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