questshock/android/app/src/main/cpp/xr_menu.c

#include "xr_menu.h"

#include <dlfcn.h>
#include <stdlib.h>

#include <android/log.h>
#include <jni.h>

#include <EGL/egl.h>
#include <GLES3/gl3.h>

#include <SDL.h>

#define TAG "QuestShock"
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, TAG, __VA_ARGS__)
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, TAG, __VA_ARGS__)

#define MENU_WIDTH 1024
#define MENU_HEIGHT 768

// Below the game quad (QUAD_DISTANCE_METERS/QUAD_WIDTH_METERS in
// xr_session.c, 2m out) so both are visible together without overlapping.
#define MENU_DISTANCE_METERS 1.5f
#define MENU_WIDTH_METERS 0.8f
#define MENU_CENTER_X_METERS 0.0f
#define MENU_CENTER_Y_METERS -0.45f

static bool g_visible = false;

static jclass g_menu_overlay_class = NULL;
static jmethodID g_native_init_method = NULL;
static jmethodID g_take_pixels_method = NULL;
static jmethodID g_dispatch_touch_method = NULL;
static jmethodID g_update_cursor_method = NULL;

// The menu overlay's content lives in this texture, uploaded by
// xr_menu_upload_source_texture_if_dirty() below. It's created through
// gl4es (glGenTextures/glBindTexture/glTexImage2D), like any other texture
// the engine itself creates, so ordinary glTexSubImage2D uploads against it
// work the normal way.
static GLuint g_source_texture = 0;
// A framebuffer with g_source_texture as its only color attachment, used as
// the read source for xr_menu_render_if_visible()'s glBlitFramebuffer()
// call. Created via the real (non-gl4es) GLES entry points below: that blit
// bypasses gl4es entirely (see xr_menu_render_if_visible() for why), so its
// source framebuffer has to be a real GL object rather than one gl4es
// tracks.
static GLuint g_source_fbo = 0;

typedef void (*PFNQSGETINTEGERV)(GLenum, GLint *);
typedef void (*PFNQSGENFRAMEBUFFERS)(GLsizei, GLuint *);
typedef void (*PFNQSDELETEFRAMEBUFFERS)(GLsizei, const GLuint *);
typedef void (*PFNQSBINDFRAMEBUFFER)(GLenum, GLuint);
typedef void (*PFNQSFRAMEBUFFERTEXTURE2D)(GLenum, GLenum, GLenum, GLuint, GLint);
typedef void (*PFNQSBLITFRAMEBUFFER)(GLint, GLint, GLint, GLint, GLint, GLint, GLint, GLint,
                                      GLbitfield, GLenum);

// The menu's source framebuffer and its glBlitFramebuffer() copy into the
// swapchain image go through the real GLES driver rather than gl4es: gl4es's
// fixed-pipeline emulation unconditionally substitutes its own shader onto
// any gl4es-routed draw call, which would silently replace the menu's
// content with whatever the game itself last rendered (see
// xr_menu_render_if_visible()). A framebuffer blit has no shader stage at
// all, so going through the real driver for it sidesteps the problem
// entirely.
static PFNQSGETINTEGERV real_glGetIntegerv;
static PFNQSGENFRAMEBUFFERS real_glGenFramebuffers;
static PFNQSDELETEFRAMEBUFFERS real_glDeleteFramebuffers;
static PFNQSBINDFRAMEBUFFER real_glBindFramebuffer;
static PFNQSFRAMEBUFFERTEXTURE2D real_glFramebufferTexture2D;
// glBlitFramebuffer is a GLES 3.0 addition; resolved via eglGetProcAddress
// rather than dlsym, since Android's driver dispatch doesn't guarantee ES3+
// symbols are dlsym-able by name from libGLESv2.so, unlike the GLES2-core
// functions above.
static PFNQSBLITFRAMEBUFFER real_glBlitFramebuffer;

static bool xr_menu_load_real_gles(void) {
    void *lib = dlopen("libGLESv2.so", RTLD_NOW | RTLD_LOCAL);
    if (lib == NULL) {
        LOGE("XR: menu dlopen(libGLESv2.so) failed: %s", dlerror());
        return false;
    }
    real_glGetIntegerv = (PFNQSGETINTEGERV)dlsym(lib, "glGetIntegerv");
    real_glGenFramebuffers = (PFNQSGENFRAMEBUFFERS)dlsym(lib, "glGenFramebuffers");
    real_glDeleteFramebuffers = (PFNQSDELETEFRAMEBUFFERS)dlsym(lib, "glDeleteFramebuffers");
    real_glBindFramebuffer = (PFNQSBINDFRAMEBUFFER)dlsym(lib, "glBindFramebuffer");
    real_glFramebufferTexture2D = (PFNQSFRAMEBUFFERTEXTURE2D)dlsym(lib, "glFramebufferTexture2D");
    real_glBlitFramebuffer = (PFNQSBLITFRAMEBUFFER)eglGetProcAddress("glBlitFramebuffer");
    return real_glGetIntegerv && real_glGenFramebuffers && real_glDeleteFramebuffers &&
           real_glBindFramebuffer && real_glFramebufferTexture2D && real_glBlitFramebuffer;
}

static uint32_t g_pixel_generation = 0;
static uint32_t g_source_uploaded_generation = (uint32_t)-1;
static uint8_t *g_pixel_cache = NULL; // MENU_WIDTH*MENU_HEIGHT*4 bytes

void xr_menu_get_content_size(int *width, int *height) {
    *width = MENU_WIDTH;
    *height = MENU_HEIGHT;
}

// FindClass() from this thread (SDL's native thread, attached to the JVM
// via AttachCurrentThread rather than spawned from Java) resolves against
// the bootstrap classloader, which only knows framework classes - it can't
// see de.ladkau.questshock.MenuOverlay at all. Routing through the
// activity's own classloader is the standard, documented workaround.
static jclass xr_menu_find_class(JNIEnv *env, jobject activity, const char *name) {
    jclass activityClass = (*env)->GetObjectClass(env, activity);
    jmethodID getClassLoader =
        (*env)->GetMethodID(env, activityClass, "getClassLoader", "()Ljava/lang/ClassLoader;");
    jobject classLoader = (*env)->CallObjectMethod(env, activity, getClassLoader);
    jclass classLoaderClass = (*env)->FindClass(env, "java/lang/ClassLoader");
    jmethodID loadClass = (*env)->GetMethodID(env, classLoaderClass, "loadClass",
                                               "(Ljava/lang/String;)Ljava/lang/Class;");
    jstring className = (*env)->NewStringUTF(env, name);
    jclass result = (jclass)(*env)->CallObjectMethod(env, classLoader, loadClass, className);
    (*env)->DeleteLocalRef(env, className);
    return result;
}

static bool xr_menu_init_jni(void) {
    JNIEnv *env = (JNIEnv *)SDL_AndroidGetJNIEnv();
    jobject activity = (jobject)SDL_AndroidGetActivity();
    if (env == NULL || activity == NULL) {
        LOGE("XR: menu - no JNIEnv/Activity from SDL");
        return false;
    }

    jclass localClass = xr_menu_find_class(env, activity, "de.ladkau.questshock.MenuOverlay");
    if (localClass == NULL) {
        LOGE("XR: menu - could not find MenuOverlay class");
        return false;
    }
    g_menu_overlay_class = (jclass)(*env)->NewGlobalRef(env, localClass);

    g_native_init_method =
        (*env)->GetStaticMethodID(env, g_menu_overlay_class, "nativeInit", "(Landroid/app/Activity;)V");
    g_take_pixels_method =
        (*env)->GetStaticMethodID(env, g_menu_overlay_class, "nativeTakePixelsIfDirty", "()[B");
    g_dispatch_touch_method =
        (*env)->GetStaticMethodID(env, g_menu_overlay_class, "nativeDispatchTouch", "(FFZ)V");
    g_update_cursor_method =
        (*env)->GetStaticMethodID(env, g_menu_overlay_class, "nativeUpdateCursor", "(FFZ)V");
    if (!g_native_init_method || !g_take_pixels_method || !g_dispatch_touch_method ||
        !g_update_cursor_method) {
        LOGE("XR: menu - could not resolve MenuOverlay JNI methods");
        return false;
    }

    (*env)->CallStaticVoidMethod(env, g_menu_overlay_class, g_native_init_method, activity);
    // CallStaticVoidMethod doesn't surface Java exceptions on its own - if
    // MenuOverlay's constructor throws (it runs its View measure/layout/
    // draw calls on this native render thread rather than the Android UI
    // thread, a plausible crash vector), the exception would otherwise be
    // left silently pending and corrupt whatever JNI call runs next.
    if ((*env)->ExceptionCheck(env)) {
        LOGE("XR: menu MenuOverlay.nativeInit() threw a pending Java exception:");
        (*env)->ExceptionDescribe(env);
        (*env)->ExceptionClear(env);
        return false;
    }
    return true;
}

static bool xr_menu_create_source_texture(void) {
    glGenTextures(1, &g_source_texture);
    glBindTexture(GL_TEXTURE_2D, g_source_texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, MENU_WIDTH, MENU_HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE,
                 NULL);

    GLint prevFbo = 0;
    real_glGetIntegerv(GL_FRAMEBUFFER_BINDING, &prevFbo);
    real_glGenFramebuffers(1, &g_source_fbo);
    real_glBindFramebuffer(GL_FRAMEBUFFER, g_source_fbo);
    real_glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
                                 g_source_texture, 0);
    real_glBindFramebuffer(GL_FRAMEBUFFER, (GLuint)prevFbo);

    return g_source_texture != 0;
}

bool xr_menu_init(XrInstance instance, XrSession session) {
    (void)instance;
    (void)session;

    if (!xr_menu_load_real_gles()) {
        LOGE("XR: menu couldn't resolve real GLES functions via dlsym/eglGetProcAddress");
        return false;
    }
    if (!xr_menu_create_source_texture())
        return false;
    if (!xr_menu_init_jni())
        return false;

    g_pixel_cache = (uint8_t *)malloc((size_t)MENU_WIDTH * MENU_HEIGHT * 4);
    if (g_pixel_cache == NULL)
        return false;

    LOGI("XR: menu overlay ready (%dx%d)", MENU_WIDTH, MENU_HEIGHT);
    return true;
}

void xr_menu_toggle_visible(void) {
    g_visible = !g_visible;
    LOGI("XR: menu quad now %s", g_visible ? "visible" : "hidden");
}

bool xr_menu_is_visible(void) { return g_visible; }

void xr_menu_get_quad_extent(float *center_x_m, float *center_y_m, float *distance_m,
                              float *half_width_m, float *half_height_m) {
    *center_x_m = MENU_CENTER_X_METERS;
    *center_y_m = MENU_CENTER_Y_METERS;
    *distance_m = MENU_DISTANCE_METERS;
    *half_width_m = MENU_WIDTH_METERS * 0.5f;
    *half_height_m = MENU_WIDTH_METERS * 0.5f * (float)MENU_HEIGHT / (float)MENU_WIDTH;
}

void xr_menu_touch(float u, float v, bool down) {
    if (g_menu_overlay_class == NULL)
        return;
    JNIEnv *env = (JNIEnv *)SDL_AndroidGetJNIEnv();
    if (env == NULL)
        return;
    // Passed via CallStaticVoidMethodA/jvalue rather than the variadic
    // Call*Method form - deliberately sidesteps relying on JNI
    // implementations correctly un-doing C's float-to-double default
    // argument promotion for varargs float parameters (a well-known JNI
    // footgun; Android's ART handles it correctly, but there's no reason
    // to depend on that when the jvalue form is unambiguous either way).
    jvalue args[3];
    args[0].f = u;
    args[1].f = v;
    args[2].z = (jboolean)down;
    (*env)->CallStaticVoidMethodA(env, g_menu_overlay_class, g_dispatch_touch_method, args);
}

void xr_menu_update_cursor(float u, float v, bool visible) {
    if (g_menu_overlay_class == NULL)
        return;
    JNIEnv *env = (JNIEnv *)SDL_AndroidGetJNIEnv();
    if (env == NULL)
        return;
    // Same jvalue-form rationale as xr_menu_touch() above.
    jvalue args[3];
    args[0].f = u;
    args[1].f = v;
    args[2].z = (jboolean)visible;
    (*env)->CallStaticVoidMethodA(env, g_menu_overlay_class, g_update_cursor_method, args);
}

// Pulls MenuOverlay's latest pixels (if it redrew since the last check)
// into g_pixel_cache and bumps g_pixel_generation - called once per visible
// frame, before deciding whether g_source_texture needs a fresh upload.
static void xr_menu_refresh_pixel_cache(void) {
    JNIEnv *env = (JNIEnv *)SDL_AndroidGetJNIEnv();
    if (env == NULL)
        return;
    jbyteArray pixels =
        (jbyteArray)(*env)->CallStaticObjectMethod(env, g_menu_overlay_class, g_take_pixels_method);
    // CallStaticObjectMethod also doesn't surface Java exceptions on its
    // own - if nativeTakePixelsIfDirty() itself throws, it would otherwise
    // silently look identical to "nothing changed yet" (a null return).
    if ((*env)->ExceptionCheck(env)) {
        LOGE("XR: menu nativeTakePixelsIfDirty() threw a pending Java exception:");
        (*env)->ExceptionDescribe(env);
        (*env)->ExceptionClear(env);
        return;
    }
    if (pixels == NULL)
        return;
    (*env)->GetByteArrayRegion(env, pixels, 0, MENU_WIDTH * MENU_HEIGHT * 4, (jbyte *)g_pixel_cache);
    (*env)->DeleteLocalRef(env, pixels);
    g_pixel_generation++;
}

// Uploads g_pixel_cache into g_source_texture via plain (gl4es-routed)
// glBindTexture/glTexSubImage2D, matching how the texture was created.
// Skipped when nothing changed since the last upload. Texture-unit-0 state
// is saved and restored around the upload, since this call is gl4es-routed
// and the engine's own next-frame rendering assumes nothing touched its
// texture bindings since it last drew.
static void xr_menu_upload_source_texture_if_dirty(void) {
    if (g_source_uploaded_generation == g_pixel_generation)
        return;

    GLint prevActiveTexture = GL_TEXTURE0;
    glGetIntegerv(GL_ACTIVE_TEXTURE, &prevActiveTexture);
    glActiveTexture(GL_TEXTURE0);
    GLint prevTexture2D = 0;
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &prevTexture2D);

    glBindTexture(GL_TEXTURE_2D, g_source_texture);
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, MENU_WIDTH, MENU_HEIGHT, GL_RGBA, GL_UNSIGNED_BYTE,
                     g_pixel_cache);
    g_source_uploaded_generation = g_pixel_generation;

    glBindTexture(GL_TEXTURE_2D, (GLuint)prevTexture2D);
    if (prevActiveTexture != GL_TEXTURE0)
        glActiveTexture((GLenum)prevActiveTexture);
}

void xr_menu_render_if_visible(void) {
    if (g_source_fbo == 0)
        return;

    xr_menu_refresh_pixel_cache();
    xr_menu_upload_source_texture_if_dirty();

    // Copies g_source_texture (via g_source_fbo) directly into the
    // currently-bound framebuffer - the menu's own dedicated swapchain
    // image, sized to exactly MENU_WIDTH x MENU_HEIGHT (see xr_session.c),
    // so the destination is always the whole image - using the real GLES3
    // hardware blit (glBlitFramebuffer) rather than a shader-based
    // full-screen-quad draw. A blit has no vertex/fragment shading stage,
    // no shader program, and no texture units involved at all, so gl4es's
    // fixed-pipeline-emulation layer - which unconditionally substitutes a
    // customized shader (reproducing the game's own last-bound
    // texture/fixed-function state) onto any gl4es-routed draw call - has
    // nothing to intercept here. It also never touches gl4es's own tracked
    // program/vertex-array/texture-binding shadow state, so the only piece
    // of state that needs save/restore is the READ framebuffer binding;
    // binding only GL_READ_FRAMEBUFFER, rather than the combined
    // GL_FRAMEBUFFER target, leaves the DRAW side (the swapchain image
    // itself) untouched throughout.
    //
    // Y is flipped between source and destination: g_source_texture's texel
    // row v=0 holds MenuOverlay's Bitmap row 0 (the top of the rendered
    // content, standard top-row-first raster order), and reading that same
    // texture via an attached FBO, framebuffer y=0 accesses that identical
    // row. The destination swapchain framebuffer follows the opposite
    // convention - its own y=0 is its bottom edge - so swapping dstY0/dstY1
    // keeps the menu content right-side up (glBlitFramebuffer supports
    // inverted src/dst rects for exactly this).
    GLint prevReadFbo = 0;
    real_glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &prevReadFbo);

    real_glBindFramebuffer(GL_READ_FRAMEBUFFER, g_source_fbo);
    real_glBlitFramebuffer(0, 0, MENU_WIDTH, MENU_HEIGHT, 0, MENU_HEIGHT, MENU_WIDTH, 0,
                            GL_COLOR_BUFFER_BIT, GL_LINEAR);
    real_glBindFramebuffer(GL_READ_FRAMEBUFFER, (GLuint)prevReadFbo);
}

void xr_menu_shutdown(void) {
    if (g_source_texture != 0)
        glDeleteTextures(1, &g_source_texture);
    g_source_texture = 0;
    g_source_uploaded_generation = (uint32_t)-1;

    if (g_source_fbo != 0 && real_glDeleteFramebuffers != NULL)
        real_glDeleteFramebuffers(1, &g_source_fbo);
    g_source_fbo = 0;

    if (g_menu_overlay_class != NULL) {
        JNIEnv *env = (JNIEnv *)SDL_AndroidGetJNIEnv();
        if (env != NULL)
            (*env)->DeleteGlobalRef(env, g_menu_overlay_class);
    }
    g_menu_overlay_class = NULL;
    g_native_init_method = NULL;
    g_take_pixels_method = NULL;
    g_dispatch_touch_method = NULL;
    g_update_cursor_method = NULL;

    free(g_pixel_cache);
    g_pixel_cache = NULL;
    g_pixel_generation = 0;

    g_visible = false;
}