Why is there a black lag every time a WPF window is resized?

Question

Other questions on SE address how to speed up nested UI control resizing, but- what if there aren\'t any controls?

As you drag the edge of a WPF window, even a main

Answer 1

You could update your graphic card and try it out again but that wont change anything. The reason is pretty simple. We all get to see this sometimes based how fast/slow our computer is. Sometimes it runs smooth because we do not have many visuals to draw. The reason is no proper background color is found in graphic card at that moment in redrawing process. Your drivers are fine, and its not just because you use Wpf. Other techniques use the same mechanism behind redrawing.

The first thing WPF will do is clear out the dirty region that is going to redraw. The purpose of dirty regions is to reduce the amount of pixels sent to the output merger stage of the GPU pipeline. Here is where we see the black color. Window itself at that point has no background color or its background color is set to transparent and so to us the GPU draws the black background. Things run async in wpf which is good so.

To fix this you could set a fix color such as "White" to the Window. Then the WPF system will clean out the dirty region but fill it automatically with white color instead of black. This usually helps.

Match the window color or the color of top most layer. Dont let GPU use black and you should do fine. Btw Wpf is faster than WinForm so dont worry.