Re: Some options for vertically-scrollable manga (was re: Dropbox has epub viewer)

Hello Florian,

The right approach also depends what target you're considering.

It's a very different choice if we're talking EPUB 3.2 or Web Publication.

In practice, this is indeed true. At the same time, I don't think UAs are
> strictly required to hold all images in memory all the time. They typically
> do, but a UA optimized for low footprint could flush them to disk when out
> of the viewport, and load them on demand when needed.
>

This is something very hard to do for most EPUB reading systems out there.
In practice, most apps are stuck with the default behaviour and APIs
available for a webview.

To optimize for low footprint, you'd probably have to do some JS trickery
that would block images from loading while off-screen, but I can imagine
quite a few side effects (including the fact that JS is not well supported
in such readers, especially on reflowable resources).


The fact that the viewport is unpredictable is a feature, not a bug: it is
> the natural consequence of allowing people to read on any device they want.
> The question is what can an author do in response to viewport size changes,
> and CSS gives quite a lot of flexibility. It is possible to use:
>
> * the width, height, max-width, max-height, min-width, min-height either
> on the image container, or on the images individually, to control their size
>
> * the px, %, vh (viewport height) or vw (viewport width) units when doing
> so
>
> * the object-fit property to decide what to do if the image's size or
> aspect ratio does not match the size or aspect ratio imposed by the
> width/heigh/etc properties https://developer.mozilla.org/
> en-US/docs/Web/CSS/object-fit
>
> * media queries to switch layout at different sizes
>
> * CSS Grid to provide different non-linear, possibly overlapping,
> arrangement as desired, for example at large screen sizes.
>
> * css scroll snap to force the UA to scroll step-by-step / image-by-image
> if desired.
>

This is all true for WP, but keep in mind that for EPUB right now, most of
the properties that you're listing would be:

   - unsupported or unavailable
   - overwritten by the RS that injects its own CSS instead

Could you clarify what's the target for this vertically-scrollable manga
profile?

Best,
Hadrien