Reopening the preview widget doesn't update the thumbnail

[BigRoy]

Problem

When the preview widget was previously opened (thus initialized) for the current open capture gui, then closed and then reopened the thumbnail is not automatically updated; this means the preview doesn't correspond with the current settings which might be unclear to artist.

Solutions

1. Remove the "initialized" state and always trigger a refresh when reopening the widget, this forces it to be up-to-date.
2. Maybe we should also clarify in a way that clicking the image will force an update; currently it's not clear that it won't update automatically and how the user would go about forcefully updating it. (Should this be a separate issue?)

[aardschok]

I think solution 1 is not really an option, that means it might take a long time before the widget opens when the scene is heavy.
I opt for solution 2, just add it in the title of the preview widget, "Click to update preview" in a smaller font and right aligned?

[BigRoy]

Regarding solution 1 I was referring to the fact that it would always refresh only when one opens the "Preview" box. It does not refresh when running capture gui since the preview box isn't open by default. Currently the behavior is relatively similar, it refreshes on the first open of the "preview" box... but subsequent opens do not. Do you still feel the same?

Regarding point 2, we should also add a tooltip to the playblast image. :) Other than that, let's give this a go.

[BigRoy]

I implemented what I meant with the options in BigRoy@0b00f54 but I believe we should still look for better ways to communicate how to update the image (clicking it). :)