Add a character based text height calculation method to QgsTextRenderer

qgis · Jul 8, 2020 · 573e46b · 573e46b
1 parent fd6dcf3
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diff --git a/python/core/auto_generated/textrenderer/qgstextrenderer.sip.in b/python/core/auto_generated/textrenderer/qgstextrenderer.sip.in
@@ -186,6 +186,19 @@ Returns the height of a text based on a given format.
 :param textLines: list of lines of text to calculate width from
 :param mode: draw mode
 :param fontMetrics: font metrics
+%End
+
+    static double textHeight( const QgsRenderContext &context, const QgsTextFormat &format, QChar character, bool includeEffects = false );
+%Docstring
+Returns the height of a character when rendered with the specified text ``format``.
+
+:param context: render context
+:param format: text format
+:param character: character to determine height of. If ``character`` is invalid, then the maximum character height will be returned.
+:param includeEffects: if ``True``, then the size of formatting effects such as buffers and shadows will be considered in the
+                       returned height. If ``False``, then the returned size considers the character only.
+
+.. versionadded:: 3.16
 %End
 
     static const double FONT_WORKAROUND_SCALE;

diff --git a/src/core/textrenderer/qgstextrenderer.cpp b/src/core/textrenderer/qgstextrenderer.cpp
@@ -533,6 +533,39 @@ double QgsTextRenderer::textHeight( const QgsRenderContext &context, const QgsTe
   }
 }
 
+double QgsTextRenderer::textHeight( const QgsRenderContext &context, const QgsTextFormat &format, QChar character, bool includeEffects )
+{
+  const double scaleFactor = ( context.flags() & QgsRenderContext::ApplyScalingWorkaroundForTextRendering ) ? FONT_WORKAROUND_SCALE : 1.0;
+  const QFont baseFont = format.scaledFont( context, scaleFactor );
+  const QFontMetrics fm( baseFont );
+  const double height = ( character.isNull() ? fm.height() : fm.boundingRect( character ).height() ) / scaleFactor;
+
+  if ( !includeEffects )
+    return height;
+
+  double maxExtension = 0;
+  if ( format.buffer().enabled() )
+  {
+    maxExtension += context.convertToPainterUnits( format.buffer().size(), format.buffer().sizeUnit(), format.buffer().sizeMapUnitScale() );
+  }
+  if ( format.shadow().enabled() )
+  {
+    maxExtension += context.convertToPainterUnits( format.shadow().offsetDistance(), format.shadow().offsetUnit(), format.shadow().offsetMapUnitScale() )
+                    + context.convertToPainterUnits( format.shadow().blurRadius(), format.shadow().blurRadiusUnit(), format.shadow().blurRadiusMapUnitScale() );
+  }
+  if ( format.background().enabled() )
+  {
+    maxExtension += context.convertToPainterUnits( std::fabs( format.background().offset().y() ), format.background().offsetUnit(), format.background().offsetMapUnitScale() )
+                    + context.convertToPainterUnits( format.background().strokeWidth(), format.background().strokeWidthUnit(), format.background().strokeWidthMapUnitScale() ) / 2.0;
+    if ( format.background().sizeType() == QgsTextBackgroundSettings::SizeBuffer && format.background().size().height() > 0 )
+    {
+      maxExtension += context.convertToPainterUnits( format.background().size().height(), format.background().sizeUnit(), format.background().sizeMapUnitScale() );
+    }
+  }
+
+  return height + maxExtension;
+}
+
 double QgsTextRenderer::textHeight( const QgsRenderContext &context, const QgsTextFormat &format, const QgsTextDocument &document, DrawMode mode )
 {
   //calculate max height of text lines

diff --git a/src/core/textrenderer/qgstextrenderer.h b/src/core/textrenderer/qgstextrenderer.h
@@ -199,6 +199,19 @@ class CORE_EXPORT QgsTextRenderer
     static double textHeight( const QgsRenderContext &context, const QgsTextFormat &format, const QStringList &textLines, DrawMode mode = Point,
                               QFontMetricsF *fontMetrics = nullptr );
 
+    /**
+     * Returns the height of a character when rendered with the specified text \a format.
+     *
+     * \param context render context
+     * \param format text format
+     * \param character character to determine height of. If \a character is invalid, then the maximum character height will be returned.
+     * \param includeEffects if TRUE, then the size of formatting effects such as buffers and shadows will be considered in the
+     * returned height. If FALSE, then the returned size considers the character only.
+     *
+     * \since QGIS 3.16
+     */
+    static double textHeight( const QgsRenderContext &context, const QgsTextFormat &format, QChar character, bool includeEffects = false );
+
     /**
      * Scale factor for upscaling font sizes and downscaling destination painter devices.
      *