Added glyph rendering using stb_truetype

glyph/shaders/font_vert.glsl

@@ -0,0 +1,45 @@
+#version 450 core
+#extension GL_ARB_texture_rectangle: enable
+
+
+layout(location=0) uniform vec2 half_viewport_size;
+
+//layout(location=0) in uvec2 ltrb_index;
+layout(location=0) in vec4  rect_ltrb;
+layout(location=1) in vec4  rect_tex_ltrb;
+layout(location=2) in vec4  rect_color;
+//layout(location=4) in uint  index;
+layout(location=3) in float rect_subpixel_shift;
+
+
+flat out vec2  tex_coords;
+flat out vec4  color;
+flat out float subpixel_shift;
+flat out uint   index_out;
+
+
+void main(){
+  uvec2[6] rect_vertices = {
+    {0, 1}, //left top
+    {0, 3}, //left buttom
+    {2, 1}, //right top
+    {0, 3}, //Left buttom
+    {2, 3}, //right bottom
+    {2, 1}, //right top
+  };
+  //Convert color to pre-multipled alpha
+
+  uvec2 indexx =  rect_vertices[gl_VertexID];
+
+  color = vec4(rect_color.rgb * rect_color.a, rect_color.a);
+
+  vec2 pos   = vec2(    rect_ltrb[indexx.x],     rect_ltrb[indexx.y]);
+  tex_coords = vec2(rect_tex_ltrb[indexx.x], rect_tex_ltrb[indexx.y]);
+  subpixel_shift = rect_subpixel_shift;
+  //index_out      = index;
+
+
+  vec2 axes_flip  = vec2(1, -1); // to flip y axis from bottom up
+  vec2 pos_in_ndc = (pos / half_viewport_size - 1.0) * axes_flip;
+  gl_Position = vec4(pos_in_ndc, 0, 1);
+}