For the Visual Studio C compiler we need to annotate our public symbols
with `__declspec(dllimport)` to ensure they are visible when dynamically
linking to Epoxy's DLL.
This is needed because under Windows we use a dispatch table, instead of
wrapper functions, thus the symbol visibility rules change. Compiling
with MingW will automatically add `__declspec(dllimport)` for us.
Thanks to Nirbheek Chauhan for the help in debugging the issue.
Fixes#104
This way we can take a dist tarball created through autotools, and use
Meson to build it.
Once Meson gets support for disting, we'll do the same with the
autotools build files, and call the result a "Buildoboros".
PyLint raises a bunch of issues on the dispatch generation script with
regards to best practices; most of those issues are real, so let's fix
the code to be more Pythonic.
On Linux and other Unix variants we may not have access to GLX and EGL
at run time. Dependent libraries can only discover this by using dlsym()
on various symbols, because as soon as they attempt to call those
symbols through Epoxy, Epoxy will abort. This means that a bunch of code
needs to be copy-pasted between projects, with the high chance of
somebody getting it wrong.
Epoxy already has all the internals needed to detect whether GLX and EGL
are available, so exposing a simple API is a better alternative.
Fixes#73
Since Epoxy can be built with different platform-specific API, having a
way for dependent projects to discover those capabilities without
necessarily crashing the minute they attempt to use them is a good
feature to have.
We strongly direct library and application developers to use pkg-config
in order to use Epoxy, so it makes sense to add variables to the
epoxy.pc file that can be easily extracted at configuration time.
Currently, GLX support in libepoxy at build time is hard coded, but
various platforms have expressed their preference for having a
configure-time option for it.
For instance:
- various embedded distributors do not ship with X11, but wish to use
libraries that depend on libepoxy now that Wayland is available
- distributors for macOS still wish to retain the ability to ship
their software with X11 enabled
By default, we want epoxy to build with GLX enabled pretty much
everywhere it makes sense, since it's only a build-time option and it's
not a run-time dependency.
Libraries and applications that depend on Epoxy currently have no way to
safely degrade functionality if they are used on a platform without GLX
support; the only way to achieve that is to perform a symbol check
themselves, by essentially copying what Epoxy already does.
By exposing `epoxy_has_glx()`, those libraries and applications now have
the chance of querying Epoxy itself and gracefully handle failure.
When checking whether GLX or EGL are available on the system, we don't
want to use the internal API that forces an exit() on missing libraries
and symbols — as that would defeat the point.
Instead, we should have safe functions to call internally that simply
return a NULL pointer, so we can bail out ourselves in a controlled
fashion.
The build is conditional on:
* using the Meson build
* passing the `-Denable-docs=true` configuration switch
* having `doxygen` installed
Currently, the generated HTML is kind of empty, but it works.
We don't really use `sudo` anywhere, except for installing packages;
this means we should be able to use the faster container-based
environment on Travis, instead of the VM-based one.
Older versions of the Microsoft Visual C compiler do not support C99 and
do not have stdbool.h.
Additionally, Epoxy is pretty much C89 compliant, and stdbool.h is part
of C99.
We can add a simple fallback for MSVC, in case we end up getting built
with it.
This reverts commit de84448e3a.
In order to make Epoxy build on Travis with the Precise package set, we
need to revert this commit, as the autotools version shipped on Ubuntu
12.04 bail out at the missing macro directory — whereas newer versions
just create it if needed.
Updating the Travis environment to Trusty allows the build to finish,
but have the knock-on effect of making more tests run — and the
EGL-without-GLX tests fail. Since there's nothing newer than Trusty on
Travis, we should back out this change until we have the ability to
build a suitable test/CI environment.
The new GL registry XML contains the 'glsc2' identifier for the OpenGL
SC 2.0 API. We can safely ignore it, since we don't really know what to
do with it, at the moment.
We should explicitly add the include directory under the mingw64
toolchain to the C arguments when cross-compiling, just like we add the
libdir to the link flags.
On UNIX-like OSes, the OS will read the shebang and use the correct
interpreter, and on Windows, Meson will read the shebang and use the
correct interpreter.
Adding it manually will cause python to try to interpret python
Use the appropriate Markdown syntax (with GitHub extensions) for code
blocks and preformatted bits, and update the build instructions and
dependencies for Meson and Ninja.
To avoid a symbols file on Windows, Epoxy annotates all the publicly
visible symbols directly in the source, but uses the default symbol
visibility everywhere else. This means that only some symbols are
annotated as `EPOXY_IMPORTEXPORT`, and generally only on Windows.
Additionally, Epoxy has a private 'PUBLIC' pre-processor macro for
internal use, which duplicates the `EPOXY_IMPORTEXPORT` but contains
more logic to detect GCC, in case we're building with GCC on Windows.
This would be enough, except that EGL is also available on Windows,
which means we'd have to annotate the exported `epoxy_*` API inside
epoxy/egl.h as well. At that point, though, we should probably avoid
any confusion, and adopt a single symbol visibility policy across the
board.
This requires some surgery of the generated and common dispatch sources,
but cuts down the overall complexity:
- there is only one annotation, `EPOXY_PUBLIC`, used everywhere
- the annotation detection is done at Epoxy configuration time
- only annotated symbols are public, on every platform
- annotated symbols are immediately visible from the header
We're going to use this header to provide shared macros. Right now, we
can use it to replace the:
#ifdef __cplusplus
extern "C" {
#endif
…
#ifdef __cplusplus
}
#endif
Stanzas for every installed header, with easier to read macros in the
same spirit of Cairo and GLib.
We need to explicitly link against gdi32 in order to access
SetPixelFormat and ChoosetPixelFormat, and the order of the linking is
relevant when using static libraries. This is a slight workaround to the
order of compiler arguments generated by Meson, and it's supposed to go
away in the near future.
Meson uses plain text files for describing the cross-compilation
environment, binaries, and properties.
The values are taken from the mingw wrapper around configure that
Fedora provides for autotools projects.
Instead of using a generator and having to deal with tweaking the
inclusion paths, we can use a custom target rule, which will do the
right thing and put the generate files where we expect them to be.
Due to how Meson and Ninja work we need to be a bit more careful as to
how we deal with dependencies and generated files, especially since
Epoxy is built on the assumption that the only inclusion path for the
headers lies under the 'include' sub-directory.
First of all, we need to split the dispatch table generation into two
separate steps, one for the headers and one for the source files.
Additionally, we need to munge the paths of the non-generated headers
so that we reference them by their correct path.
These changes are necessary to ensure that Epoxy can be built on a
system without Epoxy installed already; the previous Meson-based build
system relied on the headers being installed in a system directory.
Meson is a Python-based build system that generates build rules of
Ninja, Visual Studio, and XCode. It's designed to be fast, and have a
small, non-Turing complete language to describe the build process,
tests, and dependencies. It's simpler than CMake, and faster than
autotools.
As a direct comparison in terms of speed, three build and check runs for
libepoxy from a clean Git repository clone yield these results on my
Kabylake Core i7 7500U (nproc=4):
- Autotools (make)
Run #1 (cold) real: 22.384s, user: 20.011s, sys: 3.689s
Run #2 (warm) real: 22.429s, user: 20.220s, sys: 3.708s
Run #3 (warm) real: 22.068s, user: 19.743s, sys: 3.594s
- Meson (ninja)
Run #1 (cold) real: 5.932s, user: 9.371s, sys: 1.625s
Run #2 (warm) real: 6.273s, user: 10.066, sys: 1.740s
Run #3 (warm) real: 5.796s, user: 9.233s, sys: 1.607s
Which means that Meson and ninja are approximately 4x faster than
autotools.
In terms of simplicity, the autotools build takes six files and a total
of 645 lines; Meson requires 3 files, and 361 lines to achieve the same
result. Additionally, Meson automatically builds in a separate build
directory and does not leave files inside the source directory; and Meson
does not use libtool.
Since Meson is quite new and still actively developed, we're going to
leave the autotools build in place for a while, with the intention of
switching to Meson in the future.
The gen_dispatch.py script relies on the source and include directories
to exist before dumping the files in there, split by type, in order to
sustain the split of the headers existing in a separate root from the
source files. This causes a spooky-action-at-a-distance scenario where
headers are generated by rules inside the source directory but influence
the contents of a separate directory — and require a separate set of
rules to install those headers.
Different build systems would require either splitting the generation in
to two separate passes (which is more expensive and time consuming), or
generate the header and source files in the same directory, and just
tweak the inclusion paths accordingly.
Since we want to maintain this fiction for the autotools build, but
ignore it for different build systems, let's add a separate set of
arguments for gen_dispatch.py that make the rules inside Makefile.am
work appropriately.
Emmanuele Bassi
Emmanuele Bassi
Nirbheek Chauhan
Patrick Griffis