add an overdraw buffer to allow for layered rendering

src/engine/render/misc.c

@@ -2,16 +2,36 @@
 #include <dangerzone/render/misc.h>
 #include <dangerzone/render/rect.h>
 
+#include "internal/engine_internal.h"
 #include "internal/util/error.h"
+
 #include <stdint.h>
 
+// helper function to return the correct pointer to a framebuffer for drawing selection
+uint32_t*
+get_framebuffer(
+    framebuffer_e framebuffer
+) {
+    switch (framebuffer) {
+    case BASE:
+        return game_state->framebuffer_base;
+    case OVERDRAW:
+        return game_state->framebuffer_overdraw;
+    default:
+        return game_state->framebuffer_base;
+    }
+}
+
 // alter a pixel at an imaginary x & y coordinates
 void 
 put_pixel(
+    framebuffer_e framebuffer,
 	unsigned int x, 
 	unsigned int y, 
 	uint32_t color
 ) {
+    uint32_t *current_framebuffer = get_framebuffer(framebuffer);
+
 	uint16_t w = game_state->width;
 	uint16_t h = game_state->height;
 
@@ -21,7 +41,7 @@ put_pixel(
 			"at x = %d, y = %d", x, y
 		);
 	} else {
-		game_state->framebuffer[game_state->width * y + x]
+		current_framebuffer[game_state->width * y + x]
 			= color;
 
 	    mark_dirty_rect(x, y, 1, 1);
@@ -31,12 +51,15 @@ put_pixel(
 // fill the entire framebuffer with a given color
 void
 clear_framebuffer(
+    framebuffer_e framebuffer,
 	uint32_t color
 ) {
+    uint32_t *current_framebuffer = get_framebuffer(framebuffer);
+    
     for (size_t i = 0;
          i < (size_t)game_state->width * game_state->height;
          ++i) {
-        game_state->framebuffer[i] = color;
+        current_framebuffer[i] = color;
     }
 
     mark_dirty_rect(
@@ -45,4 +68,4 @@ clear_framebuffer(
         game_state->width,
         game_state->height
     );
-}
+}