Select › Color Range: sampled colours, Fuzziness, Invert, a live preview and the panel (13.3b)

src/UI/SampleButton.h

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+#pragma once
+#include "Document/HueSaturation.h"
+#include <QToolButton>
+#include <functional>
+
+// Swift's plain sampling buttons: a glyph, tinted when chosen.
+class SampleButton : public QToolButton {
+    Q_OBJECT
+public:
+    SampleButton(std::function<void(QPainter &, const QColor &)> glyph, QWidget *parent);
+
+protected:
+    void paintEvent(QPaintEvent *event) override;
+
+private:
+    const std::function<void(QPainter &, const QColor &)> m_glyph;
+};
+
+// Swift's eyedropper, badged plus or minus for Add and Remove.
+void sampleEyedropper(QPainter &painter, HueSampleMode mode, const QColor &ink);