显示时，Delphi表单会始终触发OnResize吗？ [英] Will a Delphi form always fire OnResize when it's shown?

问题描述

如果我创建一个新的Delphi表单，钩住它的OnResize事件，然后运行该应用程序，则会在显示窗口之前触发OnResize。我不知道对于任何窗口，这种情况是否会一直发生。

If I create a new Delphi form, hook its OnResize event, and run the app, OnResize is fired before the window is shown. What I don't know is whether this will always happen, for any window.

（对于熟悉Windows API的任何人，我都将其追溯到ShowWindow调用在TCustomForm.ShowingChanged（Delphi 2007中的Forms.pas第5503行）中，至少对于未设置其他属性的新窗口，它显然触发了 WM_SIZE ...。尚未看到ShowWindow总是触发 WM_SIZE 的记录，所以我不知道我是否可以依靠它。）

(For anyone familiar with the Windows API, I've traced it to the ShowWindow call in TCustomForm.ShowingChanged (Forms.pas line 5503 in Delphi 2007), which apparently triggers a WM_SIZE... at least, for a new window with no other properties set. I haven't seen it documented that ShowWindow always fires WM_SIZE, so I don't know whether I can count on this or not.)

因此：在首次显示OnResize时，我是否可以依靠TForm 始终触发它？还是有这种情况（例如，如果窗口不可调整大小，也许，如果Position属性具有某些值，等等。）在第一次显示该窗口之前可能不会触发OnResize吗？

So: Can I rely on a TForm always firing OnResize when it's first shown? Or are there circumstances (maybe if the window is non-resizable, maybe if the Position property has certain values, etc.) where OnResize might not fire before the window is first shown?

推荐答案

否，取决于BorderStyle之类的内容，此事件并不总是在表单显示时触发。例如，对于bsSingle，它会在启动时触发，而对于bsDialog，则不会。

No, this event doesn't always fire when the form shows, depending on things like BorderStyle. For example, it fires on startup for bsSingle, but not for bsDialog.

易于测试。只需在主窗体的OnResize事件中添加一些日志记录代码，更改BorderStyle并运行您的应用即可。

It's easy to test. Just add some logging code to the main form's OnResize event, change the BorderStyle and run your app.

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