Add transparency support

[vilhalmer]

This was a much smaller diff than anticipated! Colors are now accepted with or without a fourth pair of hex values for alpha. Without alpha specified, it defaults to FF as you would expect.

[vilhalmer]

This fixes #71.

[Cloudef]

Very nice! Did you test this on which platform? X11 might need RGBA bits set on window creation. Wayland i think would work without any changes.

[vilhalmer]

Just fixed up clearing the cairo surface, missed pushing that up. I've only tested on wayland, I can take a look at X tomorrow morning.

[Cloudef]

If you are willing to do X support as well. I'll wait until that before merging this. Looks good.

[Cloudef]

Also note that X11 most likely won't work without a compositor. Fake transparency could be done for non compositor support. But that could as very well be another feature, another pr.

[panaman67]

Suggested change

	if (matched != 3 && matched != 4)
	if (matched < 3)

[Cloudef]

That would make it accept color codes with more than 4 components, so not sure if that's good idea 🤔

[vilhalmer]

I'm fine with either way, but only checking < 3 will allow extra characters to slip by.

[vilhalmer]

If you are willing to do X support as well

I have no experience with Xlib, so if you'd rather handle that I will defer to you. But I'm also willing to learn a bit. :)

[Cloudef]

https://gist.github.com/je-so/903479/834dfd78705b16ec5f7bbd10925980ace4049e17#file-testprogram-c-L53-L55
Basically these are the only bits you should need in bm_x11_window_create. Fallback to defaultvisual and defaultdepth if creating window with 32 bit visual and depth fails.

[Cloudef]

I think if you are testing in XWayland, that should already be composed (by the wayland composer), so RGBA should work fine there.

[vilhalmer]

I've pushed what I believe to be the correct solution. However, I'm unable to test properly because even current master refuses to start for me in Xwayland with BEMENU_BACKEND=x11. :(

I was able to test that it still runs correctly under native X, but I don't have an X compositor installed to see if it really becomes transparent.

[Cloudef]

Compton is something you could use to test the X11 side quickly. https://github.com/chjj/compton

[Earnestly]

Now developed in this fork: https://github.com/yshui/picom

[Cloudef]

Tested it! Seems to work.

[Cloudef]

if I do bemenu-run -l 15 -nb #00000000 and go down the list, it acts bit strangely. I guess there are no clears before redrawing?

[Cloudef]

Also, the transparency seems to work even without a compositor. I guess either cairo or x11 does the fake transparency for you.

[vilhalmer]

I guess there are no clears before redrawing?

Hmm, I thought this was fixed in ffd773f. Maybe cairo behaves differently when using the X backend?

[vilhalmer]

I'm not sure that dc33df1 fixes the redrawing issue on X, but it makes more sense to use CAIRO_OPERATOR_CLEAR to clear either way. :)

[vilhalmer]

The good news is I got transparency to work in X, not sure what I was doing wrong before. The bad news is that I've been bashing my head against bm_x11_window_render for a while and I have no idea what is going wrong. It seems like the cairo group is being used instead of a real double buffer, which I'm not sure works with transparency? Any change I make to the function either does nothing or eliminates the transparency.

[Cloudef]

Why do you need to edit bm_x11_window_render?

[Cloudef]

Ah, I just tested your new code. I see the issue now. Lemme send you a patch that should fix it in a moment.

[Cloudef]

diff --git a/lib/renderers/x11/window.c b/lib/renderers/x11/window.c
index bca1003..daf129a 100644
--- a/lib/renderers/x11/window.c
+++ b/lib/renderers/x11/window.c
@@ -94,8 +94,11 @@ bm_x11_window_render(struct window *window, const struct bm_menu *menu)
     }
 
     if (buffer->created) {
+        cairo_save(buffer->cairo.cr);
+        cairo_set_operator(buffer->cairo.cr, CAIRO_OPERATOR_SOURCE);
         cairo_paint(buffer->cairo.cr);
         cairo_surface_flush(buffer->cairo.surface);
+        cairo_restore(buffer->cairo.cr);
     }
 }

This should do it. It will only work with compositor. Doing pseudo-transparency would involve using XCopyArea or other tricks. But that would be separate thing.

[Cloudef]

Note with latest diff. Not sure if the clearing and such is needed in cairo render, but maybe they are still for wayland?

[vilhalmer]

(Sorry, have been busy with other things. Will get back to this soon!)

[vilhalmer]

Alright! With your patch and picom running, looks good on X. I think this is ready to go. Do you want me to squash things into a nicer set of commits, or will you handle that when merging?

[Cloudef]

Lets see how github's "squash and merge" works

[Cloudef]

Merged, thank you!

[vilhalmer]

Thanks for your help!