optimize: use QTextEdit::insertFromMimeData to process pasting images instead of manipulating context menu

ui/widgets/messagetextedit.h

@@ -0,0 +1,30 @@
+#ifndef MESSAGETEXTEDIT_H
+#define MESSAGETEXTEDIT_H
+
+#include <QTextEdit>
+#include <QObject>
+#include <QWidget>
+
+namespace Ui
+{
+class MessageTextEdit;
+}
+
+class MessageTextEdit : public QTextEdit
+{
+    Q_OBJECT
+public:
+    explicit MessageTextEdit(QWidget *parent = nullptr) : QTextEdit(parent) {}
+    explicit MessageTextEdit(const QString &text, QWidget *parent = nullptr) : QTextEdit(text, parent) {}
+
+signals:
+    void imageInserted(const QImage& image);
+    void fileInserted(const QString& localPath);
+
+protected:
+    bool canInsertFromMimeData(const QMimeData* source) const override;
+    void insertFromMimeData(const QMimeData* source) override;
+
+};
+
+#endif // MESSAGETEXTEDIT_H