wire_canvas_drag()

MAYAFLUX_API void MayaFlux::Portal::Forma::Geometry::wire_canvas_drag	(	Context &	ctx,
		uint32_t	id,
		std::shared_ptr< MappedState< std::vector< float > > >	state,
		Kinesis::AABB2D	bounds
	)

Wire drag interaction for a drawable canvas element.

Registers a left-button drag callback on ctx that maps NDC cursor position to a sample index and amplitude, writes into state, and increments the version. Linear interpolation fills the range between the previously touched index and the current one, preventing sparse samples under fast drag.

Parameters

ctx	Context owning the element.
id	Element id from the Mapped.
state	MappedState<vector<float>> to write into.
bounds	Canvas NDC bounds — must match those passed to drawable_canvas().

Definition at line 387 of file FormFactory.cpp.

{
    struct DragState {
        std::optional<size_t> prev_index;
    };
    auto ds = std::make_shared<DragState>();
 
    ctx.on_drag(id, IO::MouseButtons::Left,
        [state, bounds, ds](uint32_t, glm::vec2 ndc) {
            auto& v = state->value;
            if (v.empty())
                return;
 
            const float t = (ndc.x - bounds.min.x) / bounds.width();
            const float a = (ndc.y - bounds.min.y) / bounds.height();
            const size_t n = v.size();
            const size_t idx = static_cast<size_t>(
                std::clamp(t, 0.F, 1.F) * static_cast<float>(n - 1));
            const float amp = std::clamp(a, 0.F, 1.F);
 
            if (ds->prev_index && *ds->prev_index != idx) {
                const size_t lo = std::min(*ds->prev_index, idx);
                const size_t hi = std::max(*ds->prev_index, idx);
                const float v0 = v[*ds->prev_index];
                const auto span = static_cast<float>(hi - lo);
                for (size_t i = lo; i <= hi; ++i) {
                    const float f = span > 0.F
                        ? static_cast<float>(i - lo) / span
                        : 1.F;
                    v[i] = glm::mix(v0, amp, f);
                }
            } else {
                v[idx] = amp;
            }
 
            ds->prev_index = idx;
            ++state->version;
        });
 
    ctx.on_release(id, IO::MouseButtons::Left, [ds](uint32_t, glm::vec2) {
        ds->prev_index = std::nullopt;
    });
}

References a, MayaFlux::Kinesis::AABB2D::height(), hi, MayaFlux::IO::Left, lo, MayaFlux::Kinesis::AABB2D::min, MayaFlux::Portal::Forma::Context::on_drag(), MayaFlux::Portal::Forma::Context::on_release(), and MayaFlux::Kinesis::AABB2D::width().

Referenced by paint_over().

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