Re: goffice and cairo

[Jean Bréfort <jean brefort normalesup org>]

Le mardi 23 mai 2006 �1:04 +0200, Emmanuel Pacaud a �it :
> Hi,
> 
> Here's some words on what I'm working on currently.
> 
> Last weeks, I've tried to finalize the cairo SVG backend for its
> inclusion as supported backend. So I hope next stable cairo will have
> good PDF, PS and SVG backends.
> 
> It will then be possible to ditch our current rendering engine and
> replace it by a simplified one, based on cairo.
> 
> So my plan is to implement this simplified engine, and validate it by
> using it in two plot plugins, via a new GogView::cairo_render.
> 
> Here's the current in-progress API:
> 
> typedef struct _GOPathPoint 	  GOPathPoint;
> 
> GOPath *go_path_new 	      (void);
> GOPath *go_path_new_with_size (int size);
> void    go_path_free          (GOPath *path);
> 
> void go_path_set_sharp  (GOPath *path, gboolean sharp);
> 
> void go_path_move_to 	(GOPath *path, double x, double y);
> void go_path_line_to 	(GOPath *path, double x, double y);
> void go_path_curve_to 	(GOPath *path, double x0, double y0, 
> 			 	       double x1, double y1, 
> 				       double x2, double y2);
> void go_path_rectangle  (GOPath *path, double x, double y, 
> 			 	       double width, double height);
> void go_path_ring_wedge (GOPath *path, double cx, double xy,
> 			 	       double rx_out, double ry_out, 
> 			 	       double rx_in, double ry_in, 
> 				       double th0, double th1);
> void go_path_arc 	(GOPath *path, double cx, double cy, 
> 			 	       double rx, double ry, 
> 				       double th0, double th1);
> void go_path_pie_wedge  (GOPath *path, double cx, double cy, 
> 			 	       double rx, double ry, 
> 				       double th0, double th1);
> void go_path_marker 	(GOPath *path);
> void go_path_close 	(GOPath *path);
> 
> typedef struct _GOCairo GOCairo;
> 
> GOCairo *go_cairo_new		(void);
> void go_cairo_free 		(GOCairo *gcairo);
> 
> void go_cairo_push_style	(GOCairo *gcairo, GogStyle const *style);
> void go_cairo_pop_style		(GOCairo *gcairo);
> 
> void go_cairo_push_clip 	(GOCairo *gcairo, GOPath const *path);
> void go_cairo_pop_clip  	(GOCairo *gcairo);
> 
> void go_cairo_stroke		(GOCairo *gcairo, GOPath const *path);
> void go_cairo_fill		(GOCairo *gcairo, GOPath const *path);
> void go_cairo_draw_shape	(GOCairo *gcairo, GOPath const *path);
> void go_cairo_draw_markers	(GOCairo *gcairo, GOPath const *path);
> void go_cairo_draw_text		(GOCairo *gcairo, double x, double y, char
> const *text, GtkAnchorType anchor);
> 
> void go_cairo_get_text_OBR	(GOCairo *gcairo, char const *text,
> GOGeometryOBR *obr);
> void go_cairo_get_text_AABR	(GOCairo *gcairo, char const *text,
> GOGeometryAABR *aabr);
> 
> double go_cairo_line_size	(GOCairo const *gcairo, double width);
> double go_cairo_pt_2r_x		(GOCairo const *gcairo, double d);
> double go_cairo_pt_2r_y		(GOCairo const *gcairo, double d);
> double go_cairo_pt_2r		(GOCairo const *gcairo, double d);
> 
> void go_cairo_render (GOCairo *gcairo, cairo_surface_t *surface);

All that might be included in the GOImage code I'm currently working on,
IMHO. I hope I can have something operational as soon as tomorrow ;-)

> The final step would be to port all existing plot plugins. I think I'll
> move pixbuf caching to gog_control_foo_canvas, and image_export and
> get_pixbuf to GogGraphView.
> 
> Regarding printing, since there's no gnome-print backend for cairo, I
> guess we can just render graphs as raster image.

Please, don't do that! It would be a serious regression (unless you use
high resolution. Let's use the gnome-print renderer as long as we use
gnome-print (hopefully not too long).

Cheers,
Jean