Allow relative resource paths in GLFW embedding (#16944)

Currently every Linux runner has this code to allow relative resource paths; this moves it into the framework so that any embedder can get this behavior without that code needing to be in the template.

Rolls buildroot to pick up std::filesystem support in our libc++

BUILD.gn

@@ -75,6 +75,7 @@ group("flutter") {
       "//flutter/lib/ui:ui_unittests",
       "//flutter/runtime:runtime_unittests",
       "//flutter/shell/common:shell_unittests",
+      "//flutter/shell/platform/common/cpp:common_cpp_core_unittests",
       "//flutter/shell/platform/common/cpp/client_wrapper:client_wrapper_unittests",
       "//flutter/shell/platform/embedder:embedder_unittests",
       "//flutter/shell/platform/glfw/client_wrapper:client_wrapper_glfw_unittests",

DEPS

@@ -137,7 +137,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + 'd14f3c708fb132381f7053b4ee9e628be915ed96',
+  'src': 'https://github.com/flutter/buildroot.git' + '@' + '4489a78bf94bb9d8ea6a127106f85b7710d57f70',
 
    # Fuchsia compatibility
    #

ci/licenses_golden/licenses_flutter

@@ -798,6 +798,9 @@ FILE: ../../../flutter/shell/platform/common/cpp/client_wrapper/standard_message
 FILE: ../../../flutter/shell/platform/common/cpp/client_wrapper/standard_method_codec_unittests.cc
 FILE: ../../../flutter/shell/platform/common/cpp/incoming_message_dispatcher.cc
 FILE: ../../../flutter/shell/platform/common/cpp/incoming_message_dispatcher.h
+FILE: ../../../flutter/shell/platform/common/cpp/path_utils.cc
+FILE: ../../../flutter/shell/platform/common/cpp/path_utils.h
+FILE: ../../../flutter/shell/platform/common/cpp/path_utils_unittests.cc
 FILE: ../../../flutter/shell/platform/common/cpp/public/flutter_export.h
 FILE: ../../../flutter/shell/platform/common/cpp/public/flutter_messenger.h
 FILE: ../../../flutter/shell/platform/common/cpp/public/flutter_plugin_registrar.h

shell/platform/common/cpp/BUILD.gn

@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//flutter/testing/testing.gni")
+
 config("desktop_library_implementation") {
   defines = [ "FLUTTER_DESKTOP_LIBRARY" ]
 }
@@ -49,6 +51,10 @@ source_set("common_cpp") {
     "//flutter/shell/platform/embedder:embedder_with_symbol_prefix",
   ]
 
+  public_deps = [
+    ":common_cpp_core",
+  ]
+
   # TODO: Remove once text input model refactor lands, at which point this code
   # won't have a JSON dependency.
   defines = [ "USE_RAPID_JSON" ]
@@ -60,6 +66,41 @@ source_set("common_cpp") {
   }
 }
 
+# The portion of common_cpp that has no dependencies on the public/
+# headers. This division should be revisited once the Linux GTK
+# embedding is futher along and it's clearer how much, if any, shared
+# API surface there will be.
+source_set("common_cpp_core") {
+  public = [
+    "path_utils.h",
+  ]
+
+  sources = [
+    "path_utils.cc",
+  ]
+}
+
+test_fixtures("common_cpp_core_fixtures") {
+  fixtures = []
+}
+
+executable("common_cpp_core_unittests") {
+  testonly = true
+
+  sources = [
+    "path_utils_unittests.cc",
+  ]
+
+  deps = [
+    ":common_cpp_core",
+    ":common_cpp_core_fixtures",
+    "//flutter/testing",
+    "//third_party/dart/runtime:libdart_jit",
+  ]
+
+  public_configs = [ "//flutter:config" ]
+}
+
 copy("publish_headers") {
   sources = _public_headers
   outputs = [

shell/platform/common/cpp/path_utils.cc

+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/common/cpp/path_utils.h"
+
+#if defined(_WIN32)
+#include <windows.h>
+#elif defined(__linux__)
+#include <linux/limits.h>
+#include <unistd.h>
+#endif
+
+namespace flutter {
+
+std::filesystem::path GetExecutableDirectory() {
+#if defined(_WIN32)
+  wchar_t buffer[MAX_PATH];
+  if (GetModuleFileName(nullptr, buffer, MAX_PATH) == 0) {
+    return std::filesystem::path();
+  }
+  std::filesystem::path executable_path(buffer);
+  return executable_path.remove_filename();
+#elif defined(__linux__)
+  char buffer[PATH_MAX + 1];
+  ssize_t length = readlink("/proc/self/exe", buffer, sizeof(buffer));
+  if (length > PATH_MAX) {
+    return std::filesystem::path();
+  }
+  std::filesystem::path executable_path(std::string(buffer, length));
+  return executable_path.remove_filename();
+#else
+  return std::filesystem::path();
+#endif
+}
+
+}  // namespace flutter

shell/platform/common/cpp/path_utils.h

+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_GLFW_PATH_UTILS_H_
+#define FLUTTER_SHELL_PLATFORM_GLFW_PATH_UTILS_H_
+
+#include <filesystem>
+
+namespace flutter {
+
+// Returns the path of the directory containing this executable, or an empty
+// path if the directory cannot be found.
+std::filesystem::path GetExecutableDirectory();
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_GLFW_PATH_UTILS_H_

shell/platform/common/cpp/path_utils_unittests.cc

+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/common/cpp/path_utils.h"
+
+#include "gtest/gtest.h"
+
+namespace flutter {
+
+// Tests that GetExecutableDirectory returns a valid, absolute path.
+TEST(PathUtilsTest, ExecutableDirector) {
+  std::filesystem::path exe_directory = GetExecutableDirectory();
+#if defined(__linux__) || defined(_WIN32)
+  EXPECT_EQ(exe_directory.empty(), false);
+  EXPECT_EQ(exe_directory.is_absolute(), true);
+#else
+  // On platforms where it's not implemented, it should indicate that
+  // by returning an empty path.
+  EXPECT_EQ(exe_directory.empty(), true);
+#endif
+}
+
+}  // namespace flutter

shell/platform/glfw/flutter_glfw.cc

@@ -10,10 +10,12 @@
 #include <algorithm>
 #include <chrono>
 #include <cstdlib>
+#include <filesystem>
 #include <iostream>
 
 #include "flutter/shell/platform/common/cpp/client_wrapper/include/flutter/plugin_registrar.h"
 #include "flutter/shell/platform/common/cpp/incoming_message_dispatcher.h"
+#include "flutter/shell/platform/common/cpp/path_utils.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 #include "flutter/shell/platform/glfw/glfw_event_loop.h"
 #include "flutter/shell/platform/glfw/key_event_handler.h"
@@ -507,6 +509,25 @@ static FLUTTER_API_SYMBOL(FlutterEngine)
                 &engine_properties.switches[engine_properties.switches_count]);
   }
 
+  std::filesystem::path assets_path =
+      std::filesystem::u8path(engine_properties.assets_path);
+  std::filesystem::path icu_path =
+      std::filesystem::u8path(engine_properties.icu_data_path);
+  if (assets_path.is_relative() || icu_path.is_relative()) {
+    // Treat relative paths as relative to the directory of this executable.
+    std::filesystem::path executable_location =
+        flutter::GetExecutableDirectory();
+    if (executable_location.empty()) {
+      std::cerr << "Unable to find executable location to resolve paths."
+                << std::endl;
+      return nullptr;
+    }
+    assets_path = std::filesystem::path(executable_location) / assets_path;
+    icu_path = std::filesystem::path(executable_location) / icu_path;
+  }
+  std::string assets_path_string = assets_path.u8string();
+  std::string icu_path_string = assets_path.u8string();
+
   FlutterRendererConfig config = {};
   if (window == nullptr) {
     config.type = kOpenGL;
@@ -528,8 +549,8 @@ static FLUTTER_API_SYMBOL(FlutterEngine)
   }
   FlutterProjectArgs args = {};
   args.struct_size = sizeof(FlutterProjectArgs);
-  args.assets_path = engine_properties.assets_path;
-  args.icu_data_path = engine_properties.icu_data_path;
+  args.assets_path = assets_path_string.c_str();
+  args.icu_data_path = icu_path_string.c_str();
   args.command_line_argc = static_cast<int>(argv.size());
   args.command_line_argv = &argv[0];
   args.platform_message_callback = GLFWOnFlutterPlatformMessage;

shell/platform/glfw/public/flutter_glfw.h

@@ -38,8 +38,12 @@ typedef struct {
 // Properties for configuring a Flutter engine instance.
 typedef struct {
   // The path to the flutter_assets folder for the application to be run.
+  // This can either be an absolute path, or on Windows or Linux, a path
+  // relative to the directory containing the executable.
   const char* assets_path;
   // The path to the icudtl.dat file for the version of Flutter you are using.
+  // This can either be an absolute path, or on Windows or Linux, a path
+  // relative to the directory containing the executable.
   const char* icu_data_path;
   // The switches to pass to the Flutter engine.
   //

testing/run_tests.py

@@ -108,6 +108,8 @@ def RunCCTests(build_dir, filter):
 
   RunEngineExecutable(build_dir, 'client_wrapper_glfw_unittests', filter, shuffle_flags)
 
+  RunEngineExecutable(build_dir, 'common_cpp_core_unittests', filter, shuffle_flags)
+
   RunEngineExecutable(build_dir, 'client_wrapper_unittests', filter, shuffle_flags)
 
   # https://github.com/flutter/flutter/issues/36294