Code walkthrough

• The TTile class has an additional function, ContainsPoint, that determines whether the tile contains a particular point.
• The TTilesView class mixes in the MMouseEventHandler class.
• TTilesView overrides MMouseEventHandler::MouseDown.
• TTilesView::HandleAfterConnectionToViewRoot adds a call requesting that mouse-event positions be returned in the view's local coordinate system.

bool    ContainsPoint(const TGPoint&) const;

The implementation of the TTile::ContainsPoint function simply calls the TGRect::Contains function on the TTile data member representing the bounds of the tile. TTile::ContainsPoint is implemented in the file
./TilesTutorial/02.MouseEvents/Tiles/TilesModel.C:

  bool
  TTile::ContainsPoint(const TGPoint& point) const
  {
      return fBounds.Contains(point);
  }

Mixing in MMouseEventHandler

The new code in the TTilesView header, declared in the file
./TilesTutorial/02.MouseEvents/Tiles/TilesView.h, is listed in bold below.

  // Copyright (C) 1995 Taligent, Inc. All rights reserved.
  // Mixes in MMouseEventHandler and overrides MouseDown.
  class TTilesView : public TDocumentComponentView, public MMouseEventHandler {
  public:
      // TTilesView public constructor, destructor, and macro call are unchanged.
  
      virtual bool    MouseDown(TMouseDownEvent&);
      
  protected:
      // Adds new initialization routines to this function.
      virtual void    HandleAfterConnectionToViewRoot();
      virtual void    HandleBeforeDisconnectionFromViewRoot();
      // TTilesView drawing functions and protected constructors unchanged.
  }

  // Copyright (C) 1995 Taligent, Inc. All rights reserved.
  // Return value indicates whether the event was handled.
  bool
  TTilesView::MouseDown (TMouseDownEvent& mouseDownEvent)
  {
      TileIndex whichTile; 
      
      // Gets the position of the mouse down.
      TGPoint mousePoint = mouseDownEvent.GetEventPosition();
  
      {
          // Creates a smart pointer to the model.
          const TModelPointerTo<TTilesModel> model(GetModelReference());
          
  
          // Determines which tile, if any, was clicked on.
          for (whichTile = model->GetNumTiles() - 1; whichTile >= 0; whichTile--) {
              if (model->GetTileForReading(whichTile)->ContainsPoint(mousePoint)) {
                  break;
              }
          }
          
  
          // Prints index of selected tile to the console.
          if (whichTile >= 0) {
              ::qprintf("The user clicked on tile %d.\n", whichTile);
          }
      }
  
      // The model is unlocked at the end of the scope.
      return TRUE;
  }

  // Copyright (C) 1995 Taligent, Inc. All rights reserved.
  void
  TTilesView::HandleAfterConnectionToViewRoot()
  {
      TDocumentComponentView::HandleAfterConnectionToViewRoot ();
      BuildTilesGraphicsMapToModel();
      SetAllocatedArea(TGArea(TGRect(TGPoint(0,0), TGPoint(200, 100))));
      
      // Takes a references to the local view. TViewHandle is a light-weight reference
      // to a view that can be passed between threads.
      SetCoordinateView(TViewHandle(*this));
  }