Litecad Events

Events

Event processing permits you to control user actions while the user is running your application. LiteCAD features several types of events that can be used to instantiate additional procedural code. For each of these events you create an "event procedure" in your application. It has the following syntax:

void __stdcall EventProc (
HANDLE hEvent
);

You have to define only those event procedures that you intend to use. Whenever the user performs any specified action, LiteCAD calls your previously defined corresponding procedure. Some events are manifested by setting a return value, in those cases, LiteCAD's behavior is dependant upon the return value.

These are service functions used to control events:

Function	Event
lcEventSetProc	Defines an application-defined event procedure for specific event
lcEventReturnCode	Defines return code of event procedure
lcEventsEnable	Enables or disables events generation

LiteCAD has the following types of events (defined by LC_PROP_EVENT_TYPE property):

Event type	Meaning
Mouse and keyboard
LC_EVENT_MOUSEMOVE	Window cursor position has been changed
LC_EVENT_LBDOWN	Left mouse button has been pressed
LC_EVENT_LBUP	Left mouse button has been released
LC_EVENT_LBDBLCLK	Left mouse button double click
LC_EVENT_RBDOWN	Right mouse button has been pressed
LC_EVENT_RBUP	Right mouse button has been released
LC_EVENT_SNAP	Allows a mouse to stick to specific points
LC_EVENT_KEYDOWN	Keyboard key has been pressed
View
LC_EVENT_PAINT	LiteCAD window is being redrawn
LC_EVENT_WNDVIEW	View position has been changed in LiteCAD window
LC_EVENT_FILETAB	User selects File Tab (to change active drawing in a window)
LC_EVENT_VIEWBLOCK	Window has changed active block
Entity
LC_EVENT_ADDENTITY	Graphic entity has been added
LC_EVENT_ENTPROP	Entity's property value has been changed
LC_EVENT_ENTMOVE	Entity has been moved
LC_EVENT_ENTSCALE	Entity has been scaled
LC_EVENT_ENTROTATE	Entity has been rotated
LC_EVENT_ENTMIRROR	Entity has been mirrored
LC_EVENT_ENTERASE	Entity flag "Deleted" was changed
LC_EVENT_GRIPMOVE	User has moved entity's grip
LC_EVENT_GRIPDRAG	User is dragging entity's grip
LC_EVENT_PICKENT	User clicks on entity
LC_EVENT_SELECT	Selection set has been changed
LC_EVENT_DRAWIMAGE	Draw custom images
Drawing
LC_EVENT_DRWPROP	Drawing's property value has been changed
LC_EVENT_FILE	Drawing has been loaded from a file or saved to a file
LC_EVENT_EXTENTS	Drawing's extents has been changed
Custom command
LC_EVENT_ADDCMD	LiteCAD initializes commands. Use this event to add custom commands.
LC_EVENT_CCMD	Custom command interface
LC_EVENT_WAITPOINT	Generated on mouse move while the function lcWndWaitPoint is running
Other
LC_EVENT_ADDSTR	LiteCAD initializes GUI strings
LC_EVENT_HELP	User clicks on "Help" button in LiteCAD dialog
LC_EVENT_MAGNIFIER	Magnifier property has been changed
LC_EVENT_NAVIGATOR	Navigator (aerial view) property has been changed
LC_EVENT_GRID	Coordinate grid property has been changed
LC_EVENT_OSNAP	Object snap property has been changed
LC_EVENT_PTRACK	Polar tracking property has been changed
LC_EVENT_ORTHO	"Ortho mode" property has been changed

Some events are manifested by setting a return value, in those cases, LiteCAD's behavior is dependant upon the return value.
The function lcEventReturnCode is used to set event return code.

Inside the event procedure, you can access the following event properties by using the hEvent parameter:

Property	Type	Access	Meaning
LC_PROP_EVENT_TYPE	int	R	Event type (LC_EVENT_MOUSEMOVE and other)
LC_PROP_EVENT_APPPRM1	int	R	Application-defined parameter 1
LC_PROP_EVENT_APPPRM2	handle	R	Application-defined parameter 2
LC_PROP_EVENT_WND	handle	R	LiteCAD design window
LC_PROP_EVENT_DRW	handle	R	Drawing
LC_PROP_EVENT_BLOCK	handle	R	Block
LC_PROP_EVENT_ENTITY	handle	R	Entity
LC_PROP_EVENT_HDC	handle	R	Device context
LC_PROP_EVENT_HCMD	handle	R	Object defined in a custom command
LC_PROP_EVENT_INT1 LC_PROP_EVENT_INT2 LC_PROP_EVENT_INT3 LC_PROP_EVENT_INT4 LC_PROP_EVENT_INT5	int	RW	Integer value. The meaning depends on event type.
LC_PROP_EVENT_FLOAT1 LC_PROP_EVENT_FLOAT2 LC_PROP_EVENT_FLOAT3 LC_PROP_EVENT_FLOAT4 LC_PROP_EVENT_FLOAT5 LC_PROP_EVENT_FLOAT6	float	RW	Float value. The meaning depends on event type.
LC_PROP_EVENT_STR1 LC_PROP_EVENT_STR2 LC_PROP_EVENT_STR3	string	RW	string value. The meaning depends on event type.

Code sample:

// LiteCAD event procedure
//-----------------------------------------------
void CALLBACK EventProc (HANDLE hEvent)
{
  int EventType;
  LcApplication* pApp = (LcApplication*)lcPropGetHandle( hEvent, LC_PROP_EVENT_APPPRM2 );
  if (pApp){
    EventType = lcPropGetInt( hEvent, LC_PROP_EVENT_TYPE );
    switch( EventType ){
      case LC_EVENT_MOUSEMOVE:  pApp->OnMouseMove( hEvent );  break;
      case LC_EVENT_KEYDOWN:    pApp->OnKeyDown( hEvent ); break;
	  ...
    }
  }
}

//-----------------------------------------------
bool LcApplication::Init (HINSTANCE hInst, LPCWSTR szAppDir)
{
  BOOL  bInit;
  ...
  lcEventSetProc( LC_EVENT_MOUSEMOVE, EventProc, 0, (HANDLE)this );
  lcEventSetProc( LC_EVENT_KEYDOWN, EventProc, 0, (HANDLE)this );
  ...
  bInit = lcInitialize();
  ...
}

//-----------------------------------------------
void LcApplication::OnMouseMove (HANDLE hEvent)
{
  WCHAR szBuf[256], szNum[16];
  double X, Y;
  HANDLE hLcWnd = lcPropGetHandle( hEvent, LC_PROP_EVENT_WND );

  X = lcPropGetFloat( hLcWnd, LC_PROP_WND_CURX );
  Y = lcPropGetFloat( hLcWnd, LC_PROP_WND_CURY );

  // X
  okDblToStr( X, szNum );
  swprintf( szBuf, L"X: %s", szNum );
  lcStatbarText( m_hStatBar, 1, szBuf );
  // Y
  okDblToStr( Y, szNum );
  swprintf( szBuf, L"Y: %s", szNum );
  lcStatbarText( m_hStatBar, 2, szBuf );

  lcStatbarRedraw( m_hStatBar );
}

//-----------------------------------------------
void LcApplication::OnKeyDown (HANDLE hEvent)
{
  UINT VirtKey, Flags;
  BOOL bShift, bCtrl;
  double X, Y;
  HANDLE hLcWnd, hLcDrw, hBlock;

  VirtKey = lcPropGetInt( hEvent, LC_PROP_EVENT_INT1 );
  Flags   = lcPropGetInt( hEvent, LC_PROP_EVENT_INT2 );
  bShift  = lcPropGetInt( hEvent, LC_PROP_EVENT_INT3 );
  bCtrl   = lcPropGetInt( hEvent, LC_PROP_EVENT_INT4 );
  X = lcPropGetFloat( hEvent, LC_PROP_EVENT_FLOAT1 );
  Y = lcPropGetFloat( hEvent, LC_PROP_EVENT_FLOAT2 );
  hLcWnd = lcPropGetHandle( hEvent, LC_PROP_EVENT_WND );
  hLcDrw = lcPropGetHandle( hEvent, LC_PROP_EVENT_DRW );
  hBlock = lcPropGetHandle( hEvent, LC_PROP_EVENT_BLOCK );

  if (OnKeyDown( VirtKey, Flags )){
    lcEventReturnCode( 1 );
  }
  ...
}