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Get several entities by LC_EVENT_LBDOWN event

When user presses left mouse button and <Ctrl> key, we try to retrieve all entities at cursor position. For each found entity, we change its color to yellow/red.

...
lcEventSetProc( LC_EVENT_LBDOWN, EventProc, 0, 0 );
...
  
//-----------------------------------------------
void CALLBACK EventProc (HANDLE hEvent)
{
  int EventType;
  EventType = lcPropGetInt( hEvent, LC_PROP_EVENT_TYPE );
  switch( EventType ){
    ...
    case LC_EVENT_LBDOWN:  
      OnLBDown( hEvent );  
      break;
    ...
  }
}

//-----------------------------------------------
void OnLBDown (HANDLE hEvent)
{
  HANDLE hLcWnd, hEnt;
  int    i, nEnts, Color, Xwin, Ywin;
  BOOL   bCtrl;
  // State of Ctrl key: 1-pressed, 0-released
  bCtrl = lcPropGetInt( hEvent, LC_PROP_EVENT_INT4 ); 
  if (bCtrl){
    // graphics window handle
    hLcWnd = lcPropGetHandle( hEvent, LC_PROP_EVENT_WND );
    // get cursor coordinates (window coordinate space, pixels)
    Xwin = lcPropGetInt( hEvent, LC_PROP_EVENT_INT1 );
    Ywin = lcPropGetInt( hEvent, LC_PROP_EVENT_INT2 );
    // get entities under cursor position
    nEnts = lcWndGetEntsByPoint( hLcWnd, Xwin, Ywin, -1 );
    if (nEnts > 0){
      for (i=0; i<nEnts; ++i){
        hEnt = lcWndGetEntity( i );
        // change entity color
        Color = lcPropGetInt( hEnt, LC_PROP_ENT_COLOR );
        if (Color == RGB(255,0,0)){
          lcPropPutInt( hEnt, LC_PROP_ENT_COLOR, RGB(255,255,0) );
          lcPropPutInt( hEnt, LC_PROP_ENT_FCOLOR, RGB(255,255,0) );
        }else{
          lcPropPutInt( hEnt, LC_PROP_ENT_COLOR, RGB(255,0,0) );
          lcPropPutInt( hEnt, LC_PROP_ENT_FCOLOR, RGB(255,0,0) );
        }
      }
      lcWndGetEntity( -1 );  // free memory
      lcWndRedraw( hLcWnd );
    }
    // disable LiteCAD default actions on this event
    lcEventReturnCode( 1 );
  }
}
See Also:

Get several entities by "MouseLBDown" event (lcWndGetEntsByRect)
Get one entity by "MouseLBDown" event
Get polyline vertex by "MouseLBDown" event