Also do registering on OSX and Linux.

src/discord_register_osx.m

@@ -0,0 +1,95 @@
+#include <stdio.h>
+#include <sys/stat.h>
+
+#import <AppKit/AppKit.h>
+
+static bool Mkdir(const char* path)
+{
+    int result = mkdir(path, 0755);
+    if (result == 0) {
+        return true;
+    }
+    if (errno == EEXIST) {
+        return true;
+    }
+    return false;
+}
+
+static void RegisterCommand(const char* applicationId, const char* command)
+{
+    // There does not appear to be a way to register arbitrary commands on OSX, so instead we'll save the command
+    // to a file in the Discord config path, and when it is needed, Discord can try to load the file there, open
+    // the command therein (will pass to js's window.open, so requires a url-like thing)
+
+    const char* home = getenv("HOME");
+    if (!home) {
+        return;
+    }
+
+    char path[2048];
+    sprintf(path, "%s/Library/Application Support/discord", home);
+    Mkdir(path);
+    strcat(path, "/games");
+    Mkdir(path);
+    strcat(path, "/");
+    strcat(path, applicationId);
+    strcat(path, ".json");
+
+    FILE* f = fopen(path, "w");
+    if (f) {
+        char jsonBuffer[2048];
+        int len = snprintf(jsonBuffer, sizeof(jsonBuffer), "{\"command\": \"%s\"}", command);
+        fwrite(jsonBuffer, len, 1, f);
+        fclose(f);
+    }
+}
+
+static void RegisterURL(const char* applicationId)
+{
+    char url[256];
+    snprintf(url, sizeof(url), "discord-%s", applicationId);
+    CFStringRef cfURL = CFStringCreateWithCString(NULL, url, kCFStringEncodingUTF8);
+
+    NSString* myBundleId = [[NSBundle mainBundle] bundleIdentifier];
+    if (!myBundleId) {
+        fprintf(stderr, "No bundle id found\n");
+        return;
+    }
+
+    NSURL* myURL = [[NSBundle mainBundle] bundleURL];
+    if (!myURL) {
+        fprintf(stderr, "No bundle url found\n");
+        return;
+    }
+
+    OSStatus status = LSSetDefaultHandlerForURLScheme(cfURL, (__bridge CFStringRef)myBundleId);
+    if (status != noErr) {
+        fprintf(stderr, "Error in LSSetDefaultHandlerForURLScheme: %d\n", (int)status);
+        return;
+    }
+
+    status = LSRegisterURL((__bridge CFURLRef)myURL, true);
+    if (status != noErr) {
+        fprintf(stderr, "Error in LSRegisterURL: %d\n", (int)status);
+    }
+}
+
+void Discord_Register(const char* applicationId, const char* command)
+{
+    if (command) {
+        RegisterCommand(applicationId, command);
+    }
+    else {
+        // raii lite
+        void* pool = [[NSAutoreleasePool alloc] init];
+        RegisterURL(applicationId);
+        [(id)pool drain];
+    }
+}
+
+void Discord_RegisterSteamGame(const char* applicationId, const char* steamId)
+{
+    char command[256];
+    sprintf(command, "steam://run/%s", steamId);
+    Discord_Register(applicationId, command);
+}