AdiIRC

Per Amundsen wrote in #note-1:

Stretch is working as expected, it keeps the aspect ratio while trying to fit the image in you window size.

You'll either have to resize the image or resize your window.

But I used Pixel Zoomer to measure my chatarea size & resized the wallpaper, & it still had a gap ! I believe my scrollbar (which I've made bigger with WinAero Tweaker) is causing the image to overflow. Please check with a tweaked Scrollbar width & test for yourself. The gap was on the left [& right ?] of the chatarea.

You have to resize the image in a way so it fits your specific window size, you can't just measure it because it's already resized by AdiIRC according to the aspect ratio, you'll need to break the ratio and make the image the exact size as your window.

What you really want is a "fill" mode which fills the image into the window size and ignores the aspect ratio, but AdiIRC does not currently support that, it will some day.

I don't think changing scrollbars has any effect since adiirc knows the width of the scrollbar, otherwise your messages would be inside the scrollbar.

Per Amundsen wrote in #note-3:

You have to resize the image in a way so it fits your specific window size, you can't just measure it because it's already resized by AdiIRC according to the aspect ratio, you'll need to break the ratio and make the image the exact size as your window.

What you really want is a "fill" mode which fills the image into the window size and ignores the aspect ratio, but AdiIRC does not currently support that, it will some day.

I don't think changing scrollbars has any effect since adiirc knows the width of the scrollbar, otherwise your messages would be inside the scrollbar.

Alright, thank you ! & you're probably right, MS Paint isn't all that reliable.