Android: Amend backend and examples with minor consistency tweaks. (#3446)

backends/imgui_impl_android.cpp

@@ -3,9 +3,13 @@
 
 // Implemented features:
 //  [X] Platform: Keyboard arrays indexed using AKEYCODE_* codes, e.g. ImGui::IsKeyPressed(AKEYCODE_SPACE).
+// Missing features:
 //  [ ] Platform: Clipboard support.
 //  [ ] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [ ] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'. FIXME: Check if this is even possible with Android.
+// Important:
+//  - FIXME: On-screen keyboard currently needs to be enabled by the application (see examples/ and issue #3446)
+//  - FIXME: Unicode character inputs needs to be passed by Dear ImGui by the application (see examples/ and issue #3446)
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
@@ -13,39 +17,35 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
-//  2021-03-02: Support for physical pointer device input (such as physical mouse)
+//  2021-03-04: Initial version.
-//  2020-09-13: Support for Unicode characters
-//  2020-08-31: On-screen and physical keyboard input (ASCII characters only)
-//  2020-03-02: basic draft, touch input
 
 #include "imgui.h"
 #include "imgui_impl_android.h"
 #include <time.h>
 #include <map>
 #include <queue>
-
-// Android
 #include <android/native_window.h>
 #include <android/input.h>
 #include <android/keycodes.h>
 #include <android/log.h>
 
+// Android data
 static double                                   g_Time = 0.0;
 static ANativeWindow*                           g_Window;
-static char                                     g_LogTag[] = "ImguiExample";
+static char                                     g_LogTag[] = "ImGuiExample";
 static std::map<int32_t, std::queue<int32_t>>   g_KeyEventQueues; // FIXME: Remove dependency on map and queue once we use upcoming input queue.
 
-int32_t ImGui_ImplAndroid_HandleInputEvent(AInputEvent* inputEvent)
+int32_t ImGui_ImplAndroid_HandleInputEvent(AInputEvent* input_event)
 {
     ImGuiIO& io = ImGui::GetIO();
-    int32_t event_type = AInputEvent_getType(inputEvent);
+    int32_t event_type = AInputEvent_getType(input_event);
     switch (event_type)
     {
     case AINPUT_EVENT_TYPE_KEY:
     {
-        int32_t event_key_code = AKeyEvent_getKeyCode(inputEvent);
+        int32_t event_key_code = AKeyEvent_getKeyCode(input_event);
-        int32_t event_action = AKeyEvent_getAction(inputEvent);
+        int32_t event_action = AKeyEvent_getAction(input_event);
-        int32_t event_meta_state = AKeyEvent_getMetaState(inputEvent);
+        int32_t event_meta_state = AKeyEvent_getMetaState(input_event);
 
         io.KeyCtrl = ((event_meta_state & AMETA_CTRL_ON) != 0);
         io.KeyShift = ((event_meta_state & AMETA_SHIFT_ON) != 0);
@@ -53,10 +53,9 @@ int32_t ImGui_ImplAndroid_HandleInputEvent(AInputEvent* inputEvent)
 
         switch (event_action)
         {
-        // FIXME: AKEY_EVENT_ACTION_DOWN and AKEY_EVENT_ACTION_UP occur at once
+        // FIXME: AKEY_EVENT_ACTION_DOWN and AKEY_EVENT_ACTION_UP occur at once as soon as a touch pointer
-        // as soon as a touch pointer goes up from a key. We use a simple key event queue
+        // goes up from a key. We use a simple key event queue/ and process one event per key per frame in
-        // and process one event per key per ImGui frame in ImGui_ImplAndroid_NewFrame().
+        // ImGui_ImplAndroid_NewFrame()...or consider using IO queue, if suitable: https://github.com/ocornut/imgui/issues/2787
-        // ...or consider ImGui IO queue, if suitable: https://github.com/ocornut/imgui/issues/2787
         case AKEY_EVENT_ACTION_DOWN:
         case AKEY_EVENT_ACTION_UP:
             g_KeyEventQueues[event_key_code].push(event_action);
@@ -68,7 +67,7 @@ int32_t ImGui_ImplAndroid_HandleInputEvent(AInputEvent* inputEvent)
     }
     case AINPUT_EVENT_TYPE_MOTION:
     {
-        int32_t event_action = AMotionEvent_getAction(inputEvent);
+        int32_t event_action = AMotionEvent_getAction(input_event);
         int32_t event_pointer_index = (event_action & AMOTION_EVENT_ACTION_POINTER_INDEX_MASK) >> AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT;
         event_action &= AMOTION_EVENT_ACTION_MASK;
         switch (event_action)
@@ -78,19 +77,17 @@ int32_t ImGui_ImplAndroid_HandleInputEvent(AInputEvent* inputEvent)
             // Physical mouse buttons (and probably other physical devices) also invoke the actions AMOTION_EVENT_ACTION_DOWN/_UP,
             // but we have to process them separately to identify the actual button pressed. This is done below via
             // AMOTION_EVENT_ACTION_BUTTON_PRESS/_RELEASE. Here, we only process "FINGER" input (and "UNKNOWN", as a fallback).
-            if((AMotionEvent_getToolType(inputEvent, event_pointer_index) == AMOTION_EVENT_TOOL_TYPE_FINGER)
+            if((AMotionEvent_getToolType(input_event, event_pointer_index) == AMOTION_EVENT_TOOL_TYPE_FINGER)
-            || (AMotionEvent_getToolType(inputEvent, event_pointer_index) == AMOTION_EVENT_TOOL_TYPE_UNKNOWN))
+            || (AMotionEvent_getToolType(input_event, event_pointer_index) == AMOTION_EVENT_TOOL_TYPE_UNKNOWN))
             {
                 io.MouseDown[0] = (event_action == AMOTION_EVENT_ACTION_DOWN) ? true : false;
-                io.MousePos = ImVec2(
+                io.MousePos = ImVec2(AMotionEvent_getX(input_event, event_pointer_index), AMotionEvent_getY(input_event, event_pointer_index));
-                        AMotionEvent_getX(inputEvent, event_pointer_index),
-                        AMotionEvent_getY(inputEvent, event_pointer_index));
             }
             break;
         case AMOTION_EVENT_ACTION_BUTTON_PRESS:
         case AMOTION_EVENT_ACTION_BUTTON_RELEASE:
             {
-                int32_t button_state = AMotionEvent_getButtonState(inputEvent);
+                int32_t button_state = AMotionEvent_getButtonState(input_event);
                 io.MouseDown[0] = (button_state & AMOTION_EVENT_BUTTON_PRIMARY) ? true : false;
                 io.MouseDown[1] = (button_state & AMOTION_EVENT_BUTTON_SECONDARY) ? true : false;
                 io.MouseDown[2] = (button_state & AMOTION_EVENT_BUTTON_TERTIARY) ? true : false;
@@ -98,13 +95,11 @@ int32_t ImGui_ImplAndroid_HandleInputEvent(AInputEvent* inputEvent)
             break;
         case AMOTION_EVENT_ACTION_HOVER_MOVE: // Hovering: Tool moves while NOT pressed (such as a physical mouse)
         case AMOTION_EVENT_ACTION_MOVE:       // Touch pointer moves while DOWN
-            io.MousePos = ImVec2(
+            io.MousePos = ImVec2(AMotionEvent_getX(input_event, event_pointer_index), AMotionEvent_getY(input_event, event_pointer_index));
-                AMotionEvent_getX(inputEvent, event_pointer_index),
-                AMotionEvent_getY(inputEvent, event_pointer_index));
             break;
         case AMOTION_EVENT_ACTION_SCROLL:
-            io.MouseWheel = AMotionEvent_getAxisValue(inputEvent, AMOTION_EVENT_AXIS_VSCROLL, event_pointer_index);
+            io.MouseWheel = AMotionEvent_getAxisValue(input_event, AMOTION_EVENT_AXIS_VSCROLL, event_pointer_index);
-            io.MouseWheelH = AMotionEvent_getAxisValue(inputEvent, AMOTION_EVENT_AXIS_HSCROLL, event_pointer_index);
+            io.MouseWheelH = AMotionEvent_getAxisValue(input_event, AMOTION_EVENT_AXIS_HSCROLL, event_pointer_index);
             break;
         default:
             break;
@@ -123,11 +118,11 @@ bool ImGui_ImplAndroid_Init(ANativeWindow* window)
     g_Window = window;
     g_Time = 0.0;
 
-    // Setup back-end capabilities flags
+    // Setup backend capabilities flags
     ImGuiIO& io = ImGui::GetIO();
     io.BackendPlatformName = "imgui_impl_android";
 
-    // Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
+    // Keyboard mapping. Dear ImGui will use those indices to peek into the io.KeysDown[] array.
     io.KeyMap[ImGuiKey_Tab] = AKEYCODE_TAB;
     io.KeyMap[ImGuiKey_LeftArrow] = AKEYCODE_DPAD_LEFT;   // also covers physical keyboard arrow key
     io.KeyMap[ImGuiKey_RightArrow] = AKEYCODE_DPAD_RIGHT; // also covers physical keyboard arrow key
@@ -161,10 +156,10 @@ void ImGui_ImplAndroid_Shutdown()
 void ImGui_ImplAndroid_NewFrame()
 {
     ImGuiIO& io = ImGui::GetIO();
-    IM_ASSERT(io.Fonts->IsBuilt() && "Font atlas not built! It is generally built by the renderer back-end. Missing call to renderer _NewFrame() function? e.g. ImGui_ImplOpenGL3_NewFrame().");
+    IM_ASSERT(io.Fonts->IsBuilt() && "Font atlas not built! It is generally built by the renderer backend. Missing call to renderer _NewFrame() function? e.g. ImGui_ImplOpenGL3_NewFrame().");
 
     // Process queued key events
-    // FIXME: This is a workaround for multiple key event actions occuring at once (see above) and can be removed once we use upcoming input queue.
+    // FIXME: This is a workaround for multiple key event actions occurring at once (see above) and can be removed once we use upcoming input queue.
     for (auto& key_queue : g_KeyEventQueues)
     {
         if (key_queue.second.empty())

backends/imgui_impl_android.h

@@ -3,9 +3,13 @@
 
 // Implemented features:
 //  [X] Platform: Keyboard arrays indexed using AKEYCODE_* codes, e.g. ImGui::IsKeyPressed(AKEYCODE_SPACE).
+// Missing features:
 //  [ ] Platform: Clipboard support.
 //  [ ] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [ ] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'. FIXME: Check if this is even possible with Android.
+// Important:
+//  - FIXME: On-screen keyboard currently needs to be enabled by the application (see examples/ and issue #3446)
+//  - FIXME: Unicode character inputs needs to be passed by Dear ImGui by the application (see examples/ and issue #3446)
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
@@ -16,7 +20,7 @@
 struct ANativeWindow;
 struct AInputEvent;
 
-IMGUI_IMPL_API int32_t  ImGui_ImplAndroid_HandleInputEvent(AInputEvent* inputEvent);
 IMGUI_IMPL_API bool     ImGui_ImplAndroid_Init(ANativeWindow* window);
+IMGUI_IMPL_API int32_t  ImGui_ImplAndroid_HandleInputEvent(AInputEvent* input_event);
 IMGUI_IMPL_API void     ImGui_ImplAndroid_Shutdown();
 IMGUI_IMPL_API void     ImGui_ImplAndroid_NewFrame();

backends/imgui_impl_glfw.cpp

@@ -149,7 +149,7 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
     io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;          // We can honor io.WantSetMousePos requests (optional, rarely used)
     io.BackendPlatformName = "imgui_impl_glfw";
 
-    // Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
+    // Keyboard mapping. Dear ImGui will use those indices to peek into the io.KeysDown[] array.
     io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;
     io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
     io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;

backends/imgui_impl_marmalade.cpp

@@ -220,7 +220,8 @@ bool    ImGui_Marmalade_Init(bool install_callbacks)
     ImGuiIO& io = ImGui::GetIO();
     io.BackendPlatformName = io.BackendRendererName = "imgui_impl_marmalade";
 
-    io.KeyMap[ImGuiKey_Tab] = s3eKeyTab;                     // Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
+    // Keyboard mapping. Dear ImGui will use those indices to peek into the io.KeysDown[] array.
+    io.KeyMap[ImGuiKey_Tab] = s3eKeyTab
     io.KeyMap[ImGuiKey_LeftArrow] = s3eKeyLeft;
     io.KeyMap[ImGuiKey_RightArrow] = s3eKeyRight;
     io.KeyMap[ImGuiKey_UpArrow] = s3eKeyUp;

backends/imgui_impl_sdl.cpp

@@ -138,7 +138,7 @@ static bool ImGui_ImplSDL2_Init(SDL_Window* window)
     io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;        // We can honor io.WantSetMousePos requests (optional, rarely used)
     io.BackendPlatformName = "imgui_impl_sdl";
 
-    // Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
+    // Keyboard mapping. Dear ImGui will use those indices to peek into the io.KeysDown[] array.
     io.KeyMap[ImGuiKey_Tab] = SDL_SCANCODE_TAB;
     io.KeyMap[ImGuiKey_LeftArrow] = SDL_SCANCODE_LEFT;
     io.KeyMap[ImGuiKey_RightArrow] = SDL_SCANCODE_RIGHT;

backends/imgui_impl_wgpu.cpp

@@ -731,7 +731,7 @@ void ImGui_ImplWGPU_InvalidateDeviceObjects()
 
 bool ImGui_ImplWGPU_Init(WGPUDevice device, int num_frames_in_flight, WGPUTextureFormat rt_format)
 {
-    // Setup back-end capabilities flags
+    // Setup backend capabilities flags
     ImGuiIO& io = ImGui::GetIO();
     io.BackendRendererName = "imgui_impl_webgpu";
     io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.

backends/imgui_impl_win32.cpp

@@ -91,7 +91,7 @@ bool    ImGui_ImplWin32_Init(void* hwnd)
     io.BackendPlatformName = "imgui_impl_win32";
     io.ImeWindowHandle = hwnd;
 
-    // Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array that we will update during the application lifetime.
+    // Keyboard mapping. Dear ImGui will use those indices to peek into the io.KeysDown[] array that we will update during the application lifetime.
     io.KeyMap[ImGuiKey_Tab] = VK_TAB;
     io.KeyMap[ImGuiKey_LeftArrow] = VK_LEFT;
     io.KeyMap[ImGuiKey_RightArrow] = VK_RIGHT;

docs/CHANGELOG.txt

@@ -58,6 +58,7 @@ Other Changes:
 - ImDrawList: AddCircle, AddCircleFilled(): Tweaked default segment count calculation to honor MaxError
   with more accuracy. Made default segment count always even for better looking result. (#3808) [@thedmd]
 - ImDrawList: AddCircle, AddCircleFilled(): New default for style.
+- Backends: Android: Added native Android backend. (#3446) [@duddel]
 - Backends: Win32: Added ImGui_ImplWin32_EnableAlphaCompositing() to facilitate experimenting with 
   alpha compositing and transparent windows. (#2766, #3447 etc.).
 - Backends: OpenGL, Vulkan, DX9, DX10, DX11, DX12, Metal, WebGPU, Allegro: Rework blending equation to
@@ -66,6 +67,7 @@ Other Changes:
   (#2693, #2764, #2766, #2873, #3447, #3813, #3816) [@ocornut, @thedmd, @ShawnM427, @Ubpa, @aiekick]
 - Backends: DX9: Fix to support IMGUI_USE_BGRA_PACKED_COLOR. (#3844) [@Xiliusha]
 - Backends: DX9: Fix to support colored glyphs, using newly introduced 'TexPixelsUseColors' info. (#3844)
+- Examples: Android: Added Android + GL ES2 example. (#3446) [@duddel]
 - Examples: Reworked setup of clear color to be compatible with transparent values.
 - CI: Use a dedicated "scheduled" workflow to trigger scheduled builds. Forks may disable this workflow if
   scheduled builds builds are not required. [@rokups]

examples/example_android_opengl3/CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.6)
 
-project(ImguiExample)
+project(ImGuiExample)
 
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)

examples/example_android_opengl3/android/app/src/main/AndroidManifest.xml

@@ -3,7 +3,7 @@
     package="imgui.example.android">
 
     <application
-        android:label="ImguiExample"
+        android:label="ImGuiExample"
         android:allowBackup="false"
         android:fullBackupContent="false"
         android:hasCode="true">
@@ -13,7 +13,7 @@
             android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
             android:configChanges="orientation|keyboardHidden|screenSize">
             <meta-data android:name="android.app.lib_name"
-                android:value="ImguiExample" />
+                android:value="ImGuiExample" />
 
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

examples/example_android_opengl3/main.cpp

@@ -10,98 +10,18 @@
 #include <EGL/egl.h>
 #include <GLES3/gl3.h>
 
+// Data
 static EGLDisplay           g_EglDisplay = EGL_NO_DISPLAY;
 static EGLSurface           g_EglSurface = EGL_NO_SURFACE;
 static EGLContext           g_EglContext = EGL_NO_CONTEXT;
 static struct android_app*  g_App = NULL;
 static bool                 g_Initialized = false;
-static char                 g_LogTag[] = "ImguiExample";
+static char                 g_LogTag[] = "ImGuiExample";
 
-// Unfortunately, there is no way to show the on-screen input from native code.
+// Forward declarations of helper functions
-// Therefore, we call showSoftInput() of the main activity implemented in MainActivity.kt via JNI.
+static int ShowSoftKeyboardInput();
-static int showSoftInput()
+static int PollUnicodeChars();
-{
+static int GetAssetData(const char* filename, void** out_data);
-    JavaVM* java_vm = g_App->activity->vm;
-    JNIEnv* java_env = NULL;
-
-    jint jni_return = java_vm->GetEnv((void**)&java_env, JNI_VERSION_1_6);
-    if (jni_return == JNI_ERR)
-        return -1;
-
-    jni_return = java_vm->AttachCurrentThread(&java_env, NULL);
-    if (jni_return != JNI_OK)
-        return -2;
-
-    jclass native_activity_clazz = java_env->GetObjectClass(g_App->activity->clazz);
-    if (native_activity_clazz == NULL)
-        return -3;
-
-    jmethodID method_id = java_env->GetMethodID(native_activity_clazz, "showSoftInput", "()V");
-    if (method_id == NULL)
-        return -4;
-
-    java_env->CallVoidMethod(g_App->activity->clazz, method_id);
-
-    jni_return = java_vm->DetachCurrentThread();
-    if (jni_return != JNI_OK)
-        return -5;
-
-    return 0;
-}
-
-// Unfortunately, the native KeyEvent implementation has no getUnicodeChar() function.
-// Therefore, we implement the processing of KeyEvents in MainActivity.kt and poll
-// the resulting Unicode characters here via JNI and send them to Dear ImGui.
-static int pollUnicodeChars()
-{
-    JavaVM* java_vm = g_App->activity->vm;
-    JNIEnv* java_env = NULL;
-
-    jint jni_return = java_vm->GetEnv((void**)&java_env, JNI_VERSION_1_6);
-    if (jni_return == JNI_ERR)
-        return -1;
-
-    jni_return = java_vm->AttachCurrentThread(&java_env, NULL);
-    if (jni_return != JNI_OK)
-        return -2;
-
-    jclass native_activity_clazz = java_env->GetObjectClass(g_App->activity->clazz);
-    if (native_activity_clazz == NULL)
-        return -3;
-
-    jmethodID method_id = java_env->GetMethodID(native_activity_clazz, "pollUnicodeChar", "()I");
-    if (method_id == NULL)
-        return -4;
-
-    // Send the actual characters to Dear ImGui
-    ImGuiIO& io = ImGui::GetIO();
-    jint unicode_character;
-    while ((unicode_character = java_env->CallIntMethod(g_App->activity->clazz, method_id)) != 0)
-    {
-        io.AddInputCharacter(unicode_character);
-    }
-
-    jni_return = java_vm->DetachCurrentThread();
-    if (jni_return != JNI_OK)
-        return -5;
-
-    return 0;
-}
-
-static int GetAssetData(const char* filename, void** outData)
-{
-    int num_bytes = 0;
-    AAsset* asset_descriptor = AAssetManager_open(g_App->activity->assetManager, filename, AASSET_MODE_BUFFER);
-    if(asset_descriptor)
-    {
-        num_bytes = AAsset_getLength(asset_descriptor);
-        *outData = IM_ALLOC(num_bytes);
-        int64_t num_bytes_read = AAsset_read(asset_descriptor, *outData, num_bytes);
-        AAsset_close(asset_descriptor);
-        IM_ASSERT(num_bytes_read == num_bytes);
-    }
-    return num_bytes;
-}
 
 void init(struct android_app* app)
 {
@@ -113,30 +33,22 @@ void init(struct android_app* app)
 
     // Initialize EGL
     // This is mostly boilerplate code for EGL...
+    {
         g_EglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
-
         if (g_EglDisplay == EGL_NO_DISPLAY)
             __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglGetDisplay(EGL_DEFAULT_DISPLAY) returned EGL_NO_DISPLAY");
 
         if (eglInitialize(g_EglDisplay, 0, 0) != EGL_TRUE)
-        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglInitialize(..) returned with an error");
+            __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglInitialize() returned with an error");
-
-    const EGLint egl_attributes[] = {
-        EGL_BLUE_SIZE, 8,
-        EGL_GREEN_SIZE, 8,
-        EGL_RED_SIZE, 8,
-        EGL_DEPTH_SIZE, 24,
-        EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
-        EGL_NONE};
 
+        const EGLint egl_attributes[] = { EGL_BLUE_SIZE, 8, EGL_GREEN_SIZE, 8, EGL_RED_SIZE, 8, EGL_DEPTH_SIZE, 24, EGL_SURFACE_TYPE, EGL_WINDOW_BIT, EGL_NONE };
         EGLint num_configs = 0;
         if (eglChooseConfig(g_EglDisplay, egl_attributes, nullptr, 0, &num_configs) != EGL_TRUE)
-        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglChooseConfig(..) returned with an error");
+            __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglChooseConfig() returned with an error");
-
         if (num_configs == 0)
-        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglChooseConfig(..) returned 0 matching configs");
+            __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglChooseConfig() returned 0 matching config");
 
-    // Get the (first) matching config
+        // Get the first matching config
         EGLConfig egl_config;
         eglChooseConfig(g_EglDisplay, egl_attributes, &egl_config, 1, &num_configs);
         EGLint egl_format;
@@ -147,31 +59,40 @@ void init(struct android_app* app)
         g_EglContext = eglCreateContext(g_EglDisplay, egl_config, EGL_NO_CONTEXT, egl_context_attributes);
 
         if (g_EglContext == EGL_NO_CONTEXT)
-        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglCreateContext(..) returned EGL_NO_CONTEXT");
+            __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglCreateContext() returned EGL_NO_CONTEXT");
 
         g_EglSurface = eglCreateWindowSurface(g_EglDisplay, egl_config, g_App->window, NULL);
         eglMakeCurrent(g_EglDisplay, g_EglSurface, g_EglSurface, g_EglContext);
+    }
 
-    // Dear Imgui
+    // Setup Dear ImGui context
     IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO();
+
+    // Disable loading/saving of .ini file from disk.
+    // FIXME: Consider using LoadIniSettingsFromMemory() / SaveIniSettingsToMemory() to save in appropriate location for Android.
     io.IniFilename = NULL;
+
+    // Setup Dear ImGui style
     ImGui::StyleColorsDark();
+    //ImGui::StyleColorsClassic();
+
+    // Setup Platform/Renderer backends
     ImGui_ImplAndroid_Init(g_App->window);
     ImGui_ImplOpenGL3_Init("#version 300 es");
 
     // Load Fonts
     // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
-    // - add_font_from_assets_ttf() will return the ImFont* so you can store it if you need to select the font among multiple.
     // - If the file cannot be loaded, the function will return NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
     // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
     // - Read 'docs/FONTS.md' for more instructions and details.
     // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
-    // - The TTF files have to be placed into the assets/ directory (android/app/src/main/assets).
+    // - Android: The TTF files have to be placed into the assets/ directory (android/app/src/main/assets), we use our GetAssetData() helper to retrieve them.
 
     // We load the default font with increased size to improve readability on many devices with "high" DPI.
-    // FIXME: Put some effort into DPI awareness
+    // FIXME: Put some effort into DPI awareness.
+    // Important: when calling AddFontFromMemoryTTF(), ownership of font_data is transfered by Dear ImGui by default (deleted is handled by Dear ImGui), unless we set FontDataOwnedByAtlas=false in ImFontConfig
     ImFontConfig font_cfg;
     font_cfg.SizePixels = 22.0f;
     io.Fonts->AddFontDefault(&font_cfg);
@@ -179,19 +100,19 @@ void init(struct android_app* app)
     //int font_data_size;
     //ImFont* font;
     //font_data_size = GetAssetData("Roboto-Medium.ttf", &font_data);
-    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 16.0f); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
+    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 16.0f);
     //IM_ASSERT(font != NULL);
     //font_data_size = GetAssetData("Cousine-Regular.ttf", &font_data);
-    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 15.0f); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
+    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 15.0f);
     //IM_ASSERT(font != NULL);
     //font_data_size = GetAssetData("DroidSans.ttf", &font_data);
-    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 16.0f); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
+    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 16.0f);
     //IM_ASSERT(font != NULL);
     //font_data_size = GetAssetData("ProggyTiny.ttf", &font_data);
-    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 10.0f); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
+    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 10.0f);
     //IM_ASSERT(font != NULL);
     //font_data_size = GetAssetData("ArialUni.ttf", &font_data);
-    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese()); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
+    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
     //IM_ASSERT(font != NULL);
 
     // Arbitrary scale-up
@@ -203,23 +124,23 @@ void init(struct android_app* app)
 
 void tick()
 {
-    // Our state (Dear Imgui)
+    ImGuiIO& io = ImGui::GetIO();
+    if (g_EglDisplay == EGL_NO_DISPLAY)
+        return;
+
+    // Our state
     static bool show_demo_window = true;
     static bool show_another_window = false;
     static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
 
-    if (g_EglDisplay != EGL_NO_DISPLAY)
-    {
-        ImGuiIO& io = ImGui::GetIO();
-
     // Poll Unicode characters via JNI
     // FIXME: do not call this every frame because of JNI overhead
-        pollUnicodeChars();
+    PollUnicodeChars();
 
-        // Open on-screen (soft) input if demanded by Dear ImGui
+    // Open on-screen (soft) input if requested by Dear ImGui
     static bool WantTextInputLast = false;
     if (io.WantTextInput && !WantTextInputLast)
-            showSoftInput();
+        ShowSoftKeyboardInput();
     WantTextInputLast = io.WantTextInput;
 
     // Start the Dear ImGui frame
@@ -267,19 +188,18 @@ void tick()
     // Rendering
     ImGui::Render();
     glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
-        glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
+    glClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
     glClear(GL_COLOR_BUFFER_BIT);
     ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
     eglSwapBuffers(g_EglDisplay, g_EglSurface);
 }
-}
 
 void shutdown()
 {
     if (!g_Initialized)
         return;
 
-    // Cleanup (Dear Imgui)
+    // Cleanup
     ImGui_ImplOpenGL3_Shutdown();
     ImGui_ImplAndroid_Shutdown();
     ImGui::DestroyContext();
@@ -362,3 +282,88 @@ void android_main(struct android_app* app)
         tick();
     }
 }
+
+// Unfortunately, there is no way to show the on-screen input from native code.
+// Therefore, we call ShowSoftKeyboardInput() of the main activity implemented in MainActivity.kt via JNI.
+static int ShowSoftKeyboardInput()
+{
+    JavaVM* java_vm = g_App->activity->vm;
+    JNIEnv* java_env = NULL;
+
+    jint jni_return = java_vm->GetEnv((void**)&java_env, JNI_VERSION_1_6);
+    if (jni_return == JNI_ERR)
+        return -1;
+
+    jni_return = java_vm->AttachCurrentThread(&java_env, NULL);
+    if (jni_return != JNI_OK)
+        return -2;
+
+    jclass native_activity_clazz = java_env->GetObjectClass(g_App->activity->clazz);
+    if (native_activity_clazz == NULL)
+        return -3;
+
+    jmethodID method_id = java_env->GetMethodID(native_activity_clazz, "showSoftInput", "()V");
+    if (method_id == NULL)
+        return -4;
+
+    java_env->CallVoidMethod(g_App->activity->clazz, method_id);
+
+    jni_return = java_vm->DetachCurrentThread();
+    if (jni_return != JNI_OK)
+        return -5;
+
+    return 0;
+}
+
+// Unfortunately, the native KeyEvent implementation has no getUnicodeChar() function.
+// Therefore, we implement the processing of KeyEvents in MainActivity.kt and poll
+// the resulting Unicode characters here via JNI and send them to Dear ImGui.
+static int PollUnicodeChars()
+{
+    JavaVM* java_vm = g_App->activity->vm;
+    JNIEnv* java_env = NULL;
+
+    jint jni_return = java_vm->GetEnv((void**)&java_env, JNI_VERSION_1_6);
+    if (jni_return == JNI_ERR)
+        return -1;
+
+    jni_return = java_vm->AttachCurrentThread(&java_env, NULL);
+    if (jni_return != JNI_OK)
+        return -2;
+
+    jclass native_activity_clazz = java_env->GetObjectClass(g_App->activity->clazz);
+    if (native_activity_clazz == NULL)
+        return -3;
+
+    jmethodID method_id = java_env->GetMethodID(native_activity_clazz, "pollUnicodeChar", "()I");
+    if (method_id == NULL)
+        return -4;
+
+    // Send the actual characters to Dear ImGui
+    ImGuiIO& io = ImGui::GetIO();
+    jint unicode_character;
+    while ((unicode_character = java_env->CallIntMethod(g_App->activity->clazz, method_id)) != 0)
+        io.AddInputCharacter(unicode_character);
+
+    jni_return = java_vm->DetachCurrentThread();
+    if (jni_return != JNI_OK)
+        return -5;
+
+    return 0;
+}
+
+// Helper to retrieve data placed into the assets/ directory (android/app/src/main/assets)
+static int GetAssetData(const char* filename, void** outData)
+{
+    int num_bytes = 0;
+    AAsset* asset_descriptor = AAssetManager_open(g_App->activity->assetManager, filename, AASSET_MODE_BUFFER);
+    if (asset_descriptor)
+    {
+        num_bytes = AAsset_getLength(asset_descriptor);
+        *outData = IM_ALLOC(num_bytes);
+        int64_t num_bytes_read = AAsset_read(asset_descriptor, *outData, num_bytes);
+        AAsset_close(asset_descriptor);
+        IM_ASSERT(num_bytes_read == num_bytes);
+    }
+    return num_bytes;
+}

imgui.h

@@ -2767,7 +2767,7 @@ enum ImGuiViewportFlags_
 struct ImGuiViewport
 {
     ImGuiViewportFlags  Flags;                  // See ImGuiViewportFlags_
-    ImVec2              Pos;                    // Main Area: Position of the viewport (Dear Imgui coordinates are the same as OS desktop/native coordinates)
+    ImVec2              Pos;                    // Main Area: Position of the viewport (Dear ImGui coordinates are the same as OS desktop/native coordinates)
     ImVec2              Size;                   // Main Area: Size of the viewport.
     ImVec2              WorkPos;                // Work Area: Position of the viewport minus task bars, menus bars, status bars (>= Pos)
     ImVec2              WorkSize;               // Work Area: Size of the viewport minus task bars, menu bars, status bars (<= Size)