How to draw something to the screen and have the underlying ui interactive

Question

I seeking solution for Windows first. I need to add visual effects to screen image without breaking the interactivity of all and every controls, that are on this screen. The solution can be straightforward: 1. take a screenshot 2. show this screenshot in a separate window, above other windows 3. apply the effect to image, being shown on this window But, this window (containing screenshot) makes any buttons and other controls below, unreachable for mouse interaction (clicking, hovering)

Is there any way to do this ?

Answer 1

From MSDN's documentation on layered windows...

"Hit testing of a layered window is based on the shape and transparency of the window. This means that the areas of the window that are color-keyed or whose alpha value is zero will let the mouse messages through. However, if the layered window has the WS_EX_TRANSPARENT extended window style, the shape of the layered window will be ignored and the mouse events will be passed to other windows underneath the layered window."

Here's an article about it. Notice this additional warning:

"setting the WS_EX_TRANSPARENT attribute affects the entire window: the user can't close the window using the 'x' button, select it with the mouse, or select any controls on the window. The application can still close the window programmatically."

Depending on what you're actually drawing and where, it might be more appropriate to use Owner-Drawn Controls rather than hover an "onion skin" over your whole window.