WideCharRepro

Wide Character Rendering ReproductionA minimal reproduction app demonstrating incorrect wide/fullwidth Unicode character rendering in terminal emulators.## The ProblemTerminal emulators must advance the cursor by 2 columns for "wide" Unicode characters (East Asian Width = Wide/Fullwidth, emoji with presentation selectors). Some terminals incorrectly advance by only 1 column, causing:- Grid misalignment / display "tearing"- Overlapping text- Broken TUI (text user interface) applications## Screenshots### Correct rendering (Windows Terminal)All grid separators (Γöé) are vertically aligned. Each wide character occupies exactly 2 terminal columns.### Broken rendering (affected terminals)Grid separators are misaligned. Wide characters only advance the cursor by 1 column, causing all subsequent content on the line to shift left.## Running the Reproductionbashdotnet runRequirements: .NET 10 SDK (or change TargetFramework in .csproj to your installed version, e.g., net8.0 or net9.0).## What to Look For1. Test 1ΓÇô2 (Emoji / CJK grids): The Γöé separators should form perfectly vertical columns.2. Test 3 (Mixed content): Lines with mixed narrow + wide characters should fit within the box.3. Test 4 (Programmatic grid): Another grid alignment test with diverse wide characters.4. Test 5 (Column verification): The X markers should all appear at column 20.If any of these are misaligned, the terminal has a wide-character width calculation bug.## Technical DetailsWide characters affected:- Emoji (U+1F600ΓÇôU+1F64F, U+1F900ΓÇôU+1F9FF, etc.)- CJK Unified Ideographs (U+4E00ΓÇôU+9FFF)- CJK Compatibility Ideographs (U+F900ΓÇôU+FAFF)- Fullwidth Forms (U+FF01ΓÇôU+FF60)- Any character with East_Asian_Width property = W (Wide) or F (Fullwidth)The terminal must use the Unicode East_Asian_Width property (or an equivalent wcwidth implementation) to determine cursor advancement after printing each character.## Related Standards- Unicode TR#11 ΓÇô East Asian Width- POSIX wcwidth(3)- Unicode Emoji Presentation