Tweak logic regarding page item margins following forced re-render

of layout items when exporting (i.e. disabling of cached item render) The old issue of semi-transparent pixels around the edge of the page had reared again. This is caused by the antialiasing while rendering the page symbol. In order to avoid this, we cater to the most common use case of having pages with a solid, borderless fill and slightly extend the fill symbol polygon outside the page by 2 pixels (determined by trial-and-error). The less common use case of having a page symbol containing a border suffers by this border being clipped by a couple of pixels, but we must address the much more common use case over this.
qgis · Dec 17, 2017 · 2b0ed50 · 2b0ed50
1 parent d3aee95
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Showing 2 changed files with 3 additions and 2 deletions.
diff --git a/src/core/layout/qgslayoutitempage.cpp b/src/core/layout/qgslayoutitempage.cpp
@@ -216,10 +216,11 @@ void QgsLayoutItemPage::draw( QgsRenderContext &context, const QStyleOptionGraph
   //Now subtract 1 pixel to prevent semi-transparent borders at edge of solid page caused by
   //anti-aliased painting. This may cause a pixel to be cropped from certain edge lines/symbols,
   //but that can be counteracted by adding a dummy transparent line symbol layer with a wider line width
-  maxBleedPixels--;
+  maxBleedPixels = std::floor( maxBleedPixels - 2 );
 
+  // round up
   QPolygonF pagePolygon = QPolygonF( QRectF( maxBleedPixels, maxBleedPixels,
-                                     ( rect().width() * scale - 2 * maxBleedPixels ), ( rect().height() * scale - 2 * maxBleedPixels ) ) );
+                                     std::ceil( rect().width() * scale ) - 2 * maxBleedPixels, std::ceil( rect().height() * scale ) - 2 * maxBleedPixels ) );
   QList<QPolygonF> rings; //empty list
 
   symbol->renderPolygon( pagePolygon, &rings, nullptr, context );

diff --git a/...ected_composerpaper_markerborder/layout/expected_composerpaper_markerborder.png b/...ected_composerpaper_markerborder/layout/expected_composerpaper_markerborder.png