sx/library/modules/ui/events.sx

#import "modules/std.sx";
#import "modules/ffi/sdl3.sx";
#import "modules/ui/types.sx";

MouseButton :: enum {
    none;
    left;
    middle;
    right;
}

MouseButtonData :: struct { position: Point; button: MouseButton; }
MouseMotionData :: struct { position: Point; delta: Point; }
MouseWheelData  :: struct { position: Point; delta: Point; }

// Platform-neutral keycode. Each backend translates its native codes to this
// (see `keycode_from_sdl`), so app code never depends on a platform key enum.
Keycode :: enum {
    unknown;
    escape;
    enter;
    space;
    tab;
    backspace;
    delete;
    left;
    right;
    up;
    down;
}

KeyData         :: struct { key: Keycode; }
ResizeData      :: struct { size: Size; }

Event :: enum {
    none;
    quit;
    mouse_down: MouseButtonData;
    mouse_up: MouseButtonData;
    mouse_moved: MouseMotionData;
    mouse_wheel: MouseWheelData;
    key_down: KeyData;
    key_up: KeyData;
    text_input: string;
    window_resize: ResizeData;
}

event_position :: (e: *Event) -> ?Point {
    if e == {
        case .mouse_down: (d) { return d.position; }
        case .mouse_up: (d) { return d.position; }
        case .mouse_moved: (d) { return d.position; }
        case .mouse_wheel: (d) { return d.position; }
    }
    null
}

// Map a platform (SDL) keycode to the neutral `Keycode`. Only the keys the app
// consumes are mapped; everything else is `.unknown`. Letters/digits arrive via
// `text_input`, not here.
// TODO: extend as more keys are needed.
keycode_from_sdl :: (k: SDL_Keycode) -> Keycode {
    if k == {
        case .escape:     return .escape;
        case .return_key: return .enter;
        case .space:      return .space;
        case .tab:        return .tab;
        case .backspace:  return .backspace;
        case .delete_key: return .delete;
        case .left:       return .left;
        case .right:      return .right;
        case .up:         return .up;
        case .down:       return .down;
    }
    .unknown
}

// Translate SDL_Event → our Event type
translate_sdl_event :: (sdl: *SDL_Event) -> Event {
    if sdl == {
        case .quit: {
            return .quit;
        }
        case .key_down: (data) {
            return .key_down(.{ key = keycode_from_sdl(data.key) });
        }
        case .key_up: (data) {
            return .key_up(.{ key = keycode_from_sdl(data.key) });
        }
        case .mouse_motion: (data) {
            return .mouse_moved(.{
                position = .{ x = data.x, y = data.y },
                delta = .{ x = data.xrel, y = data.yrel }
            });
        }
        case .mouse_button_down: (data) {
            btn :MouseButton = if data.button == {
                case 1: .left;
                case 2: .middle;
                case 3: .right;
                else: .none;
            };
            return .mouse_down(.{
                position = .{ x = data.x, y = data.y },
                button = btn
            });
        }
        case .mouse_button_up: (data) {
            btn :MouseButton = if data.button == {
                case 1: .left;
                case 2: .middle;
                case 3: .right;
                else: .none;
            };
            return .mouse_up(.{
                position = .{ x = data.x, y = data.y },
                button = btn
            });
        }
        case .mouse_wheel: (data) {
            return .mouse_wheel(.{
                position = .{ x = data.mouse_x, y = data.mouse_y },
                delta = .{ x = data.x, y = data.y }
            });
        }
        case .window_resized: (data) {
            return .window_resize(.{
                size = .{ width = xx data.data1, height = xx data.data2 }
            });
        }
    }
    .none
}