Add image::Viewer widget

[tarkah]

This isn't complete, but the zooming and panning features "work". If an image handle's dimensions are larger than the dimensions of the ImagePane, it is scaled down to fit inside the pane. Images smaller than the pane won't get rescaled until the mouse wheel is scrolled.

Some improvements needed before merging:

• Image should be centered inside the ImagePane. Can't implement this until negative offsets are allowed inside Clip primitive
• Clipping offset should get updated when scaling the image to "zoom" around wherever the cursor is placed. Right now offset doesn't change on scaling, so image just zooms out from top left corner.
• Add builder methods for State to allow specifying the min / max scale factor and step size

Let me know what you think and if there are any other features / defaults that should be added!

resolves #306

[hecrj]

This looks great! Thank you.

I think we could put this new widget inside the current image module, as it seems to be an Image variation of some sort. Maybe we could call it Viewer or something similar. That way, users would use it as image::Viewer.

Image should be centered inside the ImagePane. Can't implement this until negative offsets are allowed inside Clip primitive

I will try to get this ready soon!

Clipping offset should get updated when scaling the image to "zoom" around wherever the cursor is placed. Right now offset doesn't change on scaling, so image just zooms out from top left corner.

I implemented some logic to do this in the new game_of_life example. We probably shouldn't copy the behavior verbatim, but it may be useful for inspiration.

Add builder methods for State to allow specifying the min / max scale factor and step size

I'd probably put these in ImagePane itself. This way, we let users decide how to derive these values in view logic.

[tarkah]

Thanks for taking a look! I'll definitely move this into the image module and look to incorporate your other suggestions.

[tarkah]

I went ahead and renamed it ImageViewer since it's being re-exported to the root of the Iced crate, and Viewer seems a little generic for it there. Unless you don't want it re-exported to the root.

I'm going to hold off on implementing logic for zooming to the cursor until we can center the image inside the Clipping primitive, as to not have to rewrite anything. I'll implement the builder methods then as well.

[hecrj]

Unless you don't want it re-exported to the root.

Yeah, I tend to only re-export the types that have the same name as the module.

I'm going to hold off on implementing logic for zooming to the cursor until we can center the image inside the Clipping primitive

Since #325, there is a new Translate primitive that we should be able to use here. I forgot about this! It's very likely we will end up dropping the offset from Clipping and just use this new primitive instead.

[tarkah]

Yeah, I tend to only re-export the types that have the same name as the module.

Ok, I renamed to image::Viewer and removed the re-export.

Since #325, there is a new Translate primitive that we should be able to use here. I forgot about this! It's very likely we will end up dropping the offset from Clipping and just use this new primitive instead.

Awesome! Looking forward to this change

[hecrj]

Awesome! Looking forward to this change

The new primitive already landed in master. We should be able to use to move the Image primitive even with a clipping offset of (0, 0).

[tarkah]

Nice, I wrapped the Image primitive in a Translate and applied the inverse of my original offset to this, then left the Clip primitive offset as (0, 0) and it worked! I'll get this PR hopefully wrapped up by end of week. Thanks!

[tarkah]

Ok, everything should be implemented! After performing mental gymnastics all morning, I finally got the calculations worked out to translate the image so it's centred with the proper adjustments made for smooth scaling in / out from cursor location.

Note that currently image panning is bounded to the edges of the image, so you cannot infinitely pan past the image and therefore panning is only enabled when the image becomes clipped by it's width and/or height.

[hecrj]

Awesome! Thanks. I will review the changes soon.

Merging #354 seems to have caused some conflicts. But don't worry about it, I should be able to fix them.

[hecrj]

I think I've brought this up to speed! 🎉

I have replaced the old Image with this new widget in the pokedex example. I tried to describe all the other changes in the commit history.

I think this should be ready to merge. Hopefully I didn't break anything. Let me know!

[tarkah]

This is awesome! I'll test it out today and let you know :)

[tarkah]

@hecrj I've tested on my old project and it works great. Thanks for getting master back-merged into this properly!

[hecrj]

Awesome! We can finally merge this then!

Thank you again 🥂