Add Linux support

Oh boy this was a bit of a hassle lol - dynamic loading was the easiest
part... but then came both sound and x11

Using SDL for now but I'd really like to change it for even lower layer,
but then I might have to make my own mixer... oh no.

3 files changed, 169 insertions, 4 deletions

diff --git a/platform/linux.c b/platform/linux.c
new file mode 100644
index 0000000..6793abc
--- /dev/null
+++ b/platform/linux.c
@@ -0,0 +1,165 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <signal.h>
+#include <dlfcn.h>
+
+/* Audio with SDL for now (would prefer something more direct but it's proving hard) */
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_mixer.h>
+
+/* Capture input with XInput Extensions 2 */
+#include <X11/Xlib.h>
+#include <X11/extensions/XInput2.h>
+
+#include "platform.h"
+#include "../board/board.h"
+
+#define MIXER_FREQ 44100
+#define MIXER_FORMAT AUDIO_S16LSB
+#define MIXER_CHANNELS 2
+#define MIXER_CHUNKSIZE 64
+
+extern void keyboard_on_down(void);
+extern void keyboard_on_up(void);
+
+static bool running = true;
+static Display *display;
+static int xi_opcode;
+
+bool sound_init(float volume)
+{
+	if (SDL_Init(SDL_INIT_AUDIO) < 0) {
+		printf("ERROR: Could not initialise SDL for audio.\n");
+		return false;
+	}
+
+	if (Mix_OpenAudio(MIXER_FREQ, MIXER_FORMAT, MIXER_CHANNELS, MIXER_CHUNKSIZE)) {
+		printf("ERROR: SDL mixer audio device open fail.\n");
+		return false;
+	}
+
+	Mix_Volume(-1, volume * MIX_MAX_VOLUME); // set for all channels
+	return true;
+}
+
+// TODO: get rid of this with proper cache thing - only supports 1 sound for now
+static Mix_Chunk *loaded_chunk = NULL;
+
+void sound_play(unsigned char *buffer, unsigned int buffer_len)
+{
+	/* Load sample into SDL memory thing then into the mixer */
+	// TODO: Cache these samples as loaded into SDL
+	if (loaded_chunk == NULL) {
+		SDL_RWops *sample_rw = SDL_RWFromMem(buffer, buffer_len);
+		loaded_chunk = Mix_LoadWAV_RW(sample_rw, 1);
+		if (loaded_chunk == NULL) {
+			printf("ERROR: Sample load fail - %s\n", Mix_GetError());
+			running = false;
+			return;
+		}
+	}
+	
+	/* -1 means not-in-use channel */
+	Mix_PlayChannel(-1, loaded_chunk, 0);
+}
+
+/* 
+ * Uses XInput2 extensions to hook into the keyboard.
+ * Noticed this was possible when I used:
+ *   $ xinput test-xi2 --root
+ * Resources used:
+ *   - https://github.com/freedesktop/xorg-xinput/blob/master/src/test_xi2.c 
+ *   - https://cgit.freedesktop.org/xorg/proto/inputproto/commit/?id=f4f09d40e0fd94d267b280f2a82385dca1141347
+ */
+bool keyboard_hook(void)
+{
+	fprintf(stderr, "Setting up keyboard hook...\n");
+
+	/* Connect to X, then use XI2 to grab events */
+	display = XOpenDisplay(NULL);
+	if (display == NULL) {
+		printf("ERROR: Could not open X display.\n");
+		return false;
+	}
+	Window root_window = DefaultRootWindow(display);
+
+	int xi_event, xi_error;
+	if (!XQueryExtension(display, "XInputExtension", &xi_opcode, &xi_event, &xi_error)) {
+		printf("ERROR: Could not find XInputExtension.\n");
+		return false;
+	}
+
+	fprintf(stderr, "Setting up XInput2 filter...\n");
+	unsigned char mask[XIMaskLen(XI_RawKeyPress) + XIMaskLen(XI_RawKeyRelease)] = {0};
+	XISetMask(mask, XI_RawKeyPress);
+	XISetMask(mask, XI_RawKeyRelease);
+	XIEventMask event_mask = {
+		.deviceid = XIAllMasterDevices,
+		.mask_len = sizeof(mask)/sizeof(mask[0]),
+		.mask = mask,
+	};
+	XISelectEvents(display, root_window, &event_mask, 1);
+	return true;
+}
+
+void keyboard_unhook(void)
+{
+	fprintf(stderr, "Cleaning up audio system and hooks...\n");
+	Mix_Quit();
+	SDL_Quit();
+	XCloseDisplay(display);
+}
+
+void handle_signal(int)
+{
+	running = false;
+}
+void enter_idle(void)
+{
+	struct sigaction sa = { .sa_handler = handle_signal };
+	sigaction(SIGINT, &sa, NULL);
+
+	XGenericEventCookie event;
+	while (running) {
+		XNextEvent(display, (XEvent *) &event);
+		/* XGenEventData fails if it isn't a XGenericEventCookie anyway */
+		if (XGetEventData(display, &event) && event.type == GenericEvent && event.extension == xi_opcode) {
+			/* char *ur = event.evtype == XI_RawKeyPress ? "press" : "release"; */
+			/* unsigned int kc = ((XIDeviceEvent *) event.data)->detail; */
+
+			if (event.evtype == XI_RawKeyPress) {
+				keyboard_on_down();
+			} else if (event.evtype == XI_RawKeyRelease) {
+				keyboard_on_up();
+			}
+		}
+		XFreeEventData(display, &event);
+	}
+}
+
+struct board *load_board(char *board_name)
+{
+	char so_name[100];
+	int r = snprintf(so_name, 100, "./board/%s.so", board_name);
+	if (r < 0 || r >= 100) {
+		printf("ERROR: Invalid board name.\n");
+		return false;
+	}
+
+	void *board_module = dlopen(so_name, RTLD_LAZY);
+	if (board_module == NULL) {
+		printf("ERROR: Could not load board module.\n");
+		return false;
+	}
+	// HACK: Cast to void function ptr then cast back, otherwise types are incompatible to the compiler.
+	fn_board_init board_init = dlsym(board_module, "board_init");
+	if (board_init == NULL) {
+		printf("ERROR: No board initialisation function could be loaded.\n");
+		return false;
+	}
+
+	struct board_data data = {
+		.sound_play = &sound_play
+	};
+	return board_init(data);
+}
diff --git a/platform/platform.h b/platform/platform.h
index a5e5db4..ca07789 100644
--- a/platform/platform.h
+++ b/platform/platform.h
@@ -8,11 +8,11 @@
 struct board *load_board(char *board_name);
 
 bool sound_init(float volume);
-void sound_play(unsigned char *buffer);
+void sound_play(unsigned char *buffer, unsigned int buffer_len);
 
 void keyboard_unhook(void);
 bool keyboard_hook(void);
 
 void enter_idle(void);
 
-#endif /* CLAK_PLATFORM_H_ */
\ No newline at end of file
+#endif /* CLAK_PLATFORM_H_ */
diff --git a/platform/win32.c b/platform/win32.c
index 1dccc7b..0b1da80 100644
--- a/platform/win32.c
+++ b/platform/win32.c
@@ -19,7 +19,7 @@ bool sound_init(float volume)
 	return true;
 }
 
-void sound_play(unsigned char *buffer)
+void sound_play(unsigned char *buffer, unsigned int)
 {
 	PlaySound((const char *) buffer, NULL, SND_MEMORY | SND_ASYNC | SND_NODEFAULT);
 }
@@ -107,4 +107,4 @@ struct board *load_board(char *board_name)
 		.sound_play = &sound_play
 	};
 	return board_init(data);
-}
\ No newline at end of file
+}