fix(tui): track rendered spaces for selection copy

- add a written-cell bitmap so selection can distinguish rendered spaces from blank padding
- preserve code indentation without markdown-specific rendering hacks

ui-tui/packages/hermes-ink/src/ink/screen.ts

@@ -436,6 +436,13 @@ export type Screen = Size & {
    */
   noSelect: Uint8Array
 
+  /**
+   * Per-cell written bitmap. A written plain space and never-written padding
+   * share the same packed cell value, so selection needs this side channel to
+   * preserve code indentation without selecting blank UI margins.
+   */
+  written: Uint8Array
+
   /**
    * Per-ROW soft-wrap continuation marker. softWrap[r]=N>0 means row r
    * is a word-wrap continuation of row r-1 (the `\n` before it was
@@ -475,6 +482,14 @@ export function isEmptyCellAt(screen: Screen, x: number, y: number): boolean {
   return isEmptyCellByIndex(screen, y * screen.width + x)
 }
 
+export function isWrittenCellAt(screen: Screen, x: number, y: number): boolean {
+  if (x < 0 || y < 0 || x >= screen.width || y >= screen.height) {
+    return false
+  }
+
+  return screen.written[y * screen.width + x] === 1
+}
+
 /**
  * Check if a Cell (view object) represents an empty cell.
  */
@@ -533,6 +548,7 @@ export function createScreen(
     emptyStyleId: styles.none,
     damage: undefined,
     noSelect: new Uint8Array(size),
+    written: new Uint8Array(size),
     softWrap: new Int32Array(height)
   }
 }
@@ -566,6 +582,7 @@ export function resetScreen(screen: Screen, width: number, height: number): void
     screen.cells = new Int32Array(buf)
     screen.cells64 = new BigInt64Array(buf)
     screen.noSelect = new Uint8Array(size)
+    screen.written = new Uint8Array(size)
   }
 
   if (screen.softWrap.length < height) {
@@ -575,6 +592,7 @@ export function resetScreen(screen: Screen, width: number, height: number): void
   // Reset all cells — single fill call, no loop
   screen.cells64.fill(EMPTY_CELL_VALUE, 0, size)
   screen.noSelect.fill(0, 0, size)
+  screen.written.fill(0, 0, size)
   screen.softWrap.fill(0, 0, height)
 
   // Update dimensions
@@ -770,6 +788,7 @@ export function setCellAt(screen: Screen, x: number, y: number, cell: Cell): voi
       if ((cells[spacerCI + 1]! & WIDTH_MASK) === CellWidth.SpacerTail) {
         cells[spacerCI] = EMPTY_CHAR_INDEX
         cells[spacerCI + 1] = packWord1(screen.emptyStyleId, 0, CellWidth.Narrow)
+        screen.written[y * screen.width + spacerX] = 0
       }
     }
   }
@@ -787,6 +806,7 @@ export function setCellAt(screen: Screen, x: number, y: number, cell: Cell): voi
       if ((cells[wideCI + 1]! & WIDTH_MASK) === CellWidth.Wide) {
         cells[wideCI] = EMPTY_CHAR_INDEX
         cells[wideCI + 1] = packWord1(screen.emptyStyleId, 0, CellWidth.Narrow)
+        screen.written[y * screen.width + x - 1] = 0
         clearedWideX = x - 1
       }
     }
@@ -795,6 +815,7 @@ export function setCellAt(screen: Screen, x: number, y: number, cell: Cell): voi
   // Pack cell data into cells array
   cells[ci] = internCharString(screen, cell.char)
   cells[ci + 1] = packWord1(cell.styleId, internHyperlink(screen, cell.hyperlink), cell.width)
+  screen.written[y * screen.width + x] = 1
 
   // Track damage - expand bounds in place instead of allocating new objects
   // Include the main cell position and any cleared orphan cells
@@ -841,11 +862,13 @@ export function setCellAt(screen: Screen, x: number, y: number, cell: Cell): voi
         if (spacerX + 1 < screen.width && (cells[orphanCI + 1]! & WIDTH_MASK) === CellWidth.SpacerTail) {
           cells[orphanCI] = EMPTY_CHAR_INDEX
           cells[orphanCI + 1] = packWord1(screen.emptyStyleId, 0, CellWidth.Narrow)
+          screen.written[y * screen.width + spacerX + 1] = 0
         }
       }
 
       cells[spacerCI] = SPACER_CHAR_INDEX
       cells[spacerCI + 1] = packWord1(screen.emptyStyleId, 0, CellWidth.SpacerTail)
+      screen.written[y * screen.width + spacerX] = 1
 
       // Expand damage to include SpacerTail so diff() scans it
       const d = screen.damage
@@ -929,6 +952,8 @@ export function blitRegion(
   const dstCells = dst.cells
   const srcNoSel = src.noSelect
   const dstNoSel = dst.noSelect
+  const srcWritten = src.written
+  const dstWritten = dst.written
 
   // softWrap is per-row — copy the row range regardless of stride/width.
   // Partial-width blits still carry the row's wrap provenance since the
@@ -947,6 +972,7 @@ export function blitRegion(
     const nsStart = regionY * src.width
     const nsLen = (maxY - regionY) * src.width
     dstNoSel.set(srcNoSel.subarray(nsStart, nsStart + nsLen), nsStart)
+    dstWritten.set(srcWritten.subarray(nsStart, nsStart + nsLen), nsStart)
   } else {
     // Per-row copy for partial-width or mismatched-stride regions
     let srcRowCI = regionY * srcStride + (regionX << 1)
@@ -957,6 +983,7 @@ export function blitRegion(
     for (let y = regionY; y < maxY; y++) {
       dstCells.set(srcCells.subarray(srcRowCI, srcRowCI + rowBytes), dstRowCI)
       dstNoSel.set(srcNoSel.subarray(srcRowNS, srcRowNS + rowLen), dstRowNS)
+      dstWritten.set(srcWritten.subarray(srcRowNS, srcRowNS + rowLen), dstRowNS)
       srcRowCI += srcStride
       dstRowCI += dstStride
       srcRowNS += src.width
@@ -989,6 +1016,7 @@ export function blitRegion(
       if ((srcCells[srcLastCI + 1]! & WIDTH_MASK) === CellWidth.Wide) {
         dstCells[dstSpacerCI] = SPACER_CHAR_INDEX
         dstCells[dstSpacerCI + 1] = packWord1(dst.emptyStyleId, 0, CellWidth.SpacerTail)
+        dstWritten[y * dst.width + maxX] = 1
         wroteSpacerOutsideRegion = true
       }
 
@@ -1030,6 +1058,7 @@ export function clearRegion(
 
   const cells = screen.cells
   const cells64 = screen.cells64
+  const written = screen.written
   const screenWidth = screen.width
   const rowBase = startY * screenWidth
   let damageMinX = startX
@@ -1040,6 +1069,7 @@ export function clearRegion(
   if (startX === 0 && maxX === screenWidth) {
     // Full-width: single fill, no boundary checks needed
     cells64.fill(EMPTY_CELL_VALUE, rowBase, rowBase + (maxY - startY) * screenWidth)
+    written.fill(0, rowBase, rowBase + (maxY - startY) * screenWidth)
   } else {
     // Partial-width: single loop handles boundary cleanup and fill per row.
     const stride = screenWidth << 1 // 2 Int32s per cell
@@ -1062,6 +1092,7 @@ export function clearRegion(
           if ((cells[prevW1]! & WIDTH_MASK) === CellWidth.Wide) {
             cells[prevW1 - 1] = EMPTY_CHAR_INDEX
             cells[prevW1] = packWord1(screen.emptyStyleId, 0, CellWidth.Narrow)
+            written[y * screenWidth + startX - 1] = 0
             damageMinX = startX - 1
           }
         }
@@ -1078,12 +1109,14 @@ export function clearRegion(
           if ((cells[nextW1]! & WIDTH_MASK) === CellWidth.SpacerTail) {
             cells[nextW1 - 1] = EMPTY_CHAR_INDEX
             cells[nextW1] = packWord1(screen.emptyStyleId, 0, CellWidth.Narrow)
+            written[y * screenWidth + maxX] = 0
             damageMaxX = maxX + 1
           }
         }
       }
 
       cells64.fill(EMPTY_CELL_VALUE, fillStart, fillStart + rowLen)
+      written.fill(0, fillStart, fillStart + rowLen)
       leftEdge += stride
       rightEdge += stride
       fillStart += screenWidth
@@ -1120,12 +1153,14 @@ export function shiftRows(screen: Screen, top: number, bottom: number, n: number
   const w = screen.width
   const cells64 = screen.cells64
   const noSel = screen.noSelect
+  const written = screen.written
   const sw = screen.softWrap
   const absN = Math.abs(n)
 
   if (absN > bottom - top) {
     cells64.fill(EMPTY_CELL_VALUE, top * w, (bottom + 1) * w)
     noSel.fill(0, top * w, (bottom + 1) * w)
+    written.fill(0, top * w, (bottom + 1) * w)
     sw.fill(0, top, bottom + 1)
 
     return
@@ -1135,17 +1170,21 @@ export function shiftRows(screen: Screen, top: number, bottom: number, n: number
     // SU: row top+n..bottom → top..bottom-n; clear bottom-n+1..bottom
     cells64.copyWithin(top * w, (top + n) * w, (bottom + 1) * w)
     noSel.copyWithin(top * w, (top + n) * w, (bottom + 1) * w)
+    written.copyWithin(top * w, (top + n) * w, (bottom + 1) * w)
     sw.copyWithin(top, top + n, bottom + 1)
     cells64.fill(EMPTY_CELL_VALUE, (bottom - n + 1) * w, (bottom + 1) * w)
     noSel.fill(0, (bottom - n + 1) * w, (bottom + 1) * w)
+    written.fill(0, (bottom - n + 1) * w, (bottom + 1) * w)
     sw.fill(0, bottom - n + 1, bottom + 1)
   } else {
     // SD: row top..bottom+n → top-n..bottom; clear top..top-n-1
     cells64.copyWithin((top - n) * w, top * w, (bottom + n + 1) * w)
     noSel.copyWithin((top - n) * w, top * w, (bottom + n + 1) * w)
+    written.copyWithin((top - n) * w, top * w, (bottom + n + 1) * w)
     sw.copyWithin(top - n, top, bottom + n + 1)
     cells64.fill(EMPTY_CELL_VALUE, top * w, (top - n) * w)
     noSel.fill(0, top * w, (top - n) * w)
+    written.fill(0, top * w, (top - n) * w)
     sw.fill(0, top, top - n)
   }
 }

ui-tui/packages/hermes-ink/src/ink/selection.test.ts

@@ -19,8 +19,6 @@ const screenWithText = () => {
   return { screen, styles }
 }
 
-const styledSpace = (styles: StylePool) => styles.intern([{ code: '\x1b[4m', endCode: '\x1b[24m', type: 'ansi' }])
-
 describe('selection whitespace handling', () => {
   it('does not copy whitespace-only selections', () => {
     const { screen } = screenWithText()
@@ -45,11 +43,10 @@ describe('selection whitespace handling', () => {
   it('preserves selected indentation when spaces are rendered content', () => {
     const styles = new StylePool()
     const screen = createScreen(10, 1, styles, new CharPool(), new HyperlinkPool())
-    const indentStyle = styledSpace(styles)
     const selection = createSelectionState()
 
-    setCellAt(screen, 0, 0, { char: ' ', hyperlink: undefined, styleId: indentStyle, width: CellWidth.Narrow })
+    setCellAt(screen, 0, 0, { char: ' ', hyperlink: undefined, styleId: screen.emptyStyleId, width: CellWidth.Narrow })
-    setCellAt(screen, 1, 0, { char: ' ', hyperlink: undefined, styleId: indentStyle, width: CellWidth.Narrow })
+    setCellAt(screen, 1, 0, { char: ' ', hyperlink: undefined, styleId: screen.emptyStyleId, width: CellWidth.Narrow })
     setCellAt(screen, 2, 0, { char: 'x', hyperlink: undefined, styleId: screen.emptyStyleId, width: CellWidth.Narrow })
 
     startSelection(selection, 0, 0)

ui-tui/packages/hermes-ink/src/ink/selection.ts

@@ -12,7 +12,7 @@
 
 import { clamp } from './layout/geometry.js'
 import type { Screen, StylePool } from './screen.js'
-import { cellAt, cellAtIndex, CellWidth, isEmptyCellAt, setCellStyleId } from './screen.js'
+import { cellAt, cellAtIndex, CellWidth, isWrittenCellAt, setCellStyleId } from './screen.js'
 
 type Point = { col: number; row: number }
 
@@ -847,7 +847,7 @@ function selectableCell(screen: Screen, row: number, col: number): boolean {
 
   return (
     screen.noSelect[row * screen.width + col] !== 1 &&
-    !isEmptyCellAt(screen, col, row) &&
+    isWrittenCellAt(screen, col, row) &&
     !!cell &&
     cell.width !== CellWidth.SpacerTail &&
     cell.width !== CellWidth.SpacerHead

ui-tui/src/components/markdown.tsx

@@ -114,25 +114,6 @@ const renderTable = (k: number, rows: string[][], t: Theme) => {
   )
 }
 
-const codeText = (text: string, color: string | undefined, key: number | string, t: Theme) => (
-  <Text color={color ?? (text.trim() ? undefined : t.color.dim)} key={key}>
-    {text}
-  </Text>
-)
-
-const plainCodeLine = (text: string, t: Theme) => {
-  const indent = text.match(/^\s+/)?.[0] ?? ''
-
-  return indent ? (
-    <>
-      {codeText(indent, undefined, 'indent', t)}
-      {text.slice(indent.length)}
-    </>
-  ) : (
-    text
-  )
-}
-
 function MdInline({ t, text }: { t: Theme; text: string }) {
   const parts: ReactNode[] = []
 
@@ -335,7 +316,19 @@ function MdImpl({ compact, t, text }: MdProps) {
 
             {block.map((l, j) => {
               if (highlighted) {
-                return <Text key={j}>{highlightLine(l, lang, t).map(([color, text], kk) => codeText(text, color, kk, t))}</Text>
+                return (
+                  <Text key={j}>
+                    {highlightLine(l, lang, t).map(([color, text], kk) =>
+                      color ? (
+                        <Text color={color} key={kk}>
+                          {text}
+                        </Text>
+                      ) : (
+                        <Text key={kk}>{text}</Text>
+                      )
+                    )}
+                  </Text>
+                )
               }
 
               const add = isDiff && l.startsWith('+')
@@ -349,7 +342,7 @@ function MdImpl({ compact, t, text }: MdProps) {
                   dimColor={isDiff && !add && !del && !hunk && l.startsWith(' ')}
                   key={j}
                 >
-                  {plainCodeLine(l, t)}
+                  {l}
                 </Text>
               )
             })}