On Mon, Jun 9, 2014 at 1:28 PM, Benoit Jacob <jacob.benoi...@gmail.com> wrote:
> 2014-06-09 16:12 GMT-04:00 Benoit Jacob <jacob.benoi...@gmail.com>: > > > > > > > > > 2014-06-09 15:56 GMT-04:00 Botond Ballo <bba...@mozilla.com>: > > > > ----- Original Message ----- > >> > From: "Benoit Jacob" <jacob.benoi...@gmail.com> > >> > To: "Botond Ballo" <bba...@mozilla.com> > >> > Cc: "dev-platform" <dev-platform@lists.mozilla.org> > >> > Sent: Monday, June 9, 2014 3:45:20 PM > >> > Subject: Re: C++ standards proposals of potential interest, and > >> upcoming committee meeting > >> > > >> > 2014-06-09 15:31 GMT-04:00 Botond Ballo <bba...@mozilla.com>: > >> > > >> > > Cairo-based 2D drawing API (latest revision): > >> > > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4021.pdf > >> > > > >> > > >> > I would like the C++ committee's attention to be drawn to the dangers, > >> for > >> > committee, to try to make decisions outside of its domain of > expertise. > >> I > >> > see more potential for harm than for good in having the C++ committee > >> join > >> > the ranks of non graphics specialists thinking they know how to do > >> > graphics... > >> > >> Does this caution apply even if the explicit goal of this API is to > allow > >> people learning C++ and/or creating simple graphical applications to be > >> able to do so with minimal overhead (setting up third-party libraries > and > >> such), rather than necessarily provide a tool for > expert-level/heavy-duty > >> graphics work? > >> > > > > That would ease my concerns a lot, if that were the case, but skimming > > through the proposal, it explicitly seems not to be the case. > > > > The "Motivation and Scope" section shows that this aims to target drawing > > GUIs and cover other needs of graphical applications, so it's not just > > about learning or tiny use cases. > > > > Even more worryingly, the proposal talks about GPUs and Direct3D and > > OpenGL and even Mantle, and that scares me, given what we know about how > > sad it is to have to take an API like Cairo (or Skia, or Moz2D, or Canvas > > 2D, it doesn't matter) and try to make it efficiently utilize GPUs. The > > case of a Cairo-like or Skia-like API could totally be made, but the only > > mention of GPUs should be to say that they are mostly outside of its > scope; > > anything more enthusiastic than that confirms fears that the proposal's > > authors are not talking out of experience. > > > > It's actually even worse than I realized: the proposal is peppered with > performance-related comments about GPUs. Just search for "GPU" in it, there > are 42 matches, most of them scarily talking about GPU performance > characteristics (a typical one is "GPU resources are expensive to copy"). > > This proposal should either not care at all about GPU details, which would > be totally fine for a basic software 2D renderer, which could already cover > the needs of many applications; or, if it were to seriously care about > running fast on GPUs, it would not use Cairo as its starting point and it > would look totally different (it would try to lend itself ot seamlessly > batching and reordering drawing primitives; typically, a declarative / > scene-graph API would be a better starting point). > This is a terrible proposal. For instance: class surface { ... void finish(); void flush(); ::std::shared_ptr<device> get_device(); content get_content(); void mark_dirty(); void mark_dirty_rectangle(const rectangle& rect); void set_device_offset(const point& offset); void get_device_offset(point& offset); void write_to_png(const ::std::string& filename); image_surface map_to_image(const rectangle& extents); void unmap_image(image_surface& image); bool has_surface_resource() const; They simply took the Cairo C library and wrapped it up in classes. Taking something like the Canvas 2D API and adding support for layers, filters and proper text support would be a better way to go. _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
