| 957 | * Handles wide character boundary cleanup at region edges. |
| 958 | */ |
| 959 | export function clearRegion( |
| 960 | screen: Screen, |
| 961 | regionX: number, |
| 962 | regionY: number, |
| 963 | regionWidth: number, |
| 964 | regionHeight: number, |
| 965 | ): void { |
| 966 | const startX = Math.max(0, regionX) |
| 967 | const startY = Math.max(0, regionY) |
| 968 | const maxX = Math.min(regionX + regionWidth, screen.width) |
| 969 | const maxY = Math.min(regionY + regionHeight, screen.height) |
| 970 | if (startX >= maxX || startY >= maxY) return |
| 971 | |
| 972 | const cells = screen.cells |
| 973 | const cells64 = screen.cells64 |
| 974 | const screenWidth = screen.width |
| 975 | const rowBase = startY * screenWidth |
| 976 | let damageMinX = startX |
| 977 | let damageMaxX = maxX |
| 978 | |
| 979 | // EMPTY_CELL_VALUE (0n) matches the zero-initialized state: |
| 980 | // word0=EMPTY_CHAR_INDEX(0), word1=packWord1(0,0,0)=0 |
| 981 | if (startX === 0 && maxX === screenWidth) { |
| 982 | // Full-width: single fill, no boundary checks needed |
| 983 | cells64.fill( |
| 984 | EMPTY_CELL_VALUE, |
| 985 | rowBase, |
| 986 | rowBase + (maxY - startY) * screenWidth, |
| 987 | ) |
| 988 | } else { |
| 989 | // Partial-width: single loop handles boundary cleanup and fill per row. |
| 990 | const stride = screenWidth << 1 // 2 Int32s per cell |
| 991 | const rowLen = maxX - startX |
| 992 | const checkLeft = startX > 0 |
| 993 | const checkRight = maxX < screenWidth |
| 994 | let leftEdge = (rowBase + startX) << 1 |
| 995 | let rightEdge = (rowBase + maxX - 1) << 1 |
| 996 | let fillStart = rowBase + startX |
| 997 | |
| 998 | for (let y = startY; y < maxY; y++) { |
| 999 | // Left boundary: if cell at startX is a SpacerTail, the Wide char |
| 1000 | // at startX-1 (outside the region) will be orphaned. Clear it. |
| 1001 | if (checkLeft) { |
| 1002 | // leftEdge points to word0 of cell at startX; +1 is its word1 |
| 1003 | if ((cells[leftEdge + 1]! & WIDTH_MASK) === CellWidth.SpacerTail) { |
| 1004 | // word1 of cell at startX-1 is leftEdge-1; word0 is leftEdge-2 |
| 1005 | const prevW1 = leftEdge - 1 |
| 1006 | if ((cells[prevW1]! & WIDTH_MASK) === CellWidth.Wide) { |
| 1007 | cells[prevW1 - 1] = EMPTY_CHAR_INDEX |
| 1008 | cells[prevW1] = packWord1(screen.emptyStyleId, 0, CellWidth.Narrow) |
| 1009 | damageMinX = startX - 1 |
| 1010 | } |
| 1011 | } |
| 1012 | } |
| 1013 | |
| 1014 | // Right boundary: if cell at maxX-1 is Wide, its SpacerTail at maxX |
| 1015 | // (outside the region) will be orphaned. Clear it. |
| 1016 | if (checkRight) { |