fix device size in decoration item

the size should take the device pixel ration into account
fixes #20321

Author: 3nids

src/app/decorations/qgsdecorationcopyright.cpp

@@ -124,8 +124,14 @@ void QgsDecorationCopyright::render( const QgsMapSettings &mapSettings, QgsRende
   double textWidth = QgsTextRenderer::textWidth( context, mTextFormat, displayStringList, &fm );
   double textHeight = QgsTextRenderer::textHeight( context, mTextFormat, displayStringList, QgsTextRenderer::Point, &fm );
 
-  int deviceHeight = context.painter()->device()->height();
-  int deviceWidth = context.painter()->device()->width();
+  QPaintDevice *device = context.painter()->device();
+#if QT_VERSION < 0x050600
+  int deviceHeight = device->height() / device->devicePixelRatio();
+  int deviceWidth = device->width() / device->devicePixelRatio();
+#else
+  int deviceHeight = device->height() / device->devicePixelRatioF();
+  int deviceWidth = device->width() / device->devicePixelRatioF();
+#endif
 
   float xOffset( 0 ), yOffset( 0 );
 

src/app/decorations/qgsdecorationnortharrow.cpp

@@ -168,8 +168,14 @@ void QgsDecorationNorthArrow::render( const QgsMapSettings &mapSettings, QgsRend
                                      ( centerYDouble * std::cos( radiansDouble ) )
                                    ) - centerYDouble );
     // need width/height of paint device
-    int deviceHeight = context.painter()->device()->height();
-    int deviceWidth = context.painter()->device()->width();
+    QPaintDevice *device = context.painter()->device();
+#if QT_VERSION < 0x050600
+    int deviceHeight = device->height() / device->devicePixelRatio();
+    int deviceWidth = device->width() / device->devicePixelRatio();
+#else
+    int deviceHeight = device->height() / device->devicePixelRatioF();
+    int deviceWidth = device->width() / device->devicePixelRatioF();
+#endif
 
     // Set  margin according to selected units
     int xOffset = 0;

src/app/decorations/qgsdecorationscalebar.cpp

@@ -177,8 +177,14 @@ void QgsDecorationScaleBar::render( const QgsMapSettings &mapSettings, QgsRender
     return;
 
   //Get canvas dimensions
-  int deviceHeight = context.painter()->device()->height();
-  int deviceWidth = context.painter()->device()->width();
+  QPaintDevice *device = context.painter()->device();
+#if QT_VERSION < 0x050600
+  int deviceHeight = device->height() / device->devicePixelRatio();
+  int deviceWidth = device->width() / device->devicePixelRatio();
+#else
+  int deviceHeight = device->height() / device->devicePixelRatioF();
+  int deviceWidth = device->width() / device->devicePixelRatioF();
+#endif
 
   //Get map units per pixel. This can be negative at times (to do with
   //projections) and that just confuses the rest of the code in this