Hello,

I am glad that this patch can be merged. On my GNOME desktop, I use kvantum to decorate Qt applications, but I am not sure if it is necessary for other DEs besides GNOME. This patch mainly fixes the problem of a black title bar appearing in a light theme, and the issue of rounded corners or shadow effects of submenus possibly obscuring the right menu button.

Regarding the first fix, I believe this is a bug upstream, and it might be more appropriate to submit a fix to https://github.com/vinceliuice/WhiteSur-kde?

For the second fix, the original outline of the dropdown submenu was rounded, which seemed to cover more pixels than it actually did. This caused the focus to be on the dropdown submenu instead of the menu entry above it when the mouse passed over the menu entry from left to right after activating the dropdown menu. Therefore, if I want to find a submenu option, I have to traverse the menu entry from right to left. After the fix, the submenu became square, which greatly reduces the focus error problem, but it looks much less aesthetically pleasing.

I have not installed other DEs, so I am not sure if these bugs exist on other DEs. If they do not, I believe these two patches should not be merged. Otherwise, reporting to upstream might be a good idea. Moreover, the current fix for submenus is a matter of personal preference, and some people may feel that this fix undermines the consistency of the appearance.