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Update: the colleague mentioned below was looking at the wrong machine. See also conversation with @Sam of Simple Samples - I would still be interested in knowing why this setting might be missing on some machines, but there is a lot less of an urgency about this now.
Hello there......
We have created an Outlook Add-in that we've used without problems for years. One of the things this Add-in does is show dialogs from which users can select files to either attach to an email they're composing or files attached to an incoming email they're processing with our Add-in.
As an added feature we allow the user to view the document.
Traditionally we have always used a WebBrowser control for this. The dialogs are WPF windows. We would convert each document to a HTML representation of same and then show that HTML document in the WebBrowser control.
Lately we have started getting occasional reports from users that this Preview is no longer working. The users are also reporting the appearance of "phantom" dialogs when hovering over the Outlook thumbnail in their task bar when this preview fails
The good news is that this can be addressed quite simply by setting an outlook setting. Go to File - Options and on the General tab there is a section "User Interface Options" and if you choose "Optimize for compatibility" there the problem goes away.
Great, right?
Until I asked my colleague who had the problem to do this. On his machine the options simply weren't there. I also looked at his registry, and while in my own registry the value RenderForMonitorDpi was present in HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\Options, in his registry that value was completely missing.
What's going on here and what could I do about it?
"Optimize for compatibility" strongly implies there is a compatibility problem. You need to determine what old library is causing that and then modernize what you use. Nearly certainly it is the WebBrowser control. It has been more than two years since I have done that type of thing but apparently you need to convert to the WebView2 Class (WebView2 control).
I have already implemented WebView2 and instead of converting documents to HTML I am converting them to XPS and using a DocumentViewer instead. It works fine and dandy.
But as sure as hell we'll get a customer who doesn't like it. Who preferred the "old way". Who is lagging behind in Windows versions so either the WebView2 or the DocumentViewer don't work, for whatever reason, on their PC.
So regardless of how much I modernise our Previewer, we must ALWAYS keep an option available to the user to revert to "legacy" versions of the Previewer
So I need to find an answer to the question as originally posted.
Sorry. Perhaps I posted this to the wrong question. There was a question that asked about WebBrowser and WebView2. Should I delete my response?
Not at all. You still make a valid point here, worth noting.
Hello @Sam of Simple Samples
I'm going to accept your answer but I'll just comment here that I was given the wrong information.
The colleague in question has his own PC and he does testing on a VM. He was experiencing the issue with the "phantom dialogs" on the VM. When I asked him to check those settings he checked them on his own PC.....
When we realised this he went and checked them on his VM and lo and behold, the settings were there, both in File - Options and in the Registry. So he CAN change them.
What I don't yet know is whether the problem could possibly be an issue at all on machines like his own PC where he can't change the setting, as he has not experienced the same problem on his own PC.
Thanks for your patience :)