HiDPI is very common nowadays.  Internally Emacs has decent support for HiDPI displays.  However elisp code, that generates non-svg images don't have any idea that logical pixel may differ from physical one, resulting in generating images in low resolution on HiDPI displays.

Emacs internally has a notion about HiDPI displays, such as `x_get_scale_factor`, maybe expose this function to elisp level, so packages may utilize it to generate images in highres?

Or `(> (round (/ (display-pixel-height) (/ (display-mm-height) 25.4))) 96)` is good enough to detect HiDPI displays?

Thanks

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