Fix bug on tile rendering

1 files changed, 11 insertions, 10 deletions

diff --git a/src/renderer.c b/src/renderer.c
index 4318610..afc9904 100644
--- a/src/renderer.c
+++ b/src/renderer.c
@@ -294,7 +294,8 @@ draw_tile(size_t x, size_t y, Tile *tile, bool merge) {
     // higher than 1.
     size_t shift_left = start_col * 4;
     size_t shift_right = (8 - start_col) * 4;
-    u32 row_mask = merge ? 0 : 0xFFFFFFFF << shift_left;
+    u32 row_mask_left = merge ? 0 : 0xFFFFFFFF << shift_left;
+    u32 row_mask_right = merge ? 0 : 0xFFFFFFFF >> shift_right;
 
     // Draw the tiles. There are 4 possible cases:
     //     1. The tile is exactly at the tile boundary.
@@ -304,40 +305,40 @@ draw_tile(size_t x, size_t y, Tile *tile, bool merge) {
     if (start_col == 0 && start_row == 0) {
         for (size_t i = 0; i < (8 - start_row); i++, backbuffer++) {
             BOUNDCHECK_SCREEN(x, y + i);
-            backbuffer[0] = (backbuffer[0] & ~row_mask) | row[i];
+            backbuffer[0] = (backbuffer[0] & ~row_mask_left) | row[i];
         }
         dirty_tiles[tile_y] |= 1 << tile_x;
     } else if (start_row == 0) {
         for (size_t i = 0; i < 8; i++, backbuffer++) {
             BOUNDCHECK_SCREEN(x, y + i);
-            backbuffer[0] = (backbuffer[0] & ~row_mask) | (row[i] << shift_left);
-            backbuffer[8] = (backbuffer[8] & row_mask) | (row[i] >> shift_right);
+            backbuffer[0] = (backbuffer[0] & ~row_mask_left) | (row[i] << shift_left);
+            backbuffer[8] = (backbuffer[8] & ~row_mask_right) | (row[i] >> shift_right);
         }
         dirty_tiles[tile_y] |= 1 << tile_x;
         dirty_tiles[tile_y] |= 1 << (tile_x + 1);
     } else if (start_col == 0) {
         for (size_t i = 0; i < (8 - start_row); i++, backbuffer++) {
             BOUNDCHECK_SCREEN(x, y + i);
-            backbuffer[0] = (backbuffer[0] & ~row_mask) | row[i];
+            backbuffer[0] = (backbuffer[0] & ~row_mask_left) | row[i];
         }
         backbuffer += 8 * 31;
         for (size_t i = (8 - start_row); i < 8; i++, backbuffer++) {
             BOUNDCHECK_SCREEN(x, y + i);
-            backbuffer[0] = (backbuffer[0] & ~row_mask) | row[i];
+            backbuffer[0] = (backbuffer[0] & ~row_mask_left) | row[i];
         }
         dirty_tiles[tile_y] |= 1 << tile_x;
         dirty_tiles[tile_y + 1] |= 1 << tile_x;
     } else {
         for (size_t i = 0; i < (8 - start_row); i++, backbuffer++) {
             BOUNDCHECK_SCREEN(x, y + i);
-            backbuffer[0] = (backbuffer[0] & ~row_mask) | (row[i] << shift_left);
-            backbuffer[8] = (backbuffer[8] & row_mask) | (row[i] >> shift_right);
+            backbuffer[0] = (backbuffer[0] & ~row_mask_left) | (row[i] << shift_left);
+            backbuffer[8] = (backbuffer[8] & ~row_mask_right) | (row[i] >> shift_right);
         }
         backbuffer += 8 * 31;
         for (size_t i = (8 - start_row); i < 8; i++, backbuffer++) {
             BOUNDCHECK_SCREEN(x, y + i);
-            backbuffer[0] = (backbuffer[0] & ~row_mask) | (row[i] << shift_left);
-            backbuffer[8] = (backbuffer[8] & row_mask) | (row[i] >> shift_right);
+            backbuffer[0] = (backbuffer[0] & ~row_mask_left) | (row[i] << shift_left);
+            backbuffer[8] = (backbuffer[8] & ~row_mask_right) | (row[i] >> shift_right);
         }
         dirty_tiles[tile_y] |= 1 << tile_x;
         dirty_tiles[tile_y] |= 1 << (tile_x + 1);