Add reusable compact multi-select Essence popup filter

cockatrice/src/interface/widgets/cards/additional_info/essence_filter_picker.h

@@ -0,0 +1,38 @@
+#ifndef CONTINUUMATRICE_ESSENCE_FILTER_PICKER_H
+#define CONTINUUMATRICE_ESSENCE_FILTER_PICKER_H
+
+#include <QChar>
+#include <QHash>
+#include <QSet>
+#include <QToolButton>
+
+class QMenu;
+
+/**
+ * Compact, reusable multi-select Essence picker for the deck and card database
+ * toolbars. The menu contains all fifteen Essence symbols in a 5x3 icon grid.
+ * Clicking a symbol does not close the popup; programmatic synchronization
+ * does not emit a user-selection signal.
+ */
+class EssenceFilterPicker final : public QToolButton
+{
+    Q_OBJECT
+
+public:
+    explicit EssenceFilterPicker(QWidget *parent = nullptr);
+
+    [[nodiscard]] QSet<QChar> activeEssences() const;
+    void setEssenceActive(QChar essence, bool active);
+    void retranslateUi();
+
+signals:
+    void essenceToggled(QChar essence, bool active);
+
+private:
+    void updateSummary();
+
+    QHash<QChar, QToolButton *> buttons;
+    QMenu *popupMenu = nullptr;
+};
+
+#endif // CONTINUUMATRICE_ESSENCE_FILTER_PICKER_H