Add double buffering with dirty squares flip option

1 files changed, 40 insertions, 2 deletions

diff --git a/src/renderer_m0.c b/src/renderer_m0.c
index 745c0f9..6c509f9 100644
--- a/src/renderer_m0.c
+++ b/src/renderer_m0.c
@@ -14,7 +14,7 @@
 
 #define SUBPIXEL_LINES 1
 #define DEC_BIG_LUT 1
-#define FLIP_TYPE 2
+#define FLIP_TYPE 3
 
 // Front/back buffers for double buffering.
 #define BUF_0 ((u32*)(MEM_VRAM))
@@ -662,7 +662,6 @@ flip_buffer(void) {
         if (dirty_tiles[j] == 0) {
             continue;
         }
-        u32 offset = j * 32 * 8;
         size_t k = 1;
         for (size_t i = 0; i < 30; ++i, k <<= 1) {
             if (dirty_tiles[j] & k) {
@@ -673,6 +672,45 @@ flip_buffer(void) {
         }
         dirty_tiles[j] = 0;
     }
+
+// Mode 3: Double buffering with dirty tiles, copying the dirty tiles if needed
+// after flipping buffers.
+#elif FLIP_TYPE == 3
+    bool should_flip = false;
+    for (size_t j = 0; j < 20; ++j) {
+        if (dirty_tiles[j] == 0) {
+            continue;
+        }
+        should_flip = true;
+        break;
+    }
+    if (!should_flip) {
+        return;
+    }
+    u32 *frontbuf = backbuf;
+    if (backbuf == BUF_0) {
+        backbuf = BUF_1;
+        BG_H_SCROLL_0 = 0;
+        BG_H_SCROLL_1 = -240;
+    } else {
+        backbuf = BUF_0;
+        BG_H_SCROLL_0 = -240;
+        BG_H_SCROLL_1 = 0;
+    }
+    for (size_t j = 0; j < 20; ++j) {
+        if (dirty_tiles[j] == 0) {
+            continue;
+        }
+        size_t k = 1;
+        for (size_t i = 0; i < 30; ++i, k <<= 1) {
+            if (dirty_tiles[j] & k) {
+                Tile *mem_front = frontbuf;
+                Tile *mem_back = backbuf;
+                mem_back[i + j * 32] = mem_front[i + j * 32];
+            }
+        }
+        dirty_tiles[j] = 0;
+    }
 #endif
 }