[cairo] Cairo and ISO C++

Michael McLaughlin mikebmcl at gmail.com
Mon Jan 20 16:16:31 PST 2014


I wanted to give everyone an update. Earlier today a proposal that Herb,
Jason, and I have been working on, N3888: A Proposal to Add 2D Graphics
Rendering and Display to C++, was published here:
http://isocpp.org/files/papers/N3888.pdf . The main focus of the proposal
is a series of rules that enable a mechanical transformation from the cairo
API to an API that is in the style of the C++ Standard Library (the STL).

We expect to present the proposal for feedback at the Issaquah, WA meeting
of the ISO C++ Committee
runs from Feb. 10 - Feb. 15, 2014 (I will personally be there from
mid-day Monday through Wednesday). We do not expect that the proposal is
final and we are soliciting feedback on it from everyone who is interested.
This includes all of you. We are hopeful that you will all be receptive to
the approach we have taken and are supportive of the concept (even if you
might have some ideas about how to make technical improvements).

There is a reference implementation that is nearly ready. When it is
complete I will post a link to the Git repository for it. The
implementation right now is built on Windows using Visual Studio 2013 (it
will work fine with the free Express for Windows Desktop version), but
there's no reason it cannot run on a GNU/Linux or *BSD environment with a
few changes. I hope to have some time in the next week or two to create a
version using GCC on Ubuntu, but I can't make any promises.

For those curious about the process, we will be presenting the proposal in
Issaquah and will receive feedback on it (both there and from other places,
including here). We expect that the general concept will be well received
(though there's always a slight chance that it won't be) and that we will
get a lot of constructive criticism. We will take that feedback and proceed
to amend the proposal. Others may also propose amendments (either
informally to us or formally through an N numbered paper). When we are
ready, we will publish the amended document and present it at a future
meeting of the ISO C++ committee. (There are generally two a year; one in
North America and one in Europe or Asia, though sometimes (such as this
year) there are additional meetings). The ultimate goal is to reach a point
where everyone is satisfied with the proposal, in which case a formal vote
would take place and it would be adopted as a Technical Specification. TSs
are not formally part of the standard but are things which are likely to
become part of the standard in the future. The various compilers (GCC,
Clang, Visual C++, Intel C++, IBM C++, etc.) implement TSs so that the C++
community can experiment with them and flush out any issues or problems
that weren't discovered earlier. If all goes well, the TS would
subsequently be adopted as part of the ISO C++ language standard, at which
point it would officially become part of the C++ Standard (specifically the
C++ Standard Library). The goal of all of this is for C++ programmers to be
able to render and display 2D graphics by writing standard code which will
compile and run regardless of which compiler or operating system the
developer uses and targets. We consider portable, standards-compliant code
to be a great thing and we are excited to tackle the problem of
standardizing 2D graphics and are thrilled to create a design that uses
cairo as its basis.

If you do decide to read the paper (or play with the code once it is
released), do note that we were intentionally conservative in some of the
transformations and that we expect the proposal to evolve and change over
time. When I am back from Issaquah, I hope to be able to revisit all of the
great suggestions in this thread and work on drawing up amendments based
upon the ideas that fit with the proposal.

Thanks again for your time and for all the great work you've done
individually and as a community in creating cairo. It is a masterful
accomplishment and I'm really glad I've had the opportunity to work with it
for this project!

Respectfully yours,

Michael B. McLaughlin

On Tue, Dec 31, 2013 at 9:23 PM, Herb Sutter <herb.sutter at gmail.com> wrote:

> Hi, my name is Herb Sutter and I chair the ISO C++ standards committee.
> Behdad referred me to this list as the right place to raise this question:
> We are actively looking at the potential standardization of a basic 2D
> drawing library for ISO C++, and would like to base it on (or outright
> adopt, possibly as a binding) solid prior art in the form of an existing
> library. You can find a quick summary of goals and discussions to date in
> these two papers:
> ·         http://isocpp.org/files/papers/n3791.html
> ·         http://isocpp.org/files/papers/N3825.pdf
> As noted in the latter paper, we are currently investigating the direction
> of proposing a mechanically C++-ified version of Cairo. Specifically,
> “mechanically C++-ified” means taking Cairo as-is and transforming it with
> a one-page list of mechanical changes such as turning _create functions
> into constructors, (mystruct*, int length) function parameters to
> vector<struct>& parameters, that sort of thing – the design and
> abstractions and functions are unchanged. This would also allow us to track
> Cairo as it evolves in the future, by continuing to reapply the same rules
> to new updates to Cairo.
> We know about Cairomm but it seems to have languished so we are focused on
> current Cairo as a starting point, even though it’s not C++ -- we believe
> Cairo itself it is very well written C (already in an OO style, already
> const-correct, etc.).
> We want to make sure we’re doing this in the right way and with the
> group’s approval, so your feedback would be much appreciated. Also, we
> might want to reuse parts of the Cairo documentation in our specification,
> which we understand is governed by MPL 1.1, and we would like to know if
> this would be all right with your group.
> Thanks, and best wishes,
> Herb
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