Tk\_CanvasTextInfo(3) Tk Library Procedures Tk\_CanvasTextInfo(3)

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# [NAME](#NAME)

Tk\_CanvasTextInfo - additional information for managing text items in canvases

# [SYNOPSIS](#SYNOPSIS)

```
#include <tk.h>

Tk_CanvasTextInfo *
Tk_CanvasGetTextInfo(canvas)
```

# [ARGUMENTS](#ARGUMENTS)

Tk\_Canvas *canvas* (in)

A token that identifies a particular canvas widget.

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# [DESCRIPTION](#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_3DBorder selBorder;


    int selBorderWidth;


    XColor *selFgColorPtr;


    Tk_Item *selItemPtr;


    Tcl_Size selectFirst;


    Tcl_Size selectLast;


    Tk_Item *anchorItemPtr;


    Tcl_Size 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](#KEYWORDS)

canvas, focus, insertion cursor, selection, selection anchor, text

4.0 Tk

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Document: Tk_CanvasTextInfo(3) from tk 9.0.4-r2 (Chainguard OS)
Source: https://downloads.sourceforge.net/sourceforge/tcl/tk9.0.4-src.tar.gz