Spent days not knowing I had to click the "orb" until I finally got the answer in irc.
So, I replaced the orb on the node with an eye icon.
We briefly talked on IRC some days ago, writing down my thoughts here:
I agree that the current icon is really not fitting here, so +1 for searching for a better alternative. I'm not sure if the eye icon is the best alternative though, I would expect this to be used for muting or hiding the node. Maybe a magnifying glass or render icon? @Jonathan Williamson (carter2422), @Pablo Vazquez (venomgfx), @Paweł Łyczkowski (plyczkowski), or anyone else - opinion?
In IRC, I said that it's possible to let the interface code automatically handle the icon state (enabled or disabled), but I realized this currently only works if the interface code also handles setting the RNA property value or the bit flag controlled by the button. This however, is currently handled in NODE_OT_preview_toggle (for various reasons), so let's keep things simple and just set the icon manually :D
To avoid code duplication I'd rather do this:
const int icon = (node->flag & NODE_PREVIEW) ? ICON_RESTRICT_VIEW_OFF : ICON_RESTRICT_VIEW_ON; ... but = uiDefIconBut(..., icon, ...)
(NULL-checking previews also shouldn't be needed)
Well, I think the verb here is "to see" which means eye to me. I didn't think the original icon was a button. When the compositor loads now. The open eye with the preview thumbnail and the added nodes with the closed eye icon solve my original problem of not knowing why I couldn't 'see' the previews. So the button def should have 2 states.
Also, I thought the equiv. of hiding a node was using that triangle to minify it.
I'm not sure about having two triangles in the node title. New users would click the wrong triangle and confuse the two a lot.
The manifying glasses don't have a semi-transparent version that looks "off", so I say +1 for RESTRICT_RENDER_ON/OFF
Having little eye on each node is a little creepy - an eye is a visually intense icon (since we are wired to find faces), especially in black and white. Also the header is not that logical place for it, since this does not hide/turn off the whole node, but just the preview inside it.
So, I personally would suggest the preview on/off option for a node in the Properties sidebar - it's a feature for advanced users, so does not have to be readily available right on the node IMO.
Eye icon is used for mute already in too many places, think its confusing to use eye here.
Really not so keen on making "advanced user" unless they are really corner-cases... (feedback from other users welcome, but my impression is this isn't such an unusual thing to change)
We could just make this icon more obviously a button:
- just make this act more like a button (highlight on mouse over, tint differently when its pressed).
- use monochrome outline which fits more with the arrow on the other side: https://cdn1.iconfinder.com/data/icons/trycons/32/image-512.png