oracular (3) wxMemoryDC.3erl.gz

NAME

       wxMemoryDC - Functions for wxMemoryDC class

DESCRIPTION

       A  memory  device  context  provides  a  means to draw graphics onto a bitmap. 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 characteristics 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 function 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, nothing 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 context, and the original bitmap restored, allowing the current bitmap
              to be destroyed safely.

       destroy(This :: wxMemoryDC()) -> ok

              Destroys the object.