Add examples/SVG_File_Surface.cxx and refer to it in the doc of class Fl_Surface_Device

This example code shows how to subclass Fl_Surface_Device and Fl_Graphics_Driver to
endow FLTK with a new kind of graphics output.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12980 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

2 files changed, 11 insertions, 8 deletions

diff --git a/FL/Fl_Device.H b/FL/Fl_Device.H
index 9162d13b1..5378293f3 100644
--- a/FL/Fl_Device.H
+++ b/FL/Fl_Device.H
@@ -51,6 +51,17 @@ class Fl_Widget;
  </ol>
  For back-compatibility, it is also possible to use the Fl_Surface_Device::set_current() member function
  to change the current drawing surface, once to the new surface, once to the previous one.
+ 
+ Class Fl_Surface_Device can also be derived to define new kinds of graphical output
+ usable with FLTK drawing functions.
+ An example would be to draw to an SVG file. This would require to create a new class,
+ say SVG_Surface, derived from class Fl_Surface_Device, and another new class,
+ say SVG_Graphics_Driver, derived from class Fl_Graphics_Driver.
+ Class SVG_Graphics_Driver should implement all virtual methods of the Fl_Graphics_Driver class
+ to support all FLTK drawing functions and have them draw into SVG files. Alternatively,
+ class SVG_Graphics_Driver could implement only some virtual methods, and only part of
+ the FLTK drawing API would be usable when drawing to SVG files
+ (see examples/SVG_File_Surface.cxx for a small, working implementation of this procedure).
  */
 class FL_EXPORT Fl_Surface_Device {
   /** The graphics driver in use by this surface. */
diff --git a/FL/Fl_Graphics_Driver.H b/FL/Fl_Graphics_Driver.H
index 0255ae24f..01646b446 100644
--- a/FL/Fl_Graphics_Driver.H
+++ b/FL/Fl_Graphics_Driver.H
@@ -72,14 +72,6 @@ struct Fl_Fontdesc;
  drawing operations are directed to another drawing surface by Fl_Surface_Device::push_current() /
  Fl_Surface_Device::pop_current() / Fl_Surface_Device::set_current().
 
- The Fl_Graphics_Driver class is of interest if one wants to perform new kinds of drawing operations.
- An example would be to draw to an SVG file. This would require to create a new class,
- say SVG_Graphics_Driver, derived from class Fl_Graphics_Driver, and another new class,
- say SVG_Surface, derived from class Fl_Surface_Device. The new SVG_Graphics_Driver class should
- implement all virtual methods of the Fl_Graphics_Driver class to support all FLTK drawing functions
- and have them draw into SVG files. Alternatively, class SVG_Graphics_Driver could implement only some
- virtual methods, and only part of FLTK drawing functions would be usable when drawing to SVG files.
- 
  The Fl_Graphics_Driver class is essential for developers of the FLTK library.
  Each platform supported by FLTK requires to create a derived class of Fl_Graphics_Driver that
  implements all its virtual member functions according to the platform.