[librsvg/wip/rust-api: 7/11] librsvg_crate: Add a build.rs to find libcroco via pkg-config

[Federico Mena Quintero <federico src gnome org>]

commit 254452d4d1a1a74aced0f9379c87ba3de3d96407
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed Feb 13 18:12:32 2019 -0600

    librsvg_crate: Add a build.rs to find libcroco via pkg-config
    
    This will also pull in libxml2 automatically.

 Cargo.lock               |  1 +
 librsvg_crate/Cargo.toml |  4 +++
 librsvg_crate/build.rs   | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+)
---
diff --git a/Cargo.lock b/Cargo.lock
index 4f5f0d7b..a4145ef2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -591,6 +591,7 @@ dependencies = [
  "cairo-rs 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "gio 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "glib 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rsvg_internals 0.0.1",
  "url 1.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
diff --git a/librsvg_crate/Cargo.toml b/librsvg_crate/Cargo.toml
index 16309072..d361501e 100644
--- a/librsvg_crate/Cargo.toml
+++ b/librsvg_crate/Cargo.toml
@@ -3,6 +3,7 @@ name = "librsvg"
 version = "0.0.1"
 authors = ["Federico Mena Quintero <federico gnome org>"]
 workspace = "../"
+build = "build.rs"
 
 [lib]
 name = "librsvg"
@@ -16,3 +17,6 @@ url = "1.7.2"
 
 [dev-dependencies]
 cairo-rs = { version = "0.5.0", features = ["png"] }
+
+[build-dependencies]
+pkg-config = "0.3.14"
diff --git a/librsvg_crate/build.rs b/librsvg_crate/build.rs
new file mode 100644
index 00000000..5dc5139e
--- /dev/null
+++ b/librsvg_crate/build.rs
@@ -0,0 +1,65 @@
+extern crate pkg_config;
+
+use std::env;
+use std::io;
+use std::io::prelude::*;
+use std::process;
+
+use pkg_config::{Config, Error};
+
+fn main() {
+    // libcroco pulls in libxml2, so the first one is enough
+    if let Err(s) = find("libcroco-0.6", "0.6.1", &["croco-0.6"]) {
+        let _ = writeln!(io::stderr(), "{}", s);
+        process::exit(1);
+    }
+}
+
+// This is stolen from the -sys crates in gtk-rs
+fn find(package_name: &str, version: &str, shared_libs: &[&str]) -> Result<(), Error> {
+    if let Ok(inc_dir) = env::var("GTK_INCLUDE_DIR") {
+        println!("cargo:include={}", inc_dir);
+    }
+    if let Ok(lib_dir) = env::var("GTK_LIB_DIR") {
+        for lib_ in shared_libs.iter() {
+            println!("cargo:rustc-link-lib=dylib={}", lib_);
+        }
+        println!("cargo:rustc-link-search=native={}", lib_dir);
+        return Ok(());
+    }
+
+    let target = env::var("TARGET").unwrap();
+    let hardcode_shared_libs = target.contains("windows");
+
+    let mut config = Config::new();
+    config.atleast_version(version);
+    config.print_system_libs(false);
+
+    if hardcode_shared_libs {
+        config.cargo_metadata(false);
+    }
+    match config.probe(package_name) {
+        Ok(library) => {
+            if let Ok(paths) = std::env::join_paths(library.include_paths) {
+                // Exposed to other build scripts as DEP_CAIRO_INCLUDE; use env::split_paths
+                println!("cargo:include={}", paths.to_string_lossy());
+            }
+            if hardcode_shared_libs {
+                for lib_ in shared_libs.iter() {
+                    println!("cargo:rustc-link-lib=dylib={}", lib_);
+                }
+                for path in library.link_paths.iter() {
+                    println!("cargo:rustc-link-search=native={}", path.to_str().unwrap());
+                }
+            }
+            Ok(())
+        }
+        Err(Error::EnvNoPkgConfig(_)) | Err(Error::Command { .. }) => {
+            for lib_ in shared_libs.iter() {
+                println!("cargo:rustc-link-lib=dylib={}", lib_);
+            }
+            Ok(())
+        }
+        Err(err) => Err(err),
+    }
+}