correct SetFont() documentation: at least wxMSW and wxGTK do allow the user to pass wxNullFont (or another invalid font instance) (see #10475)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@60412 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/dc.h

@@ -751,10 +751,11 @@ public:
     int GetBackgroundMode() const;
 
     /**
-        Gets the current font. Notice that even although each device context
+        Gets the current font. 
-        object has some default font after creation, this method would return a
+        
-        ::wxNullFont initially and only after calling SetFont() a valid font is
+        Notice that even although each device context object has some default font 
-        returned.
+        after creation, this method would return a ::wxNullFont initially and only 
+        after calling SetFont() a valid font is returned.
     */
     const wxFont& GetFont() const;
 
@@ -783,14 +784,19 @@ public:
     const wxColour& GetTextForeground() const;
 
     /**
-        @a mode may be one of wxSOLID and wxTRANSPARENT. This setting
+        @a mode may be one of @c wxSOLID and @c wxTRANSPARENT. 
-        determines whether text will be drawn with a background colour or not.
+        
+        This setting determines whether text will be drawn with a background 
+        colour or not.
     */
     void SetBackgroundMode(int mode);
 
     /**
-        Sets the current font for the DC. It must be a valid font, in
+        Sets the current font for the DC. 
-        particular you should not pass wxNullFont to this method.
+
+        If the argument is ::wxNullFont (or another invalid font; see wxFont::IsOk), 
+        the current font is selected out of the device context (leaving wxDC without 
+        any valid font), allowing the current font to be destroyed safely.
 
         @see wxFont
     */
@@ -810,9 +816,11 @@ public:
     void SetTextForeground(const wxColour& colour);
 
     /**
-        Sets the current layout direction for the device context. @a dir may be
+        Sets the current layout direction for the device context. 
-        either @c wxLayout_Default, @c wxLayout_LeftToRight or
+        
-        @c wxLayout_RightToLeft.
+        @param dir 
+           May be either @c wxLayout_Default, @c wxLayout_LeftToRight or
+           @c wxLayout_RightToLeft.
 
         @see GetLayoutDirection()
     */
@@ -1083,9 +1091,9 @@ public:
     /**
         Sets the current brush for the DC.
 
-        If the argument is wxNullBrush, the current brush is selected out of
+        If the argument is ::wxNullBrush (or another invalid brush; see wxBrush::IsOk), 
-        the device context (leaving wxDC without any valid brush), allowing the
+        the current brush is selected out of the device context (leaving wxDC without 
-        current brush to be destroyed safely.
+        any valid brush), allowing the current brush to be destroyed safely.
 
         @see wxBrush, wxMemoryDC (for the interpretation of colours when
              drawing into a monochrome bitmap)
@@ -1093,9 +1101,11 @@ public:
     void SetBrush(const wxBrush& brush);
 
     /**
-        Sets the current pen for the DC. If the argument is wxNullPen, the
+        Sets the current pen for the DC. 
-        current pen is selected out of the device context (leaving wxDC without
+
-        any valid pen), allowing the current brush to be destroyed safely.
+        If the argument is ::wxNullPen (or another invalid pen; see wxPen::IsOk), 
+        the current pen is selected out of the device context (leaving wxDC without any 
+        valid pen), allowing the current pen to be destroyed safely.
 
         @see wxMemoryDC for the interpretation of colours when drawing into a
              monochrome bitmap.