chore: ajust window flags

[kegechen]

fix window flags is always Qt::Window

[deepin-bot[bot]]

Doc Check bot :green_circle: Document Coverage Check Passed!

[deepin-bot[bot]]

TAG Bot

New tag: 5.6.34 DISTRIBUTION: unstable Suggest: synchronizing this PR through rebase #382

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在fixTopLevelWindowFlags函数中，对于Qt::WindowFullscreenButtonHint的移除操作可能不必要，因为该属性在Qt的文档中没有说明是否支持在顶层窗口上设置。
• fixTopLevelWindowFlags函数中的switch语句可以简化，使用case和default直接关联所有可能的窗口类型，而不是使用Qt::Window和Qt::Dialog等。
• fixTopLevelWindowFlags函数中的if语句可以简化，直接在switch语句中设置所有所需的标志，而不是检查Qt::WindowType_Mask。
• fixTopLevelWindowFlags函数中的if语句检查(flags & Qt::WindowType_Mask) == Qt::SplashScreen，但没有考虑到Qt::SplashScreen窗口类型可能不会出现在flags中，这可能会导致未定义行为。
• fixTopLevelWindowFlags函数中的if语句检查window->isTopLevel()，但没有考虑到window可能不是顶级窗口的情况，这可能会导致未定义行为。
• fixTopLevelWindowFlags函数中的window->setFlags(windowFlags);可能会覆盖窗口的现有属性，应该先获取当前的窗口属性，然后与需要设置的属性进行合并。

是否建议立即修改: 是

[deepin-bot[bot]]

TAG Bot

New tag: 5.0.35 DISTRIBUTION: unstable Suggest: synchronizing this PR through rebase #400

[zccrs]

这是解决啥bug？

[deepin-ci-robot]

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This pull-request has been approved by: kegechen

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[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: kegechen

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files: - **[debian/deepin/OWNERS](https://github.com/linuxdeepin/dtkdeclarative/blob/master/debian/deepin/OWNERS)** Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[kegechen]

这是解决啥bug？

不算是bug，应用如果直接用dtk的 window， 就算有标题栏默认是没有最大最小关闭这些按钮的。需要手动设置 flags 才行。这里 参考widget 主动设置一下flags，当然也可以不加，要求用户自己设置。 改的就是一个默认行为而已

[deepin-bot[bot]]

TAG Bot

New tag: 5.7.1 DISTRIBUTION: unstable Suggest: synchronizing this PR through rebase #401