Forums Bug Reports 7.15 and WM_PAINT message (window redraw) problems

This is mainly a technical bug report for Khaled. Others are welcome to comment and discuss too.

Before I get started, I want to rule out the following possibilities (which are usually what people resort to blaming for problems of this nature):

- This is not caused by video card issues or driver issues. The problem is reproducible on multiple systems, both ATI and nVidia-based, using completely different cards.
- The issue has only been confirmed under Windows XP (32-bit; I don't have a way to test 64-bit, and I don't use Windows 7).
- I *do not* have East Asian Languages enabled (see my blog for why I mention this).
- No GDI hacks or "theme hacks" are in place; everything is 100% stock/standard.
- The issue is only visible (from my testing) when full window drag is enabled (which is usually the default).

The problem appears to be that mIRC is incorrectly handling WM_PAINT messages directed to it when another application/program window is dragged across the main mIRC window. The application/program window being dragged doesn't matter -- it can be anything (Firefox, Notepad, PuTTY, etc.).

The result are occasional glitches (grey lines, boxes, and sometimes window content) which are visible only within the mIRC application.

I've attached a screen shot showing what the problem is. I can also make a video demonstrating this problem if it would be of more help.

http://www.malkavian.com/~jdc/mirc_wm_paint_bug.png

The background colour (dark grey) seen in the screen shot is the "Application Background" colour per the Windows Classic UI theme I use (called Rainy Day). The vertical white-grey line seen is the leftovers of the left edge of the Firefox window I dragged over mIRC.

There are some well-established threads about this problem, most of which stem from the WM_PAINT handler in the application incorrectly returning non-zero to Windows. Here's some reference material:

http://msdn.microsoft.com/en-us/library/dd145213%28v=vs.85%29.aspx
http://winapi.freetechsecrets.com/win32/WIN32WMPAINT.htm

Similar issue:

http://www.gamedev.net/community/forums/topic.asp?topic_id=522970

I'm more than happy to try out debug builds that may or may not fix this problem. Just let me know.

I'm sure there is more to it than just an issue with mIRC. I can drag anything across mIRC and never see any graphics problems. This is true both in XP and Windows 7 (32bit each) and although I don't have Vista to look at right now, I never saw it happen when I used Vista.

That said, it could still be caused by mIRC, but only happens with certain system setups. I rarely use the newest graphics drivers and there are times with the newest drivers have issues. It's even possible for both ATI and nVidia drivers to have a similar issue in certain versions. If the drivers are related, then it wouldn't matter which card you're using since they both (at least nVidia) have driver packages that handle all their newer cards rather than individual drivers for each card. Drivers would also make it occur in any system using that driver version. Whether or not that is the case, you'd have to see. Try older versions of the drivers for the cards and you'd have a good idea if it's driver related.

Either way, it's going to be related to something on the tested systems that is different from the 3 systems I have available to test on. mIRC by itself won't display that bug from what I can test. If mIRC has a bug that is related, then it's only there if some other requirements are met -- drivers (not just graphics), hardware (not just graphics), other software being used, Windows settings, etc.

And considering mIRC's been out for a many years, if this were a widespread problem, I'm sure it would have been brought up here many times before now. That leads me to think it's probably a very limited problem that may have nothing to do with mIRC itself. Remember that mIRC draws windows differently than most other programs, so just because it doesn't happen in other programs doesn't mean it's a problem with mIRC. It only means that it's only visible in applications that draw the windows in this specific way.

Thanks, it took some effort to reproduce this issue since it very rarely happens here. This should be fixed in the next version.

Thanks Khaled! I can confirm (currently beta) mIRC 7.18 fixes this issue on all the ATI and nVidia-based systems I have access to.