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wxMemoryDC: wxCanvasDC

A memory device context provides a means to draw graphics onto a bitmap.

A bitmap must be selected into the new memory DC before it may be used for anything. Typical usage is as follows:

  // 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);
Note that the memory DC must be deleted before a bitmap can be reselected into another memory DC.

See also wxBitmap, wxDC, wxCanvasDC.

wxMemoryDC::wxMemoryDC
wxMemoryDC::SelectObject


wxMemoryDC::wxMemoryDC

void wxMemoryDC(void)

Constructs a new memory device context.

void wxMemoryDC(wxCanvasDC *oldDC)

Constructs a new memory device context with similar attributes to the given canvas device context.

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


wxMemoryDC::SelectObject

void SelectObject(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 Blit to copy the bitmap to a canvas. For this purpose, you may find wxDC::DrawIcon easier to use instead.

If the argument is NULL, the current bitmap is selected out of the device context, and the original bitmap restored, allowing the current bitmap to be destroyed safely.