Manipulating an on screen object with the mouse

User Interface

1. Begin by creating a button as described in Creating a simple button that changes state.

2. Create an additional button_id for placing the object. Do not create a item in the pane button map for this; this button_id will only be used as an event, not an actual button.

3. Create a vector of PAIR to keep track of placed objects.

4. Create a PAIR variable to keep track of the current mouse position.

5. In the on_mousemove function set the variable you created in step 4. based on the current mouse position. You will likely want to scale from window coordinates to pane coordinates

   • Example: (assume m_tMouse_Position is the variable created in step 4.)

       PAIR<unsigned int> tMouse = i_tMouse_Position;
       pane_id idMouse_Pane = Find_Pane(tMouse);
       QUAD<unsigned int> qPane_Position = Get_Pane_Position(idMouse_Pane);
       PAIR<unsigned int> tMouse_TR = tMouse - qPane_Position.m_tTR;
       tMouse -= qPane_Position.m_tBL;
       double dPane_Scale = 1.0 / (double) qPane_Position.Get_Size().m_tY;
       PAIR<double> tMouse_Scaled = tMouse * dPane_Scale;
       m_tMouse_Position = tMouse_Scaled
     

6. In the on_mouse_button_down, detect when the button is in the on state, the user clicks somewhere that is not on another button, then add an event

   • Example

       // if no button has been processed and we are in a select mode, add an event to place the selected item
       if (!bProcessed && m_mMain_Pane_Buttons[TEST_BUTTON].Get_State() == 1)
       {
           m_csEvent_Queue.Set();
           m_qEvent_List.push_back(SELECTED_OBJECT_PLACE);
           m_csEvent_Queue.Unset();
       }
     

7. In the event processing loop when the placement event occurs add the current mouse position to the back of the vector you have created, and turn off the selection mode.

   • Example:

       case SELECTED_OBJECT_PLACE:
           m_vPlaced_Objects.push_back(m_tMouse_Position);
           m_mMain_Pane_Buttons[TEST_BUTTON].Set_State(0);
           break;
     

8. In gfx, draw an object at the current mouse position.

   • Example:

       if (m_mMain_Pane_Buttons[TEST_BUTTON].Get_State() == 1)
       {
           glPushMatrix();
               glColor4d(0.0,0.0,1.0,0.0);
               glTranslated(m_tMouse_Position.m_tX,m_tMouse_Position.m_tY,0.0);
               glScaled(0.05,0.05,0.05);
               glBegin(GL_TRIANGLE_FAN);
                   glVertex3d(0.0,0.0,0.0);
                   glVertexList(g_vlEllipse);
               glEnd();
           glPopMatrix();
       }
     

9. In gfx draw the list of placed objects

   • Example:

       for (std::vector<PAIR<double> >::iterator cI = m_vPlaced_Objects.begin(); cI != m_vPlaced_Objects.end(); cI++)
       {
           glPushMatrix();
               glColor4d(0.0,0.0,1.0,0.0);
               glTranslated(cI->m_tX,cI->m_tY,0.0);
               glScaled(0.05,0.05,0.05);
               glBegin(GL_TRIANGLE_FAN);
                   glVertex3d(0.0,0.0,0.0);
                   glVertexList(g_vlEllipse);
               glEnd();
           glPopMatrix();
       }