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Drag and Drop
[Tutorial 3 - User Interaction 2]

Currently the only way to get atomics into our simple viewer application is to use the F1 key to insert a cube. It is very easy to add code to support drag and drop functionality - the skeleton provides most of the code that we need.

• Add to AppEventHandler() in main.c, code that handles the rsFILELOAD event.

  Currently in response to the F1 key we call DffLoad() and then execute some additional code to position the loaded clump in the world. We require the same code to be executed when a clump is dropped on the view.

• For now, cut-and-paste the code that handles the rsF1 case from the HandleKeyDown() function (in win/events.c) to the rsFILELOAD case statement:

              case rsFILELOAD:
              {
  

                  RpClump *clump = DffLoad("models/cube.dff");
  

                  if (clump)
                  {
                      RwV3d v = {0.0f, 0.0f, 5.0f};
                      RwFrameTranslate(RpClumpGetFrame(clump), &v, rwCOMBINEREPLACE);
                      RpWorldAddClump(World, clump);
                  }
                  return rsEVENTPROCESSED;
  

              }
              default:
              {
  

• Compile and run your code. Drag and drop any file onto the application. You should see that a cube is created, as if we had pressed the F1 key. Clearly, next we should modify our code to use the name of the file that is passed to the application. The filename is passed as the param argument to the AppEventHandler() function.

• Add code to the rsFILELOAD case to cast the param argument to a RwChar *. Debug the application to confirm that this string is correct. Then use this string as the argument to the DffLoad() function call.

              case rsFILELOAD:
              {
                  RwChar  *s     = (RwChar *)param;
                  RpClump *clump = DffLoad(s);
                  if (clump)
                  {
                      RwV3d v = {0.0f, 0.0f, 5.0f};
                      RwFrameTranslate(RpClumpGetFrame(clump), &v, rwCOMBINEREPLACE);
                      RpWorldAddClump(World, clump);
                  }
                  return rsEVENTPROCESSED;
              }
              default:
  

• Run the code and check that you can drag-and-drop .DFF files onto the application. (In the Examples/Tutorials/Tutorial3/models folder is the banana.dff clump.)
  

Next...

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