use cbindgen for FFI

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.18...4.2)
+cmake_minimum_required(VERSION 4.2)
 
 project(PROJECT-NAME VERSION 1.0.0 LANGUAGES CXX)
 
@@ -7,7 +7,9 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 find_package(Qt6 REQUIRED COMPONENTS Gui Widgets)
 find_program(CARGO cargo REQUIRED)
-set(CARGO_TARGET_DIR "${CMAKE_SOURCE_DIR}/target" CACHE PATH "Path to the Cargo target directory")
+set(CARGO_TARGET_DIR "${CMAKE_BINARY_DIR}/cargo")
+
+include(cbindgen.cmake)
 
 qt_standard_project_setup()
 

cbindgen.cmake

@@ -0,0 +1,13 @@
+option(LOCAL_CBINDGEN "Download and build `cbindgen` even if one can be found on the system")
+
+if(NOT LOCAL_CBINDGEN)
+	find_program(CBINDGEN cbindgen)
+endif()
+
+if(NOT CBINDGEN)
+	message(CONFIGURE_LOG "cbindgen not found, downloading...")
+	set(crates "${CMAKE_BINARY_DIR}/crates")
+	file(MAKE_DIRECTORY ${crates})
+	execute_process(COMMAND ${CARGO} install --root ${crates} cbindgen@0.29.4)
+	set(CACHE{CBINDGEN} TYPE FILEPATH FORCE VALUE "${crates}/bin/cbindgen")
+endif()

src/camera.rs

@@ -50,10 +50,10 @@ mod tests {
 	fn test_view() {
 		let mut ok = true;
 		for (yaw, pitch, x1, y1, z1) in [
-			(0.0, 0.0, [0., 0., -4.], [-1., 0., -3.], [0., 1., -3.]),
-			(0.5, 0.0, [-1., 0., -3.], [0., 0., -2.], [0., 1., -3.]),
-			(0.0, 0.5, [0., 1., -3.], [-1., 0., -3.], [0., 0., -2.]),
-			(0.5, 0.5, [-1., 0., -3.], [0., -1., -3.], [0., 0., -2.]),
+			(0.0, 0.0, [0., 0., 2.], [-1., 0., 3.], [0., 1., 3.]),
+			(0.5, 0.0, [1., 0., 3.], [0., 0., 2.], [0., 1., 3.]),
+			(0.0, 0.5, [0., -1., 3.], [-1., 0., 3.], [0., 0., 2.]),
+			(0.5, 0.5, [1., 0., 3.], [0., -1., 3.], [0., 0., 2.]),
 		] {
 			let m = view(yaw * PI, pitch * PI, 3.);
 			for (label, world, expected) in

ui/cbindgen.toml

@@ -0,0 +1,14 @@
+includes = ["types.hxx"]
+sys_includes = ["cstdint"]
+pragma_once = true
+no_includes = true
+namespace = "ffi"
+tab_width = 4
+language = "C++"
+
+[parse]
+parse_deps = true
+include = ["PROJECT-NAME"]
+
+[export]
+exclude = ["Box"]

ui/impl.cmake

@@ -1,33 +1,45 @@
 # build the Rust side as a static library
 set(impl_basename "${CARGO_TARGET_DIR}/release/libPROJECT_NAME_impl")
 
-set(cargo_cmake_args)
-
-if("${CMAKE_VERSION}" VERSION_GREATER_EQUAL "3.27")
-	list(APPEND cargo_cmake_args DEPENDS_EXPLICIT_ONLY)
-endif()
-
-if("${CMAKE_VERSION}" VERSION_GREATER_EQUAL "3.28")
-	list(APPEND cargo_cmake_args JOB_SERVER_AWARE TRUE)
-endif()
-
 add_custom_command(
-	OUTPUT "${impl_basename}.a"
-	COMMAND env "CARGO_TARGET_DIR=${CARGO_TARGET_DIR}" ${CARGO} build --release --package PROJECT-NAME-impl
-	WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
-	DEPFILE "${impl_basename}.d"
+	OUTPUT ${impl_basename}.a
+	COMMAND env CARGO_TARGET_DIR=${CARGO_TARGET_DIR} ${CARGO} build --release --package PROJECT-NAME-impl
+	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+	DEPFILE ${impl_basename}.d
 	USES_TERMINAL
+	JOB_SERVER_AWARE TRUE
 	VERBATIM
-	${cargo_cmake_args}
+	DEPENDS_EXPLICIT_ONLY
 )
 
 # HACK ensure CMake *actually adds* the command above
 add_custom_target(build_impl
-	DEPENDS "${impl_basename}.a"
+	DEPENDS ${impl_basename}.a
 )
 
 add_library(PROJECT_NAME_impl STATIC IMPORTED)
 
 set_target_properties(PROJECT_NAME_impl PROPERTIES
-	IMPORTED_LOCATION "${impl_basename}.a"
+	IMPORTED_LOCATION ${impl_basename}.a
+)
+
+# generate the bindings
+file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/include")
+set(bindings_basename "${CMAKE_CURRENT_BINARY_DIR}/include/bindings")
+
+add_custom_command(
+	OUTPUT ${bindings_basename}.hxx
+	COMMAND ${CBINDGEN} --only-target-dependencies --output "${bindings_basename}.hxx" --depfile "${bindings_basename}.d"
+	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+	DEPFILE ${bindings_basename}.d
+	VERBATIM
+	CODEGEN
+	DEPENDS_EXPLICIT_ONLY
+)
+
+target_sources(PROJECT_NAME_impl INTERFACE
+	${bindings_basename}.hxx
+)
+target_include_directories(PROJECT_NAME_impl INTERFACE
+	"${CMAKE_CURRENT_BINARY_DIR}/include"
 )

ui/src/api.cxx

@@ -3,13 +3,6 @@
 #include <stdexcept>
 #include <utility>
 
-namespace ffi {
-extern "C" Core* rt4_viewport_create(xcb_connection_t* connection, std::uint32_t window, std::uint32_t width, std::uint32_t height);
-extern "C" void rt4_viewport_destroy(Core* viewport);
-extern "C" void rt4_viewport_configure(Core* viewport, std::uint32_t width, std::uint32_t height);
-extern "C" void rt4_viewport_redraw(Core* viewport, const RedrawArgs* args);
-} // namespace ffi
-
 BoxCore::BoxCore(BoxCore&& b)
 	: ptr(std::exchange(b.ptr, {})) {
 }

ui/src/api.hxx

@@ -2,23 +2,10 @@
 
 #include <cstdint>
 
+#include "bindings.hxx"
+
 struct xcb_connection_t;
 
-struct alignas(16) Vec4 {
-	float x, y, z, w;
-};
-
-namespace ffi {
-struct Core;
-
-struct RedrawArgs {
-	float cam_yaw;
-	float cam_pitch;
-	float cam_distance;
-	float cam_fovy;
-};
-} // namespace ffi
-
 using ffi::RedrawArgs;
 
 class MutCore {

ui/src/types.hxx

@@ -0,0 +1,12 @@
+#pragma once
+
+struct alignas(16) Vec4 {
+	float x, y, z, w;
+};
+
+namespace ffi {
+
+template <typename T>
+using Box = T*;
+
+} // namespace ffi