I have managed to track down this issue. It is not due to the floating point consistency change that I referred to in my previous post. The reason for the decrease in display speed is a change I made relating to
this bug report.
For many years, users reported that mIRC would stop displaying background pictures in windows if they opened too many windows. It turns out that this was because, for some users, mIRC was loading bitmaps into video card memory (this depended on the type of video card and the video drivers). This also prevented some users from playing full screen games while mIRC was running.
I changed the bitmap loading method in mIRC 6.31 so that it no longer used video card memory (or at least, tried to avoid it). This resolved the background picture issue. However, it has clearly had an effect on display speed. Another user has also
reported that 6.31 now uses too much normal memory - but if you are going to use background pictures, the memory has to come from somewhere :-]
One way to resolve the /drawpic speed issue is to make it use the old bitmap loading method, while ensuring that normal background pictures continue to use the new method. I am currently looking into this.
