Shaping of text runs #12

dnkl commented 2020年09月15日 20:03:00 +02:00

Fcft now supports "grapheme" shaping (see #7).

This means we can now render e.g. emoji ZWJ sequences and other emoji modifier sequences, as well as combining marks.

We cannot, however, render entire text runs, which means no ligatures, and other more complex text shaping features.

Fcft now supports "grapheme" shaping (see https://codeberg.org/dnkl/fcft/issues/7). This means we can now render e.g. emoji ZWJ sequences and other emoji modifier sequences, as well as combining marks. We cannot, however, render entire text runs, which means no ligatures, and other more complex text shaping features.

dnkl commented 2020年09月19日 21:01:28 +02:00

Suggested algorithm:

1. Start with the primary font
2. Scan string until we hit a codepoint not in the primary font. Shape everything up to this point.
3. Find fallback font that has the codepoint, and then scan string until we a) find a codepoint that is in the primary font. Shape everything since 2) and up to this point, or b) find a codepoint that is neither in the primary font, nor the first fallback font. Goto 3)

In other words, strive to use the primary font - only use fallback fonts when necessary (pretty obvious really).

fcft will not cache runs. The calling application will have to do it on it's own if it's needed.

Question: how do we handle presentation selectors?

Suggested algorithm: 1. Start with the primary font 2. Scan string until we hit a codepoint **not** in the primary font. Shape everything up to this point. 3. Find fallback font that has the codepoint, and then scan string until we a) find a codepoint that **is** in the primary font. Shape everything since 2) and up to this point, or b) find a codepoint that is neither in the primary font, nor the first fallback font. Goto 3) In other words, strive to use the primary font - only use fallback fonts when necessary (pretty obvious really). fcft will **not** cache runs. The calling application will have to do it on it's own if it's needed. Question: how do we handle presentation selectors?

dnkl/fcft