[wxWidgets.git] / docs / latex / wx / memorydc.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}

\func{}{wxMemoryDC}{\void}

Constructs a new memory device context.

Use the {\it Ok} member to test whether the constructor was successful
in creating a usable device context. Don't forget to select a bitmap
into the DC before drawing on it.

\membersection{wxMemoryDC::SelectObject}

\func{}{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.
Commit	Line	Data
a660d684 KB	1	\section{\class{wxMemoryDC}}\label{wxmemorydc}
a660d684 KB	2
41fbc841	3	A memory device context provides a means to draw graphics onto a bitmap. When
d17f05af HH	4	drawing in to a mono-bitmap, using {\tt wxWHITE}, {\tt wxWHITE\_PEN} and
d17f05af HH	5	{\tt wxWHITE\_BRUSH}
41fbc841 RR	6	will draw the background colour (i.e. 0) whereas all other colours will draw the
41fbc841 RR	7	foreground colour (i.e. 1).
a660d684 KB	8
	9	\wxheading{Derived from}
	10
	11	\helpref{wxDC}{wxdc}\\
	12	\helpref{wxObject}{wxobject}
	13
954b8ae6 JS	14	\wxheading{Include files}
	15
	16	<wx/dcmemory.h>
	17
a660d684 KB	18	\wxheading{Remarks}
	19
	20	A bitmap must be selected into the new memory DC before it may be used
	21	for 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
	33	Note that the memory DC {\it must} be deleted (or the bitmap selected out of it) before a bitmap
	34	can 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}
	43
	44	\func{}{wxMemoryDC}{\void}
	45
	46	Constructs a new memory device context.
	47
	48	Use the {\it Ok} member to test whether the constructor was successful
2edb0bde	49	in creating a usable device context. Don't forget to select a bitmap
a660d684 KB	50	into the DC before drawing on it.
	51
	52	\membersection{wxMemoryDC::SelectObject}
	53
	54	\func{}{SelectObject}{\param{const wxBitmap\& }{bitmap}}
	55
	56	Selects the given bitmap into the device context, to use as the memory
	57	bitmap. Selecting the bitmap into a memory DC allows you to draw into
	58	the DC (and therefore the bitmap) and also to use {\bf Blit} to copy
fe604ccd	59	the bitmap to a window. For this purpose, you may find \helpref{wxDC::DrawIcon}{wxdcdrawicon}\rtfsp
a660d684 KB	60	easier to use instead.
	61
	62	If the argument is wxNullBitmap (or some other uninitialised wxBitmap) the current bitmap is selected out of the device
	63	context, and the original bitmap restored, allowing the current bitmap to
	64	be destroyed safely.
	65