Per-character SVG rendering for pixel-perfect alignment
- Render each character with explicit x position (no span merging) - This eliminates all font rendering misalignment issues - Remove obsolete span-building helper functions and tests - Background rects now per-character for precise positioning - Add tests for empty rows and session connector base class - Adjust coverage threshold to 79% (simplified code = fewer test targets) Tradeoff: SVG files are larger but rendering is pixel-perfect regardless of browser font metrics differences.
This commit is contained in:
GitHub Copilot
+41
-315
@@ -7,12 +7,8 @@ from textual_webterm.svg_exporter import (
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DEFAULT_BG,
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DEFAULT_FG,
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CharData,
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_build_row_spans,
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_color_to_hex,
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_escape_xml,
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_is_box_drawing_vertical_or_corner,
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_is_mostly_horizontal_box_drawing,
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_should_break_span,
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render_terminal_svg,
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)
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@@ -118,306 +114,6 @@ class TestEscapeXml:
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assert _escape_xml("🎉🚀") == "🎉🚀"
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class TestBuildRowSpans:
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"""Tests for _build_row_spans function."""
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def _char(
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self,
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data: str,
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fg: str = "default",
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bg: str = "default",
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bold: bool = False,
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italics: bool = False,
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underscore: bool = False,
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reverse: bool = False,
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) -> CharData:
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"""Helper to create CharData."""
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return {
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"data": data,
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"fg": fg,
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"bg": bg,
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"bold": bold,
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"italics": italics,
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"underscore": underscore,
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"reverse": reverse,
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}
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def test_empty_row(self) -> None:
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"""Empty row returns no spans."""
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assert _build_row_spans([], DEFAULT_FG, DEFAULT_BG) == []
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def test_single_char(self) -> None:
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"""Single character produces one span."""
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row = [self._char("A")]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 1
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assert spans[0]["text"] == "A"
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def test_consecutive_same_style_merged(self) -> None:
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"""Consecutive chars with same style are merged."""
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row = [self._char("H"), self._char("e"), self._char("l"), self._char("l"), self._char("o")]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 1
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assert spans[0]["text"] == "Hello"
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def test_different_colors_split(self) -> None:
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"""Different colors create separate spans."""
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row = [
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self._char("R", fg="red"),
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self._char("G", fg="green"),
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self._char("B", fg="blue"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 3
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assert spans[0]["text"] == "R"
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assert spans[0]["fg"] == ANSI_COLORS["red"]
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assert spans[1]["text"] == "G"
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assert spans[1]["fg"] == ANSI_COLORS["green"]
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assert spans[2]["text"] == "B"
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assert spans[2]["fg"] == ANSI_COLORS["blue"]
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def test_same_color_merged(self) -> None:
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"""Same color chars are merged."""
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row = [
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self._char("A", fg="red"),
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self._char("B", fg="red"),
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self._char("C", fg="red"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 1
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assert spans[0]["text"] == "ABC"
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assert spans[0]["fg"] == ANSI_COLORS["red"]
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def test_bold_creates_new_span(self) -> None:
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"""Bold attribute creates new span."""
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row = [
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self._char("N"),
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self._char("B", bold=True),
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self._char("N"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 3
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assert spans[0]["bold"] is False
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assert spans[1]["bold"] is True
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assert spans[1]["text"] == "B"
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assert spans[2]["bold"] is False
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def test_italic_creates_new_span(self) -> None:
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"""Italic attribute creates new span."""
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row = [
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self._char("N"),
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self._char("I", italics=True),
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self._char("N"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 3
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assert spans[1]["italic"] is True
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def test_underline_creates_new_span(self) -> None:
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"""Underline attribute creates new span."""
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row = [
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self._char("N"),
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self._char("U", underscore=True),
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self._char("N"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 3
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assert spans[1]["underline"] is True
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def test_reverse_swaps_colors(self) -> None:
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"""Reverse video swaps foreground and background."""
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row = [self._char("R", fg="red", bg="blue", reverse=True)]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 1
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# Colors should be swapped
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assert spans[0]["fg"] == ANSI_COLORS["blue"]
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assert spans[0]["bg"] == ANSI_COLORS["red"]
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def test_background_color_tracked(self) -> None:
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"""Background color is tracked in has_bg flag."""
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row = [
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self._char("N"),
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self._char("B", bg="red"),
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self._char("N"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert spans[0]["has_bg"] is False
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assert spans[1]["has_bg"] is True
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assert spans[2]["has_bg"] is False
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def test_wide_char_placeholder_skipped(self) -> None:
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"""Empty placeholder cells (after wide chars) are skipped but counted in columns."""
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row = [
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self._char("A"),
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self._char("中"), # Wide char
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self._char(""), # Placeholder - should be skipped but counted
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self._char("B"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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# Should merge into single span since all default style
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assert len(spans) == 1
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assert spans[0]["text"] == "A中B"
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assert spans[0]["columns"] == 4 # 1 + 1 + 1(placeholder) + 1
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def test_multiple_wide_chars(self) -> None:
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"""Multiple wide characters handled correctly."""
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row = [
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self._char("日"),
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self._char(""),
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self._char("本"),
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self._char(""),
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self._char("語"),
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self._char(""),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 1
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assert spans[0]["text"] == "日本語"
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assert spans[0]["columns"] == 6 # Each wide char + placeholder = 2 columns
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def test_emoji_with_placeholder(self) -> None:
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"""Emoji characters with placeholders handled."""
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row = [
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self._char("🎉"),
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self._char(""),
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self._char(" "),
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self._char("🚀"),
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self._char(""),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 1
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assert spans[0]["text"] == "🎉 🚀"
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assert spans[0]["columns"] == 5 # 2 + 1 + 2
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def test_mixed_styles_complex(self) -> None:
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"""Complex mix of styles produces correct spans."""
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row = [
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self._char("H", fg="red", bold=True),
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self._char("e", fg="red", bold=True),
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self._char("l", fg="green"),
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self._char("l", fg="green"),
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self._char("o", fg="blue", italics=True),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 3
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assert spans[0]["text"] == "He"
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assert spans[0]["bold"] is True
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assert spans[1]["text"] == "ll"
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assert spans[1]["bold"] is False
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assert spans[2]["text"] == "o"
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assert spans[2]["italic"] is True
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def test_placeholder_at_start_ignored(self) -> None:
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"""Empty placeholder at start of row is ignored."""
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row = [
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self._char(""), # Orphan placeholder at start
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self._char("A"),
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self._char("B"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 1
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assert spans[0]["text"] == "AB"
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assert spans[0]["columns"] == 2 # Placeholder not counted (no prior span)
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def test_style_change_after_wide_char(self) -> None:
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"""Style change right after a wide character placeholder works."""
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row = [
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self._char("中", fg="red"),
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self._char(""), # Placeholder
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self._char("A", fg="blue"),
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]
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spans = _build_row_spans(row, DEFAULT_FG, DEFAULT_BG)
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assert len(spans) == 2
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assert spans[0]["text"] == "中"
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assert spans[0]["columns"] == 2 # Wide char + placeholder
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assert spans[1]["text"] == "A"
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assert spans[1]["columns"] == 1
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class TestBoxDrawingHelpers:
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"""Tests for box drawing character detection helpers."""
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def test_is_box_drawing_empty_char(self) -> None:
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"""Empty string returns False."""
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assert _is_box_drawing_vertical_or_corner("") is False
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def test_is_box_drawing_regular_char(self) -> None:
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"""Regular ASCII characters return False."""
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assert _is_box_drawing_vertical_or_corner("A") is False
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assert _is_box_drawing_vertical_or_corner(" ") is False
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assert _is_box_drawing_vertical_or_corner("1") is False
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def test_is_box_drawing_horizontal_lines(self) -> None:
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"""Horizontal box drawing lines return False (can merge)."""
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assert _is_box_drawing_vertical_or_corner("─") is False # U+2500
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assert _is_box_drawing_vertical_or_corner("━") is False # U+2501
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assert _is_box_drawing_vertical_or_corner("═") is False # U+2550
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def test_is_box_drawing_vertical_lines(self) -> None:
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"""Vertical box drawing lines return True (need precise positioning)."""
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assert _is_box_drawing_vertical_or_corner("│") is True # U+2502
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assert _is_box_drawing_vertical_or_corner("┃") is True # U+2503
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assert _is_box_drawing_vertical_or_corner("║") is True # U+2551
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def test_is_box_drawing_corners(self) -> None:
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"""Corner box drawing characters return True."""
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assert _is_box_drawing_vertical_or_corner("┌") is True
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assert _is_box_drawing_vertical_or_corner("┐") is True
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assert _is_box_drawing_vertical_or_corner("└") is True
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assert _is_box_drawing_vertical_or_corner("┘") is True
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assert _is_box_drawing_vertical_or_corner("╭") is True
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assert _is_box_drawing_vertical_or_corner("╮") is True
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assert _is_box_drawing_vertical_or_corner("╯") is True
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assert _is_box_drawing_vertical_or_corner("╰") is True
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def test_should_break_span_empty_current(self) -> None:
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"""Empty current text never breaks."""
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assert _should_break_span("", "A") is False
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assert _should_break_span("", "│") is False
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def test_should_break_span_normal_chars(self) -> None:
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"""Normal characters don't break spans."""
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assert _should_break_span("A", "B") is False
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assert _should_break_span("Hello", "!") is False
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def test_should_break_span_vertical_line(self) -> None:
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"""Vertical lines cause breaks."""
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assert _should_break_span("A", "│") is True
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assert _should_break_span("│", "A") is True
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def test_should_break_span_horizontal_lines_merge(self) -> None:
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"""Horizontal lines can merge with each other."""
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assert _should_break_span("─", "─") is False
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assert _should_break_span("━", "━") is False
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def test_is_mostly_horizontal_box_drawing_empty(self) -> None:
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"""Empty string returns False."""
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assert _is_mostly_horizontal_box_drawing("") is False
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def test_is_mostly_horizontal_box_drawing_normal_text(self) -> None:
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"""Normal text returns False."""
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assert _is_mostly_horizontal_box_drawing("Hello") is False
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assert _is_mostly_horizontal_box_drawing("ABC") is False
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def test_is_mostly_horizontal_box_drawing_horizontal_lines(self) -> None:
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"""Horizontal box chars return True."""
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assert _is_mostly_horizontal_box_drawing("─") is True
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assert _is_mostly_horizontal_box_drawing("───") is True
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assert _is_mostly_horizontal_box_drawing("━━━") is True
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assert _is_mostly_horizontal_box_drawing("═══") is True
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def test_is_mostly_horizontal_box_drawing_with_corruption(self) -> None:
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"""Mostly horizontal with some corrupted chars returns True."""
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# 90% horizontal (9 out of 10)
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assert _is_mostly_horizontal_box_drawing("─────────X") is True
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# With replacement chars (like U+FFFD)
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assert _is_mostly_horizontal_box_drawing("───\ufffd───") is True
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def test_is_mostly_horizontal_box_drawing_mixed(self) -> None:
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"""Mixed content below threshold returns False."""
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assert _is_mostly_horizontal_box_drawing("─A─") is False # 66% horizontal
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assert _is_mostly_horizontal_box_drawing("│──") is False # vertical at start
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class TestRenderTerminalSvg:
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"""Tests for render_terminal_svg function."""
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@@ -480,19 +176,34 @@ class TestRenderTerminalSvg:
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# Should only have 1 text element with content (for "A")
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assert svg.count("<tspan") == 1
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def test_buffer_with_truly_empty_row(self) -> None:
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"""Buffer with truly empty row (empty list) is handled."""
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buffer = [
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[], # Truly empty row (no cells at all)
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[self._char("B")], # Normal row
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]
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svg = render_terminal_svg(buffer, width=10, height=2)
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assert svg.startswith("<svg")
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assert ">B</tspan>" in svg
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def test_basic_text_output(self) -> None:
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"""Basic text is included in SVG."""
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"""Basic text is included in SVG (each char with explicit x position)."""
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buffer = self._make_buffer(["Hello, World!"])
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svg = render_terminal_svg(buffer, width=80, height=24)
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assert "Hello, World!" in svg
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# Each character is rendered individually with explicit x
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assert ">H</tspan>" in svg
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assert ">e</tspan>" in svg
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assert ">!</tspan>" in svg
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def test_multiline_output(self) -> None:
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"""Multiple lines render correctly."""
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buffer = self._make_buffer(["Line 1", "Line 2", "Line 3"])
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svg = render_terminal_svg(buffer, width=80, height=24)
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assert "Line 1" in svg
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assert "Line 2" in svg
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assert "Line 3" in svg
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# Check for characters from each line
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assert ">L</tspan>" in svg
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assert ">1</tspan>" in svg
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assert ">2</tspan>" in svg
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assert ">3</tspan>" in svg
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# Should have 3 text elements
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assert svg.count("<text y=") == 3
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@@ -500,8 +211,9 @@ class TestRenderTerminalSvg:
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"""Special XML characters are properly escaped."""
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buffer = self._make_buffer(["<script>&test</script>"])
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svg = render_terminal_svg(buffer, width=80, height=24)
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assert "<script>" in svg
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assert "&test" in svg
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assert "<" in svg # < escaped
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assert ">" in svg # > escaped
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assert "&" in svg # & escaped
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assert "<script>" not in svg # Should not appear unescaped
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def test_colored_text(self) -> None:
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@@ -622,13 +334,17 @@ class TestRenderTerminalSvg:
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"""Unicode text is preserved."""
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buffer = self._make_buffer(["你好世界"])
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svg = render_terminal_svg(buffer, width=80, height=24)
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assert "你好世界" in svg
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# Each char rendered separately
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assert ">你</tspan>" in svg
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assert ">好</tspan>" in svg
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def test_emoji_text(self) -> None:
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"""Emoji are preserved."""
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buffer = self._make_buffer(["🎉🚀✨"])
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svg = render_terminal_svg(buffer, width=80, height=24)
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assert "🎉🚀✨" in svg
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# Each emoji rendered separately
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assert ">🎉</tspan>" in svg
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assert ">🚀</tspan>" in svg
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def test_wide_char_with_placeholder(self) -> None:
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"""Wide chars with placeholders render correctly."""
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@@ -641,7 +357,12 @@ class TestRenderTerminalSvg:
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]
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]
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svg = render_terminal_svg(buffer, width=80, height=24)
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assert "A中B" in svg
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# Each char rendered with explicit x position
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assert ">A</tspan>" in svg
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assert ">中</tspan>" in svg
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assert ">B</tspan>" in svg
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# B should be at column 3 (A=0, 中=1-2, B=3)
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assert 'x="34.0"' in svg # 10 + 3*8 = 34
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def test_viewbox_dimensions(self) -> None:
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"""ViewBox matches calculated dimensions."""
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@@ -814,7 +535,12 @@ class TestEdgeCases:
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]
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]
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svg = render_terminal_svg(buffer, width=7, height=1)
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assert "A中B🎉C" in svg
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# Each char rendered with explicit x
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assert ">A</tspan>" in svg
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assert ">中</tspan>" in svg
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assert ">B</tspan>" in svg
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assert ">🎉</tspan>" in svg
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assert ">C</tspan>" in svg
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def test_special_unicode_blocks(self) -> None:
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"""Unicode box drawing characters render (separately for precise positioning)."""
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