Avoid unnecessary font scaling by precalculating if format has a null

font size
qgis · Nov 10, 2022 · ed84780 · ed84780
1 parent e478a52
commit ed84780
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Showing 4 changed files with 29 additions and 23 deletions.
diff --git a/python/core/auto_generated/textrenderer/qgstextdocumentmetrics.sip.in b/python/core/auto_generated/textrenderer/qgstextdocumentmetrics.sip.in
@@ -37,6 +37,13 @@ The optional ``scaleFactor`` parameter can specify a font size scaling factor. I
 :py:class:`QgsTextRenderer`.FONT_WORKAROUND_SCALE and then manually calculations
 based on the resultant font metrics. Failure to do so will result in poor quality text rendering
 at small font sizes.
+%End
+
+    bool isNullFontSize() const;
+%Docstring
+Returns ``True`` if the metrics could not be calculated because the text format has a null font size.
+
+.. versionadded:: 3.30
 %End
 
     QSizeF documentSize( Qgis::TextLayoutMode mode, Qgis::TextOrientation orientation ) const;

diff --git a/src/core/textrenderer/qgstextdocumentmetrics.cpp b/src/core/textrenderer/qgstextdocumentmetrics.cpp
@@ -27,9 +27,8 @@ QgsTextDocumentMetrics QgsTextDocumentMetrics::calculateMetrics( const QgsTextDo
 {
   QgsTextDocumentMetrics res;
 
-  bool isNullSize = false;
-  const QFont font = format.scaledFont( context, scaleFactor, &isNullSize );
-  if ( isNullSize )
+  const QFont font = format.scaledFont( context, scaleFactor, &res.mIsNullSize );
+  if ( res.isNullFontSize() )
     return res;
 
   // for absolute line heights

diff --git a/src/core/textrenderer/qgstextdocumentmetrics.h b/src/core/textrenderer/qgstextdocumentmetrics.h
@@ -52,6 +52,13 @@ class CORE_EXPORT QgsTextDocumentMetrics
      */
     static QgsTextDocumentMetrics calculateMetrics( const QgsTextDocument &document, const QgsTextFormat &format, const QgsRenderContext &context, double scaleFactor = 1.0 );
 
+    /**
+     * Returns TRUE if the metrics could not be calculated because the text format has a null font size.
+     *
+     * \since QGIS 3.30
+     */
+    bool isNullFontSize() const { return mIsNullSize; }
+
     /**
      * Returns the overall size of the document.
      */
@@ -106,6 +113,8 @@ class CORE_EXPORT QgsTextDocumentMetrics
 
   private:
 
+    bool mIsNullSize = false;
+
     QSizeF mDocumentSizeLabelMode;
     QSizeF mDocumentSizePointRectMode;
     QSizeF mDocumentSizeVerticalOrientation;

diff --git a/src/core/textrenderer/qgstextrenderer.cpp b/src/core/textrenderer/qgstextrenderer.cpp
@@ -342,9 +342,7 @@ double QgsTextRenderer::drawBuffer( QgsRenderContext &context, const QgsTextRend
     referenceScaleOverride.emplace( QgsScopedRenderContextReferenceScaleOverride( context, -1.0 ) );
   }
 
-  bool isNullSize = false;
-  const QFont font = format.scaledFont( context, scaleFactor, &isNullSize );
-  if ( isNullSize )
+  if ( metrics.isNullFontSize() )
     return 0;
 
   referenceScaleOverride.reset();
@@ -516,9 +514,7 @@ void QgsTextRenderer::drawMask( QgsRenderContext &context, const QgsTextRenderer
     referenceScaleOverride.emplace( QgsScopedRenderContextReferenceScaleOverride( context, -1.0 ) );
   }
 
-  bool isNullSize = false;
-  const QFont font = format.scaledFont( context, scaleFactor, &isNullSize );
-  if ( isNullSize )
+  if ( metrics.isNullFontSize() )
     return;
 
   referenceScaleOverride.reset();
@@ -634,6 +630,7 @@ double QgsTextRenderer::textHeight( const QgsRenderContext &context, const QgsTe
 double QgsTextRenderer::textHeight( const QgsRenderContext &context, const QgsTextFormat &format, QChar character, bool includeEffects )
 {
   const double scaleFactor = calculateScaleFactorForFormat( context, format );
+
   bool isNullSize = false;
   const QFont baseFont = format.scaledFont( context, scaleFactor, &isNullSize );
   if ( isNullSize )
@@ -759,12 +756,10 @@ double QgsTextRenderer::textHeight( const QgsRenderContext &context, const QgsTe
   //calculate max height of text lines
   const double scaleFactor = calculateScaleFactorForFormat( context, format );
 
-  bool isNullSize = false;
-  format.scaledFont( context, scaleFactor, &isNullSize );
-  if ( isNullSize )
+  const QgsTextDocumentMetrics metrics = QgsTextDocumentMetrics::calculateMetrics( document, format, context, scaleFactor );
+  if ( metrics.isNullFontSize() )
     return 0;
 
-  const QgsTextDocumentMetrics metrics = QgsTextDocumentMetrics::calculateMetrics( document, format, context, scaleFactor );
   return metrics.documentSize( mode, format.orientation() ).height();
 }
 
@@ -1342,9 +1337,7 @@ void QgsTextRenderer::drawTextInternal( Qgis::TextComponent drawType,
     referenceScaleOverride.emplace( QgsScopedRenderContextReferenceScaleOverride( context, -1.0 ) );
   }
 
-  bool isNullSize = false;
-  format.scaledFont( context, fontScale, &isNullSize );
-  if ( isNullSize )
+  if ( metrics.isNullFontSize() )
     return;
 
   referenceScaleOverride.reset();
@@ -1608,11 +1601,10 @@ void QgsTextRenderer::drawTextInternalHorizontal( QgsRenderContext &context, con
         // to temporarily remove the reference scale here or we'll be applying the scaling twice
         referenceScaleOverride.emplace( QgsScopedRenderContextReferenceScaleOverride( context, -1.0 ) );
       }
-      bool isNullSize = false;
-      const QFont font = format.scaledFont( context, fontScale, &isNullSize );
+
       referenceScaleOverride.reset();
 
-      if ( !isNullSize )
+      if ( !metrics.isNullFontSize() )
       {
         textp.scale( 1 / fontScale, 1 / fontScale );
 
@@ -1692,7 +1684,8 @@ void QgsTextRenderer::drawTextInternalHorizontal( QgsRenderContext &context, con
             context.painter()->drawText( xOffset, 0, fragment.text() );
             context.painter()->scale( fontScale, fontScale );
 
-            xOffset += fragment.horizontalAdvance( fragmentFont, context, true, fontScale );
+            xOffset += metrics.fragmentHorizontalAdvance( blockIndex, fragmentIndex, mode );
+            fragmentIndex++;
           }
         }
       }
@@ -1717,9 +1710,7 @@ void QgsTextRenderer::drawTextInternalVertical( QgsRenderContext &context, const
     referenceScaleOverride.emplace( QgsScopedRenderContextReferenceScaleOverride( context, -1.0 ) );
   }
 
-  bool isNullSize = false;
-  const QFont font = format.scaledFont( context, fontScale, &isNullSize );
-  if ( isNullSize )
+  if ( metrics.isNullFontSize() )
     return;
 
   referenceScaleOverride.reset();