Add RGB565 support

2 files changed, 260 insertions, 8 deletions

diff --git a/frontend/libretro.c b/frontend/libretro.c
index 9bbea5b..ad209b3 100644
--- a/frontend/libretro.c
+++ b/frontend/libretro.c
@@ -29,6 +29,7 @@ static void *vout_buf;
 static int vout_width, vout_height;
 static int samples_sent, samples_to_send;
 static int plugins_opened;
+static int native_rgb565;
 
 /* PCSX ReARMed core calls and stuff */
 int in_type1, in_type2;
@@ -62,7 +63,8 @@ static void convert(void *buf, size_t bytes)
 static void *vout_flip(void)
 {
 	pl_rearmed_cbs.flip_cnt++;
-	convert(vout_buf,  vout_width * vout_height * 2);
+	if (!native_rgb565)
+		convert(vout_buf,  vout_width * vout_height * 2);
 	video_cb(vout_buf, vout_width, vout_height, vout_width * 2);
 
 	return vout_buf;
@@ -197,6 +199,12 @@ void retro_cheat_set(unsigned index, bool enabled, const char *code)
 
 bool retro_load_game(const struct retro_game_info *info)
 {
+	enum retro_pixel_format fmt = RETRO_PIXEL_FORMAT_RGB565;
+	if (!environ_cb(RETRO_ENVIRONMENT_SET_PIXEL_FORMAT, &fmt)) {
+		native_rgb565 = 1;
+		fprintf(stderr, "RGB565 supported, using it\n");
+	}
+
 	if (plugins_opened) {
 		ClosePlugins();
 		plugins_opened = 0;
diff --git a/frontend/libretro.h b/frontend/libretro.h
index 8aa579e..3eef758 100644
--- a/frontend/libretro.h
+++ b/frontend/libretro.h
@@ -3,11 +3,13 @@
 
 #include <stdint.h>
 #include <stddef.h>
+#include <limits.h>
 
+// Hack applied for MSVC when compiling in C89 mode as it isn't C99 compliant.
 #ifdef __cplusplus
 extern "C" {
 #else
-#if defined(_MSC_VER) && !defined(__cplusplus)
+#if defined(_MSC_VER) && !defined(SN_TARGET_PS3) && !defined(__cplusplus)
 #define bool unsigned char
 #define true 1
 #define false 0
@@ -16,21 +18,51 @@ extern "C" {
 #endif
 #endif
 
+// Used for checking API/ABI mismatches that can break libretro implementations.
+// It is not incremented for compatible changes.
 #define RETRO_API_VERSION         1
 
+// Libretro's fundamental device abstractions.
 #define RETRO_DEVICE_MASK         0xff
 #define RETRO_DEVICE_NONE         0
+
+// The JOYPAD is called RetroPad. It is essentially a Super Nintendo controller,
+// but with additional L2/R2/L3/R3 buttons, similar to a PS1 DualShock.
 #define RETRO_DEVICE_JOYPAD       1
+
+// The mouse is a simple mouse, similar to Super Nintendo's mouse.
+// X and Y coordinates are reported relatively to last poll (poll callback).
+// It is up to the libretro implementation to keep track of where the mouse pointer is supposed to be on the screen.
+// The frontend must make sure not to interfere with its own hardware mouse pointer.
 #define RETRO_DEVICE_MOUSE        2
+
+// KEYBOARD device lets one poll for raw key pressed.
+// It is poll based, so input callback will return with the current pressed state.
 #define RETRO_DEVICE_KEYBOARD     3
+
+// Lightgun X/Y coordinates are reported relatively to last poll, similar to mouse.
 #define RETRO_DEVICE_LIGHTGUN     4
+
+// The ANALOG device is an extension to JOYPAD (RetroPad).
+// Similar to DualShock it adds two analog sticks.
+// This is treated as a separate device type as it returns values in the full analog range
+// of [-0x8000, 0x7fff]. Positive X axis is right. Positive Y axis is down.
+// Only use ANALOG type when polling for analog values of the axes.
 #define RETRO_DEVICE_ANALOG       5
 
+// These device types are specializations of the base types above.
+// They should only be used in retro_set_controller_type() to inform libretro implementations
+// about use of a very specific device type.
+//
+// In input state callback, however, only the base type should be used in the 'device' field.
 #define RETRO_DEVICE_JOYPAD_MULTITAP        ((1 << 8) | RETRO_DEVICE_JOYPAD)
 #define RETRO_DEVICE_LIGHTGUN_SUPER_SCOPE   ((1 << 8) | RETRO_DEVICE_LIGHTGUN)
 #define RETRO_DEVICE_LIGHTGUN_JUSTIFIER     ((2 << 8) | RETRO_DEVICE_LIGHTGUN)
 #define RETRO_DEVICE_LIGHTGUN_JUSTIFIERS    ((3 << 8) | RETRO_DEVICE_LIGHTGUN)
 
+// Buttons for the RetroPad (JOYPAD).
+// The placement of these is equivalent to placements on the Super Nintendo controller.
+// L2/R2/L3/R3 buttons correspond to the PS1 DualShock.
 #define RETRO_DEVICE_ID_JOYPAD_B        0
 #define RETRO_DEVICE_ID_JOYPAD_Y        1
 #define RETRO_DEVICE_ID_JOYPAD_SELECT   2
@@ -48,16 +80,19 @@ extern "C" {
 #define RETRO_DEVICE_ID_JOYPAD_L3      14
 #define RETRO_DEVICE_ID_JOYPAD_R3      15
 
+// Index / Id values for ANALOG device.
 #define RETRO_DEVICE_INDEX_ANALOG_LEFT   0
 #define RETRO_DEVICE_INDEX_ANALOG_RIGHT  1
 #define RETRO_DEVICE_ID_ANALOG_X         0
 #define RETRO_DEVICE_ID_ANALOG_Y         1
 
+// Id values for MOUSE.
 #define RETRO_DEVICE_ID_MOUSE_X      0
 #define RETRO_DEVICE_ID_MOUSE_Y      1
 #define RETRO_DEVICE_ID_MOUSE_LEFT   2
 #define RETRO_DEVICE_ID_MOUSE_RIGHT  3
 
+// Id values for LIGHTGUN types.
 #define RETRO_DEVICE_ID_LIGHTGUN_X        0
 #define RETRO_DEVICE_ID_LIGHTGUN_Y        1
 #define RETRO_DEVICE_ID_LIGHTGUN_TRIGGER  2
@@ -66,15 +101,30 @@ extern "C" {
 #define RETRO_DEVICE_ID_LIGHTGUN_PAUSE    5
 #define RETRO_DEVICE_ID_LIGHTGUN_START    6
 
+// Returned from retro_get_region().
 #define RETRO_REGION_NTSC  0
 #define RETRO_REGION_PAL   1
 
+// Passed to retro_get_memory_data/size().
+// If the memory type doesn't apply to the implementation NULL/0 can be returned.
 #define RETRO_MEMORY_MASK        0xff
+
+// Regular save ram. This ram is usually found on a game cartridge, backed up by a battery.
+// If save game data is too complex for a single memory buffer,
+// the SYSTEM_DIRECTORY environment callback can be used.
 #define RETRO_MEMORY_SAVE_RAM    0
+
+// Some games have a built-in clock to keep track of time.
+// This memory is usually just a couple of bytes to keep track of time.
 #define RETRO_MEMORY_RTC         1
+
+// System ram lets a frontend peek into a game systems main RAM.
 #define RETRO_MEMORY_SYSTEM_RAM  2
+
+// Video ram lets a frontend peek into a game systems video RAM (VRAM).
 #define RETRO_MEMORY_VIDEO_RAM   3
 
+// Special memory types.
 #define RETRO_MEMORY_SNES_BSX_RAM             ((1 << 8) | RETRO_MEMORY_SAVE_RAM)
 #define RETRO_MEMORY_SNES_BSX_PRAM            ((2 << 8) | RETRO_MEMORY_SAVE_RAM)
 #define RETRO_MEMORY_SNES_SUFAMI_TURBO_A_RAM  ((3 << 8) | RETRO_MEMORY_SAVE_RAM)
@@ -82,11 +132,161 @@ extern "C" {
 #define RETRO_MEMORY_SNES_GAME_BOY_RAM        ((5 << 8) | RETRO_MEMORY_SAVE_RAM)
 #define RETRO_MEMORY_SNES_GAME_BOY_RTC        ((6 << 8) | RETRO_MEMORY_RTC)
 
+// Special game types passed into retro_load_game_special().
+// Only used when multiple ROMs are required.
 #define RETRO_GAME_TYPE_BSX             0x101
 #define RETRO_GAME_TYPE_BSX_SLOTTED     0x102
 #define RETRO_GAME_TYPE_SUFAMI_TURBO    0x103
 #define RETRO_GAME_TYPE_SUPER_GAME_BOY  0x104
 
+// Keysyms used for ID in input state callback when polling RETRO_KEYBOARD.
+enum retro_key
+{
+   RETROK_UNKNOWN        = 0,
+   RETROK_FIRST          = 0,
+   RETROK_BACKSPACE      = 8,
+   RETROK_TAB            = 9,
+   RETROK_CLEAR          = 12,
+   RETROK_RETURN         = 13,
+   RETROK_PAUSE          = 19,
+   RETROK_ESCAPE         = 27,
+   RETROK_SPACE          = 32,
+   RETROK_EXCLAIM        = 33,
+   RETROK_QUOTEDBL       = 34,
+   RETROK_HASH           = 35,
+   RETROK_DOLLAR         = 36,
+   RETROK_AMPERSAND      = 38,
+   RETROK_QUOTE          = 39,
+   RETROK_LEFTPAREN      = 40,
+   RETROK_RIGHTPAREN     = 41,
+   RETROK_ASTERISK       = 42,
+   RETROK_PLUS           = 43,
+   RETROK_COMMA          = 44,
+   RETROK_MINUS          = 45,
+   RETROK_PERIOD         = 46,
+   RETROK_SLASH          = 47,
+   RETROK_0              = 48,
+   RETROK_1              = 49,
+   RETROK_2              = 50,
+   RETROK_3              = 51,
+   RETROK_4              = 52,
+   RETROK_5              = 53,
+   RETROK_6              = 54,
+   RETROK_7              = 55,
+   RETROK_8              = 56,
+   RETROK_9              = 57,
+   RETROK_COLON          = 58,
+   RETROK_SEMICOLON      = 59,
+   RETROK_LESS           = 60,
+   RETROK_EQUALS         = 61,
+   RETROK_GREATER        = 62,
+   RETROK_QUESTION       = 63,
+   RETROK_AT             = 64,
+   RETROK_LEFTBRACKET    = 91,
+   RETROK_BACKSLASH      = 92,
+   RETROK_RIGHTBRACKET   = 93,
+   RETROK_CARET          = 94,
+   RETROK_UNDERSCORE     = 95,
+   RETROK_BACKQUOTE      = 96,
+   RETROK_a              = 97,
+   RETROK_b              = 98,
+   RETROK_c              = 99,
+   RETROK_d              = 100,
+   RETROK_e              = 101,
+   RETROK_f              = 102,
+   RETROK_g              = 103,
+   RETROK_h              = 104,
+   RETROK_i              = 105,
+   RETROK_j              = 106,
+   RETROK_k              = 107,
+   RETROK_l              = 108,
+   RETROK_m              = 109,
+   RETROK_n              = 110,
+   RETROK_o              = 111,
+   RETROK_p              = 112,
+   RETROK_q              = 113,
+   RETROK_r              = 114,
+   RETROK_s              = 115,
+   RETROK_t              = 116,
+   RETROK_u              = 117,
+   RETROK_v              = 118,
+   RETROK_w              = 119,
+   RETROK_x              = 120,
+   RETROK_y              = 121,
+   RETROK_z              = 122,
+   RETROK_DELETE         = 127,
+
+   RETROK_KP0            = 256,
+   RETROK_KP1            = 257,
+   RETROK_KP2            = 258,
+   RETROK_KP3            = 259,
+   RETROK_KP4            = 260,
+   RETROK_KP5            = 261,
+   RETROK_KP6            = 262,
+   RETROK_KP7            = 263,
+   RETROK_KP8            = 264,
+   RETROK_KP9            = 265,
+   RETROK_KP_PERIOD      = 266,
+   RETROK_KP_DIVIDE      = 267,
+   RETROK_KP_MULTIPLY    = 268,
+   RETROK_KP_MINUS       = 269,
+   RETROK_KP_PLUS        = 270,
+   RETROK_KP_ENTER       = 271,
+   RETROK_KP_EQUALS      = 272,
+
+   RETROK_UP             = 273,
+   RETROK_DOWN           = 274,
+   RETROK_RIGHT          = 275,
+   RETROK_LEFT           = 276,
+   RETROK_INSERT         = 277,
+   RETROK_HOME           = 278,
+   RETROK_END            = 279,
+   RETROK_PAGEUP         = 280,
+   RETROK_PAGEDOWN       = 281,
+
+   RETROK_F1             = 282,
+   RETROK_F2             = 283,
+   RETROK_F3             = 284,
+   RETROK_F4             = 285,
+   RETROK_F5             = 286,
+   RETROK_F6             = 287,
+   RETROK_F7             = 288,
+   RETROK_F8             = 289,
+   RETROK_F9             = 290,
+   RETROK_F10            = 291,
+   RETROK_F11            = 292,
+   RETROK_F12            = 293,
+   RETROK_F13            = 294,
+   RETROK_F14            = 295,
+   RETROK_F15            = 296,
+
+   RETROK_NUMLOCK        = 300,
+   RETROK_CAPSLOCK       = 301,
+   RETROK_SCROLLOCK      = 302,
+   RETROK_RSHIFT         = 303,
+   RETROK_LSHIFT         = 304,
+   RETROK_RCTRL          = 305,
+   RETROK_LCTRL          = 306,
+   RETROK_RALT           = 307,
+   RETROK_LALT           = 308,
+   RETROK_RMETA          = 309,
+   RETROK_LMETA          = 310,
+   RETROK_LSUPER         = 311,
+   RETROK_RSUPER         = 312,
+   RETROK_MODE           = 313,
+   RETROK_COMPOSE        = 314,
+
+   RETROK_HELP           = 315,
+   RETROK_PRINT          = 316,
+   RETROK_SYSREQ         = 317,
+   RETROK_BREAK          = 318,
+   RETROK_MENU           = 319,
+   RETROK_POWER          = 320,
+   RETROK_EURO           = 321,
+   RETROK_UNDO           = 322,
+
+   RETROK_LAST
+};
 
 // Environment commands.
 #define RETRO_ENVIRONMENT_SET_ROTATION  1  // const unsigned * --
@@ -99,7 +299,7 @@ extern "C" {
                                            // Boolean value whether or not the implementation should use overscan, or crop away overscan.
                                            //
 #define RETRO_ENVIRONMENT_GET_CAN_DUPE  3  // bool * --
-                                           // Boolean value whether or not RetroArch supports frame duping,
+                                           // Boolean value whether or not frontend supports frame duping,
                                            // passing NULL to video frame callback.
                                            //
 #define RETRO_ENVIRONMENT_GET_VARIABLE  4  // struct retro_variable * --
@@ -133,8 +333,9 @@ extern "C" {
                                            // about too demanding implementations.
                                            // 
                                            // The levels are "floating", but roughly defined as:
-                                           // 1: Low-powered devices such as Raspberry Pi, smart phones, tablets, etc.
-                                           // 2: Medium-spec consoles, such as PS3/360, with sub-par CPUs.
+                                           // 0: Low-powered embedded devices such as Raspberry Pi
+                                           // 1: 6th generation consoles, such as Wii/Xbox 1, and phones, tablets, etc.
+                                           // 2: 7th generation consoles, such as PS3/360, with sub-par CPUs.
                                            // 3: Modern desktop/laptops with reasonably powerful CPUs.
                                            // 4: High-end desktops with very powerful CPUs.
                                            //
@@ -154,14 +355,36 @@ extern "C" {
 #define RETRO_ENVIRONMENT_SET_PIXEL_FORMAT 10
                                            // const enum retro_pixel_format * --
                                            // Sets the internal pixel format used by the implementation.
-                                           // The default pixel format is RETRO_PIXEL_FORMAT_XRGB1555.
+                                           // The default pixel format is RETRO_PIXEL_FORMAT_0RGB1555.
+                                           // This pixel format however, is deprecated (see enum retro_pixel_format).
                                            // If the call returns false, the frontend does not support this pixel format.
                                            // This function should be called inside retro_load_game() or retro_get_system_av_info().
+                                           //
+#define RETRO_ENVIRONMENT_SET_INPUT_DESCRIPTORS 11
+                                           // const struct retro_input_descriptor * --
+                                           // Sets an array of retro_input_descriptors.
+                                           // It is up to the frontend to present this in a usable way.
+                                           // The array is terminated by retro_input_descriptor::description being set to NULL.
+                                           // This function can be called at any time, but it is recommended to call it as early as possible.
+
 
 enum retro_pixel_format
 {
-   RETRO_PIXEL_FORMAT_0RGB1555 = 0, // 0RGB1555, native endian. 0 bit must be set to 0.
-   RETRO_PIXEL_FORMAT_XRGB8888      // XRGB8888, native endian. X bits are ignored.
+   // 0RGB1555, native endian. 0 bit must be set to 0.
+   // This pixel format is default for compatibility concerns only.
+   // If a 15/16-bit pixel format is desired, consider using RGB565.
+   RETRO_PIXEL_FORMAT_0RGB1555 = 0,
+
+   // XRGB8888, native endian. X bits are ignored.
+   RETRO_PIXEL_FORMAT_XRGB8888 = 1,
+
+   // RGB565, native endian. This pixel format is the recommended format to use if a 15/16-bit format is desired
+   // as it is the pixel format that is typically available on a wide range of low-power devices.
+   // It is also natively supported in APIs like OpenGL ES.
+   RETRO_PIXEL_FORMAT_RGB565   = 2,
+
+   // Ensure sizeof() == sizeof(int).
+   RETRO_PIXEL_FORMAT_UNKNOWN  = INT_MAX
 };
 
 struct retro_message
@@ -170,8 +393,25 @@ struct retro_message
    unsigned    frames;     // Duration in frames of message.
 };
 
+// Describes how the libretro implementation maps a libretro input bind
+// to its internal input system through a human readable string.
+// This string can be used to better let a user configure input.
+struct retro_input_descriptor
+{
+   // Associates given parameters with a description.
+   unsigned port;
+   unsigned device;
+   unsigned index;
+   unsigned id;
+
+   const char *description; // Human readable description for parameters.
+                            // The pointer must remain valid until retro_unload_game() is called.
+};
+
 struct retro_system_info
 {
+   // All pointers are owned by libretro implementation, and pointers must remain valid until retro_deinit() is called.
+
    const char *library_name;      // Descriptive name of library. Should not contain any version numbers, etc.
    const char *library_version;   // Descriptive version of core.
 
@@ -240,6 +480,8 @@ typedef bool (*retro_environment_t)(unsigned cmd, void *data);
 // Render a frame. Pixel format is 15-bit 0RGB1555 native endian unless changed (see RETRO_ENVIRONMENT_SET_PIXEL_FORMAT).
 // Width and height specify dimensions of buffer.
 // Pitch specifices length in bytes between two lines in buffer.
+// For performance reasons, it is highly recommended to have a frame that is packed in memory, i.e. pitch == width * byte_per_pixel.
+// Certain graphic APIs, such as OpenGL ES, do not like textures that are not packed in memory.
 typedef void (*retro_video_refresh_t)(const void *data, unsigned width, unsigned height, size_t pitch);
 
 // Renders a single audio frame. Should only be used if implementation generates a single sample at a time.
@@ -279,6 +521,8 @@ void retro_get_system_info(struct retro_system_info *info);
 
 // Gets information about system audio/video timings and geometry.
 // Can be called only after retro_load_game() has successfully completed.
+// NOTE: The implementation of this function might not initialize every variable if needed.
+// E.g. geom.aspect_ratio might not be initialized if core doesn't desire a particular aspect ratio.
 void retro_get_system_av_info(struct retro_system_av_info *info);
 
 // Sets device to be used for player 'port'.