How to make a thumbnails widget / container?

[Goltanju]

I've been plugging away at ideas on how to do this, but all my protoypes are horribly slow and janky.

My latest attempt was to use the widget.GridWrap and make a custom Thumbnail widget with an underlying canvas.Image. That "worked" in that it displayed, but it was super slow scrolling and I think the focus / selection behavior was just horrible. As I move the mouse, the focus hover color change flickers and flashes madly, and when I select an item, it does it but only after flickering and spazing for a bit.

I've also tried using container.GridWrap inside a container/widget.Scroll and while that is nice and fast, I have no idea how to scroll to a thumbnail so it is shown on the screen -- there is just scroll to top / bottom options.

I also looked at Cards, but I'm not sure what those are really tailored for.

[Goltanju]

Haha, I forgot to scale down my images prior to giving them to canvas.NewImageFromImage. No wonder it was slow and janky. Sorry for the chatter, I think I'm on the right path again using widget.GridWrap.

[Goltanju]

Er, well to clarify a little, I was using canvas.NewImageFromFile -- but obvioiusly that doesn't do any pre-scaling so switched to opening and decoding the image not-with-Fyne, scaling it, and then handing it over to Fyne's canvas.NewImageFromImage.

Maybe adding a pre-scaling option to canvas.NewImageFromFile would be useful? Or maybe a doc note?

[andydotxyz]

The canvas primitives don't do smart things - they are used for the low-level rendering work.
Indeed for large files this is a bit of a challenge and you'll need to thumbnail for good performance.
I'm not sure if it makes sense to solve this at a generic / widget level, but a specialist image viewer could be useful. If you have more specific ideas perhaps you could work towards a proposed API or flesh out the idea and see where it goes?

[Goltanju]

Above I was just thinking about how to maybe help the next person that comes along and falls into the same trap. But I can't think of a clean way to really help here, each person will just have to work through it. Maybe a canvas.Image.Resize()? Then again I've noticed other scaling algorithms (like from github.com/disintegration/imaging) look better and I don't think Fyne should become an image processing platform. :) So... just not a big deal, but I'd popped this discussion before I realized my issue.

[andydotxyz]

You could look at the ScaleMode of Image as we offer the choice of tradeoff for speed vs precision :).