.TH wxMemoryDC 3erl "wx 2.2.2.1" "wxWidgets team." "Erlang Module Definition"
.SH NAME
wxMemoryDC \- Functions for wxMemoryDC class
.SH DESCRIPTION
.LP
A memory device context provides a means to draw graphics onto a bitmap\&. When drawing in to a mono-bitmap, using \fIwxWHITE\fR\&, \fIwxWHITE_PEN\fR\& and \fIwxWHITE_BRUSH\fR\& will draw the background colour (i\&.e\&. 0) whereas all other colours will draw the foreground colour (i\&.e\&. 1)\&.
.LP
A bitmap must be selected into the new memory DC before it may be used for anything\&. Typical usage is as follows:
.LP
Note that the memory DC must be deleted (or the bitmap selected out of it) before a bitmap can be reselected into another memory DC\&.
.LP
And, before performing any other operations on the bitmap data, the bitmap must be selected out of the memory DC:
.LP
This happens automatically when \fIwxMemoryDC\fR\& object goes out of scope\&.
.LP
See: \fIwxBitmap\fR\&, \fIwxDC\fR\& 
.LP
This class is derived (and can use functions) from: \fIwxDC\fR\&
.LP
wxWidgets docs: wxMemoryDC
.SH DATA TYPES
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\fBwxMemoryDC()\fR\& = wx:wx_object()
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.SH EXPORTS
.LP
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.B
new() -> wxMemoryDC()
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.RS
.LP
Constructs a new memory device context\&.
.LP
Use the \fIwxDC:isOk/1\fR\& 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\&.
.RE

.LP
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.B
new(Dc) -> wxMemoryDC()
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.RS
.LP
Types:

.RS 3
Dc = wxDC:wxDC() | wxBitmap:wxBitmap()
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.RS
.LP
Constructs a new memory device context having the same characteristics as the given existing device context\&.
.LP
This constructor creates a memory device context \fIcompatible\fR\& with \fIdc\fR\& in wxMSW, the argument is ignored in the other ports\&. If \fIdc\fR\& is NULL, a device context compatible with the screen is created, just as with the default constructor\&.
.RE

.LP
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.B
selectObject(This, Bitmap) -> ok
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.RS
.LP
Types:

.RS 3
This = wxMemoryDC()
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Bitmap = wxBitmap:wxBitmap()
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.RE
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.RS
.LP
Works exactly like \fIselectObjectAsSource/2\fR\& but this is the function you should use when you select a bitmap because you want to modify it, e\&.g\&.
.LP
drawing on this DC\&.
.LP
Using \fIselectObjectAsSource/2\fR\& when modifying the bitmap may incur some problems related to \fIwxBitmap\fR\& being a reference counted object (see overview_refcount)\&.
.LP
Before using the updated bitmap data, make sure to select it out of context first either by selecting ?wxNullBitmap into the device context or destroying the device context entirely\&.
.LP
If the bitmap is already selected in this device context, nothing is done\&. If it is selected in another context, the function asserts and drawing on the bitmap won\&'t work correctly\&.
.LP
See: \fIwxDC:drawBitmap/4\fR\& 
.RE

.LP
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.B
selectObjectAsSource(This, Bitmap) -> ok
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.RS
.LP
Types:

.RS 3
This = wxMemoryDC()
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Bitmap = wxBitmap:wxBitmap()
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.RE
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.RS
.LP
Selects the given bitmap into the device context, to use as the memory bitmap\&.
.LP
Selecting the bitmap into a memory DC allows you to draw into the DC (and therefore the bitmap) and also to use \fIwxDC:blit/6\fR\& to copy the bitmap to a window\&. For this purpose, you may find \fIwxDC:drawIcon/3\fR\& easier to use instead\&.
.LP
If the argument is ?wxNullBitmap (or some other uninitialised \fIwxBitmap\fR\&) the current bitmap is selected out of the device context, and the original bitmap restored, allowing the current bitmap to be destroyed safely\&.
.RE

.LP
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.B
destroy(This :: wxMemoryDC()) -> ok
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.RS
.LP
Destroys the object\&.
.RE