1Tk_CanvasTextInfo(3) Tk Library Procedures Tk_CanvasTextInfo(3)
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8 Tk_CanvasTextInfo - additional information for managing text items in
9 canvases
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12 #include <tk.h>
13 Tk_CanvasTextInfo *
15 Tk_CanvasGetTextInfo(canvas)
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18 Tk_Canvas canvas (in) A token that identifies a particular
19 canvas widget.
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23 Textual canvas items are somewhat more complicated to manage than other
24 items, due to things like the selection and the input focus. Tk_Can‐
25 vasGetTextInfo may be invoked by a type manager to obtain additional
26 information needed for items that display text. The return value from
27 Tk_CanvasGetTextInfo is a pointer to a structure that is shared between
28 Tk and all the items that display text. The structure has the follow‐
29 ing form:
30 typedef struct Tk_CanvasTextInfo {
31 Tk_3DBorder selBorder;
32 int selBorderWidth;
33 XColor *selFgColorPtr;
34 Tk_Item *selItemPtr;
35 int selectFirst;
36 int selectLast;
37 Tk_Item *anchorItemPtr;
38 int selectAnchor;
39 Tk_3DBorder insertBorder;
40 int insertWidth;
41 int insertBorderWidth;
42 Tk_Item *focusItemPtr;
43 int gotFocus;
44 int cursorOn;
45 } Tk_CanvasTextInfo;
46 The selBorder field identifies a Tk_3DBorder that should be used for
47 drawing the background under selected text. selBorderWidth gives the
48 width of the raised border around selected text, in pixels. selFgCol‐
49 orPtr points to an XColor that describes the foreground color to be
50 used when drawing selected text. selItemPtr points to the item that is
51 currently selected, or NULL if there is no item selected or if the can‐
52 vas does not have the selection. selectFirst and selectLast give the
53 indices of the first and last selected characters in selItemPtr, as re‐
54 turned by the indexProc for that item. anchorItemPtr points to the
55 item that currently has the selection anchor; this is not necessarily
56 the same as selItemPtr. selectAnchor is an index that identifies the
57 anchor position within anchorItemPtr. insertBorder contains a
58 Tk_3DBorder to use when drawing the insertion cursor; insertWidth
59 gives the total width of the insertion cursor in pixels, and insertBor‐
60 derWidth gives the width of the raised border around the insertion
61 cursor. focusItemPtr identifies the item that currently has the input
62 focus, or NULL if there is no such item. gotFocus is 1 if the canvas
63 widget has the input focus and 0 otherwise. cursorOn is 1 if the in‐
64 sertion cursor should be drawn in focusItemPtr and 0 if it should not
65 be drawn; this field is toggled on and off by Tk to make the cursor
66 blink.
67 The structure returned by Tk_CanvasGetTextInfo is shared between Tk and
69 the type managers; typically the type manager calls Tk_CanvasGetTex‐
70 tInfo once when an item is created and then saves the pointer in the
71 item's record. Tk will update information in the Tk_CanvasTextInfo;
72 for example, a configure widget command might change the selBorder
73 field, or a select widget command might change the selectFirst field,
74 or Tk might change cursorOn in order to make the insertion cursor flash
75 on and off during successive redisplays.
76 Type managers should treat all of the fields of the Tk_CanvasTextInfo
78 structure as read-only, except for selItemPtr, selectFirst, selectLast,
79 and selectAnchor. Type managers may change selectFirst, selectLast,
80 and selectAnchor to adjust for insertions and deletions in the item
81 (but only if the item is the current owner of the selection or anchor,
82 as determined by selItemPtr or anchorItemPtr). If all of the selected
83 text in the item is deleted, the item should set selItemPtr to NULL to
84 indicate that there is no longer a selection.
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87 canvas, focus, insertion cursor, selection, selection anchor, text
88Tk 4.0 Tk_CanvasTextInfo(3)