I have a hard time trying to understand
font-style during investigation of transient bugs in a SVG→PNG converter) and comparing it against rendering in browsers. Common italic fonts don’t slant such symbols as “=” and “|”, and this has a solid reason because these are signs of (mathematical etc.) operations, not letters.
After learning more about “oblique vs italic” (esp. on https://stackoverflow.com/questions/1680624/font-style-italic-vs-oblique-in-css) and playing with https://www.w3schools.com/cssref/pr_font_font-style.asp (note: the sample served doesn’t contain any of +, =, * , |, ×, but you can inject all of ’em with the DOM inspector) I want to ask:
We know that italic requires a distinct glyph for many characters, whereas oblique does not. But we also see many symbols, such as “|” and “↑”, which have the same glyph in all three
font-styles. Assuming the user agent or renderer has an appropriate Roman font, what exactly should
font-style:oblique do to each character? Or, shifting from applications to fonts proper, what is a correct oblique font with respect to a given Roman font? Which namely characters (and why) are homographical in all three styles? If a general answer is too difficult, then, at least, how should the shape of vertical ellipsis (⋮) differ between Roman/italic/oblique?