Re: are canvas coordinates limited to 32k

On Sun, 13 Apr 2025 20:44:50 -0700
et99 <et99@rocketship1.me> wrote:

I've been experimenting with placing widgets inside a canvas. When I tried to test it's performance on lots of widgets (in a column) I am seeing the last few widgets not being displayed when the code does
 
[winfo reqheight $content]
 
where content is a frame and the value returned is over 32768 (actually starts failing just shy of that value).

This is X11 heritage. On X coordinates are limited to 32767.

$ wish9.1
% frame .f -width 32768
.f
% pack .f
% X Error of failed request:  BadAlloc (insufficient resources for operation)
  Major opcode of failed request:  53 (X_CreatePixmap)
  Serial number of failed request:  137
  Current serial number in output stream:  144

This limitation is hardcoded in Tk API as well. For example, the function

  Tk_CanvasDrawableCoords(
    Tk_Canvas canvas,
    double x,
    double y,
    short *drawableXPtr,
    short *drawableYPtr);

can't return coordinates bigger than 32767 for the canvas drawable.

--
Emiliano