1\section{\class{wxMemoryDC}}\label{wxmemorydc}
2
3A memory device context provides a means to draw graphics onto a bitmap. When
4drawing in to a mono-bitmap, using {\tt wxWHITE}, {\tt wxWHITE\_PEN} and
5{\tt wxWHITE\_BRUSH}
6will draw the background colour (i.e. 0) whereas all other colours will draw the
7foreground colour (i.e. 1).
8
9\wxheading{Derived from}
10
11\helpref{wxDC}{wxdc}\\
12\helpref{wxObject}{wxobject}
13
14\wxheading{Include files}
15
16<wx/dcmemory.h>
17
18\wxheading{Remarks}
19
20A bitmap must be selected into the new memory DC before it may be used
21for anything.  Typical usage is as follows:
22
23\begin{verbatim}
24  // Create a memory DC
25  wxMemoryDC temp_dc;
26  temp_dc.SelectObject(test_bitmap);
27
28  // We can now draw into the memory DC...
29  // Copy from this DC to another DC.
30  old_dc.Blit(250, 50, BITMAP_WIDTH, BITMAP_HEIGHT, temp_dc, 0, 0);
31\end{verbatim}
32
33Note that the memory DC {\it must} be deleted (or the bitmap selected out of it) before a bitmap
34can be reselected into another memory DC.
35
36\wxheading{See also}
37
38\helpref{wxBitmap}{wxbitmap}, \helpref{wxDC}{wxdc}
39
40\latexignore{\rtfignore{\wxheading{Members}}}
41
42\membersection{wxMemoryDC::wxMemoryDC}\label{wxmemorydcctor}
43
44\func{}{wxMemoryDC}{\void}
45
46Constructs a new memory device context.
47
48Use the \helpref{IsOk}{wxdcisok} member to test whether the constructor was successful
49in creating a usable device context.
50Don't forget to select a bitmap into the DC before drawing on it.
51
52\func{}{wxMemoryDC}{\param{wxBitmap\& }{bitmap}}
53
54Constructs a new memory device context and calls \helpref{SelectObject}{wxmemorydcselectobject}
55with the given bitmap.
56Use the \helpref{IsOk}{wxdcisok} member to test whether the constructor was successful
57in creating a usable device context.
58
59
60\membersection{wxMemoryDC::SelectObject}\label{wxmemorydcselectobject}
61
62\func{void}{SelectObject}{\param{wxBitmap\& }{bitmap}}
63
64Works exactly like \helpref{SelectObjectAsSource}{wxmemorydcselectobjectassource} but
65this is the function you should use when you select a bitmap because you want to modify
66it, e.g. drawing on this DC.
67
68Be careful to use this function and not \helpref{SelectObjectAsSource}{wxmemorydcselectobjectassource}
69when you want to modify the bitmap you are selecting otherwise you may incurr in some
70problems related to wxBitmap being a reference counted object
71(see \helpref{reference counting overview}{trefcount}).
72
73\wxheading{See also}
74
75\helpref{wxDC::DrawBitmap}{wxdcdrawbitmap}
76
77
78
79\membersection{wxMemoryDC::SelectObjectAsSource}\label{wxmemorydcselectobjectassource}
80
81\func{void}{SelectObjectAsSource}{\param{const wxBitmap\& }{bitmap}}
82
83Selects the given bitmap into the device context, to use as the memory
84bitmap. Selecting the bitmap into a memory DC allows you to draw into
85the DC (and therefore the bitmap) and also to use \helpref{wxDC::Blit}{wxdcblit} to copy
86the bitmap to a window. For this purpose, you may find \helpref{wxDC::DrawIcon}{wxdcdrawicon}\rtfsp
87easier to use instead.
88
89If the argument is wxNullBitmap (or some other uninitialised wxBitmap) the current bitmap is
90selected out of the device context, and the original bitmap restored, allowing the current bitmap to
91be destroyed safely.
92
93\wxheading{See also}
94
95\helpref{wxMemoryDC::SelectObject}{wxmemorydcselectobject}
96
97