Fix TUI duplicate top bar and crash with double-width (CJK) text at the right edge

[Gabriel Dufresne (GabrielDuf)]

Cause

The TUI's page tab strip and bottom function bar sized their labels with string.Length. CJK translations take two terminal cells per character (zh_CN "帮助" is 2 chars but 4 cells), so both rows believed they fit while the real text ran to the right edge and a double-width glyph could land in the terminal's last column.

Consolonia 12.0.3.14 does not handle that:

• DrawingContextImpl keeps a wide glyph whose first cell is inside the clip, and RenderTarget passes it to the device unchanged.
• AnsiConsoleOutput.WritePixel writes two spaces before a wide glyph. In the last column that wraps the cursor: the terminal scrolls a line (or spills onto the next row) that Consolonia never tracks, leaving a stale copy of the tab strip on screen. That is the duplicate, unresponsive top bar in the issue.
• On the next redraw, RenderToDevice reads one cell past the buffer edge and the render loop dies with IndexOutOfRangeException.

Changes

• TuiChrome.Cells() measures text in terminal cells with Wcwidth, the same calculator Consolonia uses for glyph widths.
• The tab-strip density choice, the function-bar key hints, the notification variants and the badges all use it.
• When even number-only tabs do not fit, the selected tab now drops to its number too (previously it kept its full label), so on very narrow terminals no CJK glyph can reach the edge. The fitting logic moved to a static MainWindow.FitTabs so it can be tested.
• Tests: TuiFunctionBarTests.DoubleWidthLabelsAreMeasuredInTerminalCells and the new TuiTabStripTests. Both new test sets fail on the previous behaviour.

Testing

• Real console (conhost) with zh_CN fake data, switching tabs with Alt+digit at every width from 64 to 104 columns × 30 rows: the old build crashed at 73, 75, 77, 92, 94 and 96 columns and hung at 79 and 98; the fixed build was clean at all 41 widths.
• Windows Terminal at 94 columns, by hand: the old build showed the tab label spilling onto the next row and crashed on Alt+1; the fixed build stays correct through the same key sequence.
• dotnet format whitespace and style are clean for both TUI projects.

Not covered here

Other TUI layouts still measure with string.Length (menu dropdown padding, the package page's actions panel width, dialog widths, chips). None of them sits at the right edge of the terminal, so at worst they misalign rather than crash; they can be moved to TuiChrome.Cells in a follow-up.

---

Closes #5490

[Copilot]

🟡 Changes recommended

The new width helper undercounts emoji rendered as double-width by Consolonia, leaving an edge-overflow path unresolved.

1 open finding

• Emoji width measurement differs from Consolonia, causing right-edge overflow · New

What changed in this PR

Fixes TUI edge rendering by measuring labels in terminal cells rather than UTF-16 length.

Changes:

• Adds shared terminal-cell measurement.
• Updates tab and function-bar fitting.
• Adds CJK width regression tests.

File	Description
src/​UniGetUI.Tui/​Views/​MainWindow.cs	Adds testable tab-density fitting.
src/​UniGetUI.Tui/​Views/​Controls/​TuiFunctionBar.cs	Measures hints, notifications, and badges by cells.
src/​UniGetUI.Tui/​Infrastructure/​TuiChrome.cs	Adds shared cell-width calculation.
src/​UniGetUI.Tui.Tests/​TuiTabStripTests.cs	Tests CJK tab fitting.
src/​UniGetUI.Tui.Tests/​TuiFunctionBarTests.cs	Tests CJK function-bar fitting.

🧠 Review effort: Balanced

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

🟢 Approval recommended

The sizing changes address the reported failure and include focused CJK, emoji, and narrow-width regression coverage.

0 open findings

1 resolved since last review

• Emoji width measurement differs from Consolonia, causing right-edge overflow

🧠 Review effort: Balanced

[randy-but-a-ro]

🤖 Pull request was approved automatically: the AI review is complete and all its review threads are resolved. 🎉

Integration Details

{
	"deliveryId": "d9888a70-c409-11f1-989f-19c35bf64653",
	"headSha": "f886c53234a5d23c1974007d0c5765bbaec3d7a2",
	"reviewer": "copilot-pull-request-reviewer[bot]"
}