satdump/android/backend.cpp

#include "core/backend.h"
#include "core/style.h"
#include "backend.h"

extern EGLDisplay g_EglDisplay;
extern EGLSurface g_EglSurface;
extern struct android_app* g_App;

// 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;
}

static int HideSoftKeyboardInput()
{
    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, "hideSoftInput", "()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)
    {
        if (unicode_character == 0x08) // BackSpace
        {
            io.AddKeyEvent(ImGuiKey_Backspace, true);
            io.AddKeyEvent(ImGuiKey_Backspace, false);
        }
        else
            io.AddInputCharacter(unicode_character);
    }

    jni_return = java_vm->DetachCurrentThread();
    if (jni_return != JNI_OK)
        return -5;

    return 0;
}

void funcSetMousePos(int, int)
{
    // Not implemented on Android
}

std::pair<int, int> funcBeginFrame()
{
    ImGuiIO& io = ImGui::GetIO();
    if (g_EglDisplay == EGL_NO_DISPLAY)
        return;

    // Poll Unicode characters via JNI
    // FIXME: do not call this every frame because of JNI overhead
    PollUnicodeChars();

    // Open on-screen (soft) input if requested by Dear ImGui
    static bool WantTextInputLast = false;
    if (io.WantTextInput && !WantTextInputLast)
        ShowSoftKeyboardInput();
    if (!io.WantTextInput && WantTextInputLast)
        HideSoftKeyboardInput();
    WantTextInputLast = io.WantTextInput;

    // Start the Dear ImGui frame
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplAndroid_NewFrame();
    ImGui::NewFrame();

    return { (int)io.DisplaySize.x, (int)io.DisplaySize.y };
}

void funcEndFrame()
{
    ImGui::Render();
    ImGuiIO& io = ImGui::GetIO();
    glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);

    if (satdump::light_theme)
        glClearColor(0.7f, 0.7f, 0.7f, 1.0f);
    else
        glClearColor(0.0666f, 0.0666f, 0.0666f, 1.0f);
    // glClearColor(0.9f, 0.9f, 0.9f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
    eglSwapBuffers(g_EglDisplay, g_EglSurface);
}

void funcSetIcon(uint8_t*, int, int)
{
    // Not implemented on Android
}

void bindBackendFunctions()
{
    backend::setMousePos = funcSetMousePos;
    backend::beginFrame = funcBeginFrame;
    backend::endFrame = funcEndFrame;
    backend::setIcon = funcSetIcon;
}