Device Contexts

A wxDC 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 wxScreenDC, wxClientDC, wxPaintDC, and wxWindowDC. The following describes the differences between these device contexts and when you should use them.

• wxScreenDC. Use this to paint on the screen, as opposed to an individual window.
• wxClientDC. 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 wxPaintEvent.
• wxPaintDC. Use this to paint on the client area of a window, but only from within a wxPaintEvent.
• wxWindowDC. 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:

void MyWindow::OnMyCmd(wxCommandEvent& event)
{
    wxClientDC dc(window);
    DrawMyPicture(dc);
}

Try to write code so it is parameterised by wxDC - 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.

See Also

Device Contexts