viewer: don't update if gizmos haven't actually changed

Minor optimization that prevents unnecessary repaints of the viewer viewport.

app/widget/viewer/viewerdisplay.cpp

@@ -97,16 +97,20 @@ const ViewerSafeMarginInfo &ViewerDisplayWidget::GetSafeMargin() const
 
 void ViewerDisplayWidget::SetSafeMargins(const ViewerSafeMarginInfo &safe_margin)
 {
-  safe_margin_ = safe_margin;
+  if (safe_margin_ != safe_margin) {
+    safe_margin_ = safe_margin;
 
-  update();
+    update();
+  }
 }
 
 void ViewerDisplayWidget::SetGizmos(Node *node)
 {
-  gizmos_ = node;
+  if (gizmos_ != node) {
+    gizmos_ = node;
 
-  update();
+    update();
+  }
 }
 
 void ViewerDisplayWidget::SetVideoParams(const VideoRenderingParams &params)

app/widget/viewer/viewersafemargininfo.h

@@ -21,6 +21,8 @@
 #ifndef VIEWERSAFEMARGININFO_H
 #define VIEWERSAFEMARGININFO_H
 
+#include <QtMath>
+
 #include "common/define.h"
 
 OLIVE_NAMESPACE_ENTER
@@ -53,6 +55,14 @@ public:
     return ratio_;
   }
 
+  bool operator==(const ViewerSafeMarginInfo& rhs) const {
+    return (enabled_ == rhs.enabled_ && qFuzzyCompare(ratio_, rhs.ratio_));
+  }
+
+  bool operator!=(const ViewerSafeMarginInfo& rhs) const {
+    return (enabled_ != rhs.enabled_ || !qFuzzyCompare(ratio_, rhs.ratio_));
+  }
+
 private:
   bool enabled_;