[Cairo] Suggestion for replacing cairo_copy with set_gstate.

Carl Worth cworth at east.isi.edu
Fri Sep 26 11:40:18 PDT 2003

On Sep 26, Bill Spitzak wrote:
 > My recomendation:

Hi Bill,

The first 4 points in your recommendation match the status quo

The issue is that there is no way to replace en masse the contents of
the current graphics state inside a cairo_t. This deficiency has
already forced one user to ignore the stack inside cairo_t and
resort to maintaining a private stack of cairo_t objects created via
cairo_copy. That doesn't seem ideal.

The latest proposal eliminates cairo_copy, but if we look at its
potential equivalent:

	cairo_t *copy = cairo_create ();
	cairo_gstate_t *gstate = cairo_get_gstate (cr);
	cairo_set_gstate (copy, gstate);

we see that there's a memory management issue with the cairo_gstate_t
object. We could add:

	cairo_gstate_destroy (gstate);

But I don't like that as this would be the sole cairo_gstate function,
and I also don't want to require any of the object-based APIs to be
used for any core functionality, (and this seems like a core

Perhaps instead we just want a single function to copy the graphics
state from one cairo_t to another. Perhaps drop cairo_copy and add
something like:

	cairo_set_graphics_state (cr, copy);

And then if the user wants to hold on to just the graphics state, they
can just use a proxy cairo_t for that.

Does that make any sense? Hopefully I'm not talking in circles.

 > cairo_pop (or whatever it is called) will do nothing if the pop pointer is 
 > zero.

This goes to the issue of error handling. See my future email. ;-)


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