Tk_CanvasTextInfo(3)

✨ NAME ✨

okay so Tk_CanvasTextInfo — it's the extra-info situation for managing text items in canvases. That's the whole name vibe: additional information for managing text items in canvases. We're in the Tk Library Procedures manual, bestie, and this page is Tk_CanvasTextInfo(3).

🫶 SYNOPSIS 🫶

#include <tk.h>

Tk_CanvasTextInfo *
Tk_CanvasGetTextInfo(canvas)

🎀 ARGUMENTS 🎀

• Tk_Canvas canvas (in) — a token that identifies a particular canvas widget. That's it, that's the arg 💅

🦋 DESCRIPTION 🦋

Textual canvas items are somewhat more complicated to manage than other items, because of stuff like the selection and the input focus. Tk_CanvasGetTextInfo may be invoked by a type manager to get the 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 this 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;

Here's the field-by-field tea, no cap:

• selBorder — 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 — 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.
• 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

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okay that's the page, bestie 💖 source/version is Tk 4.0, the manual page is Tk_CanvasTextInfo(3), and the date spot isn't printed in this footer, so we're not making one up 😌✨