I've made a separate version of the geom shader that works with full
3D modelviewmat.
This commit also includes some fixup inside blf_batching_start().
This means smaller imm buffer usage.
This does not reduce the number of drawcalls.
This uses geometry shader which is slow for the GPU but given we are really
CPU bound on this case, it should not matter.
A perfect implementation would:
- Set the glyph coord in a bufferTexture and just send the glyph ID to the
GPU to read the bufferTexture.
- Use GWN_draw_primitive and draw 2*strllen triangle and just retrieve the
glyph ID and color based on gl_VertexID / 6.
- Stream fixed size buffer that the Driver can discard quickly but this is
the same as improving IMM directly.
Ignore texture matrix in the shader, stop messing with texture matrix in BLF code.
Use linear screen-space interpolation instead of perspective.
Avoid redundant call to glMatrixMode.
With USE_GLSL enabled, GPU_basic_shader(TEXTURE|COLOR) always rendered black. New shader uses a solid color + alpha channel of texture (which in our case is a font glyph). See fragment shader for details.
I prefer this approah -- multiple shaders that each do one thing well (and are easy to read/write/understand), instead of one shader that can do many things given the right options.
