wxPaintEvent

wxPaintEvent

A paint event is sent when a window's contents needs to be repainted.

Please notice that in general it is impossible to change the drawing of a standard control (such as wxButton) and so you shouldn't attempt to handle paint events for them as even if it might work on some platforms, this is inherently not portable and won't work everywhere.

Derived from

wxEvent
wxObject

Include files

Event table macros

To process a paint event, use this event handler macro to direct input to a member function that takes a wxPaintEvent argument.

EVT_PAINT(func) Process a wxEVT_PAINT event.

See also

Event handling overview

Remarks

Note that In a paint event handler, the application must always create a wxPaintDC object, even if you do not use it. Otherwise, under MS Windows, refreshing for this and other windows will go wrong.

For example:

  void MyWindow::OnPaint(wxPaintEvent& event)
  {
      wxPaintDC dc(this);

      DrawMyDocument(dc);
  }

You can optimize painting by retrieving the rectangles that have been damaged and only repainting these. The rectangles are in terms of the client area, and are unscrolled, so you will need to do some calculations using the current view position to obtain logical, scrolled units.

Here is an example of using the wxRegionIterator class:

// Called when window needs to be repainted.
void MyWindow::OnPaint(wxPaintEvent& event)
{
  wxPaintDC dc(this);

  // Find Out where the window is scrolled to
  int vbX,vbY;                     // Top left corner of client
  GetViewStart(&vbX,&vbY);

  int vX,vY,vW,vH;                 // Dimensions of client area in pixels
  wxRegionIterator upd(GetUpdateRegion()); // get the update rect list

  while (upd)
  {
    vX = upd.GetX();
    vY = upd.GetY();
    vW = upd.GetW();
    vH = upd.GetH();

    // Alternatively we can do this:
    // wxRect rect(upd.GetRect());

    // Repaint this rectangle
    ...some code...

    upd ++ ;
  }
}

Members

wxPaintEvent::wxPaintEvent

wxPaintEvent(int id = 0)

Constructor.