From 905b0f8d082238aa2cc6d6b07d3b5d0575a144d2 Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Mon, 25 May 2020 16:02:30 +1000
Subject: [PATCH] Speed up message bar operations when many messages are shown

Avoid unnecessary calls to setStyleSheet, which is slow when many
message bar items exists

Refs #29698
---
 python/gui/auto_generated/qgsmessagebaritem.sip.in |  1 +
 src/gui/qgsmessagebar.cpp                          |  8 +++++++-
 src/gui/qgsmessagebar.h                            |  1 +
 src/gui/qgsmessagebaritem.cpp                      | 10 +++++++---
 src/gui/qgsmessagebaritem.h                        |  5 ++++-
 5 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/python/gui/auto_generated/qgsmessagebaritem.sip.in b/python/gui/auto_generated/qgsmessagebaritem.sip.in
index c49e19f1fce3..133452ec7c4b 100644
--- a/python/gui/auto_generated/qgsmessagebaritem.sip.in
+++ b/python/gui/auto_generated/qgsmessagebaritem.sip.in
@@ -96,6 +96,7 @@ has no effect.
 %End
 
   signals:
+
     void styleChanged( const QString &styleSheet );
 %Docstring
 emitted when the message level has changed
diff --git a/src/gui/qgsmessagebar.cpp b/src/gui/qgsmessagebar.cpp
index d0a7815d4098..36db1529d836 100644
--- a/src/gui/qgsmessagebar.cpp
+++ b/src/gui/qgsmessagebar.cpp
@@ -260,7 +260,13 @@ void QgsMessageBar::showItem( QgsMessageBarItem *item )
   }
 
   connect( mCurrentItem, &QgsMessageBarItem::styleChanged, this, &QWidget::setStyleSheet );
-  setStyleSheet( item->getStyleSheet() );
+
+  if ( item->level() != mPrevLevel )
+  {
+    setStyleSheet( item->getStyleSheet() );
+    mPrevLevel = item->level();
+  }
+
   show();
 
   emit widgetAdded( item );
diff --git a/src/gui/qgsmessagebar.h b/src/gui/qgsmessagebar.h
index f97488b890ef..79f2fbae514f 100644
--- a/src/gui/qgsmessagebar.h
+++ b/src/gui/qgsmessagebar.h
@@ -164,6 +164,7 @@ class GUI_EXPORT QgsMessageBar: public QFrame
     QTimer *mCountdownTimer = nullptr;
     QProgressBar *mCountProgress = nullptr;
     QString mCountStyleSheet;
+    Qgis::MessageLevel mPrevLevel = Qgis::MessageLevel::None;
 
   private slots:
     //! updates count of items in widget list
diff --git a/src/gui/qgsmessagebaritem.cpp b/src/gui/qgsmessagebaritem.cpp
index 8993426c9a32..8dc00ff36736 100644
--- a/src/gui/qgsmessagebaritem.cpp
+++ b/src/gui/qgsmessagebaritem.cpp
@@ -220,9 +220,13 @@ QString QgsMessageBarItem::title() const
 
 QgsMessageBarItem *QgsMessageBarItem::setLevel( Qgis::MessageLevel level )
 {
-  mLevel = level;
-  writeContent();
-  emit styleChanged( mStyleSheet );
+  if ( level != mLevel )
+  {
+    mLevel = level;
+    writeContent();
+    emit styleChanged( mStyleSheet );
+  }
+
   return this;
 }
 
diff --git a/src/gui/qgsmessagebaritem.h b/src/gui/qgsmessagebaritem.h
index b7d238fc2dfe..d6b117377207 100644
--- a/src/gui/qgsmessagebaritem.h
+++ b/src/gui/qgsmessagebaritem.h
@@ -104,7 +104,10 @@ class GUI_EXPORT QgsMessageBarItem : public QWidget
     void dismiss();
 
   signals:
-    //! emitted when the message level has changed
+
+    /**
+     * emitted when the message level has changed
+     */
     void styleChanged( const QString &styleSheet );
 
   private slots: