add GPU_SHADER_TEXT for font rendering

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.

1 files changed, 14 insertions, 0 deletions

diff --git a/source/blender/gpu/shaders/gpu_shader_text_frag.glsl b/source/blender/gpu/shaders/gpu_shader_text_frag.glsl
new file mode 100644
index 00000000000..4869a6360fa
--- /dev/null
+++ b/source/blender/gpu/shaders/gpu_shader_text_frag.glsl
@@ -0,0 +1,14 @@
+
+flat varying vec4 color;
+varying vec2 texcoord;
+
+uniform sampler2D glyph;
+
+void main()
+{
+	// input color replaces texture color
+	gl_FragColor.rgb = color.rgb;
+
+	// modulate input alpha & texture alpha
+	gl_FragColor.a = color.a * texture2D(glyph, texcoord).a;
+}