Port pageItemBounds method from composer

Author: nyalldawson

src/core/layout/qgslayout.cpp

@@ -420,6 +420,32 @@ QRectF QgsLayout::layoutBounds( bool ignorePages, double margin ) const
 
 }
 
+QRectF QgsLayout::pageItemBounds( int page, bool visibleOnly ) const
+{
+  //start with an empty rectangle
+  QRectF bounds;
+
+  //add all QgsLayoutItems on page
+  const QList<QGraphicsItem *> itemList = items();
+  for ( QGraphicsItem *item : itemList )
+  {
+    const QgsLayoutItem *layoutItem = dynamic_cast<const QgsLayoutItem *>( item );
+    if ( layoutItem && layoutItem->type() != QgsLayoutItemRegistry::LayoutPage && layoutItem->page() == page )
+    {
+      if ( visibleOnly && !layoutItem->isVisible() )
+        continue;
+
+      //expand bounds with current item's bounds
+      if ( bounds.isValid() )
+        bounds = bounds.united( item->sceneBoundingRect() );
+      else
+        bounds = item->sceneBoundingRect();
+    }
+  }
+
+  return bounds;
+}
+
 void QgsLayout::addLayoutItem( QgsLayoutItem *item )
 {
   addLayoutItemPrivate( item );

src/core/layout/qgslayout.h

@@ -427,9 +427,23 @@ class CORE_EXPORT QgsLayout : public QGraphicsScene, public QgsExpressionContext
      * \param ignorePages set to true to ignore page items
      * \param margin optional marginal (in percent, e.g., 0.05 = 5% ) to add around items
      * \returns layout bounds, in layout units.
+     *
+     * \see pageItemBounds()
      */
     QRectF layoutBounds( bool ignorePages = false, double margin = 0.0 ) const;
 
+    /**
+     * Returns the bounding box of the items contained on a specified \a page.
+     * A page number of 0 represents the first page in the layout.
+     *
+     * Set \a visibleOnly to true to only include visible items.
+     *
+     * The returned bounds are in layout units.
+     *
+     * \see layoutBounds()
+     */
+    QRectF pageItemBounds( int page, bool visibleOnly = false ) const;
+
     /**
      * Adds an \a item to the layout. This should be called instead of the base class addItem()
      * method. Ownership of the item is transferred to the layout.

tests/src/core/testqgslayout.cpp

@@ -306,25 +306,23 @@ void TestQgsLayout::bounds()
   QGSCOMPARENEAR( layoutBoundsNoPage.left(), 9.85, 0.01 );
   QGSCOMPARENEAR( layoutBoundsNoPage.top(), 49.79, 0.01 );
 
-#if 0
-  QRectF page1Bounds = composition->pageItemBounds( 0, true );
+  QRectF page1Bounds = l.pageItemBounds( 0, true );
   QGSCOMPARENEAR( page1Bounds.height(), 150.36, 0.01 );
   QGSCOMPARENEAR( page1Bounds.width(), 155.72, 0.01 );
   QGSCOMPARENEAR( page1Bounds.left(), 54.43, 0.01 );
   QGSCOMPARENEAR( page1Bounds.top(), 49.79, 0.01 );
 
-  QRectF page2Bounds = composition->pageItemBounds( 1, true );
+  QRectF page2Bounds = l.pageItemBounds( 1, true );
   QGSCOMPARENEAR( page2Bounds.height(), 100.30, 0.01 );
   QGSCOMPARENEAR( page2Bounds.width(), 50.30, 0.01 );
   QGSCOMPARENEAR( page2Bounds.left(), 209.85, 0.01 );
   QGSCOMPARENEAR( page2Bounds.top(), 249.85, 0.01 );
 
-  QRectF page2BoundsWithHidden = composition->pageItemBounds( 1, false );
+  QRectF page2BoundsWithHidden = l.pageItemBounds( 1, false );
   QGSCOMPARENEAR( page2BoundsWithHidden.height(), 120.30, 0.01 );
   QGSCOMPARENEAR( page2BoundsWithHidden.width(), 250.30, 0.01 );
   QGSCOMPARENEAR( page2BoundsWithHidden.left(), 9.85, 0.01 );
   QGSCOMPARENEAR( page2BoundsWithHidden.top(), 249.85, 0.01 );
-#endif
 }
 
 void TestQgsLayout::addItem()