qt: do not notify comparison key change by default in `TextureProviderObserver`

Although it is not as rapid as size change (layer resize case), comparison key
may still change often. Now that we have a property to enable notify all
changes, we can make comparison key changes not notified by default.

modules/gui/qt/util/textureproviderobserver.cpp

@@ -282,8 +282,16 @@ void TextureProviderObserver::updateProperties()
                 // Comparison key
                 const qint64 comparisonKey = texture->comparisonKey();
 
-                if (m_comparisonKey.exchange(comparisonKey, memoryOrder) != comparisonKey)
-                    emit comparisonKeyChanged(comparisonKey);
+                if (notifyAllChanges)
+                {
+                    if (m_comparisonKey.exchange(comparisonKey, memoryOrder) != comparisonKey) {
+                        emit comparisonKeyChanged(comparisonKey);
+                    }
+                }
+                else
+                {
+                    m_comparisonKey.store(comparisonKey, memoryOrder);
+                }
             }
 
             return;

modules/gui/qt/util/textureproviderobserver.hpp

@@ -56,6 +56,7 @@ class TextureProviderObserver : public QObject
     Q_PROPERTY(QSize textureSize READ textureSize NOTIFY textureSizeChanged FINAL) // Scene graph texture size
     Q_PROPERTY(QSize nativeTextureSize READ nativeTextureSize NOTIFY nativeTextureSizeChanged FINAL) // Native texture size (e.g. for atlas textures, the atlas size)
     Q_PROPERTY(QRectF normalizedTextureSubRect READ normalizedTextureSubRect NOTIFY normalizedTextureSubRectChanged FINAL)
+    Q_PROPERTY(qint64 comparisonKey READ comparisonKey NOTIFY comparisonKeyChanged FINAL)
 
     // NOTE: Since it is not expected that these properties change rapidly, they have notify signals.
     //       These signals may be emitted in the rendering thread, thus if the connection is auto
@@ -64,7 +65,6 @@ class TextureProviderObserver : public QObject
     Q_PROPERTY(bool hasMipmaps READ hasMipmaps NOTIFY hasMipmapsChanged FINAL)
     Q_PROPERTY(bool isAtlasTexture READ isAtlasTexture NOTIFY isAtlasTextureChanged FINAL)
     Q_PROPERTY(bool isValid READ isValid NOTIFY isValidChanged FINAL) // whether a texture is provided or not
-    Q_PROPERTY(qint64 comparisonKey READ comparisonKey NOTIFY comparisonKeyChanged FINAL)
 
 public:
     explicit TextureProviderObserver(QObject *parent = nullptr);