1 files changed, 36 insertions, 19 deletions

diff --git a/src/gfx2d.c b/src/gfx2d.c
index 14e0539..eaed2b8 100644
--- a/src/gfx2d.c
+++ b/src/gfx2d.c
@@ -26,6 +26,9 @@
 /// Take the minimum of two values.
 #define min(a, b) ((a) < (b) ? (a) : (b))
 
+/// The 0-tile denotes "no tile". The renderer skips drawing 0-tiles.
+static const Tile NoTile = 0;
+
 typedef struct ivec2 {
   int x, y;
 } ivec2;
@@ -606,6 +609,10 @@ static void draw_tile_ortho(Gfx2d* gfx, Tile tile, int x, int y) {
   assert(x < gfx->map->world_width);
   assert(y < gfx->map->world_height);
 
+  if (tile == NoTile) {
+    return;
+  }
+
   const Ts_Tile* pTile  = ts_tileset_get_tile(gfx->tileset, tile);
   const Pixel*   pixels = ts_tileset_get_tile_pixels(gfx->tileset, tile);
 
@@ -626,6 +633,10 @@ static void draw_tile_iso(Gfx2d* gfx, Tile tile, int iso_x, int iso_y) {
   assert(iso_x < gfx->map->world_width);
   assert(iso_y < gfx->map->world_height);
 
+  if (tile == NoTile) {
+    return;
+  }
+
   const Ts_Tile* pTile  = ts_tileset_get_tile(gfx->tileset, tile);
   const Pixel*   pixels = ts_tileset_get_tile_pixels(gfx->tileset, tile);
 
@@ -651,16 +662,21 @@ static void draw_map_ortho(Gfx2d* gfx) {
   assert(gfx);
   assert(gfx->map);
 
+  // Render the tiles that the camera view rectangle intersects.
+  // +1 when computing x1,y1 because the screen dimensions need not be a
+  // multiple of the base tile dimensions.
+  const int x_tiles = gfx->screen.width / gfx->map->base_tile_width;
+  const int y_tiles = gfx->screen.height / gfx->map->base_tile_height;
+  const int x0      = gfx->camera.x / gfx->map->base_tile_width;
+  const int y0      = gfx->camera.y / gfx->map->base_tile_height;
+  const int x1      = min(gfx->map->world_width, x0 + x_tiles + 1);
+  const int y1      = min(gfx->map->world_height, y0 + y_tiles + 1);
+
   for (uint16_t l = 0; l < gfx->map->num_layers; ++l) {
     const Tm_Layer* layer = tm_map_get_layer(gfx->map, l);
 
-    // TODO: This currently renders with tile granularity. Do so instead in
-    //  terms of pixels for more accurate camera panning. The camera coordinates
-    //  are already given in pixels.
-    for (int wy = gfx->camera.y / gfx->map->base_tile_height;
-         wy < gfx->map->world_height; ++wy) {
-      for (int wx = gfx->camera.x / gfx->map->base_tile_width;
-           wx < gfx->map->world_width; ++wx) {
+    for (int wy = y0; wy < y1; ++wy) {
+      for (int wx = x0; wx < x1; ++wx) {
         const Tile tile = tm_layer_get_tile(gfx->map, layer, wx, wy);
         draw_tile_ortho(gfx, tile, wx, wy);
       }
@@ -672,18 +688,19 @@ static void draw_map_iso(Gfx2d* gfx) {
   assert(gfx);
   assert(gfx->map);
 
-  // TODO: Support for multiple layers.
-  const Tm_Layer* layer = tm_map_get_layer(gfx->map, 0);
-
-  // TODO: Culling.
-  //  Ex: map the screen corners to tile space to cull.
-  //  Ex: walk in screen space and fetch the tile.
-  //  The tile-centric approach might be more cache-friendly since the
-  //  screen-centric approach would juggle multiple tiles throughout the scan.
-  for (int wy = 0; wy < gfx->map->world_height; ++wy) {
-    for (int wx = 0; wx < gfx->map->world_width; ++wx) {
-      const Tile tile = tm_layer_get_tile(gfx->map, layer, wx, wy);
-      draw_tile_iso(gfx, tile, wx, wy);
+  for (uint16_t l = 0; l < gfx->map->num_layers; ++l) {
+    const Tm_Layer* layer = tm_map_get_layer(gfx->map, l);
+
+    // TODO: Culling.
+    //  Ex: map the screen corners to tile space to cull.
+    //  Ex: walk in screen space and fetch the tile.
+    //  The tile-centric approach might be more cache-friendly since the
+    //  screen-centric approach would juggle multiple tiles throughout the scan.
+    for (int wy = 0; wy < gfx->map->world_height; ++wy) {
+      for (int wx = 0; wx < gfx->map->world_width; ++wx) {
+        const Tile tile = tm_layer_get_tile(gfx->map, layer, wx, wy);
+        draw_tile_iso(gfx, tile, wx, wy);
+      }
     }
   }
 }