From 1f894bd5ba4bedd8a5afb83a2d93a0ecc81afa5a Mon Sep 17 00:00:00 2001
From: Alexander Bruy <alexander.bruy@gmail.com>
Date: Thu, 25 Jan 2024 19:40:33 +0200
Subject: [PATCH] show warning if width or height of exported image is larger
 than QPainter limit (refs #41045)

---
 src/app/qgsmapsavedialog.cpp | 15 +++++++++++++++
 src/app/qgsmapsavedialog.h   |  1 +
 src/ui/qgsmapsavedialog.ui   | 16 ++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/src/app/qgsmapsavedialog.cpp b/src/app/qgsmapsavedialog.cpp
index e1994e8f2b4e..19b2761b5834 100644
--- a/src/app/qgsmapsavedialog.cpp
+++ b/src/app/qgsmapsavedialog.cpp
@@ -161,6 +161,7 @@ void QgsMapSaveDialog::updateDpi( int dpi )
   mDpi = dpi;
 
   updateOutputSize();
+  checkOutputSize();
 }
 
 void QgsMapSaveDialog::updateOutputWidth( int width )
@@ -187,6 +188,8 @@ void QgsMapSaveDialog::updateOutputWidth( int width )
   }
 
   whileBlocking( mExtentGroupBox )->setOutputExtentFromUser( mExtent, mExtentGroupBox->currentCrs() );
+
+  checkOutputSize();
 }
 
 void QgsMapSaveDialog::updateOutputHeight( int height )
@@ -213,6 +216,8 @@ void QgsMapSaveDialog::updateOutputHeight( int height )
   }
 
   whileBlocking( mExtentGroupBox )->setOutputExtentFromUser( mExtent, mExtentGroupBox->currentCrs() );
+
+  checkOutputSize();
 }
 
 void QgsMapSaveDialog::updateExtent( const QgsRectangle &extent )
@@ -244,6 +249,7 @@ void QgsMapSaveDialog::updateExtent( const QgsRectangle &extent )
     mSize.setHeight( mSize.height() * extent.height() / mExtent.height() );
   }
   updateOutputSize();
+  checkOutputSize();
 
   mExtent = extent;
   if ( mLockAspectRatio->locked() )
@@ -270,6 +276,15 @@ void QgsMapSaveDialog::updateOutputSize()
   whileBlocking( mOutputHeightSpinBox )->setValue( mSize.height() );
 }
 
+void QgsMapSaveDialog::checkOutputSize()
+{
+  // check if image size does not exceed QPainter limitation https://doc.qt.io/qt-5/qpainter.html#limitations
+  if ( mSize.width() > 32768 || mSize.height() > 32768 )
+  {
+    mMessageBar->pushWarning( tr( "Save as image" ), tr( "Image width or height is larger than 32768 pixels. Output raster will be truncated." ) );
+  }
+}
+
 QgsRectangle QgsMapSaveDialog::extent() const
 {
   return mExtentGroupBox->outputExtent();
diff --git a/src/app/qgsmapsavedialog.h b/src/app/qgsmapsavedialog.h
index 8e59ff7d726d..b61ab20dc98f 100644
--- a/src/app/qgsmapsavedialog.h
+++ b/src/app/qgsmapsavedialog.h
@@ -92,6 +92,7 @@ class APP_EXPORT QgsMapSaveDialog: public QDialog, private Ui::QgsMapSaveDialog
 
     void lockChanged( bool locked );
     void copyToClipboard();
+    void checkOutputSize();
 
     void updateDpi( int dpi );
     void updateOutputWidth( int width );
diff --git a/src/ui/qgsmapsavedialog.ui b/src/ui/qgsmapsavedialog.ui
index 4f5fb1e41205..26e9446e2ccc 100644
--- a/src/ui/qgsmapsavedialog.ui
+++ b/src/ui/qgsmapsavedialog.ui
@@ -14,6 +14,16 @@
    <string>Save Map as Image</string>
   </property>
   <layout class="QVBoxLayout" name="verticalLayout">
+   <item>
+    <widget class="QgsMessageBar" name="mMessageBar">
+     <property name="frameShape">
+      <enum>QFrame::StyledPanel</enum>
+     </property>
+     <property name="frameShadow">
+      <enum>QFrame::Raised</enum>
+     </property>
+    </widget>
+   </item>
    <item>
     <layout class="QGridLayout" name="gridLayout" rowstretch="0,0,0,0,0,0,0,0,0,0,0,0">
      <item row="2" column="0">
@@ -401,6 +411,12 @@ Rasterizing the map is recommended when such effects are used.</string>
    <header location="global">qgscollapsiblegroupbox.h</header>
    <container>1</container>
   </customwidget>
+  <customwidget>
+   <class>QgsMessageBar</class>
+   <extends>QFrame</extends>
+   <header>qgsmessagebar.h</header>
+   <container>1</container>
+  </customwidget>
  </customwidgets>
  <tabstops>
   <tabstop>mExtentGroupBox</tabstop>