iOS: Added memory warning callbacks

modules/juce_audio_plugin_client/AU/juce_AUv3_Wrapper.mm

@@ -1556,6 +1556,13 @@ public:
         }
     }
 
+    void didReceiveMemoryWarning()
+    {
+        if (processorHolder != nullptr)
+            if (auto* processor = processorHolder->get())
+                processor->memoryWarningReceived();
+    }
+
     CGSize getPreferredContentSize() const
     {
         return CGSizeMake (static_cast<float> (preferredSize.getWidth()),
@@ -1634,11 +1641,12 @@ private:
     ScopedPointer<JuceAUViewController> cpp;
 }
 
-- (instancetype) initWithNibName: (nullable NSString*) nib bundle: (nullable NSBundle*) bndl { self = [super initWithNibName: nib bundle: bndl]; cpp = new JuceAUViewController (self); return self;}
-- (void) loadView               { cpp->loadView(); }
-- (AUAudioUnit *)createAudioUnitWithComponentDescription:(AudioComponentDescription)desc error:(NSError **)error { return cpp->createAudioUnit (desc, error); }
-- (CGSize) preferredContentSize { return cpp->getPreferredContentSize(); }
-- (void)viewDidLayoutSubviews   { return cpp->viewDidLayoutSubviews(); }
+- (instancetype) initWithNibName: (nullable NSString*) nib bundle: (nullable NSBundle*) bndl { self = [super initWithNibName: nib bundle: bndl]; cpp = new JuceAUViewController (self); return self; }
+- (void) loadView                { cpp->loadView(); }
+- (AUAudioUnit *) createAudioUnitWithComponentDescription: (AudioComponentDescription) desc error: (NSError **) error { return cpp->createAudioUnit (desc, error); }
+- (CGSize) preferredContentSize  { return cpp->getPreferredContentSize(); }
+- (void) viewDidLayoutSubviews   { cpp->viewDidLayoutSubviews(); }
+- (void) didReceiveMemoryWarning { cpp->didReceiveMemoryWarning(); }
 @end
 
 //==============================================================================
@@ -1646,7 +1654,7 @@ private:
 bool JUCE_CALLTYPE juce_isInterAppAudioConnected() { return false; }
 void JUCE_CALLTYPE juce_switchToHostApplication()  {}
 #if JUCE_MODULE_AVAILABLE_juce_gui_basics
-Image JUCE_CALLTYPE juce_getIAAHostIcon (int)      { return Image(); }
+Image JUCE_CALLTYPE juce_getIAAHostIcon (int)      { return {}; }
 #endif
 #endif
 

modules/juce_audio_processors/processors/juce_AudioProcessor.h

@@ -129,6 +129,16 @@ public:
     */
     virtual void releaseResources() = 0;
 
+    /** Called by the host to indicate that you should reduce your memory footprint.
+
+        You should override this method to free up some memory gracefully, if possible,
+        otherwise the host may forcibly unload your AudioProcessor.
+
+        At the moment this method is only called when your AudioProcessor is an AUv3
+        plug-in running on iOS.
+    */
+    virtual void memoryWarningReceived()     { jassertfalse; }
+
     /** Renders the next block.
 
         When this method is called, the buffer contains a number of channels which is

modules/juce_events/messages/juce_ApplicationBase.h

@@ -188,6 +188,16 @@ public:
                                      const String& sourceFilename,
                                      int lineNumber) = 0;
 
+    /** Called by the operating system to indicate that you should reduce your memory
+        footprint.
+
+        You should override this method to free up some memory gracefully, if possible,
+        otherwise the host may forcibly kill your app.
+
+        At the moment this method is only called on iOS.
+    */
+    virtual void memoryWarningReceived()     { jassertfalse; }
+
     //==============================================================================
     /** Override this method to be informed when the back button is pressed on a device.
         This is currently only implemented on Android devices.

modules/juce_events/native/juce_mac_MessageManager.mm

@@ -116,7 +116,7 @@ private:
             addMethod (@selector (mainMenuTrackingEnded:),          mainMenuTrackingEnded,          "v@:@");
             addMethod (@selector (dummyMethod),                     dummyMethod,                    "v@:");
 
-          #if JUCE_PUSH_NOTIFICATIONS
+           #if JUCE_PUSH_NOTIFICATIONS
             //==============================================================================
             addIvar<NSObject<NSApplicationDelegate, NSUserNotificationCenterDelegate>*> ("pushNotificationsDelegate");
 
@@ -125,7 +125,7 @@ private:
             addMethod (@selector (application:didRegisterForRemoteNotificationsWithDeviceToken:), registeredForRemoteNotifications,       "v@:@@");
             addMethod (@selector (application:didFailToRegisterForRemoteNotificationsWithError:), failedToRegisterForRemoteNotifications, "v@:@@");
             addMethod (@selector (application:didReceiveRemoteNotification:),                     didReceiveRemoteNotification,           "v@:@@");
-          #endif
+           #endif
 
             registerClass();
         }
@@ -139,7 +139,7 @@ private:
                                                                 andEventID: kAEGetURL];
         }
 
-      #if JUCE_PUSH_NOTIFICATIONS
+       #if JUCE_PUSH_NOTIFICATIONS
         static void applicationDidFinishLaunching (id self, SEL, NSNotification* notification)
         {
             if (notification.userInfo != nil)
@@ -150,7 +150,7 @@ private:
                     didReceiveRemoteNotification (self, nil, [NSApplication sharedApplication], userNotification.userInfo);
             }
         }
-      #endif
+       #endif
 
         static NSApplicationTerminateReply applicationShouldTerminate (id /*self*/, SEL, NSApplication*)
         {
@@ -241,7 +241,7 @@ private:
             return s;
         }
 
-      #if JUCE_PUSH_NOTIFICATIONS
+       #if JUCE_PUSH_NOTIFICATIONS
         //==============================================================================
         static void setPushNotificationsDelegate (id self, SEL, NSObject<NSApplicationDelegate, NSUserNotificationCenterDelegate>* delegate)
         {
@@ -306,7 +306,7 @@ private:
                 [invocation invoke];
             }
         }
-      #endif
+       #endif
     };
 };
 

modules/juce_gui_basics/native/juce_ios_Windowing.mm

@@ -57,6 +57,7 @@ namespace juce
 - (void) applicationWillResignActive: (UIApplication*) application;
 - (void) application: (UIApplication*) application handleEventsForBackgroundURLSession: (NSString*) identifier
    completionHandler: (void (^)(void)) completionHandler;
+- (void) applicationDidReceiveMemoryWarning: (UIApplication *) application;
 #if JUCE_PUSH_NOTIFICATIONS
 - (void) application: (UIApplication*) application didRegisterUserNotificationSettings: (UIUserNotificationSettings*) notificationSettings;
 - (void) application: (UIApplication*) application didRegisterForRemoteNotificationsWithDeviceToken: (NSData*) deviceToken;
@@ -92,9 +93,9 @@ namespace juce
     self = [super init];
     appSuspendTask = UIBackgroundTaskInvalid;
 
-  #if JUCE_PUSH_NOTIFICATIONS && defined (__IPHONE_10_0) && __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_10_0
+   #if JUCE_PUSH_NOTIFICATIONS && defined (__IPHONE_10_0) && __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_10_0
     [UNUserNotificationCenter currentNotificationCenter].delegate = self;
-  #endif
+   #endif
 
     return self;
 }
@@ -104,7 +105,7 @@ namespace juce
     ignoreUnused (application);
     initialiseJuce_GUI();
 
-    if (JUCEApplicationBase* app = JUCEApplicationBase::createInstance())
+    if (auto* app = JUCEApplicationBase::createInstance())
     {
         if (! app->initialiseApp())
             exit (app->shutdownApp());
@@ -174,6 +175,14 @@ namespace juce
     completionHandler();
 }
 
+- (void) applicationDidReceiveMemoryWarning: (UIApplication*) application
+{
+    ignoreUnused (application);
+
+    if (auto* app = JUCEApplicationBase::getInstance())
+        app->memoryWarningReceived();
+}
+
 - (void) setPushNotificationsDelegateToUse: (NSObject*) delegate
 {
     _pushNotificationsDelegate = delegate;