More dc* interface headers reviewed.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@53262 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/dcmemory.h

@@ -10,11 +10,35 @@
     @class wxMemoryDC
     @wxheader{dcmemory.h}
 
-    A memory device context provides a means to draw graphics onto a bitmap. When
-    drawing in to a mono-bitmap, using @c wxWHITE, @c wxWHITE_PEN and
-    @c wxWHITE_BRUSH
-    will draw the background colour (i.e. 0) whereas all other colours will draw the
-    foreground colour (i.e. 1).
+    A memory device context provides a means to draw graphics onto a bitmap.
+    When drawing in to a mono-bitmap, using @c wxWHITE, @c wxWHITE_PEN and
+    @c 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:
+
+    @code
+    // 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);
+    @endcode
+
+    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:
+
+    @code
+    temp_dc.SelectObject(wxNullBitmap);
+    @endcode
+
+    This happens automatically when wxMemoryDC object goes out of scope.
 
     @library{wxcore}
     @category{dc}
@@ -24,45 +48,51 @@
 class wxMemoryDC : public wxDC
 {
 public:
-    //@{
     /**
-        Constructs a new memory device context and calls SelectObject()
-        with the given bitmap.
-        Use the wxDC::IsOk member to test whether the constructor was successful
-        in creating a usable device context.
+        Constructs a new memory device context.
+
+        Use the wxDC::Ok() 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.
     */
     wxMemoryDC();
+    /**
+        Constructs a new memory device context and calls SelectObject() with
+        the given bitmap.
+
+        Use the wxDC::Ok() member to test whether the constructor was
+        successful in creating a usable device context.
+    */
     wxMemoryDC(wxBitmap& bitmap);
-    //@}
 
     /**
-        Works exactly like SelectObjectAsSource() 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() when modifying
-        the bitmap may incurr some problems related to wxBitmap being a reference
-        counted object
-        (see @ref overview_trefcount "reference counting overview").
-        Also, before using the updated bitmap data, make sure to select it out of
-        context first
-        (for example by selecting wxNullBitmap into the device context).
+        Works exactly like SelectObjectAsSource() 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.
 
-        @see wxDC::DrawBitmap
+        Using SelectObjectAsSource() when modifying the bitmap may incurr some
+        problems related to wxBitmap being a reference counted object (see
+        @ref overview_refcount).
+
+        Also, before using the updated bitmap data, make sure to select it out
+        of context first (for example by selecting wxNullBitmap into the device
+        context).
+
+        @see wxDC::DrawBitmap()
     */
     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 wxDC::Blit to copy
-        the bitmap to a window. For this purpose, you may find wxDC::DrawIcon
+        the DC (and therefore the bitmap) and also to use wxDC::Blit() to copy
+        the bitmap to a window. For this purpose, you may find wxDC::DrawIcon()
         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.
+
+        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.
     */
     void SelectObjectAsSource(const wxBitmap& bitmap);
 };