fix: When there are multiple lines of files in the document management system, only the last line will be displayed. When selected, a slider will be displayed, and other lines will not be displayed

[liyigang1]

Modify the sizehint of iconitemdelegate and set the maximum height when there is an extension in the last one

Log: When there are multiple lines of files in the document management system, only the last line will be displayed. When selected, a slider will be displayed, and other lines will not be displayed
Bug: https://pms.uniontech.com/bug-view-260623.html

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在FileViewHelper::isLastIndex函数中，当index.row() + 1 == rowCount时，返回true，这可能不符合预期的行为，因为通常isLastIndex意味着当前索引是最后一个索引。
• ExpandedItem::setDifferenceOfLastRow和getDifferenceOfLastRow函数的命名可能会引起误解，因为它们实际上是在设置和获取一个名为diff的属性，而不是计算“最后一个索引”和当前索引之间的差异。
• 在IconItemDelegate::paintItemFileName函数中，对singleSelected的检查被移到了if语句之外，这可能会改变原有的逻辑，需要确认这是否是预期的行为。
• IconItemDelegate::sizeHint函数中的注释提到了一个名为lastAndExpandedIndex的变量，但在代码中并没有看到它的定义或修改，需要确认这个注释是否过时或遗漏了相应的逻辑。
• ExpandedItem::setFixedWidth和setIconHeight函数的调用顺序被更改，这可能会影响布局和显示效果，需要验证新的调用顺序是否符合设计要求。

是否建议立即修改:
是

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Lighto-Ku, liyigang1, max-lvs

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[liyigang1]

/merge