From 41ee3fe4ae76d9bba450f58a09c4edde1493672d Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Sat, 6 Sep 2025 13:24:02 -0700
Subject: Draw only tiles visible in the screen in ortho maps. The same logic
 for iso maps is still missing.

---
 src/gfx2d.c | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

(limited to 'src/gfx2d.c')

diff --git a/src/gfx2d.c b/src/gfx2d.c
index 8d78c2b..e79dd3e 100644
--- a/src/gfx2d.c
+++ b/src/gfx2d.c
@@ -79,6 +79,10 @@ static inline ivec2 ivec2_add(ivec2 a, ivec2 b) {
   return (ivec2){.x = a.x + b.x, .y = a.y + b.y};
 }
 
+static inline ivec2 ivec2_mul(ivec2 a, ivec2 b) {
+  return (ivec2){.x = a.x * b.x, .y = a.y * b.y};
+}
+
 static inline ivec2 ivec2_scale(ivec2 a, int s) {
   return (ivec2){.x = a.x * s, .y = a.y * s};
 }
@@ -91,12 +95,14 @@ static inline vec2 vec2_add(vec2 a, vec2 b) {
 
 static inline vec2 ivec2_to_vec2(ivec2 a) { return (vec2){a.x, a.y}; }
 
-/// Map map coordinates to screen coordinates, both Cartesian.
-static ivec2 map2screen(
+/// Map ortho coordinates to screen coordinates.
+///
+/// Camera coordinates are in pixels. Map coordinates are in tiles.
+static ivec2 ortho2screen(
     ivec2 camera, int tile_width, int tile_height, int map_x, int map_y) {
   return ivec2_add(
       ivec2_neg(camera),
-      (ivec2){.x = map_x * tile_width, .y = map_y * tile_height});
+      ivec2_mul((ivec2){map_x, map_y}, (ivec2){tile_width, tile_height}));
 }
 
 // Not actually used because we pre-compute the two axis vectors instead.
@@ -603,7 +609,7 @@ static void draw_tile_ortho(Gfx2d* gfx, Tile tile, int x, int y) {
   const Ts_Tile* pTile  = ts_tileset_get_tile(gfx->tileset, tile);
   const Pixel*   pixels = ts_tileset_get_tile_pixels(gfx->tileset, tile);
 
-  const ivec2 screen_origin = map2screen(
+  const ivec2 screen_origin = ortho2screen(
       gfx->camera, gfx->map->base_tile_width, gfx->map->base_tile_height, x, y);
 
   draw_rect(
@@ -645,12 +651,16 @@ static void draw_map_ortho(Gfx2d* gfx) {
   assert(gfx);
   assert(gfx->map);
 
-  // TODO: Same TODOs as in draw_map_iso().
-
+  // TODO: Handle multiple layers.
   const Tm_Layer* layer = tm_map_get_layer(gfx->map, 0);
 
-  for (int wy = 0; wy < gfx->map->world_height; ++wy) {
-    for (int wx = 0; wx < gfx->map->world_width; ++wx) {
+  // 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) {
       const Tile tile = tm_layer_get_tile(gfx->map, layer, wx, wy);
       draw_tile_ortho(gfx, tile, wx, wy);
     }
@@ -711,7 +721,7 @@ static void draw_sprite_ortho(
   // Apply an offset similarly to how we offset tiles. The sprite is offset by
   // -base_tile_width/2 along the x-axis to align the sprite with the leftmost
   // edge of the tile it is on.
-  const ivec2 screen_origin = map2screen(
+  const ivec2 screen_origin = ortho2screen(
       gfx->camera, gfx->map->base_tile_width, gfx->map->base_tile_height,
       sprite->position.x, sprite->position.y);
 
-- 
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