Improved dispose pattern in ChromiumWebBrowser

[merceyz]

• Added an IsDisposed property to IWebBrowser
• Implemented a thread safe dispose pattern
• Now only disposes of managed objects when disposing is set to true
• Simplified the handling of design mode and disposing

Resolves #1954

EDIT:
As this is getting merged in parts, here are the relevant commits
OffScreen: 58fac38 b1ef9e8

[AppVeyorBot]

✅ Build CefSharp 71.0.0-CI2936 completed (commit 09afdada13 by @merceyz)

[AppVeyorBot]

✅ Build CefSharp 71.0.0-CI2937 completed (commit 3ded02c549 by @merceyz)

[amaitland]

Other than adding a comment which I've posted inline for discussion the OffScreen changes look like they can be merged.

Any objection if I merge this one class at a time? (Will take care of that manually myself). Rather than trying to review and test everything all at once, and potentially having this go stale, I think it makes sense to work through them one by one. OffScreen, WPF and WinForms is probably the order of lest to most complex.

[AppVeyorBot]

✅ Build CefSharp 71.0.0-CI2947 completed (commit d479d1f93f by @amaitland)

[merceyz]

Any objection if I merge this one class at a time?

I would like to keep these changes together and not split them up, however it's up to you.

Rather than trying to review and test everything all at once, and potentially having this go stale, I think it makes sense to work through them one by one. OffScreen, WPF and WinForms is probably the order of lest to most complex.

The code in all three is basically the same, only difference is WPF and WinForms moves the actual disposing out of the protected virtual void Dispose(bool disposing) so that the designer stays happy

[amaitland]

I would like to keep these changes together and not split them up, however it's up to you.

It'll be some time before I have a chance to review them all at once. What advantage do you see in trying to merge this all at once? They are unrelated changes from a code point of view.

The code in all three is basically the same, only difference is WPF and WinForms moves the actual disposing out of the protected virtual void Dispose(bool disposing) so that the designer stays happy

It's the sort of thing that's easy to introduce a subtle change, the structure looks fine.

[merceyz]

It'll be some time before I have a chance to review them all at once. What advantage do you see in trying to merge this all at once? They are unrelated changes from a code point of view.

Less noise in the history, but mainly because i'd like to make more changes to all three at the same time for other things. But go ahead, it's fine by me.

[amaitland]

changes to all three at the same time for other things

What sort of things exactly? Related to Dispose improvements?

[AppVeyorBot]

✅ Build CefSharp 72.0.0-CI2967 completed (commit d74425cd2e by @amaitland)

[amaitland]

OffScreen changes merged in 58fac38

Addition comment added in b1ef9e8

[AppVeyorBot]

✅ Build CefSharp 72.0.0-CI2969 completed (commit 5f087f80af by @amaitland)

[merceyz]

What sort of things exactly? Related to Dispose improvements?

First thing that comes to mind that is sort of related is a disposed check in all public functions.

[amaitland]

Please keep the scope of this PR limited to resolving #1954

[merceyz]

Of course

[AppVeyorBot]

✅ Build CefSharp 72.0.0-CI2970 completed (commit 4f094adbbd by @merceyz)

[amaitland]

Will hopefully review/merge the WPF changes in the next few days.

[AppVeyorBot]

✅ Build CefSharp 73.0.0-CI3020 completed (commit acbabb79ce by @amaitland)

[amaitland]

@merceyz Thoughts on a Breaking Changes entry for this one? I'm struggling to think of what changes users would need to make, just a slight change in behaviour. Maybe you can think of something.

[merceyz]

@amaitland The IsDisposed property added to IWebBrowser would break builds for anyone that implements that interface on their own