wxMemoryDC - Functions for wxMemoryDC class
Please see following description for synopsis
wxMemoryDC(3) Erlang Module Definition wxMemoryDC(3)
NAME
wxMemoryDC - Functions for wxMemoryDC class
DESCRIPTION
A memory device context provides a means to draw graphics onto a bit-
map. When drawing in to a mono-bitmap, using wxWHITE, wxWHITE_PEN and
wxWHITE_BRUSH will draw the background colour (i.e. 0) whereas all
other colours will draw the foreground colour (i.e. 1).
A bitmap must be selected into the new memory DC before it may be used
for anything. Typical usage is as follows:
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.
And, before performing any other operations on the bitmap data, the
bitmap must be selected out of the memory DC:
This happens automatically when wxMemoryDC object goes out of scope.
See: wxBitmap, wxDC
This class is derived (and can use functions) from: wxDC
wxWidgets docs: wxMemoryDC
DATA TYPES
wxMemoryDC() = wx:wx_object()
EXPORTS
new() -> wxMemoryDC()
Constructs a new memory device context.
Use the wxDC:isOk/1 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.
new(Dc) -> wxMemoryDC()
Types:
Dc = wxDC:wxDC() | wxBitmap:wxBitmap()
Constructs a new memory device context having the same charac-
teristics as the given existing device context.
This constructor creates a memory device context compatible with
dc in wxMSW, the argument is ignored in the other ports. If dc
is NULL, a device context compatible with the screen is created,
just as with the default constructor.
selectObject(This, Bitmap) -> ok
Types:
This = wxMemoryDC()
Bitmap = wxBitmap:wxBitmap()
Works exactly like selectObjectAsSource/2 but this is the func-
tion you should use when you select a bitmap because you want to
modify it, e.g.
drawing on this DC.
Using selectObjectAsSource/2 when modifying the bitmap may incur
some problems related to wxBitmap being a reference counted
object (see overview_refcount).
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.
If the bitmap is already selected in this device context, noth-
ing is done. If it is selected in another context, the function
asserts and drawing on the bitmap won't work correctly.
See: wxDC:drawBitmap/4
selectObjectAsSource(This, Bitmap) -> ok
Types:
This = wxMemoryDC()
Bitmap = wxBitmap:wxBitmap()
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 wxDC:blit/6 to
copy the bitmap to a window. For this purpose, you may find
wxDC:drawIcon/3 easier to use instead.
If the argument is ?wxNullBitmap (or some other uninitialised
wxBitmap) the current bitmap is selected out of the device con-
text, and the original bitmap restored, allowing the current
bitmap to be destroyed safely.
destroy(This :: wxMemoryDC()) -> ok
Destroys the object.
wxWidgets team. wx 2.1.1 wxMemoryDC(3)