  int insertBorderWidth;
43                  Tk_Item *focusItemPtr;
44                  int gotFocus;
45                  int cursorOn;
46              } Tk_CanvasTextInfo;
47       The  selBorder  field  identifies a Tk_3DBorder that should be used for
48       drawing the background under selected text.  selBorderWidth  gives  the
49       width  of the raised border around selected text, in pixels.  selFgCol‐
50       orPtr points to an XColor that describes the  foreground  color  to  be
51       used when drawing selected text.  selItemPtr points to the item that is
52       currently selected, or NULL if there is no item selected or if the can‐
53       vas  does  not have the selection.  selectFirst and selectLast give the
54       indices of the first and last selected  characters  in  selItemPtr,  as
55       returned  by  the indexProc for that item.  anchorItemPtr points to the
56       item that currently has the selection anchor;  this is not  necessarily
57       the  same  as selItemPtr.  selectAnchor is an index that identifies the
58       anchor  position  within  anchorItemPtr.    insertBorder   contains   a
59       Tk_3DBorder  to  use  when  drawing  the insertion cursor;  insertWidth
60       gives the total width of the insertion cursor in pixels, and insertBor‐
61       derWidth  gives  the  width  of the raised  border around the insertion
62       cursor.  focusItemPtr identifies the item that currently has the  input
63       focus,  or  NULL if there is no such item.  gotFocus is 1 if the canvas
64       widget has the input focus and 0  otherwise.   cursorOn  is  1  if  the
65       insertion cursor should be drawn in focusItemPtr and 0 if it should not
66       be drawn;  this field is toggled on and off by Tk to  make  the  cursor
67       blink.
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69       The structure returned by Tk_CanvasGetTextInfo is shared between Tk and
70       the type managers;  typically the type manager  calls  Tk_CanvasGetTex‐
71       tInfo  once  when  an item is created and then saves the pointer in the
72       item's record.  Tk will update information  in  the  Tk_CanvasTextInfo;
73       for  example,  a  configure  widget  command might change the selBorder
74       field, or a select widget command might change the  selectFirst  field,
75       or Tk might change cursorOn in order to make the insertion cursor flash
76       on and off during successive redisplays.
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78       Type managers should treat all of the fields of  the  Tk_CanvasTextInfo
79       structure as read-only, except for selItemPtr, selectFirst, selectLast,
80       and selectAnchor.  Type managers may  change  selectFirst,  selectLast,
81       and  selectAnchor  to  adjust  for insertions and deletions in the item
82       (but only if the item is the current owner of the selection or  anchor,
83       as  determined by selItemPtr or anchorItemPtr).  If all of the selected
84       text in the item is deleted, the item should set selItemPtr to NULL  to
85       indicate that there is no longer a selection.
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KEYWORDS

89       canvas, focus, insertion cursor, selection, selection anchor, text
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93Tk                                    4.0                 Tk_CanvasTextInfo(3)
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