Two bugs:
- There was an extra `* 4` that caused panic when the Text was clipped
- There was a bug in glyph handling when the text is being split in
several runs
Remove platform glyph abstraction, just use non-zero u16 as glyph index
like everyone else. As a bonus, this reduces the memory consumption of
the glyph buffers per glyph from a size of a pointer to the size of the
u16.
This change makes the test pass without the unicode feature.
Note that it is not possible to run the test without the unicode feature
unless one changes the Cargo.toml, so I did that locally to run the
tests
The AboutSlint text has a forced linebreak in it, which becomes a box
glyph on MCUs when the font on the host system doesn't use an empty
glyph but a box glyph for \n.
This patch explicitly excludes glyph clusters from text fragments that
feed into lines that originate from one of the three valid separators:
ascii newline, unicode paragraph and unicode line separators.
When concatenating two fragment, we should account for the trailing whitespace
in the previous fragment in the total width.
This fixes the "l" of "Ink level" not beoing drawn properly in the printer
demo with the partial renderer if the Text item (which is too small as a result
of this bug) does not overlap the dirty region, but part of the text still
need to be drawn outside before it overflows
Separate the text shaping functionality from font metrics by having a
FontMetrics trait next to the TextShaper. AbstractFont is the combining
super trait. This allows eliminating the font height member from
TextParagraphLayout and improving the overall naming of fields and
types.
Finally, this prepares the API for composability of TextShaper for font
fallback handling.
Use the term glyph cluster instead of grapheme where we're dealing with
the glyphs for line breaking. Those may coincide with grapheme
boundaries, but aren't required to.
Replace the abstract glyph trait with a glyph struct. That way the text
layout code can operate properly on a struct with fields, instead of on
functions on a trait (some of which returning a mutable reference). The
input is a glyph with offset, advance, etc. - everything needed for the
layout and the output is a position along with the platform specific
glyph data.
Remove the font reference field anymore as it's not needed anymore and
remove the manual clone implementations. Those were needed because
otherwise the TextShaper trait would have to also support clone - as
[derive(Clone)] imposes that. Now we can impose that just on Glyph and
that's easy and makes sense.
This is needed in the future to be able to roll back state within the
line breaking when we can't fit even a single word into the line and
have to go back to fitting glyph by glyph.
For the unicode line break iterator the clone is a little more complicated.
The iterator is clone, but the type is anonymous. I first had an
implementation to moved the iterator into a closure, which was cloned
via another control closure. But that's complicated and still involves
allocating the various bits & pieces the closure captures.
So instead the simpler solution used here is to allocate the breaks
into a shared vector.
The unicode linebreak iterator always produces a mandatory break at end
of text. This is not only confusing, but also inconsistent with the
simple line break iterator and with trailing spaces it could cause the
line break algorithm to emit empty lines at the end of text.
