This commit adds support for the idea of a text "Truncator", a string
that is shown at the end of truncated text to indicate that it has been
shortened because it would not fit within the requested number of lines.
When specifying a maximum number of lines, a truncator symbol is always
used. If the user does not provide one, the rune `…` is used. This
requirement results in a better user experience and significantly simpler
code, as we can rely upon the presence of one or more truncator glyphs in
the output glyph stream when truncation has occurred.
When interacting with truncated text, the truncator glyphs all act as
a single, indivisible unit. They can be selected or not, and if selected
they act as the entire contents of the truncated portion of the text.
This means that copying all of a truncated label will copy the entire
label text content, with the truncator symbol not appearing at all.
Concretely, the exposed text API now accepts a Truncator string in
text.Parameters, and there is a new glyph flag FlagTruncator which indicates
that the glyph is part of the truncator run. The truncator run will only
have a single FlagClusterBreak (even if the run would usually have many),
and the glyph with both FlagClusterBreak and FlagTruncator will have the
quantity of truncated runes in its Runes field. This necessitated increasing
the size of the Runes field from a byte to an int, as it's theoretically possible
for quite a lot of text to be truncated.
This commit necessarily bumps our go-text/typesetting dependency to the version
exposing truncation in the exported API.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit teaches the text widgets how to position their cursor according to
grapheme cluster boundaries rather than rune boundaries. While this is more work,
the results better match the expectations of users. A "grapheme cluster" is a
user-perceived character that may be composed of arbitrarily many runes.
I chose to implement this within widgets for two reasons:
- grapheme cluster boundaries would be extremely difficult to encode within the
glyph stream returned by the text shaper
- not all text needs to be segmented, only text that can be interacted with
All mutation operations exposed by widget.Editor now work in terms of grapheme
clusters instead of runes.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit allows the glyph index type to be reset and reused, preventing the
reallocation of numerous buffers when indexing glyphs.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit adds exported methods to both LabelState and Editor
allowing callers to locate the text regions representing a range
of runes. This can be used to build interactive subregions of text,
like (for instance) hyperlinks.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit adds a standalone state type for manipulating
and displaying text. It reads text from a minimal interface,
shapes it, tracks valid cursor positions, and provides sizing
and scrolling services to higher-level widgets. My long term
goal with these types is to export them to allow non-core widgets
to build atop them, but I've left them private for now.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit updates the textIterator and glyphIndex types to consume
new flag information provided on glyphs. These changes allow widget.Label
and widget.Editor to correctly compute text bounding boxes and to
generate valid cursor positions at the end of text.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit restructures the entire text shaping stack to enable lines of shaped text to
have non-homogeneous properties like which font face they belong to and which direction
a segment of text is going.
The text package now provides a concrete type text.Shaper which can be used to convert
strings into sequences of renderable text.Glyphs. At a high level, the API is used
like this:
// Prepare some fonts.
var collection []text.FontFace
// Make a shaper with those fonts loaded.
shaper := text.NewShaper(collection)
// Shape a string.
shaper.LayoutString(text.Parameters{
PxPerEm: fixed.I(12),
}, 0, 100, system.Locale{}, "Hello")
// Iterate the glyphs from that string.
for glyph, ok := shaper.NextGlyph(); ok; glyph, ok = shaper.NextGlyph() {
// Convert the glyph data into a path. In real uses, convert batches of glyphs
// rather than single glyphs to reduce the number of individual paths and offsets
// required to display your text.
shape := shaper.Shape([]text.Glyph{glyph})
// Offset the glyph to the position it declares within its fields. This will
// automatically handle correct bidirectional text glyph positioning.
offset := op.Offset(image.Pt(glyph.X.Floor(), int(glyph.Y))).Push(gtx.Ops)
// Create a clip area from the shape of the glyph.
area := clip.Outline{Path: shape}.Push(gtx.Ops)
// Paint whatever the current color is within the glyph's shape.
paint.PaintOp{}.Add(gtx.Ops)
area.Pop()
offset.Pop()
}
This API will transparently handle both font fallback (choosing appropriate fonts
from those loaded when the primary font doesn't contain a required glyph) and
bidirectional text (mixed left-to-right and right-to-left text). Glyphs are
iterated in order of the input runes, not their visual order, but proper use
of the provided offsets will ensure that text always displays correctly.
Thanks to Elias Naur for suggesting this glyph iterator strategy. It let us cut
through a lot of accumulated complexity from trying to match our old text APIs,
meaning that this change actually is a net negative change in lines of code.
This commit consumes the upstream github.com/go-text/typesetting/shaping API
now that my prior work is merged there, removing the need for the font/opentype/internal
package entirely.
As part of my efforts, I fuzzed both the low-level text shaping stack and the
editor widget extensively. I've committed regression tests found that way into
the appropriate testdata files to ensure the fuzzer re-checks them.
Fixes: https://todo.sr.ht/~eliasnaur/gio/425
Fixes: https://todo.sr.ht/~eliasnaur/gio/211
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
Chris Waldon