Support drag&drop for setting a custom cover in the properties dialog

custom_widgets/yacreader_cover_label.h

@@ -0,0 +1,29 @@
+#ifndef DROP_LABEL_H
+#define DROP_LABEL_H
+
+#include <QLabel>
+#include <QDragEnterEvent>
+#include <QDropEvent>
+#include <QMimeData>
+
+namespace YACReader {
+
+class CoverLabel : public QLabel
+{
+    Q_OBJECT
+
+public:
+    explicit CoverLabel(QWidget *parent = nullptr);
+
+protected:
+    void dragEnterEvent(QDragEnterEvent *event) override;
+    void dragMoveEvent(QDragMoveEvent *event) override;
+    void dropEvent(QDropEvent *event) override;
+
+signals:
+    void imageDropped(const QString &path);
+};
+
+}
+
+#endif // DROP_LABEL_H