Translucent form and opaque roundrect

[xinyiman]

Hi guys, I want to understand how to draw an opaque roundrect on a translucent form. I did some tests, but by making the form translucent even the roundrect that I draw in the form2 paint event becomes translucent. Try my test and press the button on the first form. You will understand what I mean.

[Pascal]

On windows you can use:
SetLayeredWindowAttributes(Handle, clFuchsia, 180, LWA_COLORKEY or LWA_ALPHA);

See attached project.

[xinyiman]

On windows you can use:
SetLayeredWindowAttributes(Handle, clFuchsia, 180, LWA_COLORKEY or LWA_ALPHA);

See attached project.

Thanks but your solution isn't cross-platform. Run only windows system.

[Pascal]

Yes, right.

Mybe someone can add a ColorKey property to TForm and uses system specific functions to set it.

There should be a Unix/OSX pendant.

[xinyiman]

sorry but don't understand

[Pascal]

We need a new property for TForm like AlphaBlend and AlphaBlendValue: ColorKey.

AlphaBlend and AlphaBlendValue are set in the Windows widgetset by SetLayeredWindowAttributes.
SetLayeredWindowAttributes can also set the ColorKey. So for Windows widgetset there is a solution.

For other widgetsets there must be an equivalent function to set the ColorKey.

If we know them we can add ColorKey property to TForm and will have a cross platform solution!

[xinyiman]

AlphaBlend and AlphaBlendValue run correctly on mac but all form and components get transparent value. For me necessity is important form with transparency and component (like a button or image) not.

[Pascal]

So my solution doesn't work either.

Have a look here: https://stackoverflow.com/questions/4928215/changing-alpha-of-window-background-not-the-whole-window

But LCL can't set alpha value of window background color.