[packagechooser] Scale screenshot

- if the screenshot is too large, scale it down
 - (doesn't react to window resizes though)

src/modules/packagechooser/PackageChooserPage.cpp

@@ -52,6 +52,37 @@ PackageChooserPage::PackageChooserPage( PackageChooserMode mode, QWidget* parent
     }
 }
 
+/** @brief size the given @p pixmap to @p size
+ * 
+ * This is "smart" in the sense that it tries to keep the image un-scaled
+ * (if it's just a little too big) and otherwise scales as needed.
+ * 
+ * Returns a copy if any modifications are done.
+ */
+static QPixmap
+smartClip( const QPixmap& pixmap, QSize size )
+{
+    auto pixSize = pixmap.size();
+    if ( ( pixSize.width() <= size.width() ) && ( pixSize.height() <= size.height() ) )
+    {
+        return pixmap;
+    }
+
+    // only slightly bigger? Trim the edges
+    constexpr int margin = 16;
+    if ( ( pixSize.width() <= size.width() + margin ) && ( pixSize.height() <= size.height() + margin ) )
+    {
+        int x = pixSize.width() <= size.width() ? 0 : ( pixSize.width() - size.width() / 2 );
+        int new_width = pixSize.width() <= size.width() ? pixSize.width() : size.width();
+        int y = pixSize.height() <= size.height() ? 0 : ( pixSize.height() - size.height() / 2 );
+        int new_height = pixSize.height() <= size.height() ? pixSize.height() : size.height();
+
+        return pixmap.copy( x, y, new_width, new_height );
+    }
+
+    return pixmap.scaled( size, Qt::KeepAspectRatio );
+}
+
 void
 PackageChooserPage::currentChanged( const QModelIndex& index )
 {
@@ -66,8 +97,17 @@ PackageChooserPage::currentChanged( const QModelIndex& index )
         const auto* model = ui->products->model();
 
         ui->productName->setText( model->data( index, PackageListModel::NameRole ).toString() );
-        ui->productScreenshot->setPixmap( model->data( index, PackageListModel::ScreenshotRole ).value< QPixmap >() );
         ui->productDescription->setText( model->data( index, PackageListModel::DescriptionRole ).toString() );
+
+        QPixmap currentScreenshot = model->data( index, PackageListModel::ScreenshotRole ).value< QPixmap >();
+        if ( currentScreenshot.isNull() )
+        {
+            ui->productScreenshot->setPixmap( m_introduction.screenshot );
+        }
+        else
+        {
+            ui->productScreenshot->setPixmap( smartClip( currentScreenshot, ui->productScreenshot->size() ) );
+        }
     }
 }