buffering *framework* in C and Windows GDI
Background : My client has a very extensive proprietary forms library which is effectively implemented in C (actually, it's a proprietary object-oriented language that basically wraps Windows controls and interacts with them with SendMessage() , SetStyle() , etc.)
Problem I want to solve : Whenever I drag/resize a top-level window (or drag a splitter) in an app implemented in the above framework, there is massive flicker. The top-level window is repainted, and any controls it contains repaint themselves.
Question 1 : Is there a way to surgically introduce double-buffering into the forms library. In particular, I want to know if I can implement double-buffering using standard Windows GDI functions.
For example, if I could cause the top-level windows to be double-buffered such that all child windows of the top-level window are automatically drawn double-buffered as well. An even better alternative would be to be able to introduce double-buffering on any arbitrary window and have all its children inherit this.
The best solution would somehow cause the BeginPaint() function for child controls to return a handle to the DC of the offscreen back buffer so that I don't have to write special code for each individual control class.
Question 2 : Is there a way (such as a set of flags) to cause generic Windows controls (EDIT, BUTTON, and so on) to draw themselves double-buffered? This would be a worse solution than a more generic approach that would just seamlessly give them the back buffer to draw on, but it might also be acceptable.
All help greatly appreciated. Please let me know if I can clarify anything for you.
Look into WS_EX_COMPOSITED, which is an extended window style that turns on double-buffering for the window. It may be enough to set this style on the parent of the controls.
You actually might be able to wrap all your window drawing code with C that executes C#, and that way there is already a double-buffered implementation for you.
How to eliminate flicker in Windows.Forms custom control when scrolling?
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