Question

Is there anyway to stop TWebBrowser from clearing when I set Self.Parent := nil;?
When it gets to that line (which is necessary for a maximizing function), all the TWebBrowsers in my form clears. Why does it do that and what can I do to avoid this?

EDIT:
‘Self’ is the current form (in this case AnsForm) being shown on the MainForm.
Previous value of Parent is a Tab in MainForm.
I tried setting Self.Parent to something else but the same thing happens.

Answer 1

Reassigning the TWinControl.Parent property causes that control (in this case, your TForm object) to destroy its HWND (as a child HWND cannot exist without a parent HWND), and a new HWND is not created until the next time that control’s Handle property is accessed (if no Parent is available by then, an exception is raised). When a control destroys its HWND, all of its child controls, and their child controls, and so on, destroy their own HWNDs as well. Without an HWND, there is nothing for a control to display, and any content stored in those HWNDs is lost. That is why your TWebBrowser objects get cleared.

Some components cache their current content in memory when their HWND is destroyed and then restore that content when a new HWND becomes available, but TWebBrowser does not (and cannot) do that. Your only option in this situation is to manually reload the current URL again. Otherwise, re-design your UI so the TWebBrowser objects do not reside on a parent control whose Parent property changes.