ENH: Mouse buttons are now binary comparable

NO_BUTTON = 0
LEFT_BUTTON = 1
MIDDLE_BUTTON = 2
RIGHT_BUTTON = 4

Charts/vtkBlockItem.cxx

@@ -36,7 +36,7 @@ vtkBlockItem::vtkBlockItem()
 {
   this->Label = NULL;
   this->MouseOver = false;
-  this->MouseButtonPressed = -1;
+  this->MouseButtonPressed = vtkContextMouseEvent::NO_BUTTON;
   this->scalarFunction = NULL;
   this->Dimensions[0]=0;
   this->Dimensions[1]=0;
@@ -172,7 +172,7 @@ bool vtkBlockItem::MouseButtonPressEvent(const vtkContextMouseEvent &mouse)
 //-----------------------------------------------------------------------------
 bool vtkBlockItem::MouseButtonReleaseEvent(const vtkContextMouseEvent &)
 {
-  this->MouseButtonPressed = -1;
+  this->MouseButtonPressed = vtkContextMouseEvent::NO_BUTTON;
   return true;
 }
 

Charts/vtkChartPie.cxx

@@ -193,7 +193,7 @@ bool vtkChartPie::MouseEnterEvent(const vtkContextMouseEvent &)
 //-----------------------------------------------------------------------------
 bool vtkChartPie::MouseMoveEvent(const vtkContextMouseEvent &mouse)
 {
-  if (mouse.Button < 0)
+  if (mouse.Button == vtkContextMouseEvent::NO_BUTTON)
     {
     this->Scene->SetDirty(true);
     this->Tooltip->SetVisible(this->LocatePointInPlots(mouse));

Charts/vtkChartXY.cxx

@@ -1021,7 +1021,7 @@ bool vtkChartXY::MouseMoveEvent(const vtkContextMouseEvent &mouse)
     // Mark the scene as dirty
     this->Scene->SetDirty(true);
     }
-  else if (mouse.Button < 0)
+  else if (mouse.Button == vtkContextMouseEvent::NO_BUTTON)
     {
     this->Scene->SetDirty(true);
     this->Tooltip->SetVisible(this->LocatePointInPlots(mouse));

Charts/vtkContextMouseEvent.h

@@ -30,9 +30,10 @@ public:
   // Description:
   // Enumeration of mouse buttons.
   enum {
-    LEFT_BUTTON = 0,
-    MIDDLE_BUTTON,
-    RIGHT_BUTTON
+    NO_BUTTON = 0,
+    LEFT_BUTTON = 1,
+    MIDDLE_BUTTON = 2,
+    RIGHT_BUTTON = 4
   };
 
   // Description:
@@ -60,7 +61,7 @@ public:
   vtkVector2i LastScreenPos;
 
   // Description:
-  // Mouse button that was pressed, using the anonymous enumeration.
+  // Mouse button that caused the event, using the anonymous enumeration.
   int Button;
 };
 //ETX

Charts/vtkContextScene.cxx

@@ -79,26 +79,26 @@ public:
           this->Target->MouseMoveEvent(x, y);
           break;
         case vtkCommand::LeftButtonPressEvent :
-          this->Target->ButtonPressEvent(0, x, y);
+          this->Target->ButtonPressEvent(vtkContextMouseEvent::LEFT_BUTTON, x, y);
           break;
         case vtkCommand::MiddleButtonPressEvent :
-          this->Target->ButtonPressEvent(1, x, y);
+          this->Target->ButtonPressEvent(vtkContextMouseEvent::MIDDLE_BUTTON, x, y);
           break;
         case vtkCommand::RightButtonPressEvent :
-          this->Target->ButtonPressEvent(2, x, y);
+          this->Target->ButtonPressEvent(vtkContextMouseEvent::RIGHT_BUTTON, x, y);
           break;
         case vtkCommand::LeftButtonReleaseEvent :
-          this->Target->ButtonReleaseEvent(0, x, y);
+          this->Target->ButtonReleaseEvent(vtkContextMouseEvent::LEFT_BUTTON, x, y);
           break;
         case vtkCommand::MiddleButtonReleaseEvent :
-          this->Target->ButtonReleaseEvent(1, x, y);
+          this->Target->ButtonReleaseEvent(vtkContextMouseEvent::MIDDLE_BUTTON, x, y);
           break;
         case vtkCommand::RightButtonReleaseEvent :
-          this->Target->ButtonReleaseEvent(2, x, y);
+          this->Target->ButtonReleaseEvent(vtkContextMouseEvent::RIGHT_BUTTON, x, y);
           break;
         case vtkCommand::MouseWheelForwardEvent :
           // There is a forward and a backward event - not clear on deltas...
-          this->Target->MouseWheelEvent(1, x, y);
+          this->Target->MouseWheelEvent(+1, x, y);
           break;
         case vtkCommand::MouseWheelBackwardEvent :
           // There is a forward and a backward event - not clear on deltas...
@@ -126,8 +126,8 @@ class vtkContextScene::Private
 public:
   Private()
     {
-    this->itemMousePressCurrent = -1;
-    this->Event.Button = -1;
+      this->itemMousePressCurrent = -1;
+    this->Event.Button = vtkContextMouseEvent::NO_BUTTON;
     this->IsDirty = true;
     }
   ~Private()
@@ -615,7 +615,7 @@ void vtkContextScene::ButtonReleaseEvent(int button, int x, int y)
         ->MouseButtonReleaseEvent(event);
     this->Storage->itemMousePressCurrent = -1;
     }
-  this->Storage->Event.Button = -1;
+  this->Storage->Event.Button = vtkContextMouseEvent::NO_BUTTON;
 }
 
 void vtkContextScene::MouseWheelEvent(int delta, int x, int y)