Scroll to navigation

Tk_CanvasTextInfo(3tk) Tk Library Procedures Tk_CanvasTextInfo(3tk) 





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







  

    4.0
    Tk