Fixed issue #532. Unexpected error occurs when zoom out image.

--HG--
branch : feature

src/libs/vwidgets/vmaingraphicsview.cpp

@@ -39,6 +39,9 @@
 #include <QMouseEvent>
 #include <qmath.h>
 
+const qreal maxScale = 50.0;  // for zoom in
+const qreal minScale = 0.004; // for zoom out
+
 //---------------------------------------------------------------------------------------------------------------------
 GraphicsViewZoom::GraphicsViewZoom(QGraphicsView* view)
   : QObject(view), _view(view), _modifiers(Qt::ControlModifier), _zoom_factor_base(1.0015),
@@ -54,13 +57,19 @@ GraphicsViewZoom::GraphicsViewZoom(QGraphicsView* view)
 
 //---------------------------------------------------------------------------------------------------------------------
 void GraphicsViewZoom::gentle_zoom(double factor)
+{
+    // We need to check current scale factor because in Windows we have an error when we zoom in or zoom out to much.
+    // See issue #532: Unexpected error occurs when zoom out image.
+    // factor > 1 for zoomIn and factor < 1 for zoomOut.
+    if ((_view->transform().m11() < maxScale && factor > 1) ||
+        (_view->transform().m11() > minScale && factor < 1))
     {
         _view->scale(factor, factor);
         if (factor < 1)
         {
             // Because QGraphicsView centers the picture when it's smaller than the view. And QGraphicsView's scrolls
-      // boundaries don't allow to put any picture point at any viewport position we will provide fictive scene size.
+            // boundaries don't allow to put any picture point at any viewport position we will provide fictive scene
-      // Temporary and bigger than view, scene size will help position an image under cursor.
+            // size. Temporary and bigger than view, scene size will help position an image under cursor.
             FictiveSceneRect(_view->scene(), _view);
         }
         _view->centerOn(target_scene_pos);
@@ -72,6 +81,7 @@ void GraphicsViewZoom::gentle_zoom(double factor)
         VMainGraphicsView::NewSceneRect(_view->scene(), _view);
         emit zoomed();
     }
+}
 
 //---------------------------------------------------------------------------------------------------------------------
 // cppcheck-suppress unusedFunction
@@ -236,19 +246,29 @@ VMainGraphicsView::VMainGraphicsView(QWidget *parent)
 
 //---------------------------------------------------------------------------------------------------------------------
 void VMainGraphicsView::ZoomIn()
+{
+    // We need to check current scale factor because in Windows we have an error when we zoom in or zoom out to much.
+    // See issue #532: Unexpected error occurs when zoom out image.
+    if (this->transform().m11() < maxScale)
     {
         scale(1.1, 1.1);
         VMainGraphicsView::NewSceneRect(this->scene(), this);
         emit NewFactor(1.1);
     }
+}
 
 //---------------------------------------------------------------------------------------------------------------------
 void VMainGraphicsView::ZoomOut()
+{
+    // We need to check current scale factor because in Windows we have an error when we zoom in or zoom out to much.
+    // See issue #532: Unexpected error occurs when zoom out image.
+    if (this->transform().m11() > minScale)
     {
         scale(1.0/1.1, 1.0/1.1);
         VMainGraphicsView::NewSceneRect(this->scene(), this);
         emit NewFactor(1.0/1.1);
     }
+}
 
 //---------------------------------------------------------------------------------------------------------------------
 void VMainGraphicsView::ZoomOriginal()