Fix crash when rendering with SVG based symbols and SVG cache is filled

When the svg cache was full, any attempt to render an svg from the cache would crash QGIS. Fixes #16643
qgis · Oct 30, 2017 · 942f431 · 942f431
1 parent b3ef4da
commit 942f431
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Showing 4 changed files with 161 additions and 32 deletions.
diff --git a/src/core/symbology/qgssvgcache.cpp b/src/core/symbology/qgssvgcache.cpp
@@ -101,6 +101,8 @@ QImage QgsSvgCache::svgAsImage( const QString &file, double size, const QColor &
   fitsInCache = true;
   QgsSvgCacheEntry *currentEntry = cacheEntry( file, size, fill, stroke, strokeWidth, widthScaleFactor, fixedAspectRatio );
 
+  QImage result;
+
   //if current entry image is 0: cache image for entry
   // checks to see if image will fit into cache
   //update stats for memory usage
@@ -134,15 +136,23 @@ QImage QgsSvgCache::svgAsImage( const QString &file, double size, const QColor &
       {
         cachePicture( currentEntry, false );
       }
+
+      // ...and render cached picture to result image
+      result = imageFromCachedPicture( *currentEntry );
     }
     else
     {
       cacheImage( currentEntry );
+      result = *( currentEntry->image );
     }
     trimToMaximumSize();
   }
+  else
+  {
+    result = *( currentEntry->image );
+  }
 
-  return *( currentEntry->image );
+  return result;
 }
 
 QPicture QgsSvgCache::svgAsPicture( const QString &path, double size, const QColor &fill, const QColor &stroke, double strokeWidth,
@@ -479,47 +489,25 @@ void QgsSvgCache::cacheImage( QgsSvgCacheEntry *entry )
   delete entry->image;
   entry->image = nullptr;
 
-  bool isFixedAR = entry->fixedAspectRatio > 0;
+  QSizeF viewBoxSize;
+  QSizeF scaledSize;
+  QSize imageSize = sizeForImage( *entry, viewBoxSize, scaledSize );
 
-  QSvgRenderer r( entry->svgContent );
-  double hwRatio = 1.0;
-  if ( r.viewBoxF().width() > 0 )
-  {
-    if ( isFixedAR )
-    {
-      hwRatio = entry->fixedAspectRatio;
-    }
-    else
-    {
-      hwRatio = r.viewBoxF().height() / r.viewBoxF().width();
-    }
-  }
-  double wSize = entry->size;
-  int wImgSize = static_cast< int >( wSize );
-  if ( wImgSize < 1 )
-  {
-    wImgSize = 1;
-  }
-  double hSize = wSize * hwRatio;
-  int hImgSize = static_cast< int >( hSize );
-  if ( hImgSize < 1 )
-  {
-    hImgSize = 1;
-  }
   // cast double image sizes to int for QImage
-  QImage *image = new QImage( wImgSize, hImgSize, QImage::Format_ARGB32_Premultiplied );
+  QImage *image = new QImage( imageSize, QImage::Format_ARGB32_Premultiplied );
   image->fill( 0 ); // transparent background
 
   QPainter p( image );
-  if ( qgsDoubleNear( r.viewBoxF().width(), r.viewBoxF().height() ) )
+  QSvgRenderer r( entry->svgContent );
+  if ( qgsDoubleNear( viewBoxSize.width(), viewBoxSize.height() ) )
   {
     r.render( &p );
   }
   else
   {
-    QSizeF s( r.viewBoxF().size() );
-    s.scale( wSize, hSize, Qt::KeepAspectRatio );
-    QRectF rect( ( wImgSize - s.width() ) / 2, ( hImgSize - s.height() ) / 2, s.width(), s.height() );
+    QSizeF s( viewBoxSize );
+    s.scale( scaledSize.width(), scaledSize.height(), Qt::KeepAspectRatio );
+    QRectF rect( ( imageSize.width() - s.width() ) / 2, ( imageSize.height() - s.height() ) / 2, s.width(), s.height() );
     r.render( &p, rect );
   }
 
@@ -906,6 +894,53 @@ void QgsSvgCache::printEntryList()
   }
 }
 
+QSize QgsSvgCache::sizeForImage( const QgsSvgCacheEntry &entry, QSizeF &viewBoxSize, QSizeF &scaledSize ) const
+{
+  bool isFixedAR = entry.fixedAspectRatio > 0;
+
+  QSvgRenderer r( entry.svgContent );
+  double hwRatio = 1.0;
+  viewBoxSize = r.viewBoxF().size();
+  if ( viewBoxSize.width() > 0 )
+  {
+    if ( isFixedAR )
+    {
+      hwRatio = entry.fixedAspectRatio;
+    }
+    else
+    {
+      hwRatio = viewBoxSize.height() / viewBoxSize.width();
+    }
+  }
+
+  // cast double image sizes to int for QImage
+  scaledSize.setWidth( entry.size );
+  int wImgSize = static_cast< int >( scaledSize.width() );
+  if ( wImgSize < 1 )
+  {
+    wImgSize = 1;
+  }
+  scaledSize.setHeight( scaledSize.width() * hwRatio );
+  int hImgSize = static_cast< int >( scaledSize.height() );
+  if ( hImgSize < 1 )
+  {
+    hImgSize = 1;
+  }
+  return QSize( wImgSize, hImgSize );
+}
+
+QImage QgsSvgCache::imageFromCachedPicture( const QgsSvgCacheEntry &entry ) const
+{
+  QSizeF viewBoxSize;
+  QSizeF scaledSize;
+  QImage image( sizeForImage( entry, viewBoxSize, scaledSize ), QImage::Format_ARGB32_Premultiplied );
+  image.fill( 0 ); // transparent background
+
+  QPainter p( &image );
+  p.drawPicture( QPoint( 0, 0 ), *entry.picture );
+  return image;
+}
+
 void QgsSvgCache::trimToMaximumSize()
 {
   //only one entry in cache

diff --git a/src/core/symbology/qgssvgcache.h b/src/core/symbology/qgssvgcache.h
@@ -275,6 +275,17 @@ class CORE_EXPORT QgsSvgCache : public QObject
     //! For debugging
     void printEntryList();
 
+    /**
+     * Returns the target size (in pixels) and calculates the \a viewBoxSize
+     * for a cache \a entry.
+     */
+    QSize sizeForImage( const QgsSvgCacheEntry &entry, QSizeF &viewBoxSize, QSizeF &scaledSize ) const;
+
+    /**
+     * Returns a rendered image for a cached picture \a entry.
+     */
+    QImage imageFromCachedPicture( const QgsSvgCacheEntry &entry ) const;
+
     //! SVG content to be rendered if SVG file was not found.
     QByteArray mMissingSvg;
 

diff --git a/tests/src/core/CMakeLists.txt b/tests/src/core/CMakeLists.txt
@@ -180,6 +180,7 @@ SET(TESTS
  testqgsstatisticalsummary.cpp
  testqgsstringutils.cpp
  testqgsstyle.cpp
+ testqgssvgcache.cpp
  testqgssvgmarker.cpp
  testqgssymbol.cpp
  testqgstaskmanager.cpp

diff --git a/tests/src/core/testqgssvgcache.cpp b/tests/src/core/testqgssvgcache.cpp
@@ -0,0 +1,82 @@
+/***************************************************************************
+     testqgssvgcache.cpp
+     --------------------
+    Date                 : October 2017
+    Copyright            : (C) 2017 by Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#include "qgstest.h"
+#include <QObject>
+#include <QString>
+#include <QStringList>
+#include <QApplication>
+#include <QFileInfo>
+#include <QDir>
+#include <QDesktopServices>
+
+#include "qgssvgcache.h"
+
+/**
+ * \ingroup UnitTests
+ * This is a unit test for QgsSvgCache.
+ */
+class TestQgsSvgCache : public QObject
+{
+    Q_OBJECT
+
+  public:
+    TestQgsSvgCache() = default;
+
+  private slots:
+    void initTestCase();// will be called before the first testfunction is executed.
+    void cleanupTestCase();// will be called after the last testfunction was executed.
+    void init() {} // will be called before each testfunction is executed.
+    void cleanup() {} // will be called after every testfunction.
+    void fillCache();
+
+};
+
+
+void TestQgsSvgCache::initTestCase()
+{
+  QgsApplication::init();
+  QgsApplication::initQgis();
+}
+
+void TestQgsSvgCache::cleanupTestCase()
+{
+}
+
+void TestQgsSvgCache::fillCache()
+{
+  QgsSvgCache cache;
+  // flood cache to fill it
+  QString svgPath = TEST_DATA_DIR + QStringLiteral( "/sample_svg.svg" );
+  bool fitInCache = false;
+
+  // we loop forever, continually increasing the size of the requested
+  // svg render. The continually changing image size should quickly fill
+  // the svg cache size, forcing use of non-cached images.
+  // We break after hitting a certain threshold of non-cached images,
+  // (after testing that the result is non-null, i.e. rendered on demand,
+  // not from cache).
+  int uncached = 0;
+  for ( double size = 1000; uncached < 10; size += 100 )
+  {
+    QImage image = cache.svgAsImage( svgPath, size, QColor( 255, 0, 0 ), QColor( 0, 255, 0 ), 1, 1, fitInCache );
+    QVERIFY( !image.isNull() );
+    if ( !fitInCache )
+      uncached++;
+  }
+}
+
+
+QGSTEST_MAIN( TestQgsSvgCache )
+#include "testqgssvgcache.moc"