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Documentation: improve description of how to use drawing surfaces

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ManoloFLTK 2024-08-07 09:26:49 +02:00
parent 666bbda70e
commit eaf62a99dc
1 changed files with 7 additions and 6 deletions
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FL/Fl_Device.H
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@ -38,16 +38,17 @@ class Fl_Image_Surface;
an instance of the Fl_Display_Device class. an instance of the Fl_Display_Device class.
A drawing surface other than the computer's display, is typically used as follows: 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). <ol><li> Create \c surface, an object from an Fl_Surface_Device derived class (e.g., Fl_Image_Surface, Fl_Printer, Fl_Copy_Surface).
<li> Call \c Fl_Surface_Device::push_current(surface); to redirect all graphics requests to <li> Call \c Fl_Surface_Device::push_current(surface); to redirect all graphics requests to
\c surface which becomes the new current drawing surface (not necessary with classes Fl_Printer / Fl_PostScript_File_Device \c surface which becomes the new current drawing surface (not necessary with classes Fl_Printer / Fl_PostScript_File_Device /
because it is done by Fl_Paged_Device::begin_page()). Fl_PDF_File_Surface because it is done by Fl_Paged_Device::begin_page()).
<li> At this point all of the \ref fl_drawings (e.g., fl_rect()) or the \ref fl_attributes or \ref drawing_images functions <li> At this point all of the \ref fl_drawings (e.g., fl_rect()) or the \ref fl_attributes or \ref drawing_images functions
(e.g., fl_draw_image(), Fl_Image::draw()) operate on the new current drawing surface. (e.g., fl_draw_image(), Fl_Image::draw()) operate on the new current drawing surface.
Drawing surfaces from Fl_Widget_Surface derived classes allow additional ways It's also possible to draw to the current surface any widget with Fl_Widget_Surface::draw(Fl_Widget*, int, int), a window and its
to draw to them (e.g., Fl_Printer::print_widget(), Fl_Image_Surface::draw()). titlebar with Fl_Widget_Surface::draw_decorated_window(), or the content of a rectangular zone of a window
with Fl_Widget_Surface::print_window_part().
<li> After all drawing requests have been performed, redirect graphics requests back to their previous destination <li> After all drawing requests have been performed, redirect graphics requests back to their previous destination
with \c Fl_Surface_Device::pop_current(); (not necessary with classes Fl_Printer / Fl_PostScript_File_Device). with \c Fl_Surface_Device::pop_current(); (not necessary with classes Fl_Printer / Fl_PostScript_File_Device / Fl_PDF_File_Surface).
<li> Delete \c surface. <li> Delete \c surface.
</ol> </ol>
For back-compatibility, it is also possible to use the Fl_Surface_Device::set_current() member function For back-compatibility, it is also possible to use the Fl_Surface_Device::set_current() member function