From afc2d008fa61c55feb4f720de9c4a1834f6145ba Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Wed, 11 Jun 2025 13:37:00 +1000
Subject: [PATCH] Only draw source once if forcing vector and any part of stack
 requires raster

Avoids multiple stacked sources when forcing vector outputs
---
 src/core/effects/qgseffectstack.cpp | 21 +++++++++++++++++++++
 src/core/effects/qgspainteffect.h   |  1 +
 2 files changed, 22 insertions(+)

diff --git a/src/core/effects/qgseffectstack.cpp b/src/core/effects/qgseffectstack.cpp
index 4857b9aebc7..0edf4d9fc02 100644
--- a/src/core/effects/qgseffectstack.cpp
+++ b/src/core/effects/qgseffectstack.cpp
@@ -94,6 +94,27 @@ void QgsEffectStack::draw( QgsRenderContext &context )
 {
   QPainter *destPainter = context.painter();
 
+  if ( context.rasterizedRenderingPolicy() == Qgis::RasterizedRenderingPolicy::ForceVector )
+  {
+    // can we render this stack if we're forcing vectors?
+    bool requiresRasterization = false;
+    for ( const QgsPaintEffect *effect : std::as_const( mEffectList ) )
+    {
+      if ( effect->enabled() && effect->flags().testFlag( Qgis::PaintEffectFlag::RequiresRasterization ) )
+      {
+        requiresRasterization = true;
+        break;
+      }
+    }
+
+    if ( requiresRasterization )
+    {
+      //just draw unmodified source, we can't render this effect stack when forcing vectors
+      drawSource( *context.painter() );
+    }
+    return;
+  }
+
   //first, we build up a list of rendered effects
   //we do this moving backwards through the stack, so that each effect's results
   //becomes the source of the previous effect
diff --git a/src/core/effects/qgspainteffect.h b/src/core/effects/qgspainteffect.h
index 1d38684bba9..d03621ccc0c 100644
--- a/src/core/effects/qgspainteffect.h
+++ b/src/core/effects/qgspainteffect.h
@@ -19,6 +19,7 @@
 
 #include "qgis_core.h"
 #include "qgis_sip.h"
+#include "qgis.h"
 #include <QPainter>
 #include <QDomDocument>
 #include <QDomElement>