Scale down the preview image to fit in the application window

On macOS the modal has some extra space around the main content
that might make it unusable with a big enough image.

include/Utils.h

@@ -33,7 +33,7 @@ ImageType
 scaleDown(uint64_t max_width, uint64_t max_height, const ImageType &source)
 {
         if (source.isNull())
-                return source;
+                return QPixmap();
 
         auto width_ratio  = (double)max_width / (double)source.width();
         auto height_ratio = (double)max_height / (double)source.height();

include/timeline/widgets/ImageItem.h

@@ -26,6 +26,10 @@
 
 #include "MatrixClient.h"
 
+namespace dialogs {
+class ImageOverlay;
+}
+
 class ImageItem : public QWidget
 {
         Q_OBJECT
@@ -75,4 +79,5 @@ private:
         mtx::events::RoomEvent<mtx::events::msg::Image> event_;
 
         QSharedPointer<MatrixClient> client_;
+        QSharedPointer<dialogs::ImageOverlay> image_dialog_;
 };

src/dialogs/PreviewUploadOverlay.cc

@@ -61,10 +61,9 @@ PreviewUploadOverlay::PreviewUploadOverlay(QWidget *parent)
 void
 PreviewUploadOverlay::init()
 {
-        auto window   = QApplication::activeWindow();
-        auto winsize  = window->frameGeometry().size();
-        auto center   = window->frameGeometry().center();
-        auto img_size = image_.size();
+        auto window  = QApplication::activeWindow();
+        auto winsize = window->frameGeometry().size();
+        auto center  = window->frameGeometry().center();
 
         fileName_.setText(QFileInfo{filePath_}.fileName());
 
@@ -87,13 +86,12 @@ PreviewUploadOverlay::init()
         if (isImage_) {
                 infoLabel_.setAlignment(Qt::AlignCenter);
 
-                // Scale image preview to the size of the current window if it is larger.
-                if ((img_size.height() * img_size.width()) > (winsize.height() * winsize.width())) {
-                        infoLabel_.setPixmap(image_.scaled(winsize, Qt::KeepAspectRatio));
-                } else {
-                        infoLabel_.setPixmap(image_);
-                        move(center.x() - (width() * 0.5), center.y() - (height() * 0.5));
-                }
+                const auto maxWidth  = winsize.width() * 0.8;
+                const auto maxHeight = winsize.height() * 0.8;
+
+                // Scale image preview to fit into the application window.
+                infoLabel_.setPixmap(utils::scaleDown<QPixmap>(maxWidth, maxHeight, image_));
+                move(center.x() - (width() * 0.5), center.y() - (height() * 0.5));
         } else {
                 infoLabel_.setAlignment(Qt::AlignLeft);
         }

src/timeline/widgets/ImageItem.cc

@@ -150,8 +150,9 @@ ImageItem::mousePressEvent(QMouseEvent *event)
         if (textRegion_.contains(event->pos())) {
                 openUrl();
         } else {
-                auto image_dialog = new dialogs::ImageOverlay(image_, this);
-                image_dialog->show();
+                image_dialog_ =
+                  QSharedPointer<dialogs::ImageOverlay>(new dialogs::ImageOverlay(image_, this));
+                image_dialog_->show();
         }
 }