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I'm trying to have in .NET 2.0 a transparent form, that is on top, invisible for mouse clicks but is possible to draw on it. I can easily reach this by setting the TransparencyKey to background color of the form. But there is one very easy to reproduce problem in all java programs (e.g. JDownloader, Vuze, Open Office): sometime when context menu is shown it leaves the part of (or whole) menu still visible after I click somewhere else. It is physically closed because it is unable to click on any item, but the image of it stays on my top invisible form - probably there was some problem in redrawing. I be very grateful for any help.

Hugo

Hugo
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1 Answers1

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A normal Windows application implements context menus as real windows, so when they're dismissed by the user all the windows underneath properly receive notification and repaint themselves, so the image of the menu isn't "left behind" anywhere.

The java apps you're having problems with most likely implement context menus by drawing directly on the screen, and when the menus are dismissed the app rolls-its-own and invalidates all the windows underneath it. I'm guessing that this method doesn't invalidate the region occupied by your app because it thinks your window is above it and it doesn't realize your app is transparent (this is speculation - I don't know for sure. if the context menus for these apps look different than the menus for a native app, then this is probably what's going on).

If this is what's happening, there's not much you can do about it. One thing you could do is draw to the screen yourself, instead of using a transparent window. Or you could just have a timer on your form periodically call refresh/invalidate.

MusiGenesis
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  • I'm afraid that it is more complex. Because according to your explanation the image of context menu should stay visible every time when it is shown. But it happens only from time to time. Moreover refresh, invalidate and neither repainting the background of my form via FillRectangle cannot erase the rest of the context menu. The only way is to move over it with some another window... – Hugo May 04 '11 at 12:03
  • I figured there's more to it, but if you're certain that you only see this problem with java applications (and never with "normal" Windows apps), then it must be caused by these applications' doing something non-standard. (to be fair, you're doing something non-standard as well, so it's not a surprise that the two aren't playing nicely together). I'd be willing to bet that iTunes would mess up your application also, since it's another app that tries to look like a native Windows app but isn't. – MusiGenesis May 04 '11 at 17:34