While Draw_Glyph does draw only one glyph at a time, it doesn't shape
the text every time, so is a major win for performance (especially
coupled with pre-shaped text).
Font and text handling is very much part of user interface and at least
partially independent of rendering, but does fit it better with GUI than
genera UI (ie, both graphics and text mode), thus libQFgui as well as
libQFui are built in the ui directory.
The existing font related builtins have been moved into the ruamoko
client library.
Currently only for gl/glsl/vulkan. However, rather than futzing with
con_width and con_height (and trying to guess good values), con_scale
(currently an integer) gives consistent pixel scaling regardless of
window size.
It handles basic cursor motion respecting \r \n \f and \t (might be a
problem for id chars), wraps at the right edge, and automatically
scrolls when the cursor tries to pass the bottom of the screen.
Clearing the buffer resets its cursor to the upper left.
This is intended for the built-in 8x8 bitmap characters and quake's
"conchars", but could potentially be used for any simple (non-composed
characters) mono-spaced font. Currently, the buffers can be created,
destroyed, cleared, scrolled vertically in either direction, and
rendered to the screen in a single blast.
One of the reasons for creating the buffer is to make it so scaling can
be supported in the sw renderer.
It's implemented only in the Vulkan renderer, partly because there's a
lot of experimenting going on with it, but the glyphs do get transferred
to the GPU (checked in render doc). No rendering is done yet: still
thinking about whether to do a quick-and-dirty test, or to add HarfBuzz
immediately, and the design surrounding that.
The software renderer uses Bresenham's line slice algorithm as presented
by Michael Abrash in his Graphics Programming Black Book Special Edition
with the serial numbers filed off (as such, more just so *I* can read
the code easily), along with the Chen-Sutherland line clipping
algorithm. The other renderers were more or less trivial in comparison.
The renderer should now be free of any direct access to client code. Even
3d rendering is now done via a function pointer.
The cshift code is done as a 2d screen function.
