Magnifier tool and recalculations

[tomczak]

I was playing with the Magnifier and Histogram tools (full disclosure: trying to think of Jonathan's explanation from a previous post how a 'downstream preview' tool could work). I was thinking that the Magnifier could be modified not to close the control panel when switching the current image and update on Apply (except showing preview of a different image), but that may not be such a good idea after all - by default, just like histogram it's associated with the current image preview.

However, there is one aspect that I noticed: while both Histogram and Magnifier tools can coexist with the control panels of the current image and remain open when the current image changes (but that closes pervious control panel), the histogram automatically updates when either the output or the image changes, but the Magnifier does not - it will get updated when triggered by changing the magnification, or pressing the mode buttons or moving the cursor.

p.s. Another idea, I'm sure not new, was that if Compare control pannel could stay open simultaneously with one of control pannels between image B and itself and only update on Apply, that could do it, but then that probably creates even more logical script flow issues and confusion as to what the preview panel shows at the moment...

I'm giving up.