diff options
| -rw-r--r-- | FL/Fl_Device.H | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/FL/Fl_Device.H b/FL/Fl_Device.H index fc12c6364..cd923c412 100644 --- a/FL/Fl_Device.H +++ b/FL/Fl_Device.H @@ -98,7 +98,9 @@ public: Typically, FLTK applications do not use directly objects from this class. Rather, they perform drawing operations (e.g., fl_rectf()) that operate on the current drawing surface (see Fl_Surface_Device). Drawing operations are functionally presented in \ref drawing and as function lists - in the \ref fl_drawings and \ref fl_attributes modules. + in the \ref fl_drawings and \ref fl_attributes modules. The \ref fl_graphics_driver global variable + gives at any time the graphics driver used by all drawing operations. Its value changes when + drawing operations are directed to another drawing surface by Fl_Surface_Device::set_current(). \p 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 a PDF file. This would involve creating a new Fl_Graphics_Driver derived @@ -532,8 +534,13 @@ public: #endif /** - \brief A drawing surface that's susceptible to receive graphical output. - A drawing surface is typically used as follows: + A drawing surface that's susceptible to receive graphical output. + Any FLTK application has at any time a current drawing surface to which all drawing requests are directed. + The current surface is given by Fl_Surface_Device::surface(). + When main() begins running, the current drawing surface has been set to the computer's display, + an instance of the Fl_Display_Device class. + + A drawing surface other than the computer's display, is typically used as follows: <ol><li> Create \c surface, an object from a particular Fl_Surface_Device derived class (e.g., Fl_Copy_Surface, Fl_Printer). <li> Memorize what is the current drawing surface with <tt> Fl_Surface_Device *old_current = Fl_Surface_Device::surface();</tt> <li> Call \c surface->set_current(); to redirect all graphics requests to \c surface which becomes the new @@ -545,7 +552,6 @@ public: with \c old_current->set_current();. <li> Delete \c surface. </ol> - The current drawing surface is initially the computer's display, an instance of the Fl_Display_Device class. */ class FL_EXPORT Fl_Surface_Device : public Fl_Device { /** \brief The graphics driver in use by this surface. */ |