Prior to this commit, a backing buffer with scale 1 was always created for
a scaled_scene_buffer before showing it, and backing buffers for specific
scales were created on output_enter events.
This commit removes this redundant re-renderings by calling
wlr_scene_buffer_set_dest_size() upon scaled_scene_buffer creation just to
receive output_enter events and delaying the first rendering to the first
output_enter event.
I needed to add font_get_buffer_size() to obtain the size of a font buffer
without actually creating it.
Arrow signs are specific to submenu items, so they would be more natural
to be handled in menu.c rather than accepting "arrow" in
font_buffer_create().
Also I allowed non-positive numbers for max_width in font_buffer_create(),
in which case the natural font width is used as the buffer width.
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".
Move font_texture_create() to font.c so it can be used for purposes other
than rendering the menu, for example server side decoration.
Refactor menu.c and menu.h to use this more generic font_texture_create()
