432efcb004
calling SelectObject itself if a valid bitmap is passed. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41989 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
67 lines
2.2 KiB
TeX
67 lines
2.2 KiB
TeX
\section{\class{wxMemoryDC}}\label{wxmemorydc}
|
|
|
|
A memory device context provides a means to draw graphics onto a bitmap. When
|
|
drawing in to a mono-bitmap, using {\tt wxWHITE}, {\tt wxWHITE\_PEN} and
|
|
{\tt wxWHITE\_BRUSH}
|
|
will draw the background colour (i.e. 0) whereas all other colours will draw the
|
|
foreground colour (i.e. 1).
|
|
|
|
\wxheading{Derived from}
|
|
|
|
\helpref{wxDC}{wxdc}\\
|
|
\helpref{wxObject}{wxobject}
|
|
|
|
\wxheading{Include files}
|
|
|
|
<wx/dcmemory.h>
|
|
|
|
\wxheading{Remarks}
|
|
|
|
A bitmap must be selected into the new memory DC before it may be used
|
|
for anything. Typical usage is as follows:
|
|
|
|
\begin{verbatim}
|
|
// Create a memory DC
|
|
wxMemoryDC temp_dc;
|
|
temp_dc.SelectObject(test_bitmap);
|
|
|
|
// We can now draw into the memory DC...
|
|
// Copy from this DC to another DC.
|
|
old_dc.Blit(250, 50, BITMAP_WIDTH, BITMAP_HEIGHT, temp_dc, 0, 0);
|
|
\end{verbatim}
|
|
|
|
Note that the memory DC {\it must} be deleted (or the bitmap selected out of it) before a bitmap
|
|
can be reselected into another memory DC.
|
|
|
|
\wxheading{See also}
|
|
|
|
\helpref{wxBitmap}{wxbitmap}, \helpref{wxDC}{wxdc}
|
|
|
|
\latexignore{\rtfignore{\wxheading{Members}}}
|
|
|
|
\membersection{wxMemoryDC::wxMemoryDC}\label{wxmemorydcctor}
|
|
|
|
\func{}{wxMemoryDC}{\param{const wxBitmap\& }{bitmap = wxNullBitmap}}
|
|
|
|
Constructs a new memory device context.
|
|
|
|
Use the {\it Ok} member to test whether the constructor was successful
|
|
in creating a usable device context. If you don't pass a valid bitmap
|
|
to the constructor, don't forget to select a bitmap into the DC before
|
|
drawing on it.
|
|
|
|
\membersection{wxMemoryDC::SelectObject}\label{wxmemorydcselectobject}
|
|
|
|
\func{void}{SelectObject}{\param{const wxBitmap\& }{bitmap}}
|
|
|
|
Selects the given bitmap into the device context, to use as the memory
|
|
bitmap. Selecting the bitmap into a memory DC allows you to draw into
|
|
the DC (and therefore the bitmap) and also to use {\bf Blit} to copy
|
|
the bitmap to a window. For this purpose, you may find \helpref{wxDC::DrawIcon}{wxdcdrawicon}\rtfsp
|
|
easier to use instead.
|
|
|
|
If the argument is wxNullBitmap (or some other uninitialised wxBitmap) the current bitmap is selected out of the device
|
|
context, and the original bitmap restored, allowing the current bitmap to
|
|
be destroyed safely.
|
|
|