src/main.c

@@ -165,11 +165,12 @@ static bool initialize(void) {
         return false;
     }
 
-    SDL_SetHint(SDL_HINT_RENDER_DRIVER, "opengl");
-
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 1);
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
+    SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 0);
+    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 8);
+    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
 
     /* init got far enough to create a window */
     ctx.window = SDL_CreateWindow("emerald",
@@ -192,6 +193,7 @@ static bool initialize(void) {
     }
 
     SDL_GL_MakeCurrent(ctx.window, ctx.gl_context);
+    SDL_GL_SetSwapInterval(1);
 
     int glad_status = gladLoadGL();
     if (glad_status == 0) {

src/rendering.c

@@ -86,16 +86,19 @@ static void render_2d(void) {
                     collect_sprite_batch(current, render_queue_len - i);
 
                 if (batch.blend) {
-                    glDisable(GL_DEPTH_TEST);
                     glEnable(GL_BLEND);
                     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+                    glEnable(GL_DEPTH_TEST);
+                    glDepthFunc(GL_ALWAYS);
+                    glDisable(GL_ALPHA_TEST);
 
                     render_sprites(current, batch.size, false);
                 } else {
-                    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-                    glEnable(GL_DEPTH_TEST);
-                    glDepthRange((double)batch_count / 65536, 1.0);
                     glDisable(GL_BLEND);
+                    glEnable(GL_DEPTH_TEST);
+                    glDepthFunc(GL_LESS);
+                    glDepthRange((double)batch_count / UINT16_MAX, 1.0);
+                    glDisable(GL_ALPHA_TEST);
 
                     render_sprites(current, batch.size, true);
                 }
@@ -167,6 +170,16 @@ void render(void) {
             GL_DEPTH_BUFFER_BIT |
             GL_STENCIL_BUFFER_BIT);
 
+    {
+        glMatrixMode(GL_PROJECTION);
+        glLoadIdentity();
+
+        glMatrixMode(GL_MODELVIEW);
+        glLoadIdentity();
+
+        render_space();
+    }
+
     {
         glMatrixMode(GL_PROJECTION);
         glLoadIdentity();
@@ -178,15 +191,5 @@ void render(void) {
         render_2d();
     }
 
-    {
-        glMatrixMode(GL_PROJECTION);
-        glLoadIdentity();
-
-        glMatrixMode(GL_MODELVIEW);
-        glLoadIdentity();
-
-        render_space();
-    }
-
     SDL_GL_SwapWindow(ctx.window);
 }

src/rendering/sprites.h

@@ -18,7 +18,8 @@
  * because they will be called multiple times in the main loop
  * before anything is really rendered
  */
-/* sprite */
+/* TODO: it might make sense to infer alpha channel presence / meaningfulness for textures in atlas */
+/* 		 so that they are rendered with no blend / batched in a way to reduce overdraw automatically */
 void push_sprite(char *path, t_frect rect) {
     struct sprite_primitive sprite = {
         .rect = rect,