[Suggestion] letter spacing / kerning setting #78

[erickosanchezj]

By kinland:

With some fonts/sizes, letters get to be too close together and sometimes blend together a bit (especially if also using bionic reading).

it'd be nice for there to be a setting to slightly increase spacing between letters by a small amount to make up for this.

More specifically, I think this is a request for kerning settings.

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[Suggestion] letter spacing / kerning setting #78

[erickosanchezj]

@kinland This seems feasible as a letter-spacing/tracking option, though the result would likely vary by font. Some fonts are already spaced generously, while others are tighter at certain sizes, so the same spacing value may not feel identical everywhere.

Just to clarify the request: Are you mainly asking for horizontal spacing between letters or would you also want related vertical spacing controls, like line spacing?

Also, do you have examples of specific fonts and font sizes where you’ve noticed the letters blending together, especially with bionic reading enabled? That would help test whether a small letter-spacing adjustment solves the issue cleanly!

[erickosanchezj]

Let me check the crash report. Still checking on adjustments for Normal Bionic (no crashes on my side). Would not be sure about how it affects customized weights, checking with default "Atkinson Hyperlegible Next".

[erickosanchezj]

Made a change where it looks better than previous version

• Normal now has a distinct heavier prefix without the obvious “letters glued together” problem.
• Subtle is close to Off, maybe almost too close, but it no longer has that transparent/all-text-weird look. Camera does not show it that well but it does look different lol.
• Off still has the cleanest natural spacing, as expected.

Regarding the crash:

• Not directly caused by the Bionic spacing code. Bionic testing may have triggered it because changing Bionic/font settings causes page/font prewarm and mini kern rebuilds. Did not experience this while exiting out of book, swapping pages, changing settings. Not sure if it's related to custom font.

[kinland]

Seems worth submitting a PR for!

[erickosanchezj]

Yeah, I will tune this a bit more and submit it. Tried with 3 other custom fonts with no issues.

[kinland]

may have found a bug. I hit page back and all text rendering got totally garbled. I unfortunately didn't take a photo. text was overlapping (i.e. the 'regular' and 'bionic' bold were double-exposed like an old film double-exposure). It's like they were rendered separately and overlayed with incorrect horizontal alignment/spacing or something.

I had to put it in sleep mode and wake it back up to fix it. Changing pages, or exiting and reopening the book, didn't seem to fix it.