.. include:: headings.inc


.. _device contexts:

===============================================
|phoenix_title|  **Device Contexts**
===============================================


A :ref:`DC` is a device context onto which graphics and text can be drawn. The device context is intended to represent
a number of output devices in a generic way, with the same API being used throughout.

Some device contexts are created temporarily in order to draw on a window. This is true of :ref:`ScreenDC`, :ref:`ClientDC`, 
:ref:`PaintDC`, and :ref:`WindowDC`. The following describes the differences between these device contexts and when you should use them.

- :ref:`ScreenDC`. Use this to paint on the screen, as opposed to an individual window.
- :ref:`ClientDC`. Use this to paint on the client area of window (the part without borders and other decorations), but do not use 
  it from within an :ref:`PaintEvent`.
- :ref:`PaintDC`. Use this to paint on the client area of a window, but only from within a :ref:`PaintEvent`.
- :ref:`WindowDC`. Use this to paint on the whole area of a window, including decorations. This may not be available on non-Windows platforms.


To use a client, paint or window device context, create an object on the stack with the window as argument, for example::

	def OnMyCmd(self, event):

	    dc = wx.ClientDC(window)
	    DrawMyPicture(dc)



Try to write code so it is parameterised by :ref:`DC` - if you do this, the same piece of code may write to a number of different devices,
by passing a different device context. This doesn't work for everything (for example not all device contexts support bitmap drawing)
but will work most of the time.