[Catalyst] Registering for & responding to AppleScript events in a Mac Catalyst app

Info.plist

<key>NSAppleScriptEnabled</key>
<true/>
<key>OSAScriptingDefinition</key>
<string>ScriptableTasks.sdef</string>

MRDScripting.h

//
//  MRDScripting.h
//  RadioIntegration
//
//  Created by Steven Troughton-Smith on 26/10/2019.
//  Copyright © 2019 High Caffeine Content. All rights reserved.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@protocol MRDScriptingDelegate <NSObject>
-(void)playRadioStation:(NSString *)station;
-(void)pause;
-(void)setVolume:(CGFloat)volume;
@end

@interface MRDScripting : NSObject

@property id <MRDScriptingDelegate> delegate;

+ (instancetype)sharedInstance;
+(void)initScripting;
@end

NS_ASSUME_NONNULL_END

MRDScripting.m

//
//  MRDScripting.m
//  RadioIntegration
//
//  Created by Steven Troughton-Smith on 26/10/2019.
//  Copyright © 2019 High Caffeine Content. All rights reserved.
//

#import "MRDScripting.h"
@import AppleScriptKit;

@implementation MRDScripting

OSErr myPauseHandler(const AppleEvent *theAppleEvent, AppleEvent *reply, SRefCon handlerRefcon)
{
	if ([MRDScripting sharedInstance].delegate && [[MRDScripting sharedInstance].delegate respondsToSelector:@selector(pause)])
		[[MRDScripting sharedInstance].delegate pause];
	
	return noErr;
}

OSErr myHandler(const AppleEvent *theAppleEvent, AppleEvent *reply, SRefCon handlerRefcon)
{
	NSLog(@"Handling Apple Event");
	
	AEDesc replyObject;
	OSErr err;
	
	err = AEGetParamDesc(theAppleEvent, keyDirectObject, typeWildCard, &replyObject);
	if (err != noErr) {
		
		NSLog(@"Error decoding %c", replyObject.descriptorType);
	}
	CFStringRef descRef = UTCreateStringForOSType(replyObject.descriptorType);
	NSString * descString = [NSString stringWithString:(__bridge NSString *)descRef];
	
	NSLog(@"Type = %@", descString);
	
	Size sz = AEGetDescDataSize(&replyObject);
	
	if (sz)
	{
		char *r = malloc(sz);
		
		AEGetDescData(&replyObject, &r[0], sz);
		
		NSString *param = [[NSString alloc] initWithBytes:r length:sz encoding:NSUTF16LittleEndianStringEncoding];
		
		if ([MRDScripting sharedInstance].delegate && [[MRDScripting sharedInstance].delegate respondsToSelector:@selector(playRadioStation:)])
			[[MRDScripting sharedInstance].delegate playRadioStation:param];
	}
	
	return noErr;
}

OSErr myVolumeHandler(const AppleEvent *theAppleEvent, AppleEvent *reply, SRefCon handlerRefcon)
{
	NSLog(@"Handling Apple Event");
	
	AEDesc replyObject;
	OSErr err;
	
	err = AEGetParamDesc(theAppleEvent, keyDirectObject, typeWildCard, &replyObject);
	if (err != noErr) {
		
		NSLog(@"Error decoding %c", replyObject.descriptorType);
	}
	CFStringRef descRef = UTCreateStringForOSType(replyObject.descriptorType);
	NSString * descString = [NSString stringWithString:(__bridge NSString *)descRef];
	
	NSLog(@"Type = %@", descString);
	
	Size sz = AEGetDescDataSize(&replyObject);
	
	if (sz)
	{
		if ([descString isEqualToString:@"doub"])
		{
			CGFloat *r = malloc(sz);
			
			AEGetDescData(&replyObject, &r[0], sz);
			
			CGFloat volume = r[0];
			
			if (volume >= 0.0 && volume <= 1.0)
			{
				NSLog(@"desired volume = %f", volume);
				
				if ([MRDScripting sharedInstance].delegate && [[MRDScripting sharedInstance].delegate respondsToSelector:@selector(setVolume:)])
					[[MRDScripting sharedInstance].delegate setVolume:volume];
			}
			else
			{
				return paramErr;
			}
		}
		else if ([descString isEqualToString:@"long"])
		{
			long *r = malloc(sz);
			
			AEGetDescData(&replyObject, &r[0], sz);
			
			long volume = r[0];
			
			if (volume >= 0.0 && volume <= 1.0)
			{
				NSLog(@"desired volume LONG = %ld", volume);
				
				if ([MRDScripting sharedInstance].delegate && [[MRDScripting sharedInstance].delegate respondsToSelector:@selector(setVolume:)])
					[[MRDScripting sharedInstance].delegate setVolume:(CGFloat)volume];
			}
			else
			{
				return paramErr;
			}
		}
		
	}
	
	return noErr;
}

+(void)initScripting
{
	AEInstallEventHandler('HCCR', 'play', myHandler, NULL, false);
	AEInstallEventHandler('HCCR', 'paus', myPauseHandler, NULL, false);
	AEInstallEventHandler('HCCR', 'volu', myVolumeHandler, NULL, false);
}

+ (instancetype)sharedInstance
{
	static dispatch_once_t once;
	static id sharedInstance;
	dispatch_once(&once, ^{
		sharedInstance = [[self alloc] init];
	});
	return sharedInstance;
}


@end

ScriptableTasks.sdef

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE dictionary SYSTEM "file://localhost/System/Library/DTDs/sdef.dtd">

<dictionary>
	<suite name="HCC Radio suite" code="HCCR" description="Standard terms for HCC Radio scripting">
		<command name="play" code="HCCRplay" description="Plays a radio station">
			<direct-parameter type="text" optional="no" description="the name of the station to play"/>
		</command>
		<command name="pause" code="HCCRpaus" description="Pauses playback">
		</command>
		<command name="set volume" code="HCCRvolu" description="Sets playback volume">
			<direct-parameter type="number" optional="no" description="the desired volume, valid from 0.0 to 1.0"/>
		</command>
	</suite>
</dictionary>

usage.m

/* Loading your AppKit bundle */
NSError *error = nil;
[[NSBundle bundleWithPath:[[[NSBundle mainBundle] privateFrameworksPath] stringByAppendingPathComponent:@"RadioIntegration.framework"]] loadAndReturnError:&error];

/* After loading your AppKit framework/bundle */
[NSClassFromString(@"MRDScripting") initScripting];

/* In class that wants to register for scripting delegate callbacks */
[[NSClassFromString(@"MRDScripting") sharedInstance] setDelegate:self];