A better display item replace method

src/components/AccountRoleComboDelegate.cpp

@@ -5,15 +5,20 @@
 #include "AccountRoleComboDelegate.h"
 #include <QComboBox>
 #include <QPainter>
+#include <QStyleOptionViewItem>
 #include "db/SQLHelper.h"
 AccountRoleComboDelegate::AccountRoleComboDelegate(QWidget *parent):QItemDelegate(parent) {
     SQLHelper::QueryMap("select RoleID,RoleName from Role",map);
 }
+//之前使用重写paint来实现了替换显示文字，效果一般
+//
+//void AccountRoleComboDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const {
+//    QItemDelegate::paint(painter, option, index);
+//}
 
-void AccountRoleComboDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const {
-
-    QString text = index.model()->data(index, Qt::DisplayRole).toString();
-
+//相较于直接在paint里面操作，这是一个更好的选择，可以直接改变Display，而不影响前后景的绘制。
+void AccountRoleComboDelegate::drawDisplay(QPainter *painter, const QStyleOptionViewItem &option, const QRect &rect,
+                                           const QString &text) const {
     //绘制文本
     painter->drawText(option.rect, Qt::TextWordWrap | Qt::AlignCenter , map[text].toString());
 }

src/components/AccountRoleComboDelegate.h

@@ -12,9 +12,10 @@ class AccountRoleComboDelegate:public QItemDelegate {
     Q_OBJECT
 public:
     explicit AccountRoleComboDelegate(QWidget *parent = nullptr);
-    void paint(QPainter *painter,
-               const QStyleOptionViewItem &option,
-               const QModelIndex &index) const override;
+
+protected:
+    void drawDisplay(QPainter *painter, const QStyleOptionViewItem &option,
+                             const QRect &rect, const QString &text) const override ;
 private:
     QAbstractItemModel* model = nullptr;
     QMap<QString,QVariant> map ;