Bug #11942

Two issues with before/after view

Added by Mladen Leskovar over 2 years ago. Updated over 2 years ago.

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To reproduce the first issue:

- I created before/after view using Snapshots and History (see Example1).
- I noticed that zoom works only on active (after) but not on snapshot (before) side (see Example2).
Before/after comparisons really make sense when both sides are viewed at the same zoom level.
Therefore both sides should zoom in/zoom out simultaneously.

Now the second issue:

- I collapsed left side panel to enlarge center area. When changing between vertical and horizontal split view
(rotating with icon) the center area becomes weirdly "sliced" (see Example3, Example4, Example5).
It seems this issue is limited to situations when at least one of the side panels is collapsed.
When both panels are expanded it works OK.

Thank you !

Example2.JPG (333 KB) Example2.JPG Mladen Leskovar, 01/17/2018 01:41 PM
Example1.JPG (295 KB) Example1.JPG Mladen Leskovar, 01/17/2018 01:41 PM
Example3.JPG (351 KB) Example3.JPG Mladen Leskovar, 01/17/2018 01:41 PM
Example4.JPG (366 KB) Example4.JPG Mladen Leskovar, 01/17/2018 01:41 PM
Example5.JPG (416 KB) Example5.JPG Mladen Leskovar, 01/17/2018 01:41 PM


#1 Updated by Peter Budai over 2 years ago

Confirmed, its very easy to repro.

#2 Updated by Peter Budai over 2 years ago

I have done further research on this:
  • The problem is not specific to Windows, all platforms are impacted
  • There is indeed a bug, namely that the snapshot image is not rendered properly if any of the sidepanels are changing their position after the snapshot was taken. So If you take a snapshot, then hide the left panel or the top panel (or any other), the snapshot will be rendered at the wrong coordinates. I have a solution for that (although still not perfect), PR will come shortly
  • The other reported problem is with the situation when after the snapshot has been taken, the user changes the zoom. This is more controversial, and I'm not convinced that it's a bug. Let me explain: when the snapshot is taken, it takes into consideration the zoom factor. It is not documented, but if you zoom in first and then take a snapshot, this zoomed in picture will be used as your reference/overlay for comparison. If you change the zoom factor after you have taken the snapshot, that only affects the currently selected active image, but NOT the snapshot. I see here a few options:
    • We need to document that the snapshot takes into account the zoom, and snapshot picture is not zoomable. Also we might document that if you want to compare image snapshots in a zoomed-in fashion, you need to take a snapshot of a zoomed in image, and not change the oom factor after that
    • We might disable the zooming while snapshot is active, in order not to confuse users

#3 Updated by Tobias Ellinghaus over 2 years ago

It's actually quite simple: snapshots are just screenshots. Anything you do to your view (zooming, panning, ...) won't affect the snapshot. There was some work once to make snapshots more powerful by storing history, source image, ... and reprocess it when needed, but that never got anywhere. It's still the right thing to do I think.

#4 Updated by Peter Budai over 2 years ago

houz, right. I have managed to adjust the position of the snapshot for left or right panel hide/unhide, but as soon as you hide/unhide the top row or the filmstip at bottom, the current active image is rescaled, but the snapshot can be rescaled as it is a simple cairo surface.

Shall we make at least the change to work with sidepanel hide/unhide alone, knowing that top row and filmstrip changes won't work?

#5 Updated by Tobias Ellinghaus over 2 years ago

Depending on aspect ratio of the image and zoom level the top/bottom panels should have the same effect as the left/right ones.

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