Properly fix translation errors in viewer

Original fix was wrong, this sorts it out I think. Delta values had to
be doubled as we're in Clip space (I think) and the matrix
multiplication order had to be swapped around.

Updated one of the signla/slot pairs to be simpler as we no longer need
to pass the zoom percentage back and forth.

app/widget/viewer/viewer.cpp

@@ -79,7 +79,7 @@ ViewerWidget::ViewerWidget(QWidget *parent) :
   connect(display_widget_, &ViewerDisplayWidget::ColorProcessorChanged, this, &ViewerWidget::ColorProcessorChanged);
   connect(display_widget_, &ViewerDisplayWidget::ColorManagerChanged, this, &ViewerWidget::ColorManagerChanged);
   connect(sizer_, &ViewerSizer::RequestMatrix, display_widget_, &ViewerDisplayWidget::SetMatrixZoom);
-  connect(sizer_, &ViewerSizer::SendZoomData, display_widget_, &ViewerDisplayWidget::SetZoomData);
+  connect(sizer_, &ViewerSizer::IsZoomed, display_widget_, &ViewerDisplayWidget::IsZoomed);
   sizer_->SetWidget(display_widget_);
 
   // Create waveform view when audio is connected and video isn't

app/widget/viewer/viewerdisplay.cpp

@@ -49,8 +49,7 @@ ViewerDisplayWidget::ViewerDisplayWidget(QWidget *parent) :
   gizmos_(nullptr),
   gizmo_click_(false),
   last_loaded_buffer_(nullptr),
-  zoomed_(false),
-  zoom_multiplier_(1.0)
+  zoomed_(false)
 {
   connect(Core::instance(), &Core::ToolChanged, this, &ViewerDisplayWidget::ToolChanged);
 
@@ -74,17 +73,13 @@ void ViewerDisplayWidget::SetMatrixZoom(const QMatrix4x4 &mat)
   update();
 }
 
-void ViewerDisplayWidget::SetZoomData(bool flag, int percent)
+void ViewerDisplayWidget::IsZoomed(bool flag)
 {
   zoomed_ = flag;
-  // If the image is smaller than the conainer widget we disable translation
+  // If the image is smaller than the container widget we disable translation
   if (!flag) {
     QMatrix4x4 mat;
     SetMatrixTranslate(mat);
-    zoom_multiplier_ = 1.0f;
-  }
-  else {
-    zoom_multiplier_ = 1.0 / (static_cast<double>(percent) * 0.01);
   }
 }
 
@@ -102,7 +97,7 @@ void ViewerDisplayWidget::ToolChanged(Tool::Item tool)
 QMatrix4x4 ViewerDisplayWidget::GetCompleteMatrix()
 {
   QMatrix4x4 mat;
-  return scale_matrix_ * translate_matrix_ * mat;
+  return translate_matrix_ * scale_matrix_ * mat;
 }
 
 void ViewerDisplayWidget::SetSignalCursorColorEnabled(bool e)
@@ -212,9 +207,9 @@ void ViewerDisplayWidget::mouseMoveEvent(QMouseEvent *event)
   // Only allow translation if the image is larger than the container widget
   if ((event->buttons() & Qt::MiddleButton || hand_tool_) && zoomed_) {
     QPointF delta = event->pos() - position_;
-    // scale delta to widget size and zoom level
-    delta.setX(zoom_multiplier_ * delta.x() / width());
-    delta.setY(zoom_multiplier_ * delta.y() / height());
+    // scale delta to widget size
+    delta.setX(2 * delta.x() / width());
+    delta.setY(2 * delta.y() / height());
 
     QMatrix4x4 mat;
     mat = GetMatrixTranslate();

app/widget/viewer/viewerdisplay.h

@@ -117,7 +117,7 @@ public slots:
    */
   void SetImage(FramePtr in_buffer);
 
-  void SetZoomData(bool flag, int percent);
+  void IsZoomed(bool flag);
 
   void ToolChanged(Tool::Item tool);
 
@@ -207,11 +207,6 @@ private:
    */
   bool zoomed_;
 
-  /**
-   * @brief Scale the translation so the image sticks to the mouse and we get sensible movement
-   */
-  double zoom_multiplier_;
-
   /**
    * @brief position of mouse to calculate delta from.
    */

app/widget/viewer/viewersizer.cpp

@@ -105,7 +105,7 @@ void ViewerSizer::UpdateSize()
       // This container is taller than the image, scale by width
       child_size = QSize(width(), qRound(child_size.width() / aspect_ratio_));
     }
-    emit SendZoomData(false, 0);
+    emit IsZoomed(false);
 
   } else {
 
@@ -134,7 +134,7 @@ void ViewerSizer::UpdateSize()
     child_matrix.scale(x_scale, y_scale, 1.0F);
 
     child_size = QSize(zoomed_width, zoomed_height);
-    emit SendZoomData(zoomed_in, zoom_);
+    emit IsZoomed(zoomed_in);
   }
 
   widget_->resize(child_size);

app/widget/viewer/viewersizer.h

@@ -65,7 +65,7 @@ public:
 
 signals:
   void RequestMatrix(const QMatrix4x4& matrix);
-  void SendZoomData(bool flag, int percent);
+  void IsZoomed(bool flag);
 
 protected:
   /**