After a roundabout discussion[1] with wlroots devs, it's become apparent
that subpixel text rendering (a.k.a. "ClearType") does not work properly
when rendering over a transparent background, as labwc currently does.
Basically it comes down to the fact that the color of semi-transparent
pixels (which is adjusted redder or bluer to compensate for RGB subpixel
alignment) depends somewhat on background color. When rendering over
transparency, the text engine doesn't know the intended background color
and can't adjust the pixel colors correctly.
With Pango/Cairo, the end result can range from grayscale rendering (no
subpixel rendering at all) to wrong/oversaturated colors (for example,
bright pink pixels when rendering white text on blue background).
This change solves the issue by first filling the text buffer with an
opaque background color before rendering the text over it. Currently,
this is easy since the background is always a solid color. It may be a
little more complex (but doable) if we implement gradients in future.
Note that GTK 4 (and to some degree, recent versions of Microsoft
Windows) avoid this issue by disabling subpixel rendering altogether. I
would much prefer that labwc NOT do this -- it results in noticeably
blurrier text on non-retina LCD screens, which are still common.
[1] https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3822
Made all header files to have LABWC_ prefix in include guard identifers.
Converted from __LABWC_ in 35 include/ files.
Converted from __LAB_ in 5 include/ files.
Added LABWC prefix to 3 include/ files.
Added include guards to 3 include/ files.
The double underscores were removed since according to C standard
those "are always reserved for any use".
Adds two new theme vars:
- menu.width.min (menu will never be smaller than this)
- menu.width.max (menu will never be wider than this + padding)
A fixed menu width can be achieved by setting
menu.width.min == menu.width.max.
IMHO it encourages better design (by making dependencies more obvious)
to have source file/header file pairs like view.c/view.h, rather than a
monolithic header like labwc.h with everything in it.
I don't think we need to break up all of labwc.h at once, but maybe we
can start pulling it apart bit by bit as it's convenient.
Also:
- Move "struct border" to ssd.h so that view.h can use it without pulling
in all of labwc.h.
- Add a missing required #include within scaled_font_buffer.h (forward
declaration of "struct font" is not enough).
