Question

The reason I’m doing this is because I’m trying to set the window in the centre of the screen. I’m using grid not pack and I have read about using wm grid but don’t understand how to set it. I also don’t understand why . cget -width is returning 0 I thought grid was supposed to set the size when not given an option?

set width [. cget -width]
set height [. cget -height]
puts $height
puts $width
set x [expr { ( [winfo vrootwidth  .] - $width  ) / 2 }]
set y [expr { ( [winfo vrootheight .] - $height ) / 2 }]


wm title . "a3q2" 
wm geometry . ${width}x${height}+${x}+${y}

What am I doing wrong this time? P.S homework I don’t just want a code post. Thanks

Answer 1

[. cget -width] and [. cget -height] return the explicitly configured width/height of the window. For most widgets in Tk you don’t explicitly configure the dimensions. Instead, the widgets have a “natural” width/height based on the contents of the widget. A label, for example, is just wide/tall enough to accommodate the text in it. A toplevel window is just big enough to fit all the widgets inside of it.

To get the actual dimensions of the window, you should use [winfo width .] and [winfo height .]. Make sure you do that after the window and all of the widgets inside it have been mapped (usually that means doing an [update] call before the [winfo ...] calls). Otherwise the geometry manager may not have updated the dimensions of the widgets/window yet.