From 6e65b0b65d633156d38e8aefbce1eb632534a9ed Mon Sep 17 00:00:00 2001
From: Mathieu Pellerin <nirvn.asia@gmail.com>
Date: Tue, 31 Oct 2023 11:44:51 +0700
Subject: [PATCH] Fix significant project load regressions when multiple layout
 legends are present

---
 vcpkg/overlay/qgis-qt6/layout_fix.patch | 90 +++++++++++++++++++++++++
 vcpkg/overlay/qgis-qt6/portfile.cmake   |  1 +
 2 files changed, 91 insertions(+)
 create mode 100644 vcpkg/overlay/qgis-qt6/layout_fix.patch

diff --git a/vcpkg/overlay/qgis-qt6/layout_fix.patch b/vcpkg/overlay/qgis-qt6/layout_fix.patch
new file mode 100644
index 0000000000..3e4c7b9f1e
--- /dev/null
+++ b/vcpkg/overlay/qgis-qt6/layout_fix.patch
@@ -0,0 +1,90 @@
+diff --git a/src/core/layout/qgslayoutitemlegend.cpp b/src/core/layout/qgslayoutitemlegend.cpp
+index b2223d74d5d..07d3c2ebd60 100644
+--- a/src/core/layout/qgslayoutitemlegend.cpp
++++ b/src/core/layout/qgslayoutitemlegend.cpp
+@@ -75,12 +75,8 @@ QgsLayoutItemLegend::QgsLayoutItemLegend( QgsLayout *layout )
+   {
+     // NOTE -- we do NOT connect to ::refresh here, as we don't want to trigger the call to onAtlasFeature() which sets mFilterAskedForUpdate to true,
+     // causing an endless loop.
+-
+-    // TODO -- the call to QgsLayoutItem::refresh() is probably NOT required!
+-    QgsLayoutItem::refresh();
+-
+-    // (this one is definitely required)
+-    clearLegendCachedData();
++    invalidateCache();
++    update();
+   } );
+ }
+ 
+@@ -1047,25 +1043,10 @@ void QgsLayoutItemLegend::mapThemeChanged( const QString &theme )
+   mThemeName = theme;
+ 
+   // map's theme has been changed, so make sure to update the legend here
+-  if ( mLegendFilterByMap )
+-  {
+-    // legend is being filtered by map, so we need to re run the hit test too
+-    // as the style overrides may also have affected the visible symbols
+-    updateFilterByMap( false );
+-  }
+-  else
+-  {
+-    if ( mThemeName.isEmpty() )
+-    {
+-      setModelStyleOverrides( QMap<QString, QString>() );
+-    }
+-    else
+-    {
+-      // get style overrides for theme
+-      const QMap<QString, QString> overrides = mLayout->project()->mapThemeCollection()->mapThemeStyleOverrides( mThemeName );
+-      setModelStyleOverrides( overrides );
+-    }
+-  }
++
++  // legend is being filtered by map, so we need to re run the hit test too
++  // as the style overrides may also have affected the visible symbols
++  updateFilterByMap( false );
+ 
+   adjustBoxSize();
+ 
+@@ -1085,22 +1066,28 @@ void QgsLayoutItemLegend::updateFilterByMap( bool redraw )
+ 
+ void QgsLayoutItemLegend::doUpdateFilterByMap()
+ {
+-  if ( mMap )
++  // There's an incompatibility here between legend handling of linked map themes and layer style overrides vs
++  // how expression evaluation is made in legend content text. The logic below is hacked together to get
++  // all the existing unit tests passing, but these two features are incompatible with each other and fixing
++  // this is extremely non-trivial. Let's just hope no-one tries to use those features together!
++  // Ideally, all the branches below would be consistently using either "setModelStyleOverrides" (which forces
++  // a rebuild of each layer's legend, and breaks legend text expression evaluation) OR
++  // "mLegendModel->setLayerStyleOverrides" which just handles the expression updates but which doesn't correctly
++  // generate the legend content from the associated theme settings.
++  if ( mMap && !mThemeName.isEmpty() )
+   {
+-    if ( !mThemeName.isEmpty() )
+-    {
+-      // get style overrides for theme
+-      const QMap<QString, QString> overrides = mLayout->project()->mapThemeCollection()->mapThemeStyleOverrides( mThemeName );
+-      mLegendModel->setLayerStyleOverrides( overrides );
+-    }
+-    else
+-    {
+-      mLegendModel->setLayerStyleOverrides( mMap->layerStyleOverrides() );
+-    }
++    // get style overrides for theme
++    const QMap<QString, QString> overrides = mLayout->project()->mapThemeCollection()->mapThemeStyleOverrides( mThemeName );
++    setModelStyleOverrides( overrides );
++  }
++  else if ( mMap )
++  {
++    mLegendModel->setLayerStyleOverrides( mMap->layerStyleOverrides() );
+   }
+   else
++  {
+     mLegendModel->setLayerStyleOverrides( QMap<QString, QString>() );
+-
++  }
+ 
+   const bool filterByExpression = QgsLayerTreeUtils::hasLegendFilterExpression( *( mCustomLayerTree ? mCustomLayerTree.get() : mLayout->project()->layerTreeRoot() ) );
+ 
diff --git a/vcpkg/overlay/qgis-qt6/portfile.cmake b/vcpkg/overlay/qgis-qt6/portfile.cmake
index 650f9dac6a..a163a6960e 100644
--- a/vcpkg/overlay/qgis-qt6/portfile.cmake
+++ b/vcpkg/overlay/qgis-qt6/portfile.cmake
@@ -25,6 +25,7 @@ vcpkg_from_github(
         exiv2-0.28.patch # Remove when updating to QGIS 3.34
         profiler.patch # Remove when updating to QGIS 3.34
         exif_orientation_fix.patch # Remove when updating to QGIS 3.34.1
+        layout_fix.patch # Remove when updating to QGIS 3.34
 )
 
 file(REMOVE ${SOURCE_PATH}/cmake/FindQtKeychain.cmake)