vDos Window refresh distraction

[whathim]

vDos 2023.05.01, Windows 10



I observe that when I have vDos running (hosting my editor) but idling, if I then open an instance of File Explorer, say, the vDos window appears to refresh or redraw (momentarily blank). It’s a fraction of a second, of course, but it’s noticeable and slightly distracting and I can’t recall seeing other applications (e.g., MS Word) affected in this way.

[Jos]

I suppose blank would be totally black, like your issue of the About popup (https://vdos.proboards.com/thread/688/invisible-popup-over-blank-window).

Although the ‘background’ of the vDos window is black, vDos doesn’t clear its window itself.
Something in your system (an utility?) seems to invoke Windows to do so. Then a WM_PAINT message would be sent to vDos to redraw the window content.
For the time vDos takes to process this message and Windows to update the content area on screen, that would then be black?
When the About popup is shown, vDos ignores this message.

With some effort you could perhaps simulate this background clearing by rapidly using Ctrl-Mouse wheel and an overall light screen background.
This would the only situation part of vDos window is normally temporary cleared, creating the added space at enlarging the window.

Jos

[whathim]

Thanks for the explanation. I’ve just tried the following on my Windows 10 desktop and my Windows 11 laptop.



With vDos running hosting my editor, I right-click the vDos title bar and select “About”. Now I open an instance of File Explorer and, as before, the vDos window goes blank (black) but this time it does not redraw. Presumable this is confirming what you say: that vDos ignores the WM_PAINT message when “About” is shown.



As far as I can tell, this issue only occurs with File Explorer. I tried starting a range of applications while vDos had “About” shown and none of them caused the black screen. These included MS Word/Excel/Edge, Notepad, Acrobat, BeyondCompare, Logitech Media Player, OE Classic, Snagit and another vDos. It’s only File Explorer that causes it. You suggest in your explanation that there is something (a utility?) in my system that seems to be invoking Windows to clear the vDos window? Seems like File Explorer, or something associated with it, is that utility.

[Jos]

I never saw this happening, but I don’t use File Explorer (FreeCommander instead).

Opening, activating, sizing a File Explorer window however doesn’t clear the vDos window on my PC’s.
So some utility, or a Windows setting would be the cause. Perhaps someone else has an idea.

The cure would be to set the vDos window (class) drawing its (black) background, so that wouldn’t be done by Windows.
Even then still no need for that being implemented. But on switching to full screen vDos relies on Windows doing that.
So vDos would have to draw the black horizontal and vertical bars in full screen itself.

Jos

[whathim]

Yes, it would be great if someone else were to give their thoughts. Am I the only one experiencing this?



I’ve just tried the same “test” as in my previous post on another Windows 10 machine and the issue doesn’t manifest there. This should be a big clue: this other machine has a very similar setup to my other two computers and yet there must be something different. I have no idea what that could be at the moment.



Anyway, thanks for the thoughts and explanations Jos. I agree this “issue” wouldn’t warrant any changes to vDos. It is, in truth, a very minor anomaly that doesn’t interfere with my work and I just hope that posting it was of some interest.

[emendelson]

I've tried to reproduce this on three different systems, and can't. Possibly something is wrong with the video driver on your Windows system?

[herman]

I see something different happening compared to the previous versions. The about screen appears sometimes automatically when the vDos screen with application runs in the background and then sees it again in the foreground, without having made it active in the taskbar.

Herman

[Jos]

Strange, the About box is only shown if the vDos window is focused.

Jos