Html viewer - monaco problem

I'm running DOpus 12.26 x64 on Win 10 Pro (21H2). For at least a few days, maybe longer (I only got 21H2 about a week ago, if that's relevant), I haven't been able to use the viewer pane for html files. The pane opens but nothing ever shows. I searched online, including this forum but didn't find anything helpful. I finally turned off "Monaco" in the viewer -> plugins -> ActiveX ->configure list. I don't know what Monaco is but had noticed that the viewer pane (when trying to view html files) had "(Monaco)" showing. Now previewing HTML files works fine. My question is: did I turn on Monaco or was it set by default in DOpus? ( suspect the latter).

There's an editor called Monaco from MS, you must have installed, and mabye it grabbed focus for preview.

Thanks - yes, I believe that must have happened after I started experimenting with MS Power Toys fairly recently. PowerToys doesn't mention Monaco by name but does talk about File Explorer viewers for various file types (no mention of HTML though). I have now disabled that (as well as deselecting Monaco in DOpus). The only thing I have enabled in Power Toys is the Keyboard Manager.

Monaco is what PowerToys installs as its preview handler for "Source code files" on its web page and "Enable developer files preview" in its config UI (under "File Explorer add-ons", which is misnamed as preview handlers work in several other Microsoft and non-Microsoft programs including Outlook and Opus).

We could divert HTML away from it by default, but I guess some people may want to view the source rather than the results.

You can change which extensions go to which preview handlers (or which preview handlers are used at all) via the ActiveX + Preview + Office + Web plugin config you found.

Thanks Leo. For me, Monaco didn't display the HTML source - the viewer pane just remained blank. Maybe I should have waited a lot longer? Anyway, I've unchecked Monaco now, in the ActiveX config. Would I be able to move Monaco down lower, so that it came after the ActiveX plugin? I wondered later if I should have tried that.

Maybe it doesn't work well yet. It is quite new. Some of the viewers PowerToys installs are complete garbage, though. Their PDF viewer is abysmal, for example. I don't know why they even include such a bad viewer since it's probably going to take over from a better viewer on most people's systems. (Especially when Edge can view PDFs much better. We'll be switching to that ourselves in the future.)

Preview Handlers are inside the ActiveX plugin, so you couldn't move them above or below it. The ActiveX plugin works as an adapter for preview handlers so they can work in Opus. It's a meta-plugin, essentially. But you can simply remove the HTML extension from Monaco, and let it drop through to the Internet Explorer (or Edge, in the future) viewer lower down the list.

Ah - yes. I have re-enabled File Explorer Addons in Power Toys, and removed .htm and .html from the Monaco file extensions in Opus / ActiveX / Configuration. Seems to be working properly.
Thanks Leo.