backends/imgui_impl_android.cpp

// dear imgui: Platform Binding for Android native app
// This needs to be used along with the OpenGL 3 Renderer (imgui_impl_opengl3)

// 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 use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this. 
// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
// Read online: https://github.com/ocornut/imgui/tree/master/docs

// CHANGELOG
// (minor and older changes stripped away, please see git history for details)
//  2021-03-04: Initial version.

#include "imgui.h"
#include "imgui_impl_android.h"
#include <time.h>
#include <map>
#include <queue>
#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 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* input_event)
{
    ImGuiIO& io = ImGui::GetIO();
    int32_t event_type = AInputEvent_getType(input_event);
    switch (event_type)
    {
    case AINPUT_EVENT_TYPE_KEY:
    {
        int32_t event_key_code = AKeyEvent_getKeyCode(input_event);
        int32_t event_action = AKeyEvent_getAction(input_event);
        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);
        io.KeyAlt = ((event_meta_state & AMETA_ALT_ON) != 0);

        switch (event_action)
        {
        // FIXME: AKEY_EVENT_ACTION_DOWN and AKEY_EVENT_ACTION_UP occur at once as soon as a touch pointer
        // goes up from a key. We use a simple key event queue/ and process one event per key per frame in
        // ImGui_ImplAndroid_NewFrame()...or consider using 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);
            break;
        default:
            break;
        }
        break;
    }
    case AINPUT_EVENT_TYPE_MOTION:
    {
        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)
        {
        case AMOTION_EVENT_ACTION_DOWN:
        case AMOTION_EVENT_ACTION_UP:
            // 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(input_event, event_pointer_index) == AMOTION_EVENT_TOOL_TYPE_FINGER)
            || (AMotionEvent_getToolType(input_event, event_pointer_index) == AMOTION_EVENT_TOOL_TYPE_UNKNOWN))
            {
                io.MouseDown[0] = (event_action == AMOTION_EVENT_ACTION_DOWN);
                io.MousePos = ImVec2(AMotionEvent_getX(input_event, event_pointer_index), AMotionEvent_getY(input_event, event_pointer_index));
            }
            break;
        case AMOTION_EVENT_ACTION_BUTTON_PRESS:
        case AMOTION_EVENT_ACTION_BUTTON_RELEASE:
            {
                int32_t button_state = AMotionEvent_getButtonState(input_event);
                io.MouseDown[0] = ((button_state & AMOTION_EVENT_BUTTON_PRIMARY) != 0);
                io.MouseDown[1] = ((button_state & AMOTION_EVENT_BUTTON_SECONDARY) != 0);
                io.MouseDown[2] = ((button_state & AMOTION_EVENT_BUTTON_TERTIARY) != 0);
            }
            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(AMotionEvent_getX(input_event, event_pointer_index), AMotionEvent_getY(input_event, event_pointer_index));
            break;
        case AMOTION_EVENT_ACTION_SCROLL:
            io.MouseWheel = AMotionEvent_getAxisValue(input_event, AMOTION_EVENT_AXIS_VSCROLL, event_pointer_index);
            io.MouseWheelH = AMotionEvent_getAxisValue(input_event, AMOTION_EVENT_AXIS_HSCROLL, event_pointer_index);
            break;
        default:
            break;
        }
    }
        return 1;
    default:
        break;
    }

    return 0;
}

bool ImGui_ImplAndroid_Init(ANativeWindow* window)
{
    g_Window = window;
    g_Time = 0.0;

    // Setup backend capabilities flags
    ImGuiIO& io = ImGui::GetIO();
    io.BackendPlatformName = "imgui_impl_android";

    // 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
    io.KeyMap[ImGuiKey_UpArrow] = AKEYCODE_DPAD_UP;       // also covers physical keyboard arrow key
    io.KeyMap[ImGuiKey_DownArrow] = AKEYCODE_DPAD_DOWN;   // also covers physical keyboard arrow key
    io.KeyMap[ImGuiKey_PageUp] = AKEYCODE_PAGE_UP;
    io.KeyMap[ImGuiKey_PageDown] = AKEYCODE_PAGE_DOWN;
    io.KeyMap[ImGuiKey_Home] = AKEYCODE_MOVE_HOME;
    io.KeyMap[ImGuiKey_End] = AKEYCODE_MOVE_END;
    io.KeyMap[ImGuiKey_Insert] = AKEYCODE_INSERT;
    io.KeyMap[ImGuiKey_Delete] = AKEYCODE_FORWARD_DEL;
    io.KeyMap[ImGuiKey_Backspace] = AKEYCODE_DEL;
    io.KeyMap[ImGuiKey_Space] = AKEYCODE_SPACE;
    io.KeyMap[ImGuiKey_Enter] = AKEYCODE_ENTER;
    io.KeyMap[ImGuiKey_Escape] = AKEYCODE_ESCAPE;
    io.KeyMap[ImGuiKey_KeyPadEnter] = AKEYCODE_NUMPAD_ENTER;
    io.KeyMap[ImGuiKey_A] = AKEYCODE_A;
    io.KeyMap[ImGuiKey_C] = AKEYCODE_C;
    io.KeyMap[ImGuiKey_V] = AKEYCODE_V;
    io.KeyMap[ImGuiKey_X] = AKEYCODE_X;
    io.KeyMap[ImGuiKey_Y] = AKEYCODE_Y;
    io.KeyMap[ImGuiKey_Z] = AKEYCODE_Z;

    return true;
}

void ImGui_ImplAndroid_Shutdown()
{
}

void ImGui_ImplAndroid_NewFrame()
{
    ImGuiIO& io = ImGui::GetIO();

    // Process queued key events
    // 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())
            continue;
        io.KeysDown[key_queue.first] = (key_queue.second.front() == AKEY_EVENT_ACTION_DOWN);
        key_queue.second.pop();
    }

    // Setup display size (every frame to accommodate for window resizing)
    int32_t window_width = ANativeWindow_getWidth(g_Window);
    int32_t window_height = ANativeWindow_getHeight(g_Window);
    int display_width = window_width;
    int display_height = window_height;

    io.DisplaySize = ImVec2((float)window_width, (float)window_height);
    if (window_width > 0 && window_height > 0)
        io.DisplayFramebufferScale = ImVec2((float)display_width / window_width, (float)display_height / window_height);

    // Setup time step
    struct timespec current_timespec;
    clock_gettime(CLOCK_MONOTONIC, &current_timespec);
    double current_time = (double)(current_timespec.tv_sec) + (current_timespec.tv_nsec / 1000000000.0);
    io.DeltaTime = g_Time > 0.0 ? (float)(current_time - g_Time) : (float)(1.0f / 60.0f);
    g_Time = current_time;
}