Add freetype feature

Uses the upstream "imgui_freetype" to "Build font atlases using FreeType instead of stb_truetype (which is the default font rasterizer)"

Closes #359

imgui-sys/Cargo.toml

@@ -18,7 +18,9 @@ chlorine = "1.0.7"
 
 [build-dependencies]
 cc = "1.0"
+pkg-config = { version="0.3", optional=true }
 
 [features]
 default = []
 wasm = []
+freetype = ["pkg-config"]

imgui-sys/build.rs

@@ -48,6 +48,20 @@ fn main() -> io::Result<()> {
             build.define(key, *value);
         }
 
+        // Freetype font rasterizer feature
+        if std::env::var_os("CARGO_FEATURE_FREETYPE").is_some() {
+            let freetype = pkg_config::Config::new().find("freetype2").unwrap();
+            for include in freetype.include_paths.iter() {
+                build.include(include);
+            }
+            build.define("IMGUI_ENABLE_FREETYPE", None);
+            println!("cargo:DEFINE_{}={}", "IMGUI_ENABLE_FREETYPE", "");
+
+            // imgui_freetype.cpp needs access to imgui.h
+            build.include(
+                manifest_dir.join("third-party/imgui/"));
+        }
+
         let compiler = build.get_compiler();
         // Avoid the if-supported flag functions for easy cases, as they're
         // kinda costly.

imgui-sys/include_all_imgui.cpp

@@ -9,4 +9,8 @@
 #include "./third-party/imgui/imgui_tables.cpp"
 #include "./third-party/cimgui.cpp"
 
+#ifdef IMGUI_ENABLE_FREETYPE
+#include "./third-party/imgui/misc/freetype/imgui_freetype.cpp"
+#endif
+
 

imgui/Cargo.toml

@@ -19,6 +19,7 @@ parking_lot = "0.11"
 
 [features]
 wasm = ["imgui-sys/wasm"]
+freetype = ["imgui-sys/freetype"]
 
 [dev-dependencies]
 memoffset = "0.6"