Re: "Fix" sag scaling for hidpi

[Alan Third]

On Thu, Feb 11, 2021 at 12:34:50PM -0500, Yuan Fu wrote:
> >> 
> >> Attached is a first go at this. I can't work out image.el and
> >> image-mode.el, so I'll either need a lot more time or someone more
> >> familiar with them can have a look.
> >> 
> >> The basic problem is that image-size returns physical pixels, and we
> >> want to calculate logical pixels. I tried a few things and failed
> >> miserably. I tried changing image-size to return logical pixels, but
> >> that just seemed to make everything worse, and I don't think it's a
> >> good idea to lie about the image size.
> > 
> > I’m not sure what do you want to achieve here. Are you trying to 
> > automatically size bitmap images when opening them, so that it is displayed 
> > 1:1 to physical pixels? If can do something like this:
> > 
> > (insert-image (create-image "~/d/Screen Shot 2021-02-09 at
> >                            10.11.56 AM.png" nil nil :scale (/ 1
> >                            (frame-scale-factor))))
> > 
> > And the image inserted is displayed 1:1 to physical pixels. But
> > :scale is not really meant for controlling pixel ratio. Maybe we
> > should add a :pixel-ratio (or :scale-factor) attribute to control
> > the default display size of a bitmap image?
> 
> Actually, :pixel-ratio probably isn’t a good idea. I guess we should
> just let the user decide what they want when inserting an image, and
> automatically add :scale in image-mode.

Yes, I agree. That's really what I was struggling with, getting
image-mode to load the image at physical pixel size. I don't do much
lisp coding, so I'm quite slow to get to understand it.

I'll keep looking, though.
-- 
Alan Third