scroll_bar.hpp

Go to the documentation of this file.

#pragma once

 
#include <algorithm>
#include <functional>
#include <pulp/view/accessibility.hpp>
#include <pulp/view/view.hpp>
 
namespace pulp::view {

class ScrollBar : public View, public AccessibilityValueInterface {
public:
    enum class Orientation { vertical, horizontal };
 
    // ── AccessibilityValueInterface ──────────────────────────────────────
    double get_current_value() const override { return value_; }
    void set_current_value(double v) override { set_value(static_cast<float>(v)); }
    double get_minimum_value() const override { return min_; }
    double get_maximum_value() const override { return max_; }
    double get_step_size() const override {
        return arrow_step_ > 0.0f
            ? arrow_step_
            : AccessibilityValueInterface::get_step_size();
    }
 
    ScrollBar() {
        // Every platform has a first-class scrollbar role (UIA ScrollBar,
        // AT-SPI SCROLL_BAR, NSAccessibilityScrollBarRole); it keeps the
        // value-bearing range contract of a slider but announces correctly.
        set_access_role(AccessRole::scroll_bar);
        set_focusable(true);
    }
 
    void set_orientation(Orientation o) { orientation_ = o; }
    Orientation orientation() const { return orientation_; }
 
    void set_range(float min_v, float max_v) {
        min_ = min_v;
        max_ = std::max(min_v, max_v);
        clamp_value();
    }
    float min_value() const { return min_; }
    float max_value() const { return max_; }

    void set_page_size(float page) { page_size_ = std::max(0.0f, page); }
    float page_size() const { return page_size_; }
 
    void set_arrow_step(float s) { arrow_step_ = std::max(0.0f, s); }
    float arrow_step() const { return arrow_step_; }
 
    void set_page_step(float s) { page_step_ = std::max(0.0f, s); }
    float page_step() const { return page_step_; }

    bool set_value(float v) {
        float clamped = std::clamp(v, min_, max_);
        if (clamped == value_) return false;
        value_ = clamped;
        if (on_change) on_change(value_);
        return true;
    }
    float value() const { return value_; }

    std::function<void(float)> on_change;
 
    // ── Input ────────────────────────────────────────────────────────────
 
    void on_mouse_event(const MouseEvent& event) override;
    void on_mouse_drag(Point pos) override;
    bool on_key_event(const KeyEvent& event) override;
    bool wants_mouse_input() const override { return true; }
 
    // ── Paint ────────────────────────────────────────────────────────────
 
    void paint(canvas::Canvas& canvas) override;
 
    // ── Test hooks (headless) ────────────────────────────────────────────

    float thumb_pixel_length() const;

    float thumb_pixel_offset() const;
 
private:
    void clamp_value() { value_ = std::clamp(value_, min_, max_); }
    float primary_axis_length() const;
    void apply_track_click(Point local);
    void apply_drag(Point local);
    bool point_in_thumb(Point local) const;
 
    Orientation orientation_ = Orientation::vertical;
    float min_ = 0.0f;
    float max_ = 1.0f;
    float value_ = 0.0f;
    float page_size_ = 0.1f;
    float arrow_step_ = 0.05f;
    float page_step_ = 0.2f;
 
    bool dragging_ = false;
    float drag_grab_offset_ = 0.0f;  // distance from thumb leading edge to grab point
};
 
} // namespace pulp::view