Merge pull request #8242 from 3nids/final_dpi

 [fix #17773] fix HiDPI in map canvas on mac

Author: 3nids

python/core/auto_generated/qgsmapsettings.sip.in

@@ -21,10 +21,12 @@ The rendering itself is done by QgsMapRendererJob subclasses.
 In order to set up QgsMapSettings instance, it is necessary to set at least
 few members: extent, output size and layers.
 
-QgsMapSettings and QgsMapRendererJob (+subclasses) are intended to replace
-QgsMapRenderer class that existed before QGIS 2.4. The advantage of the new
-classes is that they separate the settings from the rendering and provide
-asynchronous API for map rendering.
+Some systems use high DPI scaling that is an alternative to the traditional
+DPI scaling. The operating system provides Qt with a scaling ratio and it
+scales window, event, and desktop geometry. The Cocoa platform plugin sets
+the scaling ratio as QWindow.devicePixelRatio().
+To properly render the map on such systems, the map settings device pixel
+ratio shall be set accordingly.
 
 .. versionadded:: 2.4
 %End
@@ -58,6 +60,31 @@ Returns the size of the resulting map image
     void setOutputSize( QSize size );
 %Docstring
 Sets the size of the resulting map image
+%End
+
+    float devicePixelRatio() const;
+%Docstring
+Returns device pixel ratio
+Common values are 1 for normal-dpi displays and 2 for high-dpi "retina" displays.
+
+.. versionadded:: 3.4
+%End
+
+    void setDevicePixelRatio( float dpr );
+%Docstring
+Sets the device pixel ratio
+Common values are 1 for normal-dpi displays and 2 for high-dpi "retina" displays.
+
+.. versionadded:: 3.4
+%End
+
+    QSize deviceOutputSize() const;
+%Docstring
+Returns the device output size of the map canvas
+This is equivalent to the output size multiplicated
+by the device pixel ratio.
+
+.. versionadded:: 3.4
 %End
 
     double rotation() const;

src/core/qgsmaprenderercustompainterjob.cpp

@@ -60,14 +60,17 @@ void QgsMapRendererCustomPainterJob::start()
   prepareTime.start();
 
   // clear the background
-  mPainter->fillRect( 0, 0, mSettings.outputSize().width(), mSettings.outputSize().height(), mSettings.backgroundColor() );
+  mPainter->fillRect( 0, 0, mSettings.deviceOutputSize().width(), mSettings.deviceOutputSize().height(), mSettings.backgroundColor() );
 
   mPainter->setRenderHint( QPainter::Antialiasing, mSettings.testFlag( QgsMapSettings::Antialiasing ) );
 
 #ifndef QT_NO_DEBUG
   QPaintDevice *paintDevice = mPainter->device();
-  QString errMsg = QStringLiteral( "pre-set DPI not equal to painter's DPI (%1 vs %2)" ).arg( paintDevice->logicalDpiX() ).arg( mSettings.outputDpi() );
-  Q_ASSERT_X( qgsDoubleNear( paintDevice->logicalDpiX(), mSettings.outputDpi() ), "Job::startRender()", errMsg.toLatin1().data() );
+  QString errMsg = QStringLiteral( "pre-set DPI not equal to painter's DPI (%1 vs %2)" )
+                   .arg( paintDevice->logicalDpiX() )
+                   .arg( mSettings.outputDpi() );
+  Q_ASSERT_X( qgsDoubleNear( paintDevice->logicalDpiX(), mSettings.outputDpi() ),
+              "Job::startRender()", errMsg.toLatin1().data() );
 #endif
 
   mLabelingEngineV2.reset();

src/core/qgsmaprendererjob.cpp

@@ -313,6 +313,7 @@ LayerRenderJobs QgsMapRendererJob::prepareJobs( QPainter *painter, QgsLabelingEn
       job.cached = true;
       job.imageInitialized = true;
       job.img = new QImage( mCache->cacheImage( ml->id() ) );
+      job.img->setDevicePixelRatio( mSettings.devicePixelRatio() );
       job.renderer = nullptr;
       job.context.setPainter( nullptr );
       continue;
@@ -324,10 +325,9 @@ LayerRenderJobs QgsMapRendererJob::prepareJobs( QPainter *painter, QgsLabelingEn
     if ( mCache || !painter || needTemporaryImage( ml ) )
     {
       // Flattened image for drawing when a blending mode is set
-      QImage *mypFlattenedImage = nullptr;
-      mypFlattenedImage = new QImage( mSettings.outputSize().width(),
-                                      mSettings.outputSize().height(),
-                                      mSettings.outputImageFormat() );
+      QImage *mypFlattenedImage = new QImage( mSettings.deviceOutputSize(),
+                                              mSettings.outputImageFormat() );
+      mypFlattenedImage->setDevicePixelRatio( mSettings.devicePixelRatio() );
       if ( mypFlattenedImage->isNull() )
       {
         mErrors.append( Error( ml->id(), tr( "Insufficient memory for image %1x%2" ).arg( mSettings.outputSize().width() ).arg( mSettings.outputSize().height() ) ) );
@@ -366,6 +366,7 @@ LabelRenderJob QgsMapRendererJob::prepareLabelingJob( QPainter *painter, QgsLabe
     job.cached = true;
     job.complete = true;
     job.img = new QImage( mCache->cacheImage( LABEL_CACHE_ID ) );
+    Q_ASSERT( job.img->devicePixelRatio() == mSettings.devicePixelRatio() );
     job.context.setPainter( nullptr );
   }
   else
@@ -374,9 +375,9 @@ LabelRenderJob QgsMapRendererJob::prepareLabelingJob( QPainter *painter, QgsLabe
     {
       // Flattened image for drawing labels
       QImage *mypFlattenedImage = nullptr;
-      mypFlattenedImage = new QImage( mSettings.outputSize().width(),
-                                      mSettings.outputSize().height(),
+      mypFlattenedImage = new QImage( mSettings.deviceOutputSize(),
                                       mSettings.outputImageFormat() );
+      mypFlattenedImage->setDevicePixelRatio( mSettings.devicePixelRatio() );
       if ( mypFlattenedImage->isNull() )
       {
         mErrors.append( Error( QStringLiteral( "labels" ), tr( "Insufficient memory for label image %1x%2" ).arg( mSettings.outputSize().width() ).arg( mSettings.outputSize().height() ) ) );
@@ -447,7 +448,8 @@ void QgsMapRendererJob::cleanupLabelJob( LabelRenderJob &job )
 
 QImage QgsMapRendererJob::composeImage( const QgsMapSettings &settings, const LayerRenderJobs &jobs, const LabelRenderJob &labelJob )
 {
-  QImage image( settings.outputSize(), settings.outputImageFormat() );
+  QImage image( settings.deviceOutputSize(), settings.outputImageFormat() );
+  image.setDevicePixelRatio( settings.devicePixelRatio() );
   image.fill( settings.backgroundColor().rgba() );
 
   QPainter painter( &image );

src/core/qgsmaprenderersequentialjob.cpp

@@ -25,7 +25,8 @@ QgsMapRendererSequentialJob::QgsMapRendererSequentialJob( const QgsMapSettings &
 {
   QgsDebugMsgLevel( QStringLiteral( "SEQUENTIAL construct" ), 5 );
 
-  mImage = QImage( mSettings.outputSize(), mSettings.outputImageFormat() );
+  mImage = QImage( mSettings.deviceOutputSize(), mSettings.outputImageFormat() );
+  mImage.setDevicePixelRatio( mSettings.devicePixelRatio() );
   mImage.setDotsPerMeterX( 1000 * settings.outputDpi() / 25.4 );
   mImage.setDotsPerMeterY( 1000 * settings.outputDpi() / 25.4 );
   mImage.fill( Qt::transparent );

src/core/qgsmapsettings.cpp

@@ -146,8 +146,8 @@ void QgsMapSettings::updateDerived()
     }
   }
 
-  double myHeight = mSize.height();
-  double myWidth = mSize.width();
+  double myHeight = mSize.height() * mDevicePixelRatio;
+  double myWidth = mSize.width() * mDevicePixelRatio;
 
   if ( !myWidth || !myHeight )
   {
@@ -230,6 +230,21 @@ void QgsMapSettings::setOutputSize( QSize size )
   updateDerived();
 }
 
+float QgsMapSettings::devicePixelRatio() const
+{
+  return mDevicePixelRatio;
+}
+
+void QgsMapSettings::setDevicePixelRatio( float dpr )
+{
+  mDevicePixelRatio = dpr;
+}
+
+QSize QgsMapSettings::deviceOutputSize() const
+{
+  return outputSize() * mDevicePixelRatio;
+}
+
 double QgsMapSettings::outputDpi() const
 {
   return mDpi;

src/core/qgsmapsettings.h

@@ -48,10 +48,12 @@ class QgsMapRendererJob;
  * In order to set up QgsMapSettings instance, it is necessary to set at least
  * few members: extent, output size and layers.
  *
- * QgsMapSettings and QgsMapRendererJob (+subclasses) are intended to replace
- * QgsMapRenderer class that existed before QGIS 2.4. The advantage of the new
- * classes is that they separate the settings from the rendering and provide
- * asynchronous API for map rendering.
+ * Some systems use high DPI scaling that is an alternative to the traditional
+ * DPI scaling. The operating system provides Qt with a scaling ratio and it
+ * scales window, event, and desktop geometry. The Cocoa platform plugin sets
+ * the scaling ratio as QWindow::devicePixelRatio().
+ * To properly render the map on such systems, the map settings device pixel
+ * ratio shall be set accordingly.
  *
  * \since QGIS 2.4
  */
@@ -81,6 +83,28 @@ class CORE_EXPORT QgsMapSettings
     //! Sets the size of the resulting map image
     void setOutputSize( QSize size );
 
+    /**
+     * Returns device pixel ratio
+     * Common values are 1 for normal-dpi displays and 2 for high-dpi "retina" displays.
+     * \since QGIS 3.4
+     */
+    float devicePixelRatio() const;
+
+    /**
+     * Sets the device pixel ratio
+     * Common values are 1 for normal-dpi displays and 2 for high-dpi "retina" displays.
+     * \since QGIS 3.4
+     */
+    void setDevicePixelRatio( float dpr );
+
+    /**
+     * Returns the device output size of the map canvas
+     * This is equivalent to the output size multiplicated
+     * by the device pixel ratio.
+     * \since QGIS 3.4
+     */
+    QSize deviceOutputSize() const;
+
     /**
      * Returns the rotation of the resulting map image, in degrees clockwise.
      * \see setRotation()
@@ -403,6 +427,7 @@ class CORE_EXPORT QgsMapSettings
     double mDpi;
 
     QSize mSize;
+    float mDevicePixelRatio = 1.0;
 
     QgsRectangle mExtent;
 

src/gui/qgsmapcanvas.cpp

@@ -31,9 +31,11 @@ email                : sherman at mrcc.com
 #include <QRect>
 #include <QTextStream>
 #include <QResizeEvent>
+#include <QScreen>
 #include <QString>
 #include <QStringList>
 #include <QWheelEvent>
+#include <QWindow>
 
 #include "qgis.h"
 #include "qgssettings.h"
@@ -163,11 +165,17 @@ QgsMapCanvas::QgsMapCanvas( QWidget *parent )
 
   QSize s = viewport()->size();
   mSettings.setOutputSize( s );
+  mSettings.setDevicePixelRatio( devicePixelRatio() );
   setSceneRect( 0, 0, s.width(), s.height() );
   mScene->setSceneRect( QRectF( 0, 0, s.width(), s.height() ) );
 
   moveCanvasContents( true );
 
+  // keep device pixel ratio up to date on screen or resolution change
+  connect( window()->windowHandle(), &QWindow::screenChanged, this, [ = ]( QScreen * ) {mSettings.setDevicePixelRatio( devicePixelRatio() );} );
+  if ( window()->windowHandle() )
+    connect( window()->windowHandle()->screen(), &QScreen::physicalDotsPerInchChanged, [ = ]( qreal ) {mSettings.setDevicePixelRatio( devicePixelRatio() );} );
+
   connect( &mMapUpdateTimer, &QTimer::timeout, this, &QgsMapCanvas::mapUpdateTimeout );
   mMapUpdateTimer.setInterval( 250 );
 
@@ -682,7 +690,8 @@ QgsRectangle QgsMapCanvas::imageRect( const QImage &img, const QgsMapSettings &m
   // expects (encoding of position and size of the item)
   const QgsMapToPixel &m2p = mapSettings.mapToPixel();
   QgsPointXY topLeft = m2p.toMapCoordinates( 0, 0 );
-  double res = m2p.mapUnitsPerPixel();
+  Q_ASSERT( img.devicePixelRatio() == mapSettings.devicePixelRatio() );
+  double res = m2p.mapUnitsPerPixel() / img.devicePixelRatioF();
   QgsRectangle rect( topLeft.x(), topLeft.y(), topLeft.x() + img.width()*res, topLeft.y() - img.height()*res );
   return rect;
 }

src/gui/qgsmapcanvasmap.cpp

@@ -60,12 +60,20 @@ QRectF QgsMapCanvasMap::boundingRect() const
 
 void QgsMapCanvasMap::paint( QPainter *painter )
 {
-  int w = std::round( mItemSize.width() ) - 2, h = std::round( mItemSize.height() ) - 2; // setRect() makes the size +2 :-(
-  if ( mImage.size() != QSize( w, h ) )
+  // setRect() makes the size +2 :-(
+  int w = std::round( mItemSize.width() ) - 2;
+  int h = std::round( mItemSize.height() ) - 2;
+
+  bool scale = false;
+  if ( mImage.size() != QSize( w, h )*mImage.devicePixelRatioF() )
   {
-    QgsDebugMsg( QStringLiteral( "map paint DIFFERENT SIZE: img %1,%2  item %3,%4" ).arg( mImage.width() ).arg( mImage.height() ).arg( w ).arg( h ) );
+    QgsDebugMsg( QStringLiteral( "map paint DIFFERENT SIZE: img %1,%2  item %3,%4" )
+                 .arg( mImage.width() / mImage.devicePixelRatioF() )
+                 .arg( mImage.height() / mImage.devicePixelRatioF() )
+                 .arg( w ).arg( h ) );
     // This happens on zoom events when ::paint is called before
     // the renderer has completed
+    scale = true;
   }
 
   /*Offset between 0/0 and mRect.xMinimum/mRect.yMinimum.
@@ -83,7 +91,10 @@ void QgsMapCanvasMap::paint( QPainter *painter )
     painter->drawImage( QRectF( ul.x(), ul.y(), lr.x() - ul.x(), lr.y() - ul.y() ), imIt->first, QRect( 0, 0, imIt->first.width(), imIt->first.height() ) );
   }
 
-  painter->drawImage( QRect( 0, 0, w, h ), mImage );
+  if ( scale )
+    painter->drawImage( QRect( 0, 0, w, h ), mImage );
+  else
+    painter->drawImage( 0, 0, mImage );
 
   // For debugging:
 #if 0