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https://github.com/ghostty-org/ghostty.git
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65e61282a6
Embedders that render text outside the terminal grid need to predict
how many cells text will occupy once it is written to the terminal.
The existing codepoint width API exposes the table used by print, but
that is not enough for mode 2027 grapheme clustering: VS15/VS16, ZWJ
sequences, skin tone modifiers, and other continuation codepoints can
change the width of the whole cluster.
This exposes a single segment-and-measure API so callers use Ghostty
segmentation and width folding together:
uint8_t width;
size_t n = ghostty_unicode_grapheme_width(cps, len, &width);
From the Zig module:
const vt = @import("ghostty-vt");
const result = vt.unicode.graphemeWidth(u21, cps);
Callers loop until their string is consumed. The API is intentionally
not streaming: input must contain a complete first cluster or the
logical string end, so chunked readers should keep buffering when the
function consumes all available codepoints and more may arrive.
The terminal hot path now shares the width-decision func with the
API, the helper is inline and preserves the old branch structure. So
this doesn't change codegen at all.
64 lines
2.7 KiB
Zig
64 lines
2.7 KiB
Zig
pub const lut = @import("lut.zig");
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const grapheme = @import("grapheme.zig");
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pub const table = @import("props_table.zig").table;
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pub const Properties = @import("props.zig").Properties;
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pub const GraphemeWidthEffect = grapheme.GraphemeWidthEffect;
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pub const GraphemeWidth = grapheme.GraphemeWidth;
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pub const graphemeBreak = grapheme.graphemeBreak;
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pub const graphemeWidth = grapheme.graphemeWidth;
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pub const graphemeWidthEffect = grapheme.graphemeWidthEffect;
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/// Returns the terminal display width of a codepoint in terminal
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/// grid cells: 0, 1, or 2.
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///
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/// This is the same width table the terminal uses when laying out
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/// printed text: 0 for zero-width codepoints (controls, combining
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/// marks, default-ignorables, surrogates), 2 for wide codepoints
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/// (East Asian Wide/Fullwidth, regional indicators, clamped at 2),
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/// and 1 otherwise.
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///
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/// This operates on a single codepoint and cannot account for
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/// grapheme-cluster-level width rules (VS16, combining sequences);
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/// callers needing cluster-accurate widths should use graphemeWidth().
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/// Summing per-codepoint widths is only correct when mode 2027 is
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/// disabled.
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pub fn codepointWidth(cp: u21) u2 {
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return table.get(cp).width;
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}
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test "codepointWidth" {
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const testing = @import("std").testing;
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// Narrow (width 1)
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try testing.expectEqual(1, codepointWidth('a'));
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try testing.expectEqual(1, codepointWidth(' '));
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try testing.expectEqual(1, codepointWidth(0x10FFFF)); // max codepoint
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// C0/C1 control characters (width 0)
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try testing.expectEqual(0, codepointWidth(0x00)); // NUL
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try testing.expectEqual(0, codepointWidth(0x07)); // BEL
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try testing.expectEqual(0, codepointWidth(0x1B)); // ESC
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try testing.expectEqual(0, codepointWidth(0x7F)); // DEL
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try testing.expectEqual(0, codepointWidth(0x80)); // C1 PAD
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// Zero-width codepoints
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try testing.expectEqual(0, codepointWidth(0x0301)); // combining acute
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try testing.expectEqual(0, codepointWidth(0x200B)); // zero width space
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try testing.expectEqual(0, codepointWidth(0x200D)); // ZWJ
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try testing.expectEqual(0, codepointWidth(0xFE0F)); // VS16
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try testing.expectEqual(0, codepointWidth(0xD800)); // surrogate
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// Wide (width 2)
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try testing.expectEqual(2, codepointWidth(0x4E00)); // CJK ideograph
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try testing.expectEqual(2, codepointWidth(0xFF21)); // fullwidth A
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try testing.expectEqual(2, codepointWidth(0xAC00)); // Hangul syllable
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try testing.expectEqual(2, codepointWidth(0x1F600)); // emoji
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try testing.expectEqual(2, codepointWidth(0x1F1E6)); // regional indicator
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try testing.expectEqual(2, codepointWidth(0x2E3B)); // three-em dash (clamped)
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}
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test {
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@import("std").testing.refAllDecls(@This());
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}
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