Place IMGUI UIs into a separate common module (#25131)

* Modularize imgui - split windows and ready to add into any app

* Comment update

* Added extra assert

* Switch to using a work scheduler instead of a stack lock for state updates

* Restyle

* typo fix

* Update to sem_wait

* Restyle

* Generate shutdown event before stoppign the event loop task

* Restyle

* Update the code to not reference Server (would not compile otherwise)

* Use a semaphore to wait for UI to send the shutdown. Also update comments

* Restyle

---------

Co-authored-by: Andrei Litvin <andreilitvin@google.com>

examples/common/imgui_ui/BUILD.gn

@@ -0,0 +1,41 @@
+# Copyright (c) 2023 Project CHIP Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import("//build_overrides/chip.gni")
+
+import("${chip_root}/build/chip/tools.gni")
+import("${chip_root}/third_party/imgui/imgui.gni")
+
+config("imgui_ui_config") {
+  # allow including via 'imgui_ui/....'
+  include_dirs = [ "../" ]
+}
+
+static_library("imgui_ui") {
+  sources = [
+    "ui.cpp",
+    "ui.h",
+  ]
+
+  deps = [
+    "${chip_root}/examples/common/imgui_ui/windows",
+    "${chip_root}/examples/platform/linux:app-main",
+    "${chip_root}/src/lib/support",
+    "${chip_root}/third_party/imgui",
+  ]
+
+  public_configs = [
+    ":imgui_ui_config",
+    "${chip_root}/third_party/imgui:imgui_config",  # propagate enabling flag
+  ]
+}

examples/common/imgui_ui/ui.cpp

@@ -0,0 +1,230 @@
+/*
+ *
+ *    Copyright (c) 2023 Project CHIP Authors
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+#include "ui.h"
+
+#include <SDL.h>
+#include <SDL_opengl.h>
+#include <imgui.h>
+#include <imgui_impl_opengl3.h>
+#include <imgui_impl_sdl2.h>
+
+#include <lib/support/logging/CHIPLogging.h>
+
+#include <atomic>
+#include <thread>
+
+namespace example {
+namespace Ui {
+namespace {
+
+// Controls running the UI event loop
+std::atomic<bool> gUiRunning{ false };
+
+void UiInit(SDL_GLContext * gl_context, SDL_Window ** window)
+{
+    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER) != 0)
+    {
+        ChipLogError(AppServer, "SDL Init Error: %s\n", SDL_GetError());
+        return;
+    }
+
+#if defined(__APPLE__)
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG); // Always required on Mac
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
+#else
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
+#endif
+
+#ifdef SDL_HINT_IME_SHOW_UI
+    SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
+#endif
+
+    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
+    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
+    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
+    SDL_WindowFlags window_flags = (SDL_WindowFlags)(SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
+    *window     = SDL_CreateWindow("Light UI", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 720, window_flags);
+    *gl_context = SDL_GL_CreateContext(*window);
+    SDL_GL_MakeCurrent(*window, *gl_context);
+    SDL_GL_SetSwapInterval(1); // Enable vsync
+
+    // Setup Dear ImGui context
+    IMGUI_CHECKVERSION();
+    ImGui::CreateContext();
+    ImGuiIO & io = ImGui::GetIO();
+    (void) io;
+    // io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
+    // io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+
+    ImGui::StyleColorsDark();
+
+    // Setup Platform/Renderer backends
+    ImGui_ImplSDL2_InitForOpenGL(*window, *gl_context);
+    ImGui_ImplOpenGL3_Init();
+}
+
+void UiShutdown(SDL_GLContext * gl_context, SDL_Window ** window)
+{
+    ImGui_ImplOpenGL3_Shutdown();
+    ImGui_ImplSDL2_Shutdown();
+    ImGui::DestroyContext();
+
+    SDL_GL_DeleteContext(*gl_context);
+    SDL_DestroyWindow(*window);
+    SDL_Quit();
+}
+
+void EventLoop(ImguiUi * ui)
+{
+    gUiRunning = true;
+    SDL_GLContext gl_context;
+    SDL_Window * window = nullptr;
+
+    UiInit(&gl_context, &window);
+
+    ImGuiIO & io = ImGui::GetIO();
+
+    while (gUiRunning.load())
+    {
+        SDL_Event event;
+        while (SDL_PollEvent(&event))
+        {
+            ImGui_ImplSDL2_ProcessEvent(&event);
+            if ((event.type == SDL_QUIT) ||
+                (event.type == SDL_WINDOWEVENT && event.window.event == SDL_WINDOWEVENT_CLOSE &&
+                 event.window.windowID == SDL_GetWindowID(window)))
+            {
+                gUiRunning = false;
+            }
+        }
+
+        ImGui_ImplOpenGL3_NewFrame();
+        ImGui_ImplSDL2_NewFrame();
+        ImGui::NewFrame();
+
+        ui->UpdateState();
+        ui->Render();
+
+        // rendering
+        ImGui::Render();
+        glViewport(0, 0, (int) io.DisplaySize.x, (int) io.DisplaySize.y);
+        glClearColor(0, 0, 0, 0);
+        glClear(GL_COLOR_BUFFER_BIT);
+        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+        SDL_GL_SwapWindow(window);
+    }
+
+    UiShutdown(&gl_context, &window);
+
+    ChipLogProgress(AppServer, "UI thread Stopped...");
+}
+
+} // namespace
+
+void ImguiUi::RunMainLoop()
+{
+    // Guaranteed to be on the main task (no chip event loop started yet)
+    ChipLoopLoadInitialState();
+
+    // Platform event loop will be on a separate thread,
+    // while the event UI loop will be on the main thread.
+    chip::DeviceLayer::PlatformMgr().StartEventLoopTask();
+
+    // SignalSafeStopMainLoop will stop this loop below
+    // or the loop exits by itself when processing a SDL
+    // exit (generally by clicking the window close icon).
+    EventLoop(this);
+
+    // ensure shutdown events are generated (generally basic cluster
+    // will send a shutdown event to subscribers).
+    //
+    // We attempt to wait for finish as the event will be sent sync.
+    // Since the Main loop is stopped, there will be no MRP, however at least
+    // one event is attempted to be sent.
+    chip::DeviceLayer::PlatformMgr().ScheduleWork(
+        [](intptr_t arg) {
+            chip::DeviceLayer::PlatformMgr().HandleServerShuttingDown();
+            sem_t * semaphore = reinterpret_cast<sem_t *>(arg);
+            sem_post(semaphore); // notify complete
+        },
+        reinterpret_cast<intptr_t>(&mChipLoopWaitSemaphore));
+    sem_wait(&mChipLoopWaitSemaphore);
+
+    // Stop the chip main loop as well. This is expected to
+    // wait for the task to finish.
+    chip::DeviceLayer::PlatformMgr().StopEventLoopTask();
+}
+
+void ImguiUi::SignalSafeStopMainLoop()
+{
+    gUiRunning = false;
+}
+
+void ImguiUi::ChipLoopStateUpdate()
+{
+    assertChipStackLockedByCurrentThread();
+    for (auto it = mWindows.begin(); it != mWindows.end(); it++)
+    {
+        (*it)->UpdateState();
+    }
+}
+
+void ImguiUi::ChipLoopLoadInitialState()
+{
+    assertChipStackLockedByCurrentThread();
+    for (auto it = mWindows.begin(); it != mWindows.end(); it++)
+    {
+        (*it)->LoadInitialState();
+    }
+}
+
+void ImguiUi::Render()
+{
+    for (auto it = mWindows.begin(); it != mWindows.end(); it++)
+    {
+        (*it)->Render();
+    }
+}
+
+void ImguiUi::ChipLoopUpdateCallback(intptr_t self)
+{
+    ImguiUi * _this = reinterpret_cast<ImguiUi *>(self);
+    _this->ChipLoopStateUpdate();
+    sem_post(&_this->mChipLoopWaitSemaphore); // notify complete
+}
+
+void ImguiUi::UpdateState()
+{
+    CHIP_ERROR err = chip::DeviceLayer::PlatformMgr().ScheduleWork(&ChipLoopUpdateCallback, reinterpret_cast<intptr_t>(this));
+
+    if (err != CHIP_NO_ERROR)
+    {
+        ChipLogError(AppServer, "Failed to schedule state update: %" CHIP_ERROR_FORMAT, err.Format());
+        return;
+    }
+
+    // ensure update is done when exiting
+    sem_wait(&mChipLoopWaitSemaphore);
+}
+
+} // namespace Ui
+} // namespace example

examples/common/imgui_ui/ui.h

@@ -0,0 +1,65 @@
+/*
+ *
+ *    Copyright (c) 2023 Project CHIP Authors
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+#pragma once
+
+#include <AppMain.h>
+#include <imgui_ui/windows/window.h>
+
+#include <semaphore.h>
+
+#include <list>
+#include <memory>
+
+namespace example {
+namespace Ui {
+
+/**
+ * Supports showing a UI using ImGUI
+ *
+ * The UI supports several windows, such as QR codes or device control.
+ */
+class ImguiUi : public AppMainLoopImplementation
+{
+public:
+    ImguiUi() { sem_init(&mChipLoopWaitSemaphore, 0 /* shared */, 0); }
+    virtual ~ImguiUi() { sem_destroy(&mChipLoopWaitSemaphore); }
+
+    void AddWindow(std::unique_ptr<Window> window) { mWindows.push_back(std::move(window)); }
+
+    void UpdateState(); // runs a state update from ember/app
+    void Render();      // render windows to screen
+
+    // AppMainLoopImplementation
+    void RunMainLoop() override;
+    void SignalSafeStopMainLoop() override;
+
+private:
+    // First initial state load
+    void ChipLoopLoadInitialState();
+
+    // Updates the window states. Run in the CHIP main loop (has access
+    // to CHIP API calls)
+    void ChipLoopStateUpdate();
+
+    sem_t mChipLoopWaitSemaphore;
+    std::list<std::unique_ptr<Window>> mWindows;
+
+    static void ChipLoopUpdateCallback(intptr_t self);
+};
+
+} // namespace Ui
+} // namespace example

examples/common/imgui_ui/windows/BUILD.gn

@@ -0,0 +1,55 @@
+# Copyright (c) 2023 Project CHIP Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import("//build_overrides/chip.gni")
+
+import("${chip_root}/build/chip/tools.gni")
+import("${chip_root}/third_party/imgui/imgui.gni")
+
+source_set("windows") {
+  sources = [ "window.h" ]
+}
+
+static_library("qrcode") {
+  sources = [
+    "qrcode.cpp",
+    "qrcode.h",
+  ]
+
+  deps = [
+    ":windows",
+    "${chip_root}/examples/common/QRCode",
+    "${chip_root}/examples/platform/linux:app-main",
+    "${chip_root}/src/app/server",
+    "${chip_root}/src/setup_payload",
+    "${chip_root}/third_party/imgui",
+  ]
+
+  public_configs =
+      [ "${chip_root}/examples/common/QRCode:qrcode-common_config" ]
+}
+
+static_library("light") {
+  sources = [
+    "light.cpp",
+    "light.h",
+  ]
+
+  deps = [
+    ":windows",
+    "${chip_root}/src/app/common:cluster-objects",
+    "${chip_root}/third_party/imgui",
+  ]
+
+  public_configs = [ "${chip_root}/src:includes" ]
+}