From ecb4cff6f34783fd345419c0069c685793521e80 Mon Sep 17 00:00:00 2001
From: Nicholas Tay <nick@windblume.net>
Date: Sat, 7 May 2022 23:00:13 +1000
Subject: Windows low-level hook working

Had to do some stuff with the previous VK tracking, just like what I had
to do in C# with Meccha, since it keeps firing events.

GetMessage part also just blocks to ensure we keep receiving Windows
events, but not sure what to do otherwise.
---
 clak.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 85 insertions(+), 5 deletions(-)

diff --git a/clak.c b/clak.c
index 5203032..99b1482 100644
--- a/clak.c
+++ b/clak.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <string.h>
+#include <signal.h>
 
 #include <windows.h>
 
@@ -25,9 +26,9 @@ void sound_init(void)
 	waveOutSetVolume(NULL, (channel_volume << 16) | channel_volume);
 }
 
-void sound_play(unsigned char* buffer)
+void sound_play(unsigned char *buffer)
 {
-	PlaySound((const char *) buffer, NULL, SND_MEMORY | SND_SYNC | SND_NODEFAULT);
+	PlaySound((const char *) buffer, NULL, SND_MEMORY | SND_ASYNC | SND_NODEFAULT);
 }
 
 Board *get_board(char *board_name)
@@ -39,9 +40,77 @@ Board *get_board(char *board_name)
 	return NULL;
 }
 
+HHOOK keyboard_hook_windows;
+
+void keyboard_unhook(void)
+{
+	fprintf(stderr, "Cleaning up keyboard hook...\n");
+	if (!UnhookWindowsHookEx(keyboard_hook_windows))
+		printf("WARN: Windows keyboard hook could not be cleaned up! Error code: %lu\n", GetLastError());
+}
+
+void do_exit(int code)
+{
+	keyboard_unhook();
+	fprintf(stderr, "Goodbye.\n");
+	exit(code);
+}
+void on_clean_exit(void) { do_exit(0); }
+
+Board *board = NULL;
+
+void keyboard_on_down(void)
+{
+	if (board == NULL)
+		return;
+	sound_play(board->wav);
+}
+
+void keyboard_on_up(void)
+{
+	// if (board == NULL)
+	// 	return;
+}
+
+/* https://docs.microsoft.com/en-us/previous-versions/windows/desktop/legacy/ms644985(v=vs.85) */
+LRESULT CALLBACK keyboard_windows_callback(int nCode, WPARAM wParam, LPARAM lParam)
+{
+	/* Needed to prevent repeat fires */
+	static DWORD prev_vk = 0;
+
+	/* Do not handle unless nCode >= 0, pass to next hook right away */
+	if (nCode >= 0) {
+		BOOL down = wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN;
+		KBDLLHOOKSTRUCT *hook_struct = (KBDLLHOOKSTRUCT *) lParam;
+		DWORD vk = hook_struct->vkCode;
+		if (down && vk != prev_vk) {
+			keyboard_on_down();
+			prev_vk = vk;
+		} else {
+			keyboard_on_up();
+			/* Seems like repeat strokes are 0x0 or 0x1, and 'real' ones have 0x80 flag??
+			   Not really sure how to handle this one, can't find many docs...
+			   Saw this though: https://github.com/pyglet/pyglet/blob/838d004d68fcc5c3ce83b733e3d088fad0643859/pyglet/window/win32/__init__.py#L794= */
+			if (hook_struct->flags & 0x80)
+				prev_vk = 0;
+		}
+	}
+
+	return CallNextHookEx(NULL, nCode, wParam, lParam);
+}
+
+void keyboard_hook(void)
+{
+	fprintf(stderr, "Setting up keyboard hook...\n");
+	keyboard_hook_windows = SetWindowsHookEx(WH_KEYBOARD_LL, keyboard_windows_callback, NULL, 0);
+	if (keyboard_hook_windows == NULL) {
+		printf("ERROR: Could not set up Windows keyboard hook.\n");
+		do_exit(1);
+	}
+}
+
 int main(int argc, char **argv)
 {
-	Board *board;
 	if (argc < 2 || (board = get_board(argv[1])) == NULL) {
 		printf("Please provide a valid board name.\n");
 		printf("Valid boards: ");
@@ -52,8 +121,19 @@ int main(int argc, char **argv)
 	}
 
 	sound_init();
-	printf("name: %s\n", board->name);
-	sound_play(board->wav);
+	keyboard_hook();
+	atexit(on_clean_exit);
+	fprintf(stderr, "Hooks set up, welcome to Clak!\n");
+
+	MSG msg;
+	BOOL status;
+	while ((status = GetMessage(&msg, NULL, 0, 0))) {
+		if (status == -1) {
+			// error case
+			printf("ERROR: Windows error, code %lu\n", GetLastError());
+			exit(1);
+		}
+	}
 
 	return 0;
 }
\ No newline at end of file
-- 
cgit