wxWidgets/docs/latex/wx/tdc.tex
Julian Smart e2a6f23364 Split up wxStream doc files; added wxTCP... files; added wxBusyCursor;
added overloaded wxGetHostName etc. functions


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@1474 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
1999-01-25 18:33:08 +00:00

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TeX

\section{Device context overview}\label{dcoverview}
Classes: \helpref{wxDC}{wxdc}, \helpref{wxPostScriptDC}{wxpostscriptdc},\rtfsp
\rtfsp\helpref{wxMetafileDC}{wxmetafiledc}, \helpref{wxMemoryDC}{wxmemorydc}, \helpref{wxPrinterDC}{wxprinterdc},\rtfsp
\helpref{wxScreenDC}{wxscreendc}, \helpref{wxClientDC}{wxclientdc}, \helpref{wxPaintDC}{wxpaintdc},\rtfsp
\helpref{wxWindowDC}{wxwindowdc}.
A wxDC is a {\it 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 \helpref{wxScreenDC}{wxscreendc}, \helpref{wxClientDC}{wxclientdc}, \helpref{wxPaintDC}{wxpaintdc},
and \helpref{wxWindowDC}{wxwindowdc}. The following describes the differences between
these device contexts and when you should use them.
\begin{itemize}\itemsep=0pt
\item {\bf wxScreenDC.} Use this to paint on the screen, as opposed to an individual window.
\item {\bf 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 \helpref{wxWindow::OnPaint}{wxwindowonpaint} event.
\item {\bf wxPaintDC.} Use this to paint on the client area of a window, but {\it only} from
within an \helpref{wxWindow::OnPaint}{wxwindowonpaint} event.
\item {\bf wxWindowDC.} Use this to paint on the whole area of a window, including decorations.
This may not be available on non-Windows platforms.
\end{itemize}
To use a client, paint or window device context, create an object on the stack with
the window as argument, for example:
\begin{verbatim}
void MyWindow::OnMyCmd(wxCommandEvent& event)
{
wxClientDC dc(window);
DrawMyPicture(dc);
}
\end{verbatim}
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.