Use a 8:7 PAR by default

README.md

@@ -62,9 +62,16 @@ entirely with `--no-save`.
 Add `--debug` (`-g`) to show logging information while running. Pass it twice
 (`-gg`) to show more detailed logs, including an emulator trace.
 
+crater tries to reproduce the Game Gear's native display resolution, which had
+a pixel aspect ratio (PAR) of [8:7][par]; this means the pixels were slightly
+wider than square, unlike modern LCD displays with a 1:1 PAR. Add `--square`
+(`-q`) to force square pixels.
+
 `./crater -h` gives (fairly basic) command-line usage, and `./crater -v` gives
 the current version.
 
+[par]: https://pineight.com/mw/index.php?title=Dot_clock_rates
+
 ### Input
 
 crater supports keyboard and joystick/controller input.

src/config.c

@@ -44,6 +44,8 @@ static void print_help(const char *arg1)
 "                      the Game Gear does not usually require BIOS)\n"
 "    -x, --scale <n>   scale the game screen by an integer factor\n"
 "                      (applies to windowed mode only; defaults to 4)\n"
+"    -q, --square      force a square pixel aspect ratio instead of the more\n"
+"                      faithful 8:7 PAR\n"
 "    -a, --assemble <in> [<out>]\n"
 "                      convert z80 assembly source code into a binary file that\n"
 "                      can be run by crater\n"
@@ -269,6 +271,9 @@ static int parse_opt_arg(Config *config, Arguments *args, const char *arg)
         }
         config->scale = scale;
     }
+    else if (arg_check(arg, "q", "square")) {
+        config->square_par = true;
+    }
     else if (arg_check(arg, "a", "assemble")) {
         if (args->paths_read >= 1) {
             config->src_path = config->rom_path;
@@ -367,7 +372,8 @@ static bool sanity_check(Config *config)
     } else if (config->assemble && config->disassemble) {
         ERROR("cannot assemble and disassemble at the same time")
         return false;
-    } else if (assembler && (config->fullscreen || config->scale)) {
+    } else if (assembler && (config->fullscreen || config->scale ||
+                             config->square_par)) {
         ERROR("cannot specify emulator options in assembler mode")
         return false;
     } else if (assembler && !config->src_path) {
@@ -424,6 +430,7 @@ int config_create(Config** config_ptr, int argc, char* argv[])
     config->fullscreen = false;
     config->no_saving = false;
     config->scale = 0;
+    config->square_par = false;
     config->rom_path = NULL;
     config->sav_path = NULL;
     config->bios_path = NULL;
@@ -469,6 +476,7 @@ void config_dump_args(const Config* config)
     DEBUG("- fullscreen:  %s", config->fullscreen  ? "true" : "false")
     DEBUG("- no_saving:   %s", config->no_saving   ? "true" : "false")
     DEBUG("- scale:       %d", config->scale)
+    DEBUG("- square_par:  %s", config->square_par  ? "true" : "false")
     DEBUG("- rom_path:    %s", config->rom_path  ? config->rom_path  : "(null)")
     DEBUG("- sav_path:    %s", config->sav_path  ? config->sav_path  : "(null)")
     DEBUG("- bios_path:   %s", config->bios_path ? config->bios_path : "(null)")

src/config.h

@@ -14,10 +14,9 @@
 
 /*
     We need some sort of maximum scale - with a native resolution of 160 x 144,
-    a scale factor of 1024 will let us go up to 163,840 x 147,456 pixels.
-    No one has a screen this large.
+    a scale factor of 128 will let us go up to 20,480 x 18,432 pixels.
 */
-#define SCALE_MAX 1024
+#define SCALE_MAX 128
 
 /* Structs */
 
@@ -28,6 +27,7 @@ typedef struct {
     bool fullscreen;
     bool no_saving;
     unsigned scale;
+    bool square_par;
     char *rom_path;
     char *sav_path;
     char *bios_path;

src/emulator.c

@@ -88,19 +88,22 @@ static void setup_input()
 /*
     Set up SDL for drawing the game.
 */
-static void setup_graphics(bool fullscreen, unsigned scale)
+static void setup_graphics(Config *config)
 {
     SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "nearest");
 
     uint32_t flags;
-    if (fullscreen)
+    if (config->fullscreen)
         flags = SDL_WINDOW_FULLSCREEN_DESKTOP;
     else
         flags = SDL_WINDOW_RESIZABLE;
 
-    SDL_CreateWindowAndRenderer(
-        scale * GG_SCREEN_WIDTH, scale * GG_SCREEN_HEIGHT,
-        flags, &emu.window, &emu.renderer);
+    int width  = config->scale * GG_SCREEN_WIDTH;
+    int height = config->scale * GG_SCREEN_HEIGHT;
+    if (!config->square_par)
+        height = height * GG_PIXEL_HEIGHT / GG_PIXEL_WIDTH;
+    SDL_CreateWindowAndRenderer(width, height, flags,
+        &emu.window, &emu.renderer);
 
     if (!emu.window)
         FATAL("SDL failed to create a window: %s", SDL_GetError());
@@ -116,7 +119,9 @@ static void setup_graphics(bool fullscreen, unsigned scale)
     emu.pixels = cr_malloc(
         sizeof(uint32_t) * GG_SCREEN_WIDTH * GG_SCREEN_HEIGHT);
 
-    SDL_RenderSetLogicalSize(emu.renderer, GG_SCREEN_WIDTH, GG_SCREEN_HEIGHT);
+    SDL_RenderSetLogicalSize(emu.renderer,
+        config->square_par ? GG_SCREEN_WIDTH  : GG_LOGICAL_WIDTH,
+        config->square_par ? GG_SCREEN_HEIGHT : GG_LOGICAL_HEIGHT);
     SDL_SetTextureBlendMode(emu.texture, SDL_BLENDMODE_BLEND);
     SDL_SetWindowTitle(emu.window, "crater");
     SDL_ShowCursor(SDL_DISABLE);
@@ -130,13 +135,13 @@ static void setup_graphics(bool fullscreen, unsigned scale)
 /*
     Set up SDL.
 */
-static void setup_sdl(bool fullscreen, unsigned scale)
+static void setup_sdl(Config *config)
 {
     if (SDL_Init(SDL_INIT_VIDEO|SDL_INIT_GAMECONTROLLER) < 0)
         FATAL("SDL failed to initialize: %s", SDL_GetError());
 
     setup_input();
-    setup_graphics(fullscreen, scale);
+    setup_graphics(config);
 }
 
 /*
@@ -370,7 +375,7 @@ void emulate(ROM *rom, Config *config)
 
     emu.gg = gamegear_create();
     signal(SIGINT, handle_sigint);
-    setup_sdl(config->fullscreen, config->scale);
+    setup_sdl(config);
 
     gamegear_attach_callback(emu.gg, frame_callback);
     gamegear_attach_display(emu.gg, emu.pixels);

src/gamegear.h

@@ -15,6 +15,10 @@
 
 #define GG_SCREEN_WIDTH  160
 #define GG_SCREEN_HEIGHT 144
+#define GG_PIXEL_WIDTH  8
+#define GG_PIXEL_HEIGHT 7
+#define GG_LOGICAL_WIDTH  (GG_SCREEN_WIDTH  * GG_PIXEL_WIDTH)
+#define GG_LOGICAL_HEIGHT (GG_SCREEN_HEIGHT * GG_PIXEL_HEIGHT)
 
 #define GG_FPS 60
 #define GG_EXC_BUFF_SIZE 128