android-ui-dogfooding/main.odin

package main

import "shared:android"
import "base:runtime"
import "core:time"
import engine "shared:zephr"
import "jni"

device_model: string
device_sdk: i32
toast_ctx: Context
main_activity: Activity

Edge_Insets :: struct {
    left, top, right, bottom: f32
}

insets: Edge_Insets
insets_valid: bool

main :: proc() {
    // Android must not start the app from here. This library's DT_INIT points at
    // Odin's _odin_entry_point, which the dynamic loader runs the moment
    // NativeActivity dlopens libmain.so -- long before the glue spawns its
    // thread and calls android_main, and so before context.user_ptr holds the
    // android_app. Running real_main here reaches backend_init with a nil app
    // and faults writing app.onAppCmd.
    //
    // The proc still has to exist: package main requires it, and it is the
    // desktop entry point.
    when ODIN_PLATFORM_SUBTARGET != .Android {
        real_main()
    }
}

real_main :: proc() {
    engine.init("", "", {480, 1000}, false, "")
    defer engine.deinit()

    _, font_ok := engine.ui_text_register_font(#load("./assets/Roboto-VariableFont_wdth_wght.ttf"))
    ensure(font_ok)

    // Material Symbols, subset to the glyphs the app bar uses: 1.3KB of a 356KB
    // font. Its codepoints are Private Use Area, so nothing else claims them and
    // the shaper's per-codepoint fallback routes them here on its own. ☰ and ⋮
    // were rendering as tofu because Roboto has no glyph for either.
    _, icon_font_ok := engine.ui_text_register_font(#load("./assets/material_icons.ttf"))
    ensure(icon_font_ok)

    m3_init_dark()

    // Only draw when something actually changed. Without this the loop renders
    // flat out forever, which on a phone is straight battery burn.
    engine.set_render_on_change(true)

    // Rolling work-vs-swap timings to logcat, to tell a slow frame apart from a
    // frame that is merely waiting on vsync.
    engine.set_frame_stats(true)


    for !engine.should_quit() {
        engine.frame_start()
        defer engine.frame_end()

        e := engine.iter_events()
        for e != nil {
            #partial switch e.type {
            case .WINDOW_CLOSED:
                engine.quit()
            case .WINDOW_RESIZED:
                insets_valid = false
            }

            e = engine.iter_events()
        }

        if !insets_valid {
            insets_valid = refresh_insets()
            if !insets_valid {
                // The decor view attaches asynchronously and emits no event when
                // it does, so the retry has to drive itself.
                //
                // Deliberately request_render_at, not request_render: a plain
                // request made here -- before the build -- is consumed by the
                // very frame it is running in, so it schedules nothing and the
                // loop parks with insets still unresolved. A timed wake is the
                // one that survives into the next frame. It only works today
                // because the first frames redraw anyway while the tree settles.
                engine.request_render_at(engine.get_time() + 16 * time.Millisecond)
            }
        }

        window_size := engine.get_window_size()

        engine.ui_begin_build(window_size)
        engine.ui_text_set_default_pixel_size(16) // dp
        engine.ui_push_text_color(0xFFFFFF)
        draw_ui()
        engine.ui_pop_text_color()
        engine.ui_end_build()

        engine.ui_draw(engine.get_projection())
    }
}

@export
android_main :: proc "c" (state: ^android.android_app) {
    context = runtime.default_context()
    context.user_ptr = state

    // Static field reads only -- safe from the engine's thread. Anything
    // touching the UI toolkit (Toast, dialogs) needs the main looper instead.
    if jni.init(state) {
        device_model, _ = build_model()
        device_sdk, _ = build_sdk_int()
        toast_ctx = Context(jni.activity(state))
        main_activity = Activity(jni.activity(state))
    }

    real_main()
}

draw_ui :: proc() {
    m3_demo_screen()
}

// Toast needs a Java looper on this thread. Preparing one is a one-time cost
// and the native ALooper the engine polls is unaffected -- they're separate.
show_toast :: proc(msg: string) {
    // The bindings all fail closed without a VM, so this would be harmless off
    // Android -- just a pointless chain of JNI calls on every tap. Compile it
    // out instead of relying on that.
    when ODIN_PLATFORM_SUBTARGET == .Android {
        if l, ok := looper_my_looper(); ok && l == nil {
            looper_prepare()
        }

        toast, ok := toast_make_text(toast_ctx, msg, 0) // 0 = Toast.LENGTH_SHORT
        if !ok {
            return
        }
        toast_show(toast)
    }
}

// Walks Activity -> Window -> decor View -> WindowInsets. Returns false while
// the decor view is still unattached, which is normal for the first few frames.
refresh_insets :: proc() -> bool {
    // Returning true, not false: zero insets are the correct answer where there
    // are no system bars, and the caller retries every frame until this succeeds
    // -- requesting a render each time. Failing here would pin the desktop loop
    // awake forever, which is exactly what render_on_change is meant to avoid.
    when ODIN_PLATFORM_SUBTARGET != .Android {
        return true
    }

    // This runs every frame until it succeeds, and each call below returns a
    // local ref. Without a frame to scope them the ref table fills and aborts.
    env := jni.env()
    if !jni.push_frame(env) {
        return false
    }
    defer jni.pop_frame(env)

    win := activity_get_window(main_activity) or_return
    decor := window_get_decor_view(win) or_return
    wi := view_get_root_window_insets(decor) or_return
    if wi == nil {
        return false
    }

    // API 30+ typed insets. Below that both calls fail and we fall through.
    if mask, ok := insets_type_system_bars(); ok {
        if cut, got_cut := insets_type_display_cutout(); got_cut {
            mask |= cut
        }
        if ins, got := window_insets_get(wi, mask); got && ins != nil {
            l := insets_left(ins) or_return
            t := insets_top(ins) or_return
            r := insets_right(ins) or_return
            b := insets_bottom(ins) or_return
            insets = to_points({f32(l), f32(t), f32(r), f32(b)})
            return true
        }
    }

    l := window_insets_sys_left(wi) or_return
    t := window_insets_sys_top(wi) or_return
    r := window_insets_sys_right(wi) or_return
    b := window_insets_sys_bottom(wi) or_return
    insets = to_points({f32(l), f32(t), f32(r), f32(b)})
    return true
}

// WindowInsets are reported in physical pixels, but layout is in dp.
to_points :: proc(v: Edge_Insets) -> Edge_Insets {
    s := engine.get_backing_scale()
    if s <= 0 {
        s = 1
    }
    return {v.left / s, v.top / s, v.right / s, v.bottom / s}
}