In the specific case of Character Map,the chart with the characters is painted by libgucharmap7. How exactly it does it is hidden (at least until I inspect the sources) but I do not think it uses buttons, even though it emits a "button pressed" event. I would not be at all surprised to find that it does not even cache the whole table all the time but generates only the visible part dynamically. It is after all the caller's job to update the scroll position indicators, there is a callback for that.

I am actually quite getting used to the Qt version without buttons. It now looks very much like the GTK version, only with smaller cells, hence more characters fitting on the screen:



I still have the problem of how to show only the characters of the chosen code page though. If anyone has had any experience with libgucharmap, perhaps you can throw me a pointer. I have not found any documentation whatsoever.