Move QgsSymbolLayerUtils::createRenderContext to QgsRenderContext::fr…

…omQPainter This method is useful in many contexts outside of symbology
qgis · Jan 16, 2017 · 8a722d2 · 8a722d2
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Showing 12 changed files with 94 additions and 32 deletions.
diff --git a/doc/api_break.dox b/doc/api_break.dox
@@ -1688,6 +1688,7 @@ QgsSymbolLayerUtils (renamed from QgsSymbolLayerUtilsV2)        {#qgis_api_break
 - encodeOutputUnit() and decodeOutputUnit() were removed. QgsUnitTypes::encodeUnit() and QgsUnitTypes::decodeRenderUnit() should be used instead.
 - The signatures for wellKnownMarkerToSld() and wellKnownMarkerFromSld() were changed.
 - The symbolPreviewPixmap() customContext is now the fourth parameter
+- createRenderContext() was moved to QgsRenderContext::fromQPainter()
 
 
 QgsSymbolSelectorWidget        {#qgis_api_break_3_0_QgsSymbolSelectorWidget}

diff --git a/python/core/qgsrendercontext.sip b/python/core/qgsrendercontext.sip
@@ -51,6 +51,14 @@ class QgsRenderContext
     //! @note added in 2.4
     static QgsRenderContext fromMapSettings( const QgsMapSettings& mapSettings );
 
+    /**
+     * Creates a default render context given a pixel based QPainter destination.
+     * If no painter is specified or the painter has no device, then a default
+     * DPI of 88 will be assumed.
+     * @note added in QGIS 3.0
+     */
+    static QgsRenderContext fromQPainter( QPainter* painter );
+
     //getters
 
     QPainter* painter();

diff --git a/python/core/symbology-ng/qgssymbollayerutils.sip b/python/core/symbology-ng/qgssymbollayerutils.sip
@@ -430,9 +430,6 @@ class QgsSymbolLayerUtils
     /** Returns scale factor painter units -> map units*/
     static double mapUnitScaleFactor( const QgsRenderContext& c, QgsUnitTypes::RenderUnit u, const QgsMapUnitScale& scale = QgsMapUnitScale() );
 
-    /** Creates a render context for a pixel based device*/
-    static QgsRenderContext createRenderContext( QPainter* p );
-
     /** Multiplies opacity of image pixel values with a (global) transparency value*/
     static void multiplyImageOpacity( QImage* image, qreal alpha );
 

diff --git a/src/core/qgsrendercontext.cpp b/src/core/qgsrendercontext.cpp
@@ -88,6 +88,22 @@ QgsRenderContext::~QgsRenderContext()
   mFeatureFilterProvider = nullptr;
 }
 
+QgsRenderContext QgsRenderContext::fromQPainter( QPainter* painter )
+{
+  QgsRenderContext context;
+  context.setPainter( painter );
+  context.setRasterScaleFactor( 1.0 );
+  if ( painter && painter->device() )
+  {
+    context.setScaleFactor( painter->device()->logicalDpiX() / 25.4 );
+  }
+  else
+  {
+    context.setScaleFactor( 3.465 ); //assume 88 dpi as standard value
+  }
+  return context;
+}
+
 void QgsRenderContext::setFlags( QgsRenderContext::Flags flags )
 {
   mFlags = flags;

diff --git a/src/core/qgsrendercontext.h b/src/core/qgsrendercontext.h
@@ -93,6 +93,14 @@ class CORE_EXPORT QgsRenderContext
     //! @note added in 2.4
     static QgsRenderContext fromMapSettings( const QgsMapSettings& mapSettings );
 
+    /**
+     * Creates a default render context given a pixel based QPainter destination.
+     * If no painter is specified or the painter has no device, then a default
+     * DPI of 88 will be assumed.
+     * @note added in QGIS 3.0
+     */
+    static QgsRenderContext fromQPainter( QPainter* painter );
+
     //getters
 
     QPainter* painter() {return mPainter;}

diff --git a/src/core/symbology-ng/qgssymbol.cpp b/src/core/symbology-ng/qgssymbol.cpp
@@ -447,7 +447,7 @@ QColor QgsSymbol::color() const
 
 void QgsSymbol::drawPreviewIcon( QPainter* painter, QSize size, QgsRenderContext* customContext )
 {
-  QgsRenderContext context = customContext ? *customContext : QgsSymbolLayerUtils::createRenderContext( painter );
+  QgsRenderContext context = customContext ? *customContext : QgsRenderContext::fromQPainter( painter );
   context.setForceVectorOutput( true );
   QgsSymbolRenderContext symbolContext( context, outputUnit(), mAlpha, false, mRenderHints, nullptr, QgsFields(), mapUnitScale() );
 
@@ -526,7 +526,7 @@ QImage QgsSymbol::bigSymbolPreviewImage( QgsExpressionContext* expressionContext
     p.drawLine( 50, 0, 50, 100 );
   }
 
-  QgsRenderContext context = QgsSymbolLayerUtils::createRenderContext( &p );
+  QgsRenderContext context = QgsRenderContext::fromQPainter( &p );
   if ( expressionContext )
     context.setExpressionContext( *expressionContext );
 

diff --git a/src/core/symbology-ng/qgssymbollayerutils.cpp b/src/core/symbology-ng/qgssymbollayerutils.cpp
@@ -626,7 +626,7 @@ QPicture QgsSymbolLayerUtils::symbolLayerPreviewPicture( QgsSymbolLayer* layer,
   QPainter painter;
   painter.begin( &picture );
   painter.setRenderHint( QPainter::Antialiasing );
-  QgsRenderContext renderContext = createRenderContext( &painter );
+  QgsRenderContext renderContext = QgsRenderContext::fromQPainter( &painter );
   renderContext.setForceVectorOutput( true );
   QgsSymbolRenderContext symbolContext( renderContext, units, 1.0, false, 0, nullptr, QgsFields(), scale );
   layer->drawPreviewIcon( symbolContext, size );
@@ -641,7 +641,7 @@ QIcon QgsSymbolLayerUtils::symbolLayerPreviewIcon( QgsSymbolLayer* layer, QgsUni
   QPainter painter;
   painter.begin( &pixmap );
   painter.setRenderHint( QPainter::Antialiasing );
-  QgsRenderContext renderContext = createRenderContext( &painter );
+  QgsRenderContext renderContext = QgsRenderContext::fromQPainter( &painter );
   QgsSymbolRenderContext symbolContext( renderContext, u, 1.0, false, 0, nullptr, QgsFields(), scale );
   layer->drawPreviewIcon( symbolContext, size );
   painter.end();
@@ -3468,22 +3468,6 @@ double QgsSymbolLayerUtils::mapUnitScaleFactor( const QgsRenderContext &c, QgsUn
   return 1.0;
 }
 
-QgsRenderContext QgsSymbolLayerUtils::createRenderContext( QPainter* p )
-{
-  QgsRenderContext context;
-  context.setPainter( p );
-  context.setRasterScaleFactor( 1.0 );
-  if ( p && p->device() )
-  {
-    context.setScaleFactor( p->device()->logicalDpiX() / 25.4 );
-  }
-  else
-  {
-    context.setScaleFactor( 3.465 ); //assume 88 dpi as standard value
-  }
-  return context;
-}
-
 void QgsSymbolLayerUtils::multiplyImageOpacity( QImage* image, qreal alpha )
 {
   if ( !image )

diff --git a/src/core/symbology-ng/qgssymbollayerutils.h b/src/core/symbology-ng/qgssymbollayerutils.h
@@ -508,9 +508,6 @@ class CORE_EXPORT QgsSymbolLayerUtils
     //! Returns scale factor painter units -> map units
     static double mapUnitScaleFactor( const QgsRenderContext& c, QgsUnitTypes::RenderUnit u, const QgsMapUnitScale& scale = QgsMapUnitScale() );
 
-    //! Creates a render context for a pixel based device
-    static QgsRenderContext createRenderContext( QPainter* p );
-
     //! Multiplies opacity of image pixel values with a (global) transparency value
     static void multiplyImageOpacity( QImage* image, qreal alpha );
 

diff --git a/src/gui/effects/qgseffectstackpropertieswidget.cpp b/src/gui/effects/qgseffectstackpropertieswidget.cpp
@@ -212,7 +212,7 @@ void QgsEffectStackPropertiesWidget::updatePreview()
   previewImage.fill( Qt::transparent );
   painter.begin( &previewImage );
   painter.setRenderHint( QPainter::Antialiasing );
-  QgsRenderContext context = QgsSymbolLayerUtils::createRenderContext( &painter );
+  QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
   if ( !mPreviewPicture )
   {
     QPicture previewPic;

diff --git a/tests/src/core/testqgspainteffect.cpp b/tests/src/core/testqgspainteffect.cpp
@@ -336,7 +336,7 @@ void TestQgsPaintEffect::drawSource()
 
   QPainter painter;
   painter.begin( &image );
-  QgsRenderContext context = QgsSymbolLayerUtils::createRenderContext( &painter );
+  QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
 
   effect = new QgsDrawSourceEffect();
   effect->render( *mPicture, context );
@@ -410,7 +410,7 @@ void TestQgsPaintEffect::blur()
   image.fill( Qt::transparent );
   QPainter painter;
   painter.begin( &image );
-  QgsRenderContext context = QgsSymbolLayerUtils::createRenderContext( &painter );
+  QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
 
   effect = new QgsBlurEffect();
   effect->render( *mPicture, context );
@@ -508,7 +508,7 @@ void TestQgsPaintEffect::dropShadow()
   image.fill( Qt::transparent );
   QPainter painter;
   painter.begin( &image );
-  QgsRenderContext context = QgsSymbolLayerUtils::createRenderContext( &painter );
+  QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
 
   effect = new QgsDropShadowEffect();
   effect->render( *mPicture, context );
@@ -611,7 +611,7 @@ void TestQgsPaintEffect::glow()
   image.fill( Qt::transparent );
   QPainter painter;
   painter.begin( &image );
-  QgsRenderContext context = QgsSymbolLayerUtils::createRenderContext( &painter );
+  QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
 
   effect = new QgsOuterGlowEffect();
   effect->setSpread( 20 );
@@ -673,7 +673,7 @@ void TestQgsPaintEffect::stack()
   image.fill( Qt::transparent );
   QPainter painter;
   painter.begin( &image );
-  QgsRenderContext context = QgsSymbolLayerUtils::createRenderContext( &painter );
+  QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
 
   effect = new QgsEffectStack();
   QgsBlurEffect* blur = new QgsBlurEffect();

diff --git a/tests/src/python/CMakeLists.txt b/tests/src/python/CMakeLists.txt
@@ -87,6 +87,7 @@ ADD_PYTHON_TEST(PyQgsRasterColorRampShader test_qgsrastercolorrampshader.py)
 ADD_PYTHON_TEST(PyQgsRectangle test_qgsrectangle.py)
 ADD_PYTHON_TEST(PyQgsRelation test_qgsrelation.py)
 ADD_PYTHON_TEST(PyQgsRelationManager test_qgsrelationmanager.py)
+ADD_PYTHON_TEST(PyQgsRenderContext test_qgsrendercontext.py)
 ADD_PYTHON_TEST(PyQgsRenderer test_qgsrenderer.py)
 ADD_PYTHON_TEST(PyQgsRulebasedRenderer test_qgsrulebasedrenderer.py)
 ADD_PYTHON_TEST(PyQgsSingleSymbolRenderer test_qgssinglesymbolrenderer.py)

diff --git a/tests/src/python/test_qgsrendercontext.py b/tests/src/python/test_qgsrendercontext.py
@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+"""QGIS Unit tests for QgsRenderContext.
+
+.. note:: This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+"""
+__author__ = 'Nyall Dawson'
+__date__ = '16/01/2017'
+__copyright__ = 'Copyright 2017, The QGIS Project'
+# This will get replaced with a git SHA1 when you do a git archive
+__revision__ = '$Format:%H$'
+
+import qgis  # NOQA
+
+from qgis.core import QgsRenderContext
+from qgis.PyQt.QtGui import QPainter, QImage
+from qgis.testing import unittest
+
+
+class TestQgsRenderContext(unittest.TestCase):
+
+    def testFromQPainter(self):
+        """ test QgsRenderContext.fromQPainter """
+
+        # no painter
+        c = QgsRenderContext.fromQPainter(None)
+        self.assertFalse(c.painter())
+        # assuming 88 dpi as fallback
+        self.assertAlmostEqual(c.scaleFactor(), 88 / 25.4, 3)
+
+        # no painter destination
+        p = QPainter()
+        c = QgsRenderContext.fromQPainter(p)
+        self.assertEqual(c.painter(), p)
+        self.assertAlmostEqual(c.scaleFactor(), 88 / 25.4, 3)
+
+        im = QImage(1000, 600, QImage.Format_RGB32)
+        dots_per_m = 300 / 25.4 * 1000 # 300 dpi to dots per m
+        im.setDotsPerMeterX(dots_per_m)
+        im.setDotsPerMeterY(dots_per_m)
+        p = QPainter(im)
+        c = QgsRenderContext.fromQPainter(p)
+        self.assertEqual(c.painter(), p)
+        self.assertAlmostEqual(c.scaleFactor(), dots_per_m / 1000, 3) # scaleFactor should be pixels/mm
+
+
+if __name__ == '__main__':
+    unittest.main()