Re: [Gnash-dev] Renderer redesign

[Markus Gothe]

Go for it! :-D

//Markus

Udo Giacomozzi wrote:
> Hi,
> 
> I want to move discussion about specific render handler redesign steps
> in here.
> 
> Currently my plan is as follows:
> 
> - Implement a new, intermediary render_handler_impl class which acts
>   as a backward compatibility class (and base class for any
>   triangle-based renderer such as any hardware acceleration). It's a
>   descendant of the render_handler class.
> 
>   
> - Low-level virtual methods would be moved to this class, not kept
>   in the base render_handler class and thus are shielded from the rest
>   of the Gnash source. These methods should only called from within
>   the renderer itself:
>   set_matrix (?)
>   set_cxform (?)
>   draw_mesh_strip
>   draw_line_strip
>   fill_style_XXXXXX
>   line_style_XXXXXX
>   draw_bitmap (only used for glyphs!)
> 
>   
> - Instead, the base class (render_handler) defines a new method:
> 
>   virtual void draw_shape_character(shape_character_def *def,
>     character *inst) = 0;
> 
>   It must know how to draw a shape character. Note that a bitmap
>   placed on the stage is just a rectangle with bitmap fill style, so
>   draw_shape_character() can automatically draw bitmaps too.
> 
> 
> - to support drawing of glyphs another method is defined:
> 
>   render_handler::draw_glyph(shape_character_def *def,
>     const matrix *mat) = 0;
>       
>   It's very similar to draw_shape_character except that it does not
>   get passed an instance. It will be processed in a very similar way,
>   however.
>   
> 
> - render_handler_impl:draw_shape_character() (the one used for
>   compatibility) will use the old "mesh_set" class to tesselate the
>   shape. It will call the old draw_mesh_strip() and friends so
>   backends should work straight out of the box.
> 
>   
> - shape_character_def::display() is very simple now:
> 
> void    shape_character_def::display(character* inst)
> {
>   render_handler* renderer = get_render_handler();
>   renderer->draw_shape_character(this, inst);
> }
> 
> 
>   
> - I already implemented (without cache) this compatibility method and
>   it seems to work well. However, it ends by calling
>   mesh_set:display() which accesses the renderer methods directly,
>   which is not good (as these functions should not be accessible from
>   outside). To change this a few more changes will be necessary -
>   cannot tell yet.
> 
> 
> - A generic base class render_cache_object is declared in
>   render_handler.h which does not contain much members and can be used
>   by the renderer to store any kind of caching data. For
>   render_handler_impl (compatibility) a descendant is defined that
>   holds mesh sets, just like Gnash does now.
> 
> 
> - I'd really like to see AGG to be a fixed, integral part of Gnash so
>   that it can be used to render font bitmaps for OpenGL and Cairo
>   backends.
>   
> 
> Any suggestions? Problems you see?
> 
> Udo
> 
> 
> 
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