Add Linux implementation of the platform view example (#123731)

examples/platform_view/lib/main.dart

@@ -57,8 +57,9 @@ class _MyHomePageState extends State<MyHomePage> {
         return const Text('Continue in Windows view');
       case TargetPlatform.macOS:
         return const Text('Continue in macOS view');
-      case TargetPlatform.fuchsia:
       case TargetPlatform.linux:
+        return const Text('Continue in Linux view');
+      case TargetPlatform.fuchsia:
         throw UnimplementedError('Platform not yet implemented');
     }
   }

examples/platform_view/linux/CMakeLists.txt

@@ -0,0 +1,140 @@
+# Project-level configuration.
+cmake_minimum_required(VERSION 3.10)
+project(runner LANGUAGES CXX)
+set(CMAKE_CXX_STANDARD 17)
+
+# The name of the executable created for the application. Change this to change
+# the on-disk name of your application.
+set(BINARY_NAME "platform_view")
+# The unique GTK application identifier for this application. See:
+# https://wiki.gnome.org/HowDoI/ChooseApplicationID
+set(APPLICATION_ID "io.flutter.examples.platform_view")
+
+# Explicitly opt in to modern CMake behaviors to avoid warnings with recent
+# versions of CMake.
+cmake_policy(SET CMP0063 NEW)
+
+# Load bundled libraries from the lib/ directory relative to the binary.
+set(CMAKE_INSTALL_RPATH "$ORIGIN/lib")
+
+# Root filesystem for cross-building.
+if(FLUTTER_TARGET_PLATFORM_SYSROOT)
+  set(CMAKE_SYSROOT ${FLUTTER_TARGET_PLATFORM_SYSROOT})
+  set(CMAKE_FIND_ROOT_PATH ${CMAKE_SYSROOT})
+  set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+  set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
+  set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+  set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+endif()
+
+# Define build configuration options.
+if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
+  set(CMAKE_BUILD_TYPE "Debug" CACHE
+    STRING "Flutter build mode" FORCE)
+  set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS
+    "Debug" "Profile" "Release")
+endif()
+
+# Compilation settings that should be applied to most targets.
+#
+# Be cautious about adding new options here, as plugins use this function by
+# default. In most cases, you should add new options to specific targets instead
+# of modifying this function.
+function(APPLY_STANDARD_SETTINGS TARGET)
+  target_compile_features(${TARGET} PUBLIC cxx_std_14)
+  target_compile_options(${TARGET} PRIVATE -Wall -Werror)
+  target_compile_options(${TARGET} PRIVATE "$<$<NOT:$<CONFIG:Debug>>:-O3>")
+  target_compile_definitions(${TARGET} PRIVATE "$<$<NOT:$<CONFIG:Debug>>:NDEBUG>")
+endfunction()
+
+# Flutter library and tool build rules.
+set(FLUTTER_MANAGED_DIR "${CMAKE_CURRENT_SOURCE_DIR}/flutter")
+add_subdirectory(${FLUTTER_MANAGED_DIR})
+
+# System-level dependencies.
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(GTK REQUIRED IMPORTED_TARGET gtk+-3.0)
+
+add_definitions(-DAPPLICATION_ID="${APPLICATION_ID}")
+
+# Define the application target. To change its name, change BINARY_NAME above,
+# not the value here, or `flutter run` will no longer work.
+#
+# Any new source files that you add to the application should be added here.
+add_executable(${BINARY_NAME}
+  "main.cc"
+  "my_application.cc"
+  "${FLUTTER_MANAGED_DIR}/generated_plugin_registrant.cc"
+)
+
+# Apply the standard set of build settings. This can be removed for applications
+# that need different build settings.
+apply_standard_settings(${BINARY_NAME})
+
+# Add dependency libraries. Add any application-specific dependencies here.
+target_link_libraries(${BINARY_NAME} PRIVATE flutter)
+target_link_libraries(${BINARY_NAME} PRIVATE PkgConfig::GTK)
+
+# Run the Flutter tool portions of the build. This must not be removed.
+add_dependencies(${BINARY_NAME} flutter_assemble)
+
+# Only the install-generated bundle's copy of the executable will launch
+# correctly, since the resources must in the right relative locations. To avoid
+# people trying to run the unbundled copy, put it in a subdirectory instead of
+# the default top-level location.
+set_target_properties(${BINARY_NAME}
+  PROPERTIES
+  RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/intermediates_do_not_run"
+)
+
+
+# Generated plugin build rules, which manage building the plugins and adding
+# them to the application.
+include(flutter/generated_plugins.cmake)
+
+
+# === Installation ===
+# By default, "installing" just makes a relocatable bundle in the build
+# directory.
+set(BUILD_BUNDLE_DIR "${PROJECT_BINARY_DIR}/bundle")
+if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+  set(CMAKE_INSTALL_PREFIX "${BUILD_BUNDLE_DIR}" CACHE PATH "..." FORCE)
+endif()
+
+# Start with a clean build bundle directory every time.
+install(CODE "
+  file(REMOVE_RECURSE \"${BUILD_BUNDLE_DIR}/\")
+  " COMPONENT Runtime)
+
+set(INSTALL_BUNDLE_DATA_DIR "${CMAKE_INSTALL_PREFIX}/data")
+set(INSTALL_BUNDLE_LIB_DIR "${CMAKE_INSTALL_PREFIX}/lib")
+
+install(TARGETS ${BINARY_NAME} RUNTIME DESTINATION "${CMAKE_INSTALL_PREFIX}"
+  COMPONENT Runtime)
+
+install(FILES "${FLUTTER_ICU_DATA_FILE}" DESTINATION "${INSTALL_BUNDLE_DATA_DIR}"
+  COMPONENT Runtime)
+
+install(FILES "${FLUTTER_LIBRARY}" DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
+  COMPONENT Runtime)
+
+foreach(bundled_library ${PLUGIN_BUNDLED_LIBRARIES})
+  install(FILES "${bundled_library}"
+    DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
+    COMPONENT Runtime)
+endforeach(bundled_library)
+
+# Fully re-copy the assets directory on each build to avoid having stale files
+# from a previous install.
+set(FLUTTER_ASSET_DIR_NAME "flutter_assets")
+install(CODE "
+  file(REMOVE_RECURSE \"${INSTALL_BUNDLE_DATA_DIR}/${FLUTTER_ASSET_DIR_NAME}\")
+  " COMPONENT Runtime)
+install(DIRECTORY "${PROJECT_BUILD_DIR}/${FLUTTER_ASSET_DIR_NAME}"
+  DESTINATION "${INSTALL_BUNDLE_DATA_DIR}" COMPONENT Runtime)
+
+# Install the AOT library on non-Debug builds only.
+if(NOT CMAKE_BUILD_TYPE MATCHES "Debug")
+  install(FILES "${AOT_LIBRARY}" DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
+    COMPONENT Runtime)
+endif()

examples/platform_view/linux/flutter/CMakeLists.txt

@@ -0,0 +1,88 @@
+# This file controls Flutter-level build steps. It should not be edited.
+cmake_minimum_required(VERSION 3.10)
+
+set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")
+
+# Configuration provided via flutter tool.
+include(${EPHEMERAL_DIR}/generated_config.cmake)
+
+# TODO: Move the rest of this into files in ephemeral. See
+# https://github.com/flutter/flutter/issues/57146.
+
+# Serves the same purpose as list(TRANSFORM ... PREPEND ...),
+# which isn't available in 3.10.
+function(list_prepend LIST_NAME PREFIX)
+    set(NEW_LIST "")
+    foreach(element ${${LIST_NAME}})
+        list(APPEND NEW_LIST "${PREFIX}${element}")
+    endforeach(element)
+    set(${LIST_NAME} "${NEW_LIST}" PARENT_SCOPE)
+endfunction()
+
+# === Flutter Library ===
+# System-level dependencies.
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(GTK REQUIRED IMPORTED_TARGET gtk+-3.0)
+pkg_check_modules(GLIB REQUIRED IMPORTED_TARGET glib-2.0)
+pkg_check_modules(GIO REQUIRED IMPORTED_TARGET gio-2.0)
+
+set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/libflutter_linux_gtk.so")
+
+# Published to parent scope for install step.
+set(FLUTTER_LIBRARY ${FLUTTER_LIBRARY} PARENT_SCOPE)
+set(FLUTTER_ICU_DATA_FILE "${EPHEMERAL_DIR}/icudtl.dat" PARENT_SCOPE)
+set(PROJECT_BUILD_DIR "${PROJECT_DIR}/build/" PARENT_SCOPE)
+set(AOT_LIBRARY "${PROJECT_DIR}/build/lib/libapp.so" PARENT_SCOPE)
+
+list(APPEND FLUTTER_LIBRARY_HEADERS
+  "fl_basic_message_channel.h"
+  "fl_binary_codec.h"
+  "fl_binary_messenger.h"
+  "fl_dart_project.h"
+  "fl_engine.h"
+  "fl_json_message_codec.h"
+  "fl_json_method_codec.h"
+  "fl_message_codec.h"
+  "fl_method_call.h"
+  "fl_method_channel.h"
+  "fl_method_codec.h"
+  "fl_method_response.h"
+  "fl_plugin_registrar.h"
+  "fl_plugin_registry.h"
+  "fl_standard_message_codec.h"
+  "fl_standard_method_codec.h"
+  "fl_string_codec.h"
+  "fl_value.h"
+  "fl_view.h"
+  "flutter_linux.h"
+)
+list_prepend(FLUTTER_LIBRARY_HEADERS "${EPHEMERAL_DIR}/flutter_linux/")
+add_library(flutter INTERFACE)
+target_include_directories(flutter INTERFACE
+  "${EPHEMERAL_DIR}"
+)
+target_link_libraries(flutter INTERFACE "${FLUTTER_LIBRARY}")
+target_link_libraries(flutter INTERFACE
+  PkgConfig::GTK
+  PkgConfig::GLIB
+  PkgConfig::GIO
+)
+add_dependencies(flutter flutter_assemble)
+
+# === Flutter tool backend ===
+# _phony_ is a non-existent file to force this command to run every time,
+# since currently there's no way to get a full input/output list from the
+# flutter tool.
+add_custom_command(
+  OUTPUT ${FLUTTER_LIBRARY} ${FLUTTER_LIBRARY_HEADERS}
+    ${CMAKE_CURRENT_BINARY_DIR}/_phony_
+  COMMAND ${CMAKE_COMMAND} -E env
+    ${FLUTTER_TOOL_ENVIRONMENT}
+    "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.sh"
+      ${FLUTTER_TARGET_PLATFORM} ${CMAKE_BUILD_TYPE}
+  VERBATIM
+)
+add_custom_target(flutter_assemble DEPENDS
+  "${FLUTTER_LIBRARY}"
+  ${FLUTTER_LIBRARY_HEADERS}
+)

examples/platform_view/linux/main.cc

@@ -0,0 +1,10 @@
+// Copyright 2014 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 "my_application.h"
+
+int main(int argc, char** argv) {
+  g_autoptr(MyApplication) app = my_application_new();
+  return g_application_run(G_APPLICATION(app), argc, argv);
+}

examples/platform_view/linux/my_application.cc

@@ -0,0 +1,167 @@
+// Copyright 2014 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 "my_application.h"
+
+#include <flutter_linux/flutter_linux.h>
+
+#ifdef GDK_WINDOWING_X11
+#include <gdk/gdkx.h>
+#endif
+
+#include "flutter/generated_plugin_registrant.h"
+
+struct _MyApplication {
+  GtkApplication parent_instance;
+
+  // Channel to receive platform view requests from Flutter.
+  FlMethodChannel* platform_view_channel;
+
+  // Main window.
+  GtkWindow* window;
+
+  // Current counter.
+  int64_t counter;
+
+  // Request in progress.
+  FlMethodCall* method_call;
+
+  // Native window requested by Flutter.
+  GtkWindow* native_window;
+
+  // Label to show count.
+  GtkLabel* counter_label;
+};
+
+G_DEFINE_TYPE(MyApplication, my_application, GTK_TYPE_APPLICATION)
+
+static void update_counter_label(MyApplication* self) {
+  g_autofree gchar* text =
+      g_strdup_printf("Button tapped %" G_GINT64_FORMAT " %s.", self->counter,
+                      self->counter == 1 ? "time" : "times");
+  gtk_label_set_text(self->counter_label, text);
+}
+
+static void button_clicked_cb(MyApplication* self) {
+  self->counter++;
+  update_counter_label(self);
+}
+
+static void native_window_delete_event_cb(MyApplication* self,
+                                          gint response_id) {
+  g_autoptr(FlValue) counter_value = fl_value_new_int(self->counter);
+  fl_method_call_respond_success(self->method_call, counter_value, nullptr);
+  g_clear_object(&self->method_call);
+}
+
+// Handle request to switch the view.
+static void handle_switch_view(MyApplication* self, FlMethodCall* method_call) {
+  FlValue* counter_value = fl_method_call_get_args(method_call);
+  if (fl_value_get_type(counter_value) != FL_VALUE_TYPE_INT) {
+    fl_method_call_respond_error(self->method_call, "Invalid args",
+                                 "Invalid switchView args", nullptr, nullptr);
+    return;
+  }
+
+  self->counter = fl_value_get_int(counter_value);
+  self->method_call = FL_METHOD_CALL(g_object_ref(method_call));
+
+  // Show the same UI in a native window.
+  self->native_window = GTK_WINDOW(gtk_window_new(GTK_WINDOW_TOPLEVEL));
+  gtk_window_set_transient_for(self->native_window, self->window);
+  gtk_window_set_modal(self->native_window, TRUE);
+  gtk_window_set_destroy_with_parent(self->native_window, TRUE);
+  g_signal_connect_swapped(self->native_window, "delete-event",
+                           G_CALLBACK(native_window_delete_event_cb), self);
+
+  GtkWidget* box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 12);
+  gtk_widget_set_margin_start(box, 24);
+  gtk_widget_set_margin_end(box, 24);
+  gtk_widget_set_margin_top(box, 24);
+  gtk_widget_set_margin_bottom(box, 24);
+  gtk_widget_show(box);
+  gtk_container_add(GTK_CONTAINER(self->native_window), box);
+
+  self->counter_label = GTK_LABEL(gtk_label_new(""));
+  gtk_widget_show(GTK_WIDGET(self->counter_label));
+  gtk_container_add(GTK_CONTAINER(box), GTK_WIDGET(self->counter_label));
+
+  GtkWidget* button = gtk_button_new_with_label("+");
+  gtk_style_context_add_class(gtk_widget_get_style_context(GTK_WIDGET(button)),
+                              "circular");
+  gtk_widget_set_halign(button, GTK_ALIGN_CENTER);
+  gtk_widget_show(button);
+  gtk_container_add(GTK_CONTAINER(box), button);
+  g_signal_connect_swapped(button, "clicked", G_CALLBACK(button_clicked_cb),
+                           self);
+
+  update_counter_label(self);
+
+  gtk_window_present(self->native_window);
+}
+
+// Handle platform view requests from Flutter.
+static void platform_view_channel_method_cb(FlMethodChannel* channel,
+                                            FlMethodCall* method_call,
+                                            gpointer user_data) {
+  MyApplication* self = MY_APPLICATION(user_data);
+
+  const char* name = fl_method_call_get_name(method_call);
+  if (g_str_equal(name, "switchView")) {
+    handle_switch_view(self, method_call);
+  } else {
+    fl_method_call_respond_not_implemented(method_call, nullptr);
+  }
+}
+
+// Implements GObject::dispose.
+static void my_application_dispose(GObject* object) {
+  MyApplication* self = MY_APPLICATION(object);
+
+  g_clear_object(&self->platform_view_channel);
+
+  G_OBJECT_CLASS(my_application_parent_class)->dispose(object);
+}
+
+// Implements GApplication::activate.
+static void my_application_activate(GApplication* application) {
+  MyApplication* self = MY_APPLICATION(application);
+  self->window =
+      GTK_WINDOW(gtk_application_window_new(GTK_APPLICATION(application)));
+
+  gtk_window_set_default_size(self->window, 1280, 720);
+  gtk_widget_show(GTK_WIDGET(self->window));
+
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  FlView* view = fl_view_new(project);
+  gtk_widget_show(GTK_WIDGET(view));
+  gtk_container_add(GTK_CONTAINER(self->window), GTK_WIDGET(view));
+
+  // Create channel to handle platform view requests from Flutter.
+  FlEngine* engine = fl_view_get_engine(view);
+  g_autoptr(FlStandardMethodCodec) codec = fl_standard_method_codec_new();
+  self->platform_view_channel = fl_method_channel_new(
+      fl_engine_get_binary_messenger(engine),
+      "samples.flutter.io/platform_view", FL_METHOD_CODEC(codec));
+  fl_method_channel_set_method_call_handler(self->platform_view_channel,
+                                            platform_view_channel_method_cb,
+                                            self, nullptr);
+
+  fl_register_plugins(FL_PLUGIN_REGISTRY(view));
+
+  gtk_widget_grab_focus(GTK_WIDGET(view));
+}
+
+static void my_application_class_init(MyApplicationClass* klass) {
+  G_OBJECT_CLASS(klass)->dispose = my_application_dispose;
+  G_APPLICATION_CLASS(klass)->activate = my_application_activate;
+}
+
+static void my_application_init(MyApplication* self) {}
+
+MyApplication* my_application_new() {
+  return MY_APPLICATION(g_object_new(my_application_get_type(),
+                                     "application-id", APPLICATION_ID, "flags",
+                                     G_APPLICATION_NON_UNIQUE, nullptr));
+}

examples/platform_view/linux/my_application.h

@@ -0,0 +1,22 @@
+// Copyright 2014 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_MY_APPLICATION_H_
+#define FLUTTER_MY_APPLICATION_H_
+
+#include <gtk/gtk.h>
+
+G_DECLARE_FINAL_TYPE(MyApplication, my_application, MY, APPLICATION,
+                     GtkApplication)
+
+/**
+ * my_application_new:
+ *
+ * Creates a new Flutter-based application.
+ *
+ * Returns: a new #MyApplication.
+ */
+MyApplication* my_application_new();
+
+#endif  // FLUTTER_MY_APPLICATION_H_