114 lines
4 KiB
C
114 lines
4 KiB
C
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/////////////////////////////////////////////////////////////////////////////
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// Name: dcmemory.h
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// Purpose: interface of wxMemoryDC
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// Author: wxWidgets team
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// Licence: wxWindows licence
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/////////////////////////////////////////////////////////////////////////////
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/**
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@class wxMemoryDC
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A memory device context provides a means to draw graphics onto a bitmap.
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When drawing in to a mono-bitmap, using @c wxWHITE, @c wxWHITE_PEN and
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@c wxWHITE_BRUSH will draw the background colour (i.e. 0) whereas all other
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colours will draw the foreground colour (i.e. 1).
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A bitmap must be selected into the new memory DC before it may be used for
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anything. Typical usage is as follows:
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@code
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// Create a memory DC
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wxMemoryDC temp_dc;
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temp_dc.SelectObject(test_bitmap);
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// We can now draw into the memory DC...
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// Copy from this DC to another DC.
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old_dc.Blit(250, 50, BITMAP_WIDTH, BITMAP_HEIGHT, temp_dc, 0, 0);
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@endcode
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Note that the memory DC must be deleted (or the bitmap selected out of it)
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before a bitmap can be reselected into another memory DC.
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And, before performing any other operations on the bitmap data, the bitmap
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must be selected out of the memory DC:
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@code
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temp_dc.SelectObject(wxNullBitmap);
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@endcode
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This happens automatically when wxMemoryDC object goes out of scope.
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@library{wxcore}
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@category{dc}
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@see wxBitmap, wxDC
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*/
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class wxMemoryDC : public wxDC
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{
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public:
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/**
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Constructs a new memory device context.
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Use the wxDC::IsOk() member to test whether the constructor was
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successful in creating a usable device context. Don't forget to select
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a bitmap into the DC before drawing on it.
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*/
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wxMemoryDC();
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/**
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Constructs a new memory device context having the same characteristics
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as the given existing device context.
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This constructor creates a memory device context @e compatible with @a
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dc in wxMSW, the argument is ignored in the other ports. If @a dc is
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@NULL, a device context compatible with the screen is created, just as
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with the default constructor.
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*/
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wxMemoryDC(wxDC *dc);
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/**
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Constructs a new memory device context and calls SelectObject() with
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the given bitmap.
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Use the wxDC::IsOk() member to test whether the constructor was
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successful in creating a usable device context.
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*/
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wxMemoryDC(wxBitmap& bitmap);
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/**
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Works exactly like SelectObjectAsSource() but this is the function you
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should use when you select a bitmap because you want to modify it, e.g.
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drawing on this DC.
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Using SelectObjectAsSource() when modifying the bitmap may incur some
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problems related to wxBitmap being a reference counted object (see
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@ref overview_refcount).
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Before using the updated bitmap data, make sure to select it out of
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context first either by selecting ::wxNullBitmap into the device
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context or destroying the device context entirely.
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If the bitmap is already selected in this device context, nothing is
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done. If it is selected in another context, the function asserts and
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drawing on the bitmap won't work correctly.
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@see wxDC::DrawBitmap()
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*/
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void SelectObject(wxBitmap& bitmap);
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/**
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Selects the given bitmap into the device context, to use as the memory
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bitmap. Selecting the bitmap into a memory DC allows you to draw into
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the DC (and therefore the bitmap) and also to use wxDC::Blit() to copy
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the bitmap to a window. For this purpose, you may find wxDC::DrawIcon()
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easier to use instead.
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If the argument is ::wxNullBitmap (or some other uninitialised wxBitmap)
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the current bitmap is selected out of the device context, and the
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original bitmap restored, allowing the current bitmap to be destroyed
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safely.
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*/
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void SelectObjectAsSource(const wxBitmap& bitmap);
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};
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