Prepare OpenGL text rendering state only once

Date:      Sun Jan 7 17:55:38 2024 +0100

main.cpp

@@ -118,6 +118,7 @@ uint32_t hex_program;
 uint32_t texture_array;
 glm::mat4 transforms[ARRAY_LIMIT];
 int32_t letter_map[ARRAY_LIMIT];
+int32_t text_frame_idx;
 
 
 // error processing
@@ -240,27 +241,47 @@ uint32_t make_gl_program(const char *pathname_vertex, const char *pathname_fragm
     return program;
 }
 
-void render_text(const char *text, float x, float y, float scale, glm::vec3 color)
+void render_queued_text(glm::vec3 color)
+{
+    //glActiveTexture(GL_TEXTURE0);
+    //glBindTexture(GL_TEXTURE_2D_ARRAY, texture_array);
+    //glBindVertexArray(textvao);
+    //glBindBuffer(GL_ARRAY_BUFFER, textvbo);
+
+    glUniform3f(glGetUniformLocation(text_program, "text_color"), color.x, color.y, color.z);
+    glUniformMatrix4fv(glGetUniformLocation(text_program, "transforms"), text_frame_idx, GL_FALSE, &transforms[0][0][0]);
+    glUniform1iv(glGetUniformLocation(text_program, "letter_map"), text_frame_idx, &letter_map[0]);
+    glDrawArraysInstanced(GL_TRIANGLE_FAN, 0, 4, text_frame_idx);
+
+    //glBindBuffer(GL_ARRAY_BUFFER, 0);
+    //glBindVertexArray(0);
+    //glBindTexture(GL_TEXTURE_2D, 0);
+
+    text_frame_idx = 0;
+}
+
+void render_text(const char *text, float x, float y, float scale, glm::vec3 color, bool render_immediately)
 {
     // TODO: Group draw calls together instead of doing 1 draw call/character. Use an atlas with GL_TEXTURE_ARRAY
     // Take tips from https://www.youtube.com/watch?v=S0PyZKX4lyI
     scale *= 48.0f/256;
 
     // activate corresponding render state
-    glUseProgram(text_program);
-    glUniform3f(glGetUniformLocation(text_program, "text_color"), color.x, color.y, color.z);
-    glActiveTexture(GL_TEXTURE0);
-    glBindTexture(GL_TEXTURE_2D_ARRAY, texture_array);
-    glBindVertexArray(textvao);
-    glBindBuffer(GL_ARRAY_BUFFER, textvbo);
 
-    int idx = 0;
+    //glUseProgram(text_program);
+    //glActiveTexture(GL_TEXTURE0);
+    //glBindTexture(GL_TEXTURE_2D_ARRAY, texture_array);
+    //glBindVertexArray(textvao);
+    //glBindBuffer(GL_ARRAY_BUFFER, textvbo);
+
     // iterate through 128 ASCI characters
     for (const char *p = text; *p != '\0'; ++p)
     {
-        // Avoid drawing more than 400 chars at a time
+        // Avoid drawing more than ARRAY_LIMIT chars at a time
-        if (idx == ARRAY_LIMIT - 1)
+        if (text_frame_idx == ARRAY_LIMIT)
-            break;
+        {
+            render_queued_text(color);
+        }
 
         char c = *p;
         charglyph_t charglyph = glyphmap[(size_t)c];
@@ -274,20 +295,21 @@ void render_text(const char *text, float x, float y, float scale, glm::vec3 colo
         float xpos = x + charglyph.bearing.x * scale;
         float ypos = y - (256 - charglyph.bearing.y) * scale;
 
-        transforms[idx] = glm::translate(glm::mat4(1.0f), glm::vec3(xpos, ypos, 0)) * glm::scale(glm::mat4(1.0f), glm::vec3(256 * scale, 256 * scale, 0));
+        transforms[text_frame_idx] = glm::translate(glm::mat4(1.0f), glm::vec3(xpos, ypos, 0)) * glm::scale(glm::mat4(1.0f), glm::vec3(256 * scale, 256 * scale, 0));
-        letter_map[idx] = charglyph.tex;
+        letter_map[text_frame_idx] = charglyph.tex;
 
         // now advance cursors for next glyph (note that advance is number of 1/64 pixels)
         x += (charglyph.advance >> 6) * scale; // bitshift by 6 to get value in pixels (2^6 = 64)
-        ++idx;
+        ++text_frame_idx;
+    }
+    if (render_immediately)
+    {
+        render_queued_text(color);
     }
-    glUniformMatrix4fv(glGetUniformLocation(text_program, "transforms"), idx, GL_FALSE, &transforms[0][0][0]);
-    glUniform1iv(glGetUniformLocation(text_program, "letter_map"), idx, &letter_map[0]);
-    glDrawArraysInstanced(GL_TRIANGLE_FAN, 0, 4, idx);
 
-    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    // glBindBuffer(GL_ARRAY_BUFFER, 0);
-    glBindVertexArray(0);
+    // glBindVertexArray(0);
-    glBindTexture(GL_TEXTURE_2D, 0);
+    // glBindTexture(GL_TEXTURE_2D, 0);
 }
 
 bool inside_hex(hex_t *hex, glm::vec2 point)
@@ -654,8 +676,15 @@ int main([[maybe_unused]]int argc, [[maybe_unused]]char **argv)
         static char debug_text_buf[256];
         {
             TIME_BLOCK(text_render);
+            // Prepare GL state for text rendering
+            glUseProgram(text_program);
+            glActiveTexture(GL_TEXTURE0);
+            glBindTexture(GL_TEXTURE_2D_ARRAY, texture_array);
+            glBindVertexArray(textvao);
+            glBindBuffer(GL_ARRAY_BUFFER, textvbo);
+
             stbsp_snprintf(debug_text_buf, 256, "Cursor position %.0f %.0f screen %.2f %.2f world", cursor_x, cursor_y, cursor_world.x, cursor_world.y);
-            render_text(debug_text_buf, 25, 25, .5f, glm::vec3(1.0f, 1.0f, 1.0f));
+            render_text(debug_text_buf, 25, 25, .5f, glm::vec3(1.0f, 1.0f, 1.0f), true);
 
             for (int i = 0; show_hex_numbers && i < grid.rows * grid.columns; ++i)
             {
@@ -671,14 +700,19 @@ int main([[maybe_unused]]int argc, [[maybe_unused]]char **argv)
                     continue;
                 char number_string[11];
                 stbsp_snprintf(number_string, 11, "%d", i);
-                render_text(number_string, v.x, v.y, .2f + (0.3f / the_camera.size.x), glm::vec3(0.0f, 0.0f, 0.0f));
+                render_text(number_string, v.x, v.y, .2f + (0.3f / the_camera.size.x), glm::vec3(0.0f, 0.0f, 0.0f), false);
             }
+            render_queued_text(glm::vec3(0.0f, 0.0f, 0.0f));
             if (hovered_hex != -1)
             {
                 char buf[30];
                 stbsp_snprintf(buf, 30, "Cursor INSIDE hex %d", hovered_hex);
-                render_text(buf, 25.0f, window_height - 25.0f, .5f, glm::vec3(1.0f, 1.0f, 1.0f));
+                render_text(buf, 25.0f, window_height - 25.0f, .5f, glm::vec3(1.0f, 1.0f, 1.0f), true);
             }
+            // Restore GL state
+            glBindBuffer(GL_ARRAY_BUFFER, 0);
+            glBindVertexArray(0);
+            glBindTexture(GL_TEXTURE_2D, 0);
         }
 
         glDisable(GL_BLEND);