Fix translation bugs

The translation needs to be scaled relative to the zoom percentage so
we get sensible movement when dragging. Dragging is also disabled when
the image is smaller than the container widget.

Re-orders the initialisation of some variables to stop a compile
warning on Travis.

app/widget/viewer/viewersizer.cpp

@@ -105,12 +105,15 @@ void ViewerSizer::UpdateSize()
       // This container is taller than the image, scale by width
       child_size = QSize(width(), qRound(child_size.width() / aspect_ratio_));
     }
-    emit SetZoomFlag(false);
+    emit SendZoomData(false, 0);
 
   } else {
 
     float x_scale = 1.0f;
     float y_scale = 1.0f;
+    // Translation is only active if the image is bigger then the widget
+    // See ViewerDisplayWidget::SetZoomData
+    bool zoomed_in = false;
 
     int zoomed_width = qRound(width_ * static_cast<double>(zoom_) * 0.01);
     int zoomed_height = qRound(height_ * static_cast<double>(zoom_) * 0.01);
@@ -118,18 +121,20 @@ void ViewerSizer::UpdateSize()
     if (zoomed_width > width()) {
       x_scale = static_cast<double>(zoomed_width) / static_cast<double>(width());
       zoomed_width = width();
+      zoomed_in = true;
     }
 
     if (zoomed_height > height()) {
       y_scale = static_cast<double>(zoomed_height) / static_cast<double>(height());
       zoomed_height = height();
+      zoomed_in = true;
     }
 
     // Rather than make a huge surface, we still crop at our width/height and then signal a matrix
     child_matrix.scale(x_scale, y_scale, 1.0F);
 
     child_size = QSize(zoomed_width, zoomed_height);
-    emit SetZoomFlag(true);
+    emit SendZoomData(zoomed_in, zoom_);
   }
 
   widget_->resize(child_size);