[mac] display icon in notification (#7734)

there is 2 icons in notifications, one from the app itself and one set from the notification
the icon application seems not to be set correctly on mac for now
only the windon icon is set in main.cpp with myApp.setWindowIcon
the icon defined in application plist does not seem to be correctly set
...so in this PR we set the notification icon to be the QGIS one, so it looks nicer

src/gui/qgsgui.cpp

@@ -115,7 +115,9 @@ QgsGui::~QgsGui()
 QgsGui::QgsGui()
 {
 #ifdef Q_OS_MAC
-  mNative = new QgsMacNative();
+  QgsMacNative *macNative = new QgsMacNative();
+  macNative->setIconPath( QgsApplication::iconsPath() + QStringLiteral( "qgis-icon-macos.png" ) );
+  mNative = macNative;
 #elif defined (Q_OS_WIN)
   mNative = new QgsWinNative();
 #elif defined(Q_OS_LINUX)

src/native/mac/qgsmacnative.h

@@ -29,6 +29,9 @@ class NATIVE_EXPORT QgsMacNative : public QgsNative
     explicit QgsMacNative();
     ~QgsMacNative() override;
 
+    //! reset the application icon used in the notification
+    void setIconPath( const QString &iconPath = QString() );
+
     virtual const char *currentAppLocalizedName();
     void currentAppActivateIgnoringOtherApps() override;
     void openFileExplorerAndSelectFile( const QString &path ) override;

src/native/mac/qgsmacnative.mm

@@ -42,6 +42,7 @@ - ( BOOL )userNotificationCenter:( NSUserNotificationCenter * )center shouldPres
 {
   public:
     QgsUserNotificationCenterDelegate *_qgsUserNotificationCenter;
+    NSImage *_qgisIcon;
 };
 
 QgsMacNative::QgsMacNative()
@@ -57,6 +58,11 @@ - ( BOOL )userNotificationCenter:( NSUserNotificationCenter * )center shouldPres
   delete mQgsUserNotificationCenter;
 }
 
+void QgsMacNative::setIconPath( const QString &iconPath )
+{
+  mQgsUserNotificationCenter->_qgisIcon = QtMac::toNSImage( QPixmap( iconPath ) );
+}
+
 const char *QgsMacNative::currentAppLocalizedName()
 {
   return [[[NSRunningApplication currentApplication] localizedName] UTF8String];
@@ -92,7 +98,10 @@ - ( BOOL )userNotificationCenter:( NSUserNotificationCenter * )center shouldPres
   NSImage *image = nil;
   if ( settings.image.isNull() )
   {
-    image = [[NSImage imageNamed:@"NSApplicationIcon"] retain];
+    // image application (qgis.icns) seems not to be set for now, although present in the plist
+    // whenever fixed, try following line (and remove corresponding code in QgsMacNative::QgsUserNotificationCenter)
+    // image = [[NSImage imageNamed:@"NSApplicationIcon"] retain]
+    image = mQgsUserNotificationCenter->_qgisIcon;
   }
   else
   {