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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

       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_Can-
       vasGetTextInfo 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 follow-
       ing 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  index-
       Proc  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 posi-
       tion 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_CanvasGetTex-
       tInfo 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



Tk                                    4.0                 Tk_CanvasTextInfo(3)

CanvTxtInfo 8.5.4 - Generated Sat Aug 23 05:42:38 CDT 2008
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