sx/library/modules/platform/android.sx

// Android backend driven by a `#jni_main` Activity (no native_app_glue).
//
// Lifecycle:
//
//   1. Java `SxApp.onCreate(b)` → native `sx_onCreate`: stash JNIEnv* +
//      Activity globals, install the AAssetManager into the C file_utils,
//      construct a `SurfaceView`, register `SxApp` as its
//      SurfaceHolder.Callback, set as Activity content view.
//   2. Java `SxApp.surfaceCreated(holder)` → native `sx_surfaceCreated`:
//      extract the ANativeWindow from the holder's Surface, then
//      `pthread_create` the render thread on first delivery.
//   3. Render thread: brings up EGL on the ANativeWindow, then calls
//      `sx_app_main()` — the user's entry-point, which sets up the
//      AndroidPlatform / GPU / pipeline globals and ends in
//      `run_frame_loop(closure(frame))`.
//   4. `run_frame_loop` drives the loop: drain touch events queue,
//      invoke `frame_fn`, `eglSwapBuffers`, sleep ~1ms.
//   5. Java `onTouchEvent` → native `sx_onTouchEvent`: push the
//      (action,x,y) tuple onto a mutex-guarded queue. `poll_events`
//      drains the queue into the platform's standard `Event` shape.
//
// Vulkan-compatible: same ANativeWindow drives `vkCreate*SurfaceKHR`
// without changing the lifecycle.

#import "modules/std.sx";
#import "modules/compiler.sx";
#import "modules/ui/types.sx";
#import "modules/ui/events.sx";
#import "modules/platform/types.sx";
#import "modules/platform/api.sx";

// ── Foreign Java types ──────────────────────────────────────────────────

Bundle   :: #foreign #jni_class("android/os/Bundle") { }
JContext :: #foreign #jni_class("android/content/Context") {
    getAssets :: (self: *Self) -> *AssetManagerJ;
}
AssetManagerJ :: #foreign #jni_class("android/content/res/AssetManager") { }

Surface :: #foreign #jni_class("android/view/Surface") { }
SurfaceHolder :: #foreign #jni_class("android/view/SurfaceHolder") {
    getSurface  :: (self: *Self) -> *Surface;
    addCallback :: (self: *Self, cb: *SurfaceHolderCallback);
}
SurfaceView :: #foreign #jni_class("android/view/SurfaceView") {
    static new :: (ctx: *JContext) -> *Self;
    getHolder  :: (self: *Self) -> *SurfaceHolder;
}
SurfaceHolderCallback :: #foreign #jni_class("android/view/SurfaceHolder$Callback") { }

MotionEvent :: #foreign #jni_class("android/view/MotionEvent") {
    getAction :: (self: *Self) -> s32;
    getX      :: (self: *Self) -> f32;
    getY      :: (self: *Self) -> f32;
}

JView :: #foreign #jni_class("android/view/View") { }
ActivityClass :: #foreign #jni_class("android/app/Activity") {
    setContentView :: (self: *Self, v: *JView);
}

// ── Foreign C/NDK decls ─────────────────────────────────────────────────

// C side of file_utils — installs the AAssetManager so `read_file_bytes`
// can route through `AAssetManager_open` when running on Android.
sx_android_set_asset_manager :: (mgr: *void) #foreign;

__android_log_print :: (prio: s32, tag: *u8, fmt: *u8) -> s32 #foreign;
usleep              :: (us: u32) -> s32 #foreign;

// libandroid
ANativeWindow_fromSurface :: (env: *void, surface: *void) -> *void #foreign;
ANativeWindow_release     :: (window: *void) #foreign;
ANativeWindow_getWidth    :: (window: *void) -> s32 #foreign;
ANativeWindow_getHeight   :: (window: *void) -> s32 #foreign;
ANativeWindow_setBuffersGeometry :: (w: *void, width: s32, height: s32, fmt: s32) -> s32 #foreign;

AAssetManager_fromJava :: (env: *void, mgr: *void) -> *void #foreign;

// pthread (link libpthread is built into bionic).
pthread_create  :: (thread: *u64, attr: *void, start: (*void) -> *void, arg: *void) -> s32 #foreign;
pthread_mutex_init    :: (m: *void, attr: *void) -> s32 #foreign;
pthread_mutex_lock    :: (m: *void) -> s32 #foreign;
pthread_mutex_unlock  :: (m: *void) -> s32 #foreign;

// EGL. Constants from <EGL/egl.h>. We bring up an ES3 context with a
// 24-bit RGB framebuffer + 24-bit depth (same shape chess used under
// the legacy NDK path).
EGL_DEFAULT_DISPLAY    :: 0;
EGL_NO_DISPLAY         :*void: null;
EGL_NO_CONTEXT         :*void: null;
EGL_NO_SURFACE         :*void: null;
EGL_TRUE               :u32: 1;
EGL_FALSE              :u32: 0;
EGL_NONE               :s32: 0x3038;
EGL_RED_SIZE           :s32: 0x3024;
EGL_GREEN_SIZE         :s32: 0x3023;
EGL_BLUE_SIZE          :s32: 0x3022;
EGL_ALPHA_SIZE         :s32: 0x3021;
EGL_DEPTH_SIZE         :s32: 0x3025;
EGL_RENDERABLE_TYPE    :s32: 0x3040;
EGL_SURFACE_TYPE       :s32: 0x3033;
EGL_OPENGL_ES3_BIT     :s32: 0x00000040;
EGL_WINDOW_BIT         :s32: 0x0004;
EGL_NATIVE_VISUAL_ID   :s32: 0x302E;
EGL_CONTEXT_CLIENT_VERSION :s32: 0x3098;

eglGetDisplay          :: (id: u64) -> *void #foreign;
eglInitialize          :: (d: *void, major: *s32, minor: *s32) -> u32 #foreign;
eglChooseConfig        :: (d: *void, attrs: *s32, configs: **void, sz: s32, num: *s32) -> u32 #foreign;
eglGetConfigAttrib     :: (d: *void, cfg: *void, attr: s32, value: *s32) -> u32 #foreign;
eglCreateContext       :: (d: *void, cfg: *void, share: *void, attrs: *s32) -> *void #foreign;
eglCreateWindowSurface :: (d: *void, cfg: *void, window: *void, attrs: *s32) -> *void #foreign;
eglMakeCurrent         :: (d: *void, draw: *void, read: *void, ctx: *void) -> u32 #foreign;
eglSwapBuffers         :: (d: *void, surface: *void) -> u32 #foreign;
eglDestroyContext      :: (d: *void, ctx: *void) -> u32 #foreign;
eglDestroySurface      :: (d: *void, surface: *void) -> u32 #foreign;
eglTerminate           :: (d: *void) -> u32 #foreign;

// ── Module-level state ──────────────────────────────────────────────────

g_activity     : *void = null;          // global ref to the SxApp jobject (saved env can't outlive scope)
g_app_window   : *void = null;          // ANativeWindow from surfaceCreated
g_egl_display  : *void = null;
g_egl_context  : *void = null;
g_egl_surface  : *void = null;
g_egl_config   : *void = null;
g_viewport_w   : s32 = 0;
g_viewport_h   : s32 = 0;
// Defaults to 1.0 until a proper density query lands. Chess's pipeline
// uses `viewport_w/h` as the layout space and `dpi_scale` to scale
// rendering; mismatches cause layout drift / shrinking.
g_dpi_scale    : f32 = 1.0;
g_should_stop  : bool = false;
g_render_thread_started : bool = false;
g_render_thread : u64 = 0;
g_frame_fn     : Closure() = ---;
g_frame_fn_set : bool = false;

// Touch event queue. Single-producer (Java UI thread) / single-consumer
// (render thread); a small ring buffer guarded by a pthread mutex is
// enough — chess only generates touches on user interaction so contention
// is rare.
TouchEvent :: struct {
    action: s32;
    x: f32;
    y: f32;
}

g_touch_queue : [64]TouchEvent = ---;
g_touch_head  : u32 = 0;
g_touch_tail  : u32 = 0;
// pthread_mutex_t is 40 bytes on bionic (NDK 26+); over-size to 64 for safety.
g_touch_mutex_storage : [64]u8 = ---;
g_touch_mutex_inited  : bool = false;

// ── #jni_main Activity ──────────────────────────────────────────────────

// ── User-facing helpers for the consumer's `#jni_main` Activity ────────
//
// The consumer (chess, etc.) writes their own `SxApp :: #jni_main
// #jni_class("...")` declaration with `#implements SurfaceHolderCallback`
// and the standard lifecycle methods. This file provides the primitives
// those methods call:
//
//   - `sx_android_forward_assets(env, activity)` from onCreate.
//   - `sx_android_attach_window(env, holder)` from surfaceCreated.
//   - `sx_android_detach_window()` from surfaceDestroyed.
//   - `sx_android_set_viewport(w, h)` from surfaceChanged.
//   - `sx_android_start_render_thread(main_fn)` once the surface is up.
//   - `sx_android_push_touch(action, x, y)` from onTouchEvent.

// Extract the AAssetManager from the Activity and install it into the
// C file_utils so `read_file_bytes` can route through `AAssetManager_open`.
// Call this from your Activity's `onCreate` (BEFORE any asset read).
sx_android_forward_assets :: (env: *void, activity: *JContext) {
    #jni_env(env) {
        assets := activity.getAssets();
        aam := AAssetManager_fromJava(env, xx assets);
        sx_android_set_asset_manager(aam);
    }
}

// Extract the ANativeWindow from a SurfaceHolder. Call this from your
// Activity's `surfaceCreated`. The window stays valid until
// `sx_android_detach_window` runs (typically in `surfaceDestroyed`).
sx_android_attach_window :: (env: *void, holder: *SurfaceHolder) {
    #jni_env(env) {
        surface := holder.getSurface();
        g_app_window = ANativeWindow_fromSurface(env, xx surface);
    }
}

sx_android_detach_window :: () {
    if g_app_window != null {
        ANativeWindow_release(g_app_window);
        g_app_window = null;
    }
}

sx_android_set_viewport :: (w: s32, h: s32) {
    g_viewport_w = w;
    g_viewport_h = h;
}

// Start the render thread that brings up EGL on `g_app_window` and calls
// the user-supplied `entry_fn` (typically the user's `main`). Safe to
// call once after `sx_android_attach_window` has set the window.
sx_android_start_render_thread :: (entry_fn: () -> void) {
    if g_render_thread_started { return; }
    g_user_main_fn = entry_fn;
    pthread_create(@g_render_thread, null, sx_android_render_thread_entry, null);
    g_render_thread_started = true;
}

g_user_main_fn : () -> void = null;

sx_android_render_thread_entry :: (arg: *void) -> *void {
    while g_app_window == null and !g_should_stop {
        usleep(1000);
    }
    if g_should_stop { return null; }

    if !sx_android_egl_init() {
        __android_log_print(6, "sxapp".ptr, "EGL bootstrap failed\n".ptr);
        return null;
    }

    if g_user_main_fn != null {
        g_user_main_fn();
    }
    null;
}

// Bring up EGL on g_app_window. Sets g_egl_display / g_egl_context /
// g_egl_surface and makes the context current. Returns false on any
// failure — caller bails on the render thread.
sx_android_egl_init :: () -> bool {
    g_egl_display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
    if g_egl_display == EGL_NO_DISPLAY { return false; }

    major : s32 = 0;
    minor : s32 = 0;
    if eglInitialize(g_egl_display, @major, @minor) == EGL_FALSE { return false; }

    cfg_attrs : [13]s32 = .{
        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES3_BIT,
        EGL_SURFACE_TYPE,    EGL_WINDOW_BIT,
        EGL_RED_SIZE,        8,
        EGL_GREEN_SIZE,      8,
        EGL_BLUE_SIZE,       8,
        EGL_DEPTH_SIZE,      24,
        EGL_NONE,
    };
    num_cfg : s32 = 0;
    if eglChooseConfig(g_egl_display, @cfg_attrs[0], @g_egl_config, 1, @num_cfg) == EGL_FALSE { return false; }
    if num_cfg < 1 { return false; }

    visual_id : s32 = 0;
    eglGetConfigAttrib(g_egl_display, g_egl_config, EGL_NATIVE_VISUAL_ID, @visual_id);
    ANativeWindow_setBuffersGeometry(g_app_window, 0, 0, visual_id);

    ctx_attrs : [3]s32 = .{ EGL_CONTEXT_CLIENT_VERSION, 3, EGL_NONE };
    g_egl_context = eglCreateContext(g_egl_display, g_egl_config, EGL_NO_CONTEXT, @ctx_attrs[0]);
    if g_egl_context == EGL_NO_CONTEXT { return false; }

    g_egl_surface = eglCreateWindowSurface(g_egl_display, g_egl_config, g_app_window, null);
    if g_egl_surface == EGL_NO_SURFACE { return false; }

    if eglMakeCurrent(g_egl_display, g_egl_surface, g_egl_surface, g_egl_context) == EGL_FALSE { return false; }

    g_viewport_w = ANativeWindow_getWidth(g_app_window);
    g_viewport_h = ANativeWindow_getHeight(g_app_window);
    true;
}

// ── Touch event queue ───────────────────────────────────────────────────

sx_android_push_touch :: (action: s32, x: f32, y: f32) {
    sx_android_ensure_touch_mutex();
    pthread_mutex_lock(xx @g_touch_mutex_storage[0]);
    next := (g_touch_tail + 1) % 64;
    if next != g_touch_head { // drop on full
        g_touch_queue[g_touch_tail] = TouchEvent.{ action = action, x = x, y = y };
        g_touch_tail = next;
    }
    pthread_mutex_unlock(xx @g_touch_mutex_storage[0]);
}

sx_android_drain_touches :: (out: *List(Event)) {
    sx_android_ensure_touch_mutex();
    pthread_mutex_lock(xx @g_touch_mutex_storage[0]);
    while g_touch_head != g_touch_tail {
        t := g_touch_queue[g_touch_head];
        g_touch_head = (g_touch_head + 1) % 64;
        // MotionEvent actions: 0=DOWN, 1=UP, 2=MOVE. Map onto chess's
        // existing mouse Event variants — touch becomes a left-button
        // mouse on the same screen coords; delta unused on Android.
        pos : Point = .{ x = t.x, y = t.y };
        if t.action == 0 {
            out.append(.mouse_down(.{ position = pos, button = .left }));
        } else if t.action == 1 {
            out.append(.mouse_up(.{ position = pos, button = .left }));
        } else if t.action == 2 {
            out.append(.mouse_moved(.{ position = pos, delta = .{ x = 0, y = 0 } }));
        }
    }
    pthread_mutex_unlock(xx @g_touch_mutex_storage[0]);
}

sx_android_ensure_touch_mutex :: () {
    if g_touch_mutex_inited { return; }
    pthread_mutex_init(xx @g_touch_mutex_storage[0], null);
    g_touch_mutex_inited = true;
}

// ── AndroidPlatform ─────────────────────────────────────────────────────

AndroidPlatform :: struct {
    title:  [:0]u8 = "";
    width:  s32 = 0;
    height: s32 = 0;
    events: List(Event) = .{};
}

impl Platform for AndroidPlatform {
    init :: (self: *AndroidPlatform, title: [:0]u8, w: s32, h: s32) -> bool {
        self.title = title;
        self.width = w;
        self.height = h;
        true;
    }

    begin_frame :: (self: *AndroidPlatform) -> FrameContext {
        FrameContext.{
            viewport_w = xx g_viewport_w,
            viewport_h = xx g_viewport_h,
            pixel_w = g_viewport_w,
            pixel_h = g_viewport_h,
            dpi_scale = g_dpi_scale,
            delta_time = 0.016,
            target_present_time = 0.0,
        };
    }

    end_frame :: (self: *AndroidPlatform) {
        if g_egl_display != null and g_egl_surface != null {
            eglSwapBuffers(g_egl_display, g_egl_surface);
        }
    }

    poll_events :: (self: *AndroidPlatform) -> []Event {
        self.events.len = 0;
        sx_android_drain_touches(@self.events);
        result : []Event = ---;
        result.ptr = self.events.items;
        result.len = self.events.len;
        result;
    }

    safe_insets :: (self: *AndroidPlatform) -> EdgeInsets {
        EdgeInsets.{};
    }

    keyboard :: (self: *AndroidPlatform) -> KeyboardState {
        KeyboardState.zero();
    }
    show_keyboard :: (self: *AndroidPlatform) { }
    hide_keyboard :: (self: *AndroidPlatform) { }

    run_frame_loop :: (self: *AndroidPlatform, frame_fn: Closure()) {
        g_frame_fn = frame_fn;
        g_frame_fn_set = true;
        // `frame_fn` is expected to call `g_plat.end_frame()` which does
        // the `eglSwapBuffers` — don't swap again here or the back buffer
        // is presented twice per render, alternating with the previous
        // frame's contents → visible flicker.
        while !g_should_stop {
            frame_fn();
            usleep(1000);
        }
    }

    stop :: (self: *AndroidPlatform) {
        g_should_stop = true;
    }

    shutdown :: (self: *AndroidPlatform) {
        if g_egl_display != null {
            eglMakeCurrent(g_egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
            if g_egl_surface != null { eglDestroySurface(g_egl_display, g_egl_surface); g_egl_surface = null; }
            if g_egl_context != null { eglDestroyContext(g_egl_display, g_egl_context); g_egl_context = null; }
            eglTerminate(g_egl_display);
            g_egl_display = null;
        }
    }
}