Image Zoom & Pan

[tarkah]

I've searched here and Zulip and couldn't find any relevant discussion.

Are there plans to implement a widget to allow zooming in on an Image (past the dimensions of the parent element / application window) and panning?

[hecrj]

I think a widget for this would be great.

It shouldn't be too hard:

• Listen to mouse events on Widget::on_event. Zoom with the scroll wheel, pan by dragging.
• Draw using a scaled Image inside a Clip primitive with the correct offset.

[tarkah]

Yes, that'd be perfect! Hmm, I may try taking a look this week to see if this is something I could figure out.

[tarkah]

@hecrj How would you go about "scaling" the Image? I created a widget called ImagePane that takes a State and an Image. I'm comfortable with tracking an offset / scale factor in the State when an event occurs, but I'm not familiar enough with the API to know where and how to apply that scale factor to change the dimensions of the Image. Thanks!

[tarkah]

Even if I try to manually scale the image before passing it to ImagePane, I can't seem to set Length::Units greater than the actual dimensions for the image.

[tarkah]

Another issue I can't seem to work around... I have panning working great when the inner image is aligned to the top left corner. If I try to align the image to the center, I can't set a negative offset to the Clip primitive to pan to the left side of the image, since the alignment pushes it negative of the ImagePane's (0,0) bounds.

I'll go ahead an open the PR so you can get your eyes on this to make it easier to see what I am referencing.

[hecrj]

I wouldn't use the Image widget internally. Make the widget take an image::Handle instead, and then you should be able to directly produce an Image primitive with any bounds.

I can't set a negative offset to the Clip primitive

I see. We should probably change the Clip offset to support negative values too. I'll try to explore this.

[tarkah]

Ahh, that's what I was missing. Thanks!