How could one change the opacity of a TWinControl based control? And why didn’t they add this capability to TControl/TWinControl level (why only TForm)?
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How could one change the opacity of a TWinControl based control? And why didn’t they add this capability to TControl/TWinControl level (why only TForm)?
Controlling the opacity of a window is offered by a feature called layered windows. You can read more about the feature on MSDN. The feature is only available for top-level windows. As far as I can tell, Desktop Window Manager (Vista’s “glass” effect) is also only available for top-level windows.
Alternatives available for child windows are to use window regions to mark certain areas of a window as completely transparent, or to use bitmap alpha blending to draw the whole control yourself.