Add button class to interface
Check for press/drag/release of RESET button
Add FG and BG color for textport shader (for active button)
Handle RESET and REBOOT events in main loop
Multiply by a matrix in vertex shaders to convert from pixel
coordinates to window coordinates, moving that operation out to a
centralized place in the application.
Factor out shader binding for code simplification.
Factor out making vertex array in anticipation of UI buttons.
Change "mode" to "display_mode".
Fix setting of glViewport on window resize
Add lores shader and implement in redraw
Handle inverse text, but it indicates glyph lookup or raster location is off by one, not sure what's going on there.
Move to GL 3.2
Draw a quad with shaders depending on the mode in that part of the screen
HIRES shader reads from hires texture
TEXTPORT shader reads from textpor texture and indirects through a font
to get pixel values
MIXED now supported
Still to do: BLINK text, INVERSE text, LORES, gang up HGR memory updates
Why doesn't cursor flash the checkerboard?
