Add protocol handler support

This lets the user click a link in a web browser to very easily join a Quake 3 multiplayer game. As browser-based matchmaking websites become more popular, this makes it a lot more convenient and simple to play Quake 3 with others.

The links have the following URI format: quake3://connect/example.com:27950. The format has been designed to be flexible to allow more types of links in the future and avoiding having to make a breaking change. At the moment, "connect" is the only supported command.

code/sys/sys_local.h

@@ -64,3 +64,8 @@ void Sys_AnsiColorPrint( const char *msg );
 
 int Sys_PID( void );
 qboolean Sys_PIDIsRunning( int pid );
+
+#ifdef PROTOCOL_HANDLER
+char *Sys_InitProtocolHandler( void );
+char *Sys_ParseProtocolUri( const char *uri );
+#endif

code/sys/sys_main.c

@@ -642,6 +642,94 @@ void Sys_ParseArgs( int argc, char **argv )
 	}
 }
 
+#ifdef PROTOCOL_HANDLER
+/*
+=================
+Sys_InitProtocolHandler
+
+See sys_osx.m for macOS implementation.
+=================
+*/
+#ifndef __APPLE__
+char *Sys_InitProtocolHandler( void )
+{
+	return NULL;
+}
+#endif
+
+/*
+=================
+Sys_ParseProtocolUri
+
+This parses a protocol URI, e.g. "quake3://connect/example.com:27950"
+to a string that can be run in the console, or a null pointer if the
+operation is invalid or unsupported.
+At the moment only the "connect" command is supported.
+=================
+*/
+char *Sys_ParseProtocolUri( const char *uri )
+{
+	// Both "quake3://" and "quake3:" can be used
+	if ( Q_strncmp( uri, PROTOCOL_HANDLER ":", strlen( PROTOCOL_HANDLER ":" ) ) )
+	{
+		Com_Printf( "Sys_ParseProtocolUri: unsupported protocol.\n" );
+		return NULL;
+	}
+	uri += strlen( PROTOCOL_HANDLER ":" );
+	if ( !Q_strncmp( uri, "//", strlen( "//" ) ) )
+	{
+		uri += strlen( "//" );
+	}
+	Com_Printf( "Sys_ParseProtocolUri: %s\n", uri );
+
+	// At the moment, only "connect/hostname:port" is supported
+	if ( !Q_strncmp( uri, "connect/", strlen( "connect/" ) ) )
+	{
+		int i, bufsize;
+		char *out;
+
+		uri += strlen( "connect/" );
+		if ( *uri == '\0' || *uri == '?' )
+		{
+			Com_Printf( "Sys_ParseProtocolUri: missing argument.\n" );
+			return NULL;
+		}
+
+		// Check for any unsupported characters
+		// For safety reasons, the "hostname:port" part can only
+		// contain characters from: a-zA-Z0-9.:-[]
+		for ( i=0; uri[i] != '\0'; i++ )
+		{
+			if ( uri[i] == '?' )
+			{
+				// For forwards compatibility, any query string parameters are ignored (e.g. "?password=abcd")
+				// However, these are not passed on macOS, so it may be a bad idea to add them.
+				break;
+			}
+
+			if ( isalpha( uri[i] ) == 0 && isdigit( uri[i] ) == 0
+				&& uri[i] != '.' && uri[i] != ':' && uri[i] != '-'
+				&& uri[i] != '[' && uri[i] != ']' )
+			{
+				Com_Printf( "Sys_ParseProtocolUri: hostname contains unsupported character.\n" );
+				return NULL;
+			}
+		}
+
+		bufsize = strlen( "+connect " ) + i + 1;
+		out = malloc( bufsize );
+		strcpy( out, "+connect " );
+		strncat( out, uri, i );
+		return out;
+	}
+	else
+	{
+		Com_Printf( "Sys_ParseProtocolUri: unsupported command.\n" );
+		return NULL;
+	}
+}
+#endif
+
 #ifndef DEFAULT_BASEDIR
 #	ifdef __APPLE__
 #		define DEFAULT_BASEDIR Sys_StripAppBundle(Sys_BinaryPath())
@@ -690,6 +778,9 @@ int main( int argc, char **argv )
 {
 	int   i;
 	char  commandLine[ MAX_STRING_CHARS ] = { 0 };
+#ifdef PROTOCOL_HANDLER
+	char *protocolCommand = NULL;
+#endif
 
 	extern void Sys_LaunchAutoupdater(int argc, char **argv);
 	Sys_LaunchAutoupdater(argc, argv);
@@ -724,6 +815,10 @@ int main( int argc, char **argv )
 
 	Sys_PlatformInit( );
 
+#ifdef PROTOCOL_HANDLER
+	protocolCommand = Sys_InitProtocolHandler( );
+#endif
+
 	// Set the initial time base
 	Sys_Milliseconds( );
 
@@ -740,7 +835,22 @@ int main( int argc, char **argv )
 	// Concatenate the command line for passing to Com_Init
 	for( i = 1; i < argc; i++ )
 	{
-		const qboolean containsSpaces = strchr(argv[i], ' ') != NULL;
+		qboolean containsSpaces;
+
+		// For security reasons we always detect --uri, even when PROTOCOL_HANDLER is undefined
+		// Any arguments after "--uri quake3://..." is ignored
+		if ( !strcmp( argv[i], "--uri" ) )
+		{
+#ifdef PROTOCOL_HANDLER
+			if ( argc > i+1 )
+			{
+				protocolCommand = Sys_ParseProtocolUri( argv[i+1] );
+			}
+#endif
+			break;
+		}
+
+		containsSpaces = strchr(argv[i], ' ') != NULL;
 		if (containsSpaces)
 			Q_strcat( commandLine, sizeof( commandLine ), "\"" );
 
@@ -752,6 +862,14 @@ int main( int argc, char **argv )
 		Q_strcat( commandLine, sizeof( commandLine ), " " );
 	}
 
+#ifdef PROTOCOL_HANDLER
+	if ( protocolCommand != NULL )
+	{
+		Q_strcat( commandLine, sizeof( commandLine ), protocolCommand );
+		free( protocolCommand );
+	}
+#endif
+
 	CON_Init( );
 	Com_Init( commandLine );
 	NET_Init( );

code/sys/sys_osx.m

@@ -34,6 +34,10 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 #import <Carbon/Carbon.h>
 #import <Cocoa/Cocoa.h>
 
+#ifdef PROTOCOL_HANDLER
+char *protocolCommand = NULL;
+#endif
+
 /*
 ==============
 Sys_Dialog
@@ -115,3 +119,42 @@ char *Sys_StripAppBundle( char *dir )
 	Q_strncpyz(cwd, Sys_Dirname(cwd), sizeof(cwd));
 	return cwd;
 }
+
+#ifdef PROTOCOL_HANDLER
+
+@interface AppDelegate : NSObject <NSApplicationDelegate>
+@end
+
+@implementation AppDelegate
+
+- (void)handleAppleEvent:(NSAppleEventDescriptor *)event withReplyEvent: (NSAppleEventDescriptor *)replyEvent
+{
+	NSString *input = [[event paramDescriptorForKeyword:keyDirectObject] stringValue];
+	protocolCommand = Sys_ParseProtocolUri( input.UTF8String );
+}
+
+- (void)applicationDidFinishLaunching:(NSNotification *)notification
+{
+	[NSApp stop:nil];
+}
+
+@end
+
+char *Sys_InitProtocolHandler( void )
+{
+	[NSApplication sharedApplication];
+
+	AppDelegate *appDelegate = [AppDelegate new];
+	NSAppleEventManager *sharedAppleEventManager = [NSAppleEventManager new];
+	[sharedAppleEventManager setEventHandler:appDelegate
+	                             andSelector:@selector(handleAppleEvent:withReplyEvent:)
+	                           forEventClass:kInternetEventClass
+	                              andEventID:kAEGetURL];
+
+	[NSApp setDelegate:appDelegate];
+	[NSApp run];
+
+	return protocolCommand;
+}
+
+#endif