361592 - fix gfx*Surface <-> cairo_surface_t refcounting issues

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

We need to fix this once and for all; the right fix is:

- cairo_surface_t's refcount becomes the main one
- gfxASurface needs to have its own addref/release impl that chains to cairo_surface_reference/_destroy.
- we need a destructor added to userdata (the gfxASurface wrapper) on cairo_surface_t that deletes the wrapper when it goes out of scope.

Comment 1

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Attachment: tie wrapper refcount to cairo refcount

Ok, here we go.  This ties the surface wrapper refcount directly to the cairo refcount.  When we create a wrapper, we store it as user data on the surface and it's only destroyed when the cairo surface is destroyed.

There is only one tricky thing here, and that is that cairo surfaces are always returned with a refcount of 1, unlike our objects which are returned with a refcount of 0 (and expect the caller to addref right away).  So, when we created the cairo surface, we track that phantom extra ref and just ignore the first call to AddRef.

Comment 2

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Comment on attachment 250402 [details] [diff] [review]
tie wrapper refcount to cairo refcount


>@@ -135,22 +163,18 @@ protected:
>     static gfxASurface* GetSurfaceWrapper(cairo_surface_t *csurf);
>     static void SetSurfaceWrapper(cairo_surface_t *csurf, gfxASurface *asurf);
> 
>+    gfxASurface () : mTrackThis(PR_FALSE) { }
>+    PRPackedBool mTrackThis;
>+

Ignore this, I added this while doing some tracking stuff, but I took out all the other code related to it.  I'll delete this part from my patch.

Comment 3

[Boris Zbarsky [:bzbarsky]]

So.. my build is dying due to this change:

gfxSurfaceRefCountTest.cpp
ld: warning: libmozz.so, needed by ../../../dist/bin/libthebes.so, not found (try using -rpath or -rpath-link)
../../../dist/bin/libthebes.so: undefined reference to `MOZ_Z_compress'
collect2: ld returned 1 exit status
gmake[6]: *** [gfxSurfaceRefCountTest] Error 1