From 6cefdd40dd62f098874bd706720db731341bc957 Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Mon, 14 Jul 2025 08:52:15 -0700
Subject: Move file format defs to separate header

---
 include/isogfx/asset.h | 132 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 include/isogfx/asset.h

(limited to 'include')

diff --git a/include/isogfx/asset.h b/include/isogfx/asset.h
new file mode 100644
index 0000000..298c469
--- /dev/null
+++ b/include/isogfx/asset.h
@@ -0,0 +1,132 @@
+/*
+ * File format definitions for isogfx assets.
+ *
+ * All formats are defined so that they can be simply read into memory and used
+ * by the engine. Likewise, a tool that generates these formats can generate
+ * the structures in memory and then write them as is to a file.
+ */
+#pragma once
+
+#include <assert.h>
+#include <stdint.h>
+
+// Maximum length of path strings in .TS and .TM files.
+#define ISOGFX_MAX_PATH_LENGTH 128
+
+// -----------------------------------------------------------------------------
+// Tile set (TS) file format.
+// -----------------------------------------------------------------------------
+
+typedef struct Ts_Tile {
+  uint16_t width;     // Tile width in pixels.
+  uint16_t height;    // Tile height in pixels.
+  Pixel    pixels[1]; // Count: width * height.
+} Ts_Tile;
+
+typedef struct Ts_TileSet {
+  uint16_t num_tiles;
+  uint16_t max_tile_width;  // Maximum tile width in pixels.
+  uint16_t max_tile_height; // Maximum tile height in pixels.
+  Ts_Tile  tiles[1];        // Count: num_tiles.
+} Ts_TileSet;
+
+// -----------------------------------------------------------------------------
+// Tile map (TM) file format.
+// -----------------------------------------------------------------------------
+
+typedef struct Tm_Layer {
+  union {
+    char tileset_path[ISOGFX_MAX_PATH_LENGTH]; // Relative to the Tm_Map file.
+  };
+  Tile tiles[1]; // Count: world_width * world_height.
+} Tm_Layer;
+
+typedef struct Tm_Map {
+  uint16_t world_width;  // World width in number of tiles.
+  uint16_t world_height; // World height in number of tiles.
+  uint16_t base_tile_width;
+  uint16_t base_tile_height;
+  uint16_t num_layers;
+  Tm_Layer layers[1]; // Count: num_layers.
+} Tm_Map;
+
+// -----------------------------------------------------------------------------
+// Sprite sheet file format.
+// -----------------------------------------------------------------------------
+
+/// A row of sprites in a sprite sheet.
+///
+/// Each row in a sprite sheet can have a different number of columns.
+///
+/// The pixels of the row follow a "sprite-major" order. It contains the
+/// 'sprite_width * sprite_height' pixels for the first column/sprite, then the
+/// second column/sprite, etc.
+///
+/// Pixels are 8-bit indices into the sprite sheet's colour palette.
+typedef struct Ss_Row {
+  uint16_t num_cols;  /// Number of columns in this row.
+  uint8_t  pixels[1]; /// Count: num_cols * sprite_width * sprite_height.
+} Ss_Row;
+
+typedef struct Ss_Palette {
+  uint16_t num_colours;
+  Pixel    colours[1]; /// Count: num_colors.
+} Ss_Palette;
+
+/// Sprite sheet top-level data definition.
+///
+/// Sprite width and height are assumed constant throughout the sprite sheet.
+typedef struct Ss_SpriteSheet {
+  uint16_t   sprite_width;  /// Sprite width in pixels.
+  uint16_t   sprite_height; /// Sprite height in pixels.
+  uint16_t   num_rows;
+  Ss_Palette palette; /// Variable size.
+  Ss_Row     rows[1]; /// Count: num_rows. Variable offset.
+} Ss_SpriteSheet;
+
+// -----------------------------------------------------------------------------
+// Data accessors.
+// -----------------------------------------------------------------------------
+
+/// Return the next tile in the tile set.
+static inline const Ts_Tile* ts_tileset_get_next_tile(
+    const Ts_TileSet* tileset, const Ts_Tile* tile) {
+  assert(tileset);
+  assert(tile);
+  return (const Ts_Tile*)((const uint8_t*)tile + sizeof(Ts_Tile) +
+                          ((tile->width * tile->height - 1) * sizeof(Pixel)));
+}
+
+/// Return the next layer in the tile map.
+static inline const Tm_Layer* tm_map_get_next_layer(
+    const Tm_Map* map, const Tm_Layer* layer) {
+  assert(map);
+  assert(layer);
+  return (const Tm_Layer*)((const uint8_t*)layer + sizeof(Tm_Layer) +
+                           ((map->world_width * map->world_height - 1) *
+                            sizeof(Tile)));
+}
+
+/// Return the ith row in the sprite sheet.
+static inline const Ss_Row* get_sprite_sheet_row(
+    const Ss_SpriteSheet* sheet, int row) {
+  assert(sheet);
+  assert(row >= 0);
+  assert(row < sheet->num_rows);
+  // Skip over the palette.
+  const Ss_Row* rows =
+      (const Ss_Row*)(&sheet->palette.colours[0] + sheet->palette.num_colours);
+  return &rows[row];
+}
+
+/// Return the ith sprite in the row.
+static inline const uint8_t* get_sprite_sheet_sprite(
+    const Ss_SpriteSheet* sheet, const Ss_Row* row, int col) {
+  assert(sheet);
+  assert(row);
+  assert(col >= 0);
+  assert(col < row->num_cols);
+  const int sprite_offset = col * sheet->sprite_width * sheet->sprite_height;
+  const uint8_t* sprite   = &row->pixels[sprite_offset];
+  return sprite;
+}
-- 
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