Optimize text rendering for long strings

shaders/text.frag

@@ -1,12 +1,18 @@
 #version 330 core
-in vec2 texuv;
+
 out vec4 color;
 
-uniform sampler2D text;
+in VS_OUT {
+    vec2 texuv;
+    flat int index;
+} fs_in;
+
+uniform sampler2DArray text;
+uniform int letter_map[400];
 uniform vec3 text_color;
 
 void main()
-{    
-    vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, texuv).r);
+{
+    vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, vec3(fs_in.texuv.xy, letter_map[fs_in.index])).r);
     color = vec4(text_color, 1.0) * sampled;
 }

shaders/text.vert

@@ -1,13 +1,17 @@
 #version 330 core
 layout (location = 0) in vec2 vertex; // <vec2 pos>
-out vec2 texuv;
 
-uniform mat4 transform;
+out VS_OUT {
+    vec2 texuv;
+    flat int index;
+} vs_out;
+
+uniform mat4 transforms[400];
 uniform mat4 projection;
 
 void main()
 {
-    gl_Position = projection * transform * vec4(vertex.xy, 0.0, 1.0);
-    texuv = vertex.xy;
-    texuv.y=1.0f-texuv.y;
+    gl_Position = projection * transforms[gl_InstanceID] * vec4(vertex.xy, 0.0, 1.0);
+    vs_out.index = gl_InstanceID;
+    vs_out.texuv = vec2(vertex.x, 1.0f - vertex.y);
 }