GrafEdit - StartInteraction

StartInteraction

The StartInteraction function starts the real work of the selection interactor. Not only do you keep track of what is currently selected (by manipulating the MCanvasSelection* fSelection data member), but you also determine if you should start a drag operation (in case a user clicks on an object and moves it in one stroke). Note that executing the TTranslateCanvasGraphicCmd duplicates some of the work done by the TCanvasGraphicTranslatingInteractor.

  void
  TCanvasSelectionInteractor::StartInteraction ()
  {
      
      TGPoint pt = GetFirstPoint ();
      TCanvasGraphicID hit = fCanvasView->Hit (pt);
      
      if ( hit != TCanvasGraphicID::kInvalidID ) {
          if ( GetModifierKeys().IsShiftKeyDown() ) { 
              if ( fSelection->IsGraphicSelected (hit) )
                  fSelection->DeselectGraphic (hit);
              else {}
                  fSelection->SelectGraphic (hit);
                  DoBegin (*(fBinding.GetObject()));
                  }
              }
          else {          
              fSelection->DeselectAllGraphics ();
              fSelection->SelectGraphic (hit);
              DoBegin (*(fBinding.GetObject()));
          }
          fCanvasView->AdoptCurrentSelection (::CopyPointer(fSelection));
      }
      else
          fRectSelecting = true;
  }

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