wheel_handler()

std::function< void(uint32_t, glm::vec2, double, double)> MayaFlux::Portal::Forma::Scrollable::wheel_handler

(

Surface &

surface

)

const

A self-contained wheel-scroll handler bound to this Scrollable's own state.

place() wires exactly this behind the viewport's own on_scroll, but Context::handle_scroll dispatches to only the topmost element under the cursor (Layer::hit_test), so content drawn on top of the viewport - anything track()ed, since it registers after and so hit- tests first - never reaches the viewport's own on_scroll while the cursor sits over it. A caller in that position (TextField:: scrollable() is exactly this case) registers the returned function on its own element's on_scroll instead of duplicating the wheel- delta-to-content-delta conversion by hand.

Captures only this Scrollable's own shared state (scroll, offset, the tracked list, the indicator), the same shared_ptrs place()'s own wiring captures - safe to keep registered after this Scrollable value itself is destroyed, same as every other Context callback this struct wires.

Parameters

surface

Surface owning the same Layer/Context place() used.

Returns

A Context::ScrollFn-shaped callable, ready for on_scroll.

Definition at line 87 of file Scrollable.cpp.

{
    return [scroll_state = scroll, scroll_offset = offset, tracked = m_tracked,
               indicator = m_indicator, surface, speed = m_wheel_speed](
               uint32_t, glm::vec2, double dx, double dy) mutable {
        Kinesis::apply_scroll(*scroll_state,
            glm::vec2(static_cast<float>(dx), static_cast<float>(dy)) * speed);
        reflow(*scroll_state, *scroll_offset, *tracked, surface.layer(), indicator.get());
    };
}

References MayaFlux::Kinesis::apply_scroll(), indicator(), MayaFlux::Portal::Forma::Surface::layer(), m_indicator, m_tracked, m_wheel_speed, offset, and scroll.

Referenced by place(), and MayaFlux::Portal::Forma::TextField::scrollable().

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