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.
//
// State model: every piece of mutable Android-backend state lives on
// `AndroidPlatform` (the EGL handles, the ANativeWindow, the render
// thread, the touch ring, the frame closure, the user main fn, the
// touch mutex). Module-level globals are out — they shadow consumer
// globals on `#import` and produced an integer/float-shadowing render
// regression on chess before we eliminated them.
//
// Vulkan-compatible: same ANativeWindow drives `vkCreate*SurfaceKHR`
// without changing the lifecycle.

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

// ── Runtime Java types ──────────────────────────────────────────────────

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

Surface :: #jni_class("android/view/Surface") extern { }
SurfaceHolder :: #jni_class("android/view/SurfaceHolder") extern {
    getSurface  :: (self: *Self) -> *Surface;
    addCallback :: (self: *Self, cb: *SurfaceHolderCallback);
}
SurfaceView :: #jni_class("android/view/SurfaceView") extern {
    new        :: (ctx: *JContext) -> *Self;  // no `self: *Self` → class method
    getHolder  :: (self: *Self) -> *SurfaceHolder;
}
SurfaceHolderCallback :: #jni_class("android/view/SurfaceHolder$Callback") extern { }

MotionEvent :: #jni_class("android/view/MotionEvent") extern {
    getAction :: (self: *Self) -> i32;
    getX      :: (self: *Self) -> f32;
    getY      :: (self: *Self) -> f32;
}

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

// ── Extern 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) extern;

__android_log_print :: (prio: i32, tag: *u8, fmt: *u8) -> i32 extern;
usleep              :: (us: u32) -> i32 extern;

// libandroid
ANativeWindow_fromSurface :: (env: *void, surface: *void) -> *void extern;
ANativeWindow_release     :: (window: *void) extern;
ANativeWindow_getWidth    :: (window: *void) -> i32 extern;
ANativeWindow_getHeight   :: (window: *void) -> i32 extern;
ANativeWindow_setBuffersGeometry :: (w: *void, width: i32, height: i32, fmt: i32) -> i32 extern;

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

// pthread (link libpthread is built into bionic).
pthread_create  :: (thread: *u64, attr: *void, start: (*void) -> *void callconv(.c), arg: *void) -> i32 extern;
pthread_mutex_init    :: (m: *void, attr: *void) -> i32 extern;
pthread_mutex_lock    :: (m: *void) -> i32 extern;
pthread_mutex_unlock  :: (m: *void) -> i32 extern;

// 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               :i32: 0x3038;
EGL_RED_SIZE           :i32: 0x3024;
EGL_GREEN_SIZE         :i32: 0x3023;
EGL_BLUE_SIZE          :i32: 0x3022;
EGL_ALPHA_SIZE         :i32: 0x3021;
EGL_DEPTH_SIZE         :i32: 0x3025;
EGL_RENDERABLE_TYPE    :i32: 0x3040;
EGL_SURFACE_TYPE       :i32: 0x3033;
EGL_OPENGL_ES3_BIT     :i32: 0x00000040;
EGL_WINDOW_BIT         :i32: 0x0004;
EGL_NATIVE_VISUAL_ID   :i32: 0x302E;
EGL_CONTEXT_CLIENT_VERSION :i32: 0x3098;

eglGetDisplay          :: (id: u64) -> *void extern;
eglInitialize          :: (d: *void, major: *i32, minor: *i32) -> u32 extern;
eglChooseConfig        :: (d: *void, attrs: *i32, configs: **void, sz: i32, num: *i32) -> u32 extern;
eglGetConfigAttrib     :: (d: *void, cfg: *void, attr: i32, value: *i32) -> u32 extern;
eglCreateContext       :: (d: *void, cfg: *void, share: *void, attrs: *i32) -> *void extern;
eglCreateWindowSurface :: (d: *void, cfg: *void, window: *void, attrs: *i32) -> *void extern;
eglMakeCurrent         :: (d: *void, draw: *void, read: *void, ctx: *void) -> u32 extern;
eglSwapBuffers         :: (d: *void, surface: *void) -> u32 extern;
eglDestroyContext      :: (d: *void, ctx: *void) -> u32 extern;
eglDestroySurface      :: (d: *void, surface: *void) -> u32 extern;
eglTerminate           :: (d: *void) -> u32 extern;

// ── Touch ring ──────────────────────────────────────────────────────────

TouchEvent :: struct {
    action: i32;
    x: f32;
    y: f32;
}

// ── AndroidPlatform ─────────────────────────────────────────────────────
//
// Every per-instance piece of state — EGL handles, ANativeWindow, render
// thread, touch ring + mutex, frame closure, user main fn — lives here.
// No module-level globals: a previous shape had `g_viewport_w : i32` at
// module scope, which silently shadowed chess's own
// `g_viewport_w : f32` on `#import` and caused the renderer to receive
// a logical width cast to i32 instead of the physical pixel width.
//
// `logical_w` is the consumer's design width in points (e.g. chess sets
// 414 to match an iPhone 12 layout). `begin_frame` derives `dpi_scale`
// from `pixel_w / logical_w` so the renderer sees the design canvas
// regardless of physical density. Touch coords are divided by the same
// scale before delivery so layout-side hit-testing matches.

AndroidPlatform :: struct {
    title:  [:0]u8 = "";
    width:  i32 = 0;
    height: i32 = 0;

    // Set by consumer code BEFORE `init` if a fixed design width is
    // wanted (chess uses 414). When 0, the platform reports
    // viewport = pixel (1:1 logical/physical) — same as the legacy
    // hardcoded `dpi_scale = 1.0` behaviour.
    logical_w: f32 = 0.0;

    // ANativeWindow + EGL state (set up by sx_android_attach_window +
    // egl_init on the render thread).
    app_window:  *void = null;
    egl_display: *void = null;
    egl_context: *void = null;
    egl_surface: *void = null;
    egl_config:  *void = null;

    // Pixel-size from ANativeWindow_get{Width,Height}; derived dpi_scale
    // (pixel_w / logical_w when logical_w > 0, else 1.0).
    pixel_w:   i32 = 0;
    pixel_h:   i32 = 0;
    dpi_scale: f32 = 1.0;

    // Render thread lifecycle. `user_main_fn` is the consumer's `main`
    // entry, invoked once EGL is current. `should_stop` is checked in
    // the frame loop; `stop()` flips it.
    render_thread:         u64 = 0;
    render_thread_started: bool = false;
    user_main_fn:          () -> void = ---;
    should_stop:           bool = false;
    frame_closure:         ?Closure() = null;

    events: List(Event) = .{};

    // Touch ring: single-producer (Java UI thread via sx_android_push_touch)
    // / single-consumer (render thread via sx_android_drain_touches).
    // pthread_mutex_t is 40 bytes on bionic (NDK 26+); over-size to 64
    // for safety. `touch_mutex_inited` tracks lazy init on first use.
    touch_queue:           [64]TouchEvent = ---;
    touch_head:            u32 = 0;
    touch_tail:            u32 = 0;
    touch_mutex_storage:   [64]u8 = ---;
    touch_mutex_inited:    bool = false;
}

// ── 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(plat, env, holder)` from surfaceCreated.
//   - `sx_android_detach_window(plat)` from surfaceDestroyed.
//   - `sx_android_set_viewport(plat, w, h)` from surfaceChanged.
//   - `sx_android_start_render_thread(plat, main_fn)` once the surface
//     is up.
//   - `sx_android_push_touch(plat, 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 and stash it on `plat`.
// Call this from your Activity's `surfaceCreated`. The window stays
// valid until `sx_android_detach_window` runs (typically in
// `surfaceDestroyed`).
sx_android_attach_window :: (plat: *AndroidPlatform, env: *void, holder: *SurfaceHolder) {
    #jni_env(env) {
        surface := holder.getSurface();
        plat.app_window = ANativeWindow_fromSurface(env, xx surface);
    }
}

sx_android_detach_window :: (plat: *AndroidPlatform) {
    if plat.app_window != null {
        ANativeWindow_release(plat.app_window);
        plat.app_window = null;
    }
}

sx_android_set_viewport :: (plat: *AndroidPlatform, w: i32, h: i32) {
    plat.pixel_w = w;
    plat.pixel_h = h;
    sx_android_recompute_scale(plat);
}

// Start the render thread that brings up EGL on `plat.app_window` and
// calls `entry_fn` (typically the consumer's `main`). Safe to call once
// after `sx_android_attach_window` has set the window.
sx_android_start_render_thread :: (plat: *AndroidPlatform, entry_fn: () -> void) {
    if plat.render_thread_started { return; }
    plat.user_main_fn = entry_fn;
    pthread_create(@plat.render_thread, null, sx_android_render_thread_entry, xx plat);
    plat.render_thread_started = true;
}

sx_android_render_thread_entry :: (arg: *void) -> *void callconv(.c) {
    plat : *AndroidPlatform = xx arg;
    while plat.app_window == null and !plat.should_stop {
        usleep(1000);
    }
    if plat.should_stop { return null; }

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

    if plat.user_main_fn != null {
        fn := plat.user_main_fn;
        fn();
    }
    null
}

// Bring up EGL on `plat.app_window`. Sets the egl_* fields and makes
// the context current. Returns false on any failure — caller bails on
// the render thread.
sx_android_egl_init :: (plat: *AndroidPlatform) -> bool {
    plat.egl_display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
    if plat.egl_display == EGL_NO_DISPLAY { return false; }

    major : i32 = 0;
    minor : i32 = 0;
    if eglInitialize(plat.egl_display, @major, @minor) == EGL_FALSE { return false; }

    cfg_attrs : [13]i32 = .{
        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 : i32 = 0;
    if eglChooseConfig(plat.egl_display, @cfg_attrs[0], @plat.egl_config, 1, @num_cfg) == EGL_FALSE { return false; }
    if num_cfg < 1 { return false; }

    visual_id : i32 = 0;
    eglGetConfigAttrib(plat.egl_display, plat.egl_config, EGL_NATIVE_VISUAL_ID, @visual_id);
    ANativeWindow_setBuffersGeometry(plat.app_window, 0, 0, visual_id);

    ctx_attrs : [3]i32 = .{ EGL_CONTEXT_CLIENT_VERSION, 3, EGL_NONE };
    plat.egl_context = eglCreateContext(plat.egl_display, plat.egl_config, EGL_NO_CONTEXT, @ctx_attrs[0]);
    if plat.egl_context == EGL_NO_CONTEXT { return false; }

    plat.egl_surface = eglCreateWindowSurface(plat.egl_display, plat.egl_config, plat.app_window, null);
    if plat.egl_surface == EGL_NO_SURFACE { return false; }

    if eglMakeCurrent(plat.egl_display, plat.egl_surface, plat.egl_surface, plat.egl_context) == EGL_FALSE { return false; }

    plat.pixel_w = ANativeWindow_getWidth(plat.app_window);
    plat.pixel_h = ANativeWindow_getHeight(plat.app_window);
    sx_android_recompute_scale(plat);
    true
}

// Recompute `dpi_scale` from `pixel_w / logical_w`. Called on viewport
// changes and after EGL bringup populates pixel_w/h. Falls back to 1.0
// when consumer didn't set logical_w (1:1 logical/physical mode).
sx_android_recompute_scale :: (plat: *AndroidPlatform) {
    if plat.logical_w > 0.0 and plat.pixel_w > 0 {
        plat.dpi_scale = xx plat.pixel_w / plat.logical_w;
    } else {
        plat.dpi_scale = 1.0;
    }
}

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

sx_android_push_touch :: (plat: *AndroidPlatform, action: i32, x: f32, y: f32) {
    sx_android_ensure_touch_mutex(plat);
    pthread_mutex_lock(xx @plat.touch_mutex_storage[0]);
    next := (plat.touch_tail + 1) % 64;
    if next != plat.touch_head { // drop on full
        plat.touch_queue[plat.touch_tail] = TouchEvent.{ action = action, x = x, y = y };
        plat.touch_tail = next;
    }
    pthread_mutex_unlock(xx @plat.touch_mutex_storage[0]);
}

sx_android_drain_touches :: (plat: *AndroidPlatform, out: *List(Event)) {
    sx_android_ensure_touch_mutex(plat);
    pthread_mutex_lock(xx @plat.touch_mutex_storage[0]);
    inv : f32 = if plat.dpi_scale > 0.0 then 1.0 / plat.dpi_scale else 1.0;
    while plat.touch_head != plat.touch_tail {
        t := plat.touch_queue[plat.touch_head];
        plat.touch_head = (plat.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. Coords come in as physical
        // pixels; divide by dpi_scale so layout-side hit-testing
        // matches its own logical-coord frames.
        pos : Point = .{ x = t.x * inv, y = t.y * inv };
        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 @plat.touch_mutex_storage[0]);
}

sx_android_ensure_touch_mutex :: (plat: *AndroidPlatform) {
    if plat.touch_mutex_inited { return; }
    pthread_mutex_init(xx @plat.touch_mutex_storage[0], null);
    plat.touch_mutex_inited = true;
}

// ── Platform impl ───────────────────────────────────────────────────────

impl Platform for AndroidPlatform {
    init :: (self: *AndroidPlatform, title: [:0]u8, w: i32, h: i32) -> bool {
        self.title = title;
        self.width = w;
        self.height = h;
        sx_android_recompute_scale(self);
        true
    }

    // NOTE: method order must match the `Platform` protocol declaration
    // in modules/platform/api.sx. The vtable is built in impl source
    // order; mismatched order silently routes calls to the wrong method
    // (chess on Android lost touch entirely because poll_events sat in
    // begin_frame's slot, etc.).

    run_frame_loop :: (self: *AndroidPlatform, frame_fn: Closure()) {
        self.frame_closure = frame_fn;
        // `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 !self.should_stop {
            frame_fn();
            usleep(1000);
        }
    }

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

    begin_frame :: (self: *AndroidPlatform) -> FrameContext {
        // viewport_* is the logical canvas the renderer + layout see —
        // pixel_w/h divided by dpi_scale. With logical_w unset (1.0
        // scale) viewport == pixel.
        inv : f32 = if self.dpi_scale > 0.0 then 1.0 / self.dpi_scale else 1.0;
        FrameContext.{
            viewport_w = xx self.pixel_w * inv,
            viewport_h = xx self.pixel_h * inv,
            pixel_w = self.pixel_w,
            pixel_h = self.pixel_h,
            dpi_scale = self.dpi_scale,
            delta_time = 0.016,
            target_present_time = 0.0,
        }
    }

    end_frame :: (self: *AndroidPlatform) {
        if self.egl_display != null and self.egl_surface != null {
            eglSwapBuffers(self.egl_display, self.egl_surface);
        }
    }

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

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

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

    shutdown :: (self: *AndroidPlatform) {
        if self.egl_display != null {
            eglMakeCurrent(self.egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
            if self.egl_surface != null { eglDestroySurface(self.egl_display, self.egl_surface); self.egl_surface = null; }
            if self.egl_context != null { eglDestroyContext(self.egl_display, self.egl_context); self.egl_context = null; }
            eglTerminate(self.egl_display);
            self.egl_display = null;
        }
    }
}