interface/dcmemory.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        dcmemory.h
   3 // Purpose:     interface of wxMemoryDC
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /**
  10     @class wxMemoryDC
  11     @wxheader{dcmemory.h}
  12
  13     A memory device context provides a means to draw graphics onto a bitmap. When
  14     drawing in to a mono-bitmap, using @c wxWHITE, @c wxWHITE_PEN and
  15     @c wxWHITE_BRUSH
  16     will draw the background colour (i.e. 0) whereas all other colours will draw the
  17     foreground colour (i.e. 1).
  18
  19     @library{wxcore}
  20     @category{dc}
  21
  22     @see wxBitmap, wxDC
  23 */
  24 class wxMemoryDC : public wxDC
  25 {
  26 public:
  27     //@{
  28     /**
  29         Constructs a new memory device context and calls SelectObject()
  30         with the given bitmap.
  31         Use the wxDC::IsOk member to test whether the constructor was successful
  32         in creating a usable device context.
  33     */
  34     wxMemoryDC();
  35     wxMemoryDC(wxBitmap& bitmap);
  36     //@}
  37
  38     /**
  39         Works exactly like SelectObjectAsSource() but
  40         this is the function you should use when you select a bitmap because you want
  41         to modify
  42         it, e.g. drawing on this DC.
  43         Using SelectObjectAsSource() when modifying
  44         the bitmap may incurr some problems related to wxBitmap being a reference
  45         counted object
  46         (see @ref overview_trefcount "reference counting overview").
  47         Also, before using the updated bitmap data, make sure to select it out of
  48         context first
  49         (for example by selecting wxNullBitmap into the device context).
  50
  51         @see wxDC::DrawBitmap
  52     */
  53     void SelectObject(wxBitmap& bitmap);
  54
  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 wxDC::Blit to copy
  59         the bitmap to a window. For this purpose, you may find wxDC::DrawIcon
  60         easier to use instead.
  61         If the argument is wxNullBitmap (or some other uninitialised wxBitmap) the
  62         current bitmap is
  63         selected out of the device context, and the original bitmap restored, allowing
  64         the current bitmap to
  65         be destroyed safely.
  66     */
  67     void SelectObjectAsSource(const wxBitmap& bitmap);
  68 };
  69