Picom: Menues transparency does not affect content

[datalot-369]

This is a bug migration from https://github.com/chjj/compton/issues/286.
There is also a Pull Request available from the original project, and doesn't look too difficult to review for its original Developer, @tryone144: https://github.com/chjj/compton/pull/295/files

When a menu is made transparent, all of its pixels are made transparent, regardless of whether a pixel is a content or background. This means when you set the menu opacity to a very low value, you may not be able to easily see the text and icons on the menu. (See the picture)

Expected behavior.

Hope this patch would be implemented. Blur + Transparency is actually the only reason I prefer Picom over XFWM Compositor.

[yshui]

This patch introduce a dependency to gtk, which I prefer to not do.

A good mid-ground would probably be using a window shader to make a certain color transparent.

[tryone144]

Just to be clear: https://github.com/chjj/compton/pull/295 is not by me. This confusion probably stems from my PR https://github.com/yshui/picom/pull/286 having the same id as the original issue on compton.

A good mid-ground would probably be using a window shader to make a certain color transparent.

This should already be possible given the right window shader (and manually figuring out the correct color). See https://github.com/yshui/picom/issues/295#issue-548645016 for some inspiration.

The tentative implementation in https://github.com/yshui/picom/pull/507 can already be used for this as well. See this proof-of-concept I've used for testing.

This could theoretically be baked into the current window shader and given a new option (including new window-rules) if we really want to. I couldn't find a way to do the same efficiently with the xrender backend.