Show known page size when opening page properties if current page size matches

python/core/layout/qgspagesizeregistry.sip

@@ -95,6 +95,16 @@ class QgsPageSizeRegistry
  :rtype: list of QgsPageSize
 %End
 
+    QString find( const QgsLayoutSize &size ) const;
+%Docstring
+ Finds a matching page ``size`` from the registry. Returns the page size name,
+ or an empty string if no matching size could be found.
+
+ Orientation is ignored when matching page sizes, so a landscape A4 page will
+ match to the portrait A4 size in the registry.
+ :rtype: str
+%End
+
     bool decodePageSize( const QString &string, QgsPageSize &size );
 %Docstring
  Decodes a ``string`` representing a preset page size.

src/app/layout/qgslayoutpagepropertieswidget.cpp

@@ -33,8 +33,7 @@ QgsLayoutPagePropertiesWidget::QgsLayoutPagePropertiesWidget( QWidget *parent, Q
     mPageSizeComboBox->addItem( size.displayName, size.name );
   }
   mPageSizeComboBox->addItem( tr( "Custom" ) );
-  mPageSizeComboBox->setCurrentIndex( mPageSizeComboBox->count() - 1 );
-  //TODO - match to preset page sizes
+  showCurrentPageSize();
 
   mWidthSpin->setValue( mPage->pageSize().width() );
   mHeightSpin->setValue( mPage->pageSize().height() );
@@ -128,3 +127,29 @@ void QgsLayoutPagePropertiesWidget::updatePageSize()
   mPage->setPageSize( QgsLayoutSize( mWidthSpin->value(), mHeightSpin->value(), mSizeUnitsComboBox->unit() ) );
   mPage->layout()->pageCollection()->reflow();
 }
+
+void QgsLayoutPagePropertiesWidget::showCurrentPageSize()
+{
+  QgsLayoutSize paperSize = mPage->pageSize();
+  QString pageSize = QgsApplication::pageSizeRegistry()->find( paperSize );
+  if ( !pageSize.isEmpty() )
+  {
+    mPageSizeComboBox->setCurrentIndex( mPageSizeComboBox->findData( pageSize ) );
+    mWidthSpin->setEnabled( false );
+    mHeightSpin->setEnabled( false );
+    mLockAspectRatio->setEnabled( false );
+    mLockAspectRatio->setLocked( false );
+    mSizeUnitsComboBox->setEnabled( false );
+    mPageOrientationComboBox->setEnabled( true );
+  }
+  else
+  {
+    // custom
+    mPageSizeComboBox->setCurrentIndex( mPageSizeComboBox->count() - 1 );
+    mWidthSpin->setEnabled( true );
+    mHeightSpin->setEnabled( true );
+    mLockAspectRatio->setEnabled( true );
+    mSizeUnitsComboBox->setEnabled( true );
+    mPageOrientationComboBox->setEnabled( false );
+  }
+}

src/app/layout/qgslayoutpagepropertieswidget.h

@@ -53,6 +53,8 @@ class QgsLayoutPagePropertiesWidget : public QgsLayoutItemBaseWidget, private Ui
 
     QgsLayoutMeasurementConverter mConverter;
 
+    void showCurrentPageSize();
+
 };
 
 #endif // QGSLAYOUTPAGEPROPERTIESWIDGET_H

src/core/layout/qgspagesizeregistry.cpp

@@ -15,6 +15,7 @@
  ***************************************************************************/
 
 #include "qgspagesizeregistry.h"
+#include "qgslayoutmeasurementconverter.h"
 
 //
 // QgsPageSizeRegistry
@@ -83,6 +84,25 @@ QList<QgsPageSize> QgsPageSizeRegistry::find( const QString &name ) const
   return result;
 }
 
+QString QgsPageSizeRegistry::find( const QgsLayoutSize &size ) const
+{
+  //try to match to existing page size
+  QgsLayoutMeasurementConverter converter;
+  Q_FOREACH ( const QgsPageSize &pageSize, mPageSizes )
+  {
+    // convert passed size to same units
+    QgsLayoutSize xSize = converter.convert( size, pageSize.size.units() );
+
+    //consider width and height values may be exchanged
+    if ( ( qgsDoubleNear( xSize.width(), pageSize.size.width() ) && qgsDoubleNear( xSize.height(), pageSize.size.height() ) )
+         || ( qgsDoubleNear( xSize.height(), pageSize.size.width() ) && qgsDoubleNear( xSize.width(), pageSize.size.height() ) ) )
+    {
+      return pageSize.name;
+    }
+  }
+  return QString();
+}
+
 bool QgsPageSizeRegistry::decodePageSize( const QString &pageSizeName, QgsPageSize &pageSize )
 {
   QList< QgsPageSize > matches = find( pageSizeName.trimmed() );

src/core/layout/qgspagesizeregistry.h

@@ -95,6 +95,15 @@ class CORE_EXPORT QgsPageSizeRegistry
      */
     QList< QgsPageSize > find( const QString &name ) const;
 
+    /**
+     * Finds a matching page \a size from the registry. Returns the page size name,
+     * or an empty string if no matching size could be found.
+     *
+     * Orientation is ignored when matching page sizes, so a landscape A4 page will
+     * match to the portrait A4 size in the registry.
+     */
+    QString find( const QgsLayoutSize &size ) const;
+
     /**
      * Decodes a \a string representing a preset page size.
      * The decoded page size will be stored in the \a size argument.

tests/src/core/testqgspagesizeregistry.cpp

@@ -36,6 +36,7 @@ class TestQgsPageSizeRegistry : public QObject
     void instanceHasDefaultSizes(); // check that global instance is populated with default page sizes
     void addSize(); // check adding a size to the registry
     void findSize(); //find a size in the registry
+    void findBySize(); //find a matching size in the registry
     void decodePageSize(); //test decoding a page size string
 
   private:
@@ -122,6 +123,17 @@ void TestQgsPageSizeRegistry::findSize()
   QCOMPARE( results2.at( 0 ), newSize );
 }
 
+void TestQgsPageSizeRegistry::findBySize()
+{
+  QgsPageSizeRegistry *registry = QgsApplication::pageSizeRegistry();
+  QVERIFY( registry->find( QgsLayoutSize( 1, 1 ) ).isEmpty() );
+  QCOMPARE( registry->find( QgsLayoutSize( 210, 297 ) ), QStringLiteral( "A4" ) );
+  QCOMPARE( registry->find( QgsLayoutSize( 297, 210 ) ), QStringLiteral( "A4" ) );
+  QCOMPARE( registry->find( QgsLayoutSize( 125, 176 ) ), QStringLiteral( "B6" ) );
+  QCOMPARE( registry->find( QgsLayoutSize( 21, 29.7, QgsUnitTypes::LayoutCentimeters ) ), QStringLiteral( "A4" ) );
+
+}
+
 void TestQgsPageSizeRegistry::decodePageSize()
 {
   QgsPageSizeRegistry *registry = QgsApplication::pageSizeRegistry();