Documentation: homogenize to 'scale factor' and 'drawing unit'

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12737 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

documentation/src/drawing.dox

@@ -1154,6 +1154,10 @@ void fl_copy_offscreen(int x, int y, int w, int h, Fl_Offscreen osrc, int srcx,
 Copy a rectangular area of the size \p w*h from \p srcx,srcy
 in the offscreen buffer into the current drawing surface at \p x,y.
 
+void fl_scale_offscreen(Fl_Offscreen &osrc)
+\par
+Adapts the offscreen's size in pixels to a changed value of the scale factor
+while keeping the offscreen's graphical content.
 
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