Implement Focused property

[sylvain-hamel]

Issue: ChromiumWebBrowser.Focused is always false
Cause : cef does not implement focused correctly (seems related to https://code.google.com/p/chromiumembedded/issues/detail?id=563)
Fix : Manually implement Focused
How to test:

• In the Windows Form sample, replace the Go Button event handler by MessageBox.Show(((Control)Browser).Focused.ToString()).
• run
• give the focus the the browser
• click Go
• result : false
• apply fix
• tests again
• result : true
• click the address bar (to remove focus)
• click Go
• result : false

I think this should fix #570. However if it does not, then this fix is still relevant to any code that relies on the Focused property. I did not test the WPF side of this at all.

Background: We've been running with this fix for a while now (before we started contributing to this project). I recalled this fix while reading #570 so here is the PR (I'll be able to remove this from our custom ChromiumWebBrowser derived class too).

[amaitland]

I remembered there's a post in the google groups that I'd been meaning to do something about https://groups.google.com/forum/#!topic/cefsharp/myTd5OCjb5E

It relates to WinForms Focus. It appears there's two Focus methods that Cef exposes, one is OSR, the other regular. We've currently only implemented SendFocusEvent which is for OSR.

Thoughts on implementing SetFocus?

[amaitland]

I probably should have also made mention of CefFocusHandler which we only partly implement.

http://magpcss.org/ceforum/apidocs3/projects/%28default%29/CefFocusHandler.html

I think we can come up with a more elegant solution. Quite a while ago I looked at implementing CefFocusHandler it's here #341.

[amaitland]

FYI #639 has been merged, which provides a CefFocusHandler wrapper. (Replaces #341)

[sylvain-hamel]

@amaitland, IFocusHandler is useful to track focus events but does not resolve this issue. Using the FocusHandler does not make the Focused property work. It still returns false.

I tried to force the Focus() this way to see if it would set the Focused flag somehow in the control but it does not work.

public void OnGotFocus()
{
    ((Control)browser).BeginInvoke(new MethodInvoker(() => browser.Focus()));
}

So I still think this PR is necessary.

[amaitland]

@sylvain-hamel I was thinking with OnGotFocus and OnTakeFocus we just need to store the bool and override Focused. When I get a moment I'll implement a rough solution.

[sylvain-hamel]

I think the fix I proposed is better beause it fixes the problem in the core and does not force users to define a handler and to figure out how to handle the events. After all who wouldn't want Focus to retunr the right value?

[amaitland]

Plan was to implement the default behavior in ChromiumWebBrowser, no need for users to do anything 😄

[jankurianski]

Hi guys, I am currently working on a PR to implement something like what @amaitland is suggesting. (I feel a bit guilty about adding the FocusHandler but not addressing this core issue.)

I think it will turn out a bit cleaner because we won't have to rely on the Win32 APIs.

[amaitland]

@jankurianski Awesome thanks! I'll hold off on making any changes 👍

[jankurianski]

It turns out that it isn't possible to implement the Focused property via CEF's FocusHandler alone.

You can see what I tried here: https://github.com/numbersint/CefSharp/compare/fixes/winforms-focused-property

I implement the Focused property by setting the flag to true upon OnGotFocus, and false upon OnTakeFocus.

When I try the steps in the first post, the Focused property does get set to true, however it does not get set to false when I click in the address bar.

The reason for this is that FocusHandler has no method for focus loss. Here are how the methods work in common scenarios:

• Clicking onto the browser
  1. OnGotFocus
• Typing in an address and hitting Enter
  1. OnSetFocus
  2. OnGotFocus
• Clicking off the browser, onto another control
  • (nothing)
• Tab out of the browser
  1. OnTakeFocus

It would only be possible to implement the Focused property if IFocusHandler had a new method called OnLostFocus. But this would need to be an upstream CEF change.

For now, I think the solution of @sylvain-hamel here is the only way to go.

[amaitland]

@jankurianski Appreciate you taking the time to have a look. I guess short term the fix we have is workable. Strange that focus events aren't called.

So let's go with this fix for now.

[amaitland]

Can we move this class into CefSharp.WinForms? it's unlikely to be used in any of the other projects.

[amaitland]

Merged. I'm still hopeful that at some point we can get Cef to cooperate.