The logic of the shutdown sequence

[Philip Rayment]

I'm trying to understand the logic of the shutdown sequence. From the SimpleFMXBrowser example:

1. FormCloseQuery sets CanClose to FALSE calls TFMXChromium.CloseBrowser which triggers the TFMXChromium.OnClose event.

This implies that we have to close the browser before the form is closed.

2. TFMXChromium.OnClose sends a CEFBROWSER_DESTROY message to destroy CEFWindowParent1 in the main thread, which triggers the TFMXChromium.OnBeforeClose event.
3. TFMXChromium.OnBeforeClose sets FCanClose := True and sends WM_CLOSE to the form.

Given that the event handler is OnBeforeClose, step 3 implies that we have to close the form before the browser.

What am I missing?

[salvadordf]

Hi,

The names can be misleading but the sequence is this in CEF4Delphi :

• 1. Call TChromium.CloseBrowser
• 2. Event TChromium.OnClose is triggered
• 3. Event TChromium.OnBeforeClose is triggered
• 4. The application can be closed now

These are the original CEF code comments for the OnClose event when you need user confirmation before closing the application :

• 1. User clicks the window close button which sends a close notification to the application's top-level window.
• 2. Application's top-level window receives the close notification and:
  • A. Calls CefBrowserHost::CloseBrowser(false).
  • B. Cancels the window close.
• 3. JavaScript 'onbeforeunload' handler executes and shows the close confirmation dialog (which can be overridden via CefJSDialogHandler::OnBeforeUnloadDialog()).
• 4. User approves the close.
• 5. JavaScript 'onunload' handler executes.
• 6. Application's do_close() handler is called. Application will:
  • A. Set a flag to indicate that the next close attempt will be allowed.
  • B. Return false.
• 7. CEF sends an close notification to the application's top-level window.
• 8. Application's top-level window receives the close notification and allows the window to close based on the flag from #6B.
• 9. Application's top-level window is destroyed.
• 10. Application's on_before_close() handler is called and the browser object is destroyed.
• 11. Application exits by calling cef_quit_message_loop() if no other browsers exist.

The names change a little bit between C and Delphi but the logic is the same

• "CefBrowserHost::CloseBrowser(false)" is equivalent to TChromium.CloseBrowser in Delphi
• The "do_close() handler" is the TChromium.OnClose event
• The "on_before_close() handler" is the TChromium.OnBeforeClose event
• "cef_quit_message_loop()" is part of the GlobalCEFApp destruction.

It's necessary to follow these steps to close all the browsers before closing the application.