Using pre-built library?

[Fuuzetsu]

It appears glfw-sys will always compile glfw for whatever the target system is.

However we control the build system precisely and have the ability to provide it with pre-built glfw. It seems a shame/pointless to compile anyway: instead of giving it pre-built library, we instead give it all the tools to build one...

A lot of other *-sys crates allow specifying existing libraries with things like pkg-config which can also ensure all the libraries are properly presented when linking binaries later on.

Is there a reason why glfw needs to be pre-built? I'm a little confused if this is actually a requirement: the README mentions that Windows users can download pre-built glfw binaries. If so, that should imply that it's possible to use pre-compiled libraries, somehow.

[Fuuzetsu]

After some experimentation, I've come to realise that it makes no sense for this ticket to exist on glfw-sys: all glfw-sys does is build library and spit out some flags.

Instead, we should add a feature flag to glfw-rs that uses pkg-config to find the library instead of getting it via glfw-sys. I'll make a ticket there and link here.

[Fuuzetsu]

I was asked to reopen this at PistonDevelopers/glfw-rs#506 .

[Diegovsky]

Is this being worked on still?

[Fuuzetsu]

I haven't done anything but it's still desirable. I think the way to do it is you just add pkg_config to build deps and something like pkg_config::probe_library("glfw3") at start of build.rs main and in case it fails, fall back to building (current code). I guess I can try it later today if I don't forget.

[Fuuzetsu]

So, I tried a simple patch like the one at the bottom. It works in-as-so-far as getting glfw-sys to find the library and include it later. However there's an issue: once we come to try and use this in glfw-rs via glfw-sys feature flag, we get:

rust_glfw> Building src/lib.rs (glfw)
rust_glfw> Running rustc --crate-name glfw src/lib.rs --out-dir target/lib -L dependency=target/deps --cap-lints allow -L native=/nix/store/5msqd90ci50307ffs5i1avb6k78z6a41-glfw-3.3.8/lib -C opt-level=3 -C codegen-units=1 --remap-path-prefix=/build=/ --extern bitflags=/nix/store/a6bgm020s04nynwnzsbqn10ghwm5gpsf-rust_bitflags-1.3.2-lib/lib/libbitflags-25edeaf30b.rlib --extern glfw_sys=/nix/store/k4sljpxxy6c074kh5l9ajpzlw44ngzz9-rust_glfw-sys-5.0.0+3.3.9-lib/lib/libglfw_sys-29d93d1f86.rlib --extern raw_window_handle_0_5=/nix/store/9fz8iq16hmrv39qg5rjjwh874ld8xbcm-rust_raw-window-handle-0.5.2-lib/lib/libraw_window_handle-2212bb0514.rlib --cfg feature="glfw-sys" --edition 2021 -C metadata=44075dcdb8 -C extra-filename=-44075dcdb8 --crate-type lib -L native=/nix/store/5msqd90ci50307ffs5i1avb6k78z6a41-glfw-3.3.8/lib --color always
rust_glfw> error: could not find native static library `glfw3`, perhaps an -L flag is missing?
rust_glfw> error: aborting due to 1 previous error
error: builder for '/nix/store/5ijyddy0abr8cz7yswk2kj8xhvwqs8yx-rust_glfw-0.55.0.drv' failed with exit code 1;
       last 10 log lines:
       > Running phase: updateAutotoolsGnuConfigScriptsPhase
       > Running phase: configurePhase
       > Running cd .
       > Running phase: buildPhase
       > Building src/lib.rs (glfw)
       > Running rustc --crate-name glfw src/lib.rs --out-dir target/lib -L dependency=target/deps --cap-lints allow -L native=/nix/store/5msqd90ci50307ffs5i1avb6k78z6a41-glfw-3.3.8/lib -C opt-level=3 -C codegen-units=1 --remap-path-prefix=/build=/ --extern bitflags=/nix/store/a6bgm020s04nynwnzsbqn10ghwm5gpsf-rust_bitflags-1.3.2-lib/lib/libbitflags-25edeaf30b.rlib --extern glfw_sys=/nix/store/k4sljpxxy6c074kh5l9ajpzlw44ngzz9-rust_glfw-sys-5.0.0+3.3.9-lib/lib/libglfw_sys-29d93d1f86.rlib --extern raw_window_handle_0_5=/nix/store/9fz8iq16hmrv39qg5rjjwh874ld8xbcm-rust_raw-window-handle-0.5.2-lib/lib/libraw_window_handle-2212bb0514.rlib --cfg feature="glfw-sys" --edition 2021 -C metadata=44075dcdb8 -C extra-filename=-44075dcdb8 --crate-type lib -L native=/nix/store/5msqd90ci50307ffs5i1avb6k78z6a41-glfw-3.3.8/lib --color always
       > error: could not find native static library `glfw3`, perhaps an -L flag is missing?
       >
       > error: aborting due to 1 previous error
       >
       For full logs, run 'nix log /nix/store/5ijyddy0abr8cz7yswk2kj8xhvwqs8yx-rust_glfw-0.55.0.drv'.
error: 1 dependencies of derivation '/nix/store/8i5x0s9pmfp1q5pip7ak0p1njc94zpi2-rust_isim-0.1.0.drv' failed to build

We can see the -L native=/nix/store/5msqd90ci50307ffs5i1avb6k78z6a41-glfw-3.3.8/lib which is my system install that glfw-sys helpfully found. However the error message is talking about a static library! Presumably this is because of this code in glfw-rs: https://github.com/PistonDevelopers/glfw-rs/blob/b8845df2142c868557b1dc6687c0b71540203627/src/ffi/link.rs#L17 . It always assumes that glfw-sys produces a static library, which is not true anymore.

My original patch (which we are using since I made the ticket) didn't have this issue because it bypassed glfw-sys all together.

I'm not sure what the right way forward is. Should we just take off kind = "static" in link.rs? I'm not sure what the consequences are for the people using glfw-sys currently.

diff --git a/Cargo.toml b/Cargo.toml
index 720802e0..b2287c9f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,6 +17,7 @@ path = "lib.rs"
 
 [build-dependencies]
 cmake = "0.1"
+pkg-config = "0.3"
 
 [features]
 wayland = []
diff --git a/build.rs b/build.rs
index d0a2bde9..53aaeded 100644
--- a/build.rs
+++ b/build.rs
@@ -1,7 +1,15 @@
 extern crate cmake;
+extern crate pkg_config;
+
 use cmake::Config;
 
 fn main() {
+    if pkg_config::probe_library("glfw3").is_ok() {
+        // We got the library via pkg_config, we don't need to try and build it
+        // below.
+        return;
+    }
+
     let mut cfg = Config::new("glfw");
 
     cfg.define("GLFW_BUILD_EXAMPLES", "OFF")

[Fuuzetsu]

PS: In the end we also want X11 to be found by pkgconfig so we end up patching glfw-rs either way... I guess there should be x11-sys dependency that already handles this.

[Diegovsky]

Wow, thanks for working on this! It's a shame it can't be done right now tho