use viewer resolution/transform override to show cropping/stretching settings

app/dialog/export/export.cpp

@@ -145,6 +145,7 @@ ExportDialog::ExportDialog(ViewerOutput *viewer_node, QWidget *parent) :
 
   connect(video_tab_->width_slider(), SIGNAL(ValueChanged(int64_t)), this, SLOT(ResolutionChanged()));
   connect(video_tab_->height_slider(), SIGNAL(ValueChanged(int64_t)), this, SLOT(ResolutionChanged()));
+  connect(video_tab_->scaling_method_combobox(), SIGNAL(currentIndexChanged(int)), this, SLOT(UpdateViewerDimensions()));
   connect(video_tab_->maintain_aspect_checkbox(), SIGNAL(toggled(bool)), this, SLOT(ResolutionChanged()));
   connect(video_tab_->codec_combobox(), SIGNAL(currentIndexChanged(int)), this, SLOT(VideoCodecChanged()));
   connect(video_tab_, SIGNAL(DisplayChanged(const QString&)), preview_viewer_, SLOT(SetOCIODisplay(const QString&)));
@@ -155,6 +156,11 @@ ExportDialog::ExportDialog(ViewerOutput *viewer_node, QWidget *parent) :
   preview_viewer_->ConnectViewerNode(viewer_node_);
   preview_viewer_->SetColorMenuEnabled(false);
   preview_viewer_->SetOCIOParameters(video_tab_->CurrentOCIODisplay(), video_tab_->CurrentOCIOView(), video_tab_->CurrentOCIOLook());
+
+  // Update renderer
+  // FIXME: This is going to be VERY slow since it will need to hash every single frame. It would be better to have a
+  //        the renderer save the map as some sort of file that this can load.
+  viewer_node_->InvalidateCache(0, viewer_node_->Length(), viewer_node_->texture_input());
 }
 
 void ExportDialog::BrowseFilename()
@@ -219,6 +225,8 @@ void ExportDialog::ResolutionChanged()
     // Enable scaling method combobox only if width/height are not equal to sequence size
     video_tab_->scaling_method_combobox()->setEnabled(!qFuzzyCompare(current_ratio, video_aspect_ratio_));
   }
+
+  UpdateViewerDimensions();
 }
 
 void ExportDialog::VideoCodecChanged()
@@ -312,3 +320,38 @@ void ExportDialog::SetDefaultFilename()
   QString file_location = QDir(doc_location).filePath("export");
   filename_edit_->setText(file_location);
 }
+
+QMatrix4x4 ExportDialog::GenerateMatrix(ExportVideoTab::ScalingMethod method, int source_width, int source_height, int dest_width, int dest_height)
+{
+  QMatrix4x4 preview_matrix;
+
+  if (method == ExportVideoTab::kStretch) {
+    return preview_matrix;
+  }
+
+  float export_ar = static_cast<float>(dest_width) / static_cast<float>(dest_height);
+  float source_ar = static_cast<float>(source_width) / static_cast<float>(source_height);
+
+  if (qFuzzyCompare(export_ar, source_ar)) {
+    return preview_matrix;
+  }
+
+  if ((export_ar > source_ar) == (method == ExportVideoTab::kFit)) {
+    preview_matrix.scale(source_ar / export_ar, 1.0F);
+  } else {
+    preview_matrix.scale(1.0F, export_ar / source_ar);
+  }
+
+  return preview_matrix;
+}
+
+void ExportDialog::UpdateViewerDimensions()
+{
+  preview_viewer_->SetOverrideSize(video_tab_->width_slider()->GetValue(), video_tab_->height_slider()->GetValue());
+
+  preview_viewer_->SetMatrix(GenerateMatrix(static_cast<ExportVideoTab::ScalingMethod>(video_tab_->scaling_method_combobox()->currentData().toInt()),
+                                            viewer_node_->video_params().width(),
+                                            viewer_node_->video_params().height(),
+                                            video_tab_->width_slider()->GetValue(),
+                                            video_tab_->height_slider()->GetValue()));
+}

app/dialog/export/export.h

@@ -22,6 +22,8 @@ private:
   void LoadPresets();
   void SetDefaultFilename();
 
+  QMatrix4x4 GenerateMatrix(ExportVideoTab::ScalingMethod method, int source_width, int source_height, int dest_width, int height);
+
   ViewerOutput* viewer_node_;
 
   QList<ExportFormat> formats_;
@@ -76,6 +78,8 @@ private slots:
 
   void VideoCodecChanged();
 
+  void UpdateViewerDimensions();
+
 };
 
 #endif // EXPORTDIALOG_H

app/dialog/export/exportvideotab.cpp

@@ -114,9 +114,9 @@ QWidget* ExportVideoTab::SetupResolutionSection()
 
   scaling_method_combobox_ = new QComboBox();
   scaling_method_combobox_->setEnabled(false);
-  scaling_method_combobox_->addItem(tr("Fit"));
-  scaling_method_combobox_->addItem(tr("Stretch"));
-  scaling_method_combobox_->addItem(tr("Crop"));
+  scaling_method_combobox_->addItem(tr("Fit"), kFit);
+  scaling_method_combobox_->addItem(tr("Stretch"), kStretch);
+  scaling_method_combobox_->addItem(tr("Crop"), kCrop);
   layout->addWidget(scaling_method_combobox_, row, 1);
 
   row++;

app/dialog/export/exportvideotab.h

@@ -15,6 +15,12 @@ class ExportVideoTab : public QWidget
 public:
   ExportVideoTab(ColorManager* color_manager, QWidget* parent = nullptr);
 
+  enum ScalingMethod {
+    kFit,
+    kStretch,
+    kCrop
+  };
+
   QComboBox* codec_combobox() const;
 
   IntegerSlider* width_slider() const;