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count in utf-16, like a browser

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Karl Seguin committed 2026-07-27 20:27:51 +08:00
1 parent 5e6395c6ad
commit 700dfe5b74
7 files changed
+167 -35
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src/browser/tests/element/svg/text.html
+20 -6
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@@ -1,4 +1,5 @@
<!DOCTYPE html>
<meta charset=utf-8>
<script src="../../testing.js"></script>
<svg>
@@ -27,19 +28,34 @@
}
</script>
<!-- This block asserts our deterministic fallback metrics; real browsers
shape text and produce different numbers, so it is not expected to pass
there. The other blocks are browser-comparable. -->
<script id=fallbackMetrics>
{
const text = $('#text');
testing.expectEqual(6, text.getNumberOfChars());
// Characters are UTF-16 code units, like DOM strings: the emoji counts as
// two, and addressing either of its halves measures the full glyph.
testing.expectEqual(7, text.getNumberOfChars());
testing.expectEqual(80, text.getComputedTextLength());
testing.expectEqual(60, text.getSubStringLength(0, 5));
testing.expectEqual(20, text.getSubStringLength(5, 1));
testing.expectEqual(20, text.getSubStringLength(6, 1));
testing.expectEqual(32, text.getSubStringLength(4, 99));
testing.expectError('IndexSizeError', () => text.getSubStringLength(6, 1));
testing.expectError('IndexSizeError', () => text.getSubStringLength(6, 0));
testing.expectEqual(1, $('#tspan').getNumberOfChars());
testing.expectError('IndexSizeError', () => text.getSubStringLength(7, 1));
testing.expectError('IndexSizeError', () => text.getSubStringLength(7, 0));
testing.expectEqual(2, $('#tspan').getNumberOfChars());
testing.expectEqual(20, $('#tspan').getComputedTextLength());
testing.expectEqual(9.6, $('#invalidFont').getComputedTextLength());
// Chrome answers an absent textLength with the computed (shaped) text
// length; without shaping we default to 0.
testing.expectEqual(0, text.textLength.baseVal.value);
// Browsers return the shaped text box here; our text geometry is
// unmeasured, so like the other unresolved elements getBBox answers an
// empty box rather than an error.
testing.expectEqual(0, text.getBBox().width);
}
</script>
@@ -48,7 +64,6 @@
const text = $('#text');
testing.expectEqual(true, text.textLength instanceof SVGAnimatedLength);
testing.expectEqual(true, text.textLength === text.textLength);
testing.expectEqual(0, text.textLength.baseVal.value);
text.textLength.baseVal.value = 100;
testing.expectEqual('100', text.getAttribute('textLength'));
testing.expectEqual(100, text.textLength.animVal.value);
@@ -56,7 +71,6 @@
testing.expectEqual(true, text.lengthAdjust === text.lengthAdjust);
text.lengthAdjust.baseVal = 2;
testing.expectEqual('spacingAndGlyphs', text.getAttribute('lengthAdjust'));
testing.expectError('InvalidStateError', () => text.getBBox());
const textPath = $('#textPath');
testing.expectEqual('#guide', textPath.href.baseVal);
src/browser/text_measure.zig
+49 -18
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@@ -1,13 +1,40 @@
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
const std = @import("std");
// Deterministic DOM fallback only. This intentionally does not claim to shape
// scripts, apply kerning, or select fonts; a real shaping backend can replace
// this module without changing SVGTextContentElement.
pub fn countCodepoints(text: []const u8) u32 {
return @intCast(std.unicode.utf8CountCodepoints(text) catch 0);
// Character counts and indices are UTF-16 code units, to match DOM string
// semantics: an astral codepoint is two addressable characters in browsers.
pub fn utf16Length(text: []const u8) u32 {
var iterator = std.unicode.Utf8Iterator{ .bytes = text, .i = 0 };
var result: u32 = 0;
while (iterator.nextCodepoint()) |codepoint| {
result += unitLength(codepoint);
}
return result;
}
fn unitLength(codepoint: u21) u32 {
return if (codepoint >= 0x10000) 2 else 1;
}
pub fn width(text: []const u8, font_size: f64) f64 {
@@ -17,21 +44,21 @@ pub fn width(text: []const u8, font_size: f64) f64 {
return result;
}
pub fn substringWidth(text: []const u8, offset: u32, count: u32, font_size: f64) !f64 {
if (text.len == 0) return error.IndexSizeError;
pub fn substringWidth(text: []const u8, charnum: u32, nchars: u32, font_size: f64) !f64 {
if (charnum >= utf16Length(text)) return error.IndexSizeError;
const end = charnum +| nchars;
// A glyph is measured whenever its unit range intersects the request, so
// addressing either half of a surrogate pair yields the full glyph, like
// Chrome does.
var iterator = std.unicode.Utf8Iterator{ .bytes = text, .i = 0 };
var index: u32 = 0;
while (index < offset) : (index += 1) {
if (iterator.nextCodepoint() == null) return error.IndexSizeError;
}
if (offset > 0 and iterator.i == text.len) return error.IndexSizeError;
var unit: u32 = 0;
var result: f64 = 0;
var remaining = count;
while (remaining > 0) : (remaining -= 1) {
const codepoint = iterator.nextCodepoint() orelse break;
result += advance(codepoint, font_size);
while (iterator.nextCodepoint()) |codepoint| {
const units = unitLength(codepoint);
if (unit >= end) break;
if (unit + units > charnum) result += advance(codepoint, font_size);
unit += units;
}
return result;
}
@@ -70,10 +97,14 @@ fn isWide(codepoint: u21) bool {
(codepoint >= 0x20000 and codepoint <= 0x3fffd);
}
test "fallback metrics count codepoints and ignore combining marks" {
try std.testing.expectEqual(@as(u32, 3), countCodepoints("Aé界"));
test "fallback metrics count utf-16 units and ignore combining marks" {
try std.testing.expectEqual(@as(u32, 3), utf16Length("Aé界"));
try std.testing.expectEqual(@as(u32, 2), utf16Length("🌍"));
try std.testing.expectApproxEqAbs(@as(f64, 16), width("A\u{0301}界", 10), 0.0001);
try std.testing.expectApproxEqAbs(@as(f64, 10), try substringWidth("A界", 1, 1, 10), 0.0001);
try std.testing.expectApproxEqAbs(@as(f64, 10), try substringWidth("🌍", 0, 1, 10), 0.0001);
try std.testing.expectApproxEqAbs(@as(f64, 10), try substringWidth("🌍", 1, 1, 10), 0.0001);
try std.testing.expectApproxEqAbs(@as(f64, 0), try substringWidth("A界", 1, 0, 10), 0.0001);
try std.testing.expectError(error.IndexSizeError, substringWidth("A", 2, 1, 10));
try std.testing.expectError(error.IndexSizeError, substringWidth("A", 1, 0, 10));
try std.testing.expectError(error.IndexSizeError, substringWidth("", 0, 0, 10));
src/browser/webapi/element/svg/TSpan.zig
+19 -2
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@@ -1,9 +1,26 @@
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
const js = @import("../../../js/js.zig");
const Node = @import("../../Node.zig");
const Element = @import("../../Element.zig");
const TextPositioning = @import("TextPositioning.zig");
const TSpan = @This();
src/browser/webapi/element/svg/Text.zig
+19 -2
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@@ -1,9 +1,26 @@
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
const js = @import("../../../js/js.zig");
const Node = @import("../../Node.zig");
const Element = @import("../../Element.zig");
const TextPositioning = @import("TextPositioning.zig");
const Text = @This();
src/browser/webapi/element/svg/TextContent.zig
+21 -3
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@@ -1,14 +1,32 @@
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
const js = @import("../../../js/js.zig");
const Frame = @import("../../../Frame.zig");
const text_measure = @import("../../../text_measure.zig");
const Node = @import("../../Node.zig");
const Element = @import("../../Element.zig");
const AnimatedEnumeration = @import("../../svg/AnimatedEnumeration.zig");
const AnimatedLength = @import("../../svg/AnimatedLength.zig");
const Length = @import("../../svg/Length.zig");
const Graphics = @import("Graphics.zig");
pub const TextPositioning = @import("TextPositioning.zig");
@@ -57,7 +75,7 @@ fn getLengthAdjust(self: *TextContent, frame: *Frame) !*AnimatedEnumeration {
}
pub fn getNumberOfChars(self: *TextContent, frame: *Frame) u32 {
return text_measure.countCodepoints(self.text(frame));
return text_measure.utf16Length(self.text(frame));
}
pub fn getComputedTextLength(self: *TextContent, frame: *Frame) f64 {
src/browser/webapi/element/svg/TextPath.zig
+20 -2
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@@ -1,13 +1,31 @@
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
const js = @import("../../../js/js.zig");
const Frame = @import("../../../Frame.zig");
const Node = @import("../../Node.zig");
const Element = @import("../../Element.zig");
const AnimatedEnumeration = @import("../../svg/AnimatedEnumeration.zig");
const AnimatedLength = @import("../../svg/AnimatedLength.zig");
const AnimatedString = @import("../../svg/AnimatedString.zig");
const TextContent = @import("TextContent.zig");
const TextPath = @This();
src/browser/webapi/element/svg/TextPositioning.zig
+19 -2
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@@ -1,9 +1,26 @@
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
const js = @import("../../../js/js.zig");
const Node = @import("../../Node.zig");
const Element = @import("../../Element.zig");
const TextContent = @import("TextContent.zig");
pub const Text = @import("Text.zig");