Add shift range text selection

lib/src/core/buffer/range_shift.dart

@@ -0,0 +1,144 @@
+import 'package:xterm/src/core/buffer/cell_offset.dart';
+import 'package:xterm/src/core/buffer/range.dart';
+import 'package:xterm/src/core/buffer/segment.dart';
+
+/// A range of cells in the buffer that represents a shift selection.
+/// This range is used when the user holds the shift key while selecting text.
+class BufferRangeShift extends BufferRange {
+  BufferRangeShift(super.begin, super.end);
+
+  @override
+  bool get isNormalized => true;
+
+  @override
+  bool get isCollapsed => begin == end;
+
+  @override
+  BufferRange get normalized {
+    if (isNormalized) {
+      return this;
+    }
+    return BufferRangeShift(end, begin);
+  }
+
+  @override
+  List<BufferSegment> toSegments() {
+    final isReversed = begin.y > end.y || (begin.y == end.y && begin.x > end.x);
+    final segmentStart = isReversed ? end : begin;
+    final segmentEnd = isReversed ? begin : end;
+
+    if (segmentStart.y == segmentEnd.y) {
+      return [
+        BufferSegment(
+          this,
+          segmentStart.y,
+          segmentStart.x,
+          segmentEnd.x,
+        ),
+      ];
+    }
+
+    final segments = <BufferSegment>[];
+    final startLine = segmentStart.y;
+    final endLine = segmentEnd.y;
+
+    segments.add(BufferSegment(
+      this,
+      startLine,
+      segmentStart.x,
+      null,
+    ));
+
+    for (var line = startLine + 1; line < endLine; line++) {
+      segments.add(BufferSegment(
+        this,
+        line,
+        0,
+        null,
+      ));
+    }
+
+    segments.add(BufferSegment(
+      this,
+      endLine,
+      0,
+      segmentEnd.x,
+    ));
+
+    return segments;
+  }
+
+  @override
+  bool contains(CellOffset offset) {
+    final minY = begin.y < end.y ? begin.y : end.y;
+    final maxY = begin.y > end.y ? begin.y : end.y;
+
+    if (offset.y < minY || offset.y > maxY) {
+      return false;
+    }
+
+    if (begin.y == end.y) {
+      final minX = begin.x < end.x ? begin.x : end.x;
+      final maxX = begin.x > end.x ? begin.x : end.x;
+      return offset.x >= minX && offset.x <= maxX;
+    }
+
+    if (offset.y == begin.y) {
+      if (begin.y < end.y) {
+        return offset.x >= begin.x;
+      } else {
+        return offset.x <= begin.x;
+      }
+    }
+
+    if (offset.y == end.y) {
+      if (begin.y < end.y) {
+        return offset.x <= end.x;
+      } else {
+        return offset.x >= end.x;
+      }
+    }
+
+    return true;
+  }
+
+  @override
+  BufferRange merge(BufferRange other) {
+    if (other is! BufferRangeShift) {
+      final normalized = this.normalized;
+      final otherNormalized = other.normalized;
+
+      final newBegin = normalized.begin.isBefore(otherNormalized.begin)
+          ? normalized.begin
+          : otherNormalized.begin;
+
+      final newEnd = normalized.end.isAfter(otherNormalized.end)
+          ? normalized.end
+          : otherNormalized.end;
+
+      return BufferRangeShift(newBegin, newEnd);
+    }
+
+    final normalized = this.normalized;
+    final otherNormalized = other.normalized;
+
+    final newBegin = normalized.begin.isBefore(otherNormalized.begin)
+        ? normalized.begin
+        : otherNormalized.begin;
+
+    final newEnd = normalized.end.isAfter(otherNormalized.end)
+        ? normalized.end
+        : otherNormalized.end;
+
+    return BufferRangeShift(newBegin, newEnd);
+  }
+
+  @override
+  BufferRange extend(CellOffset newEnd) {
+    if (begin.y < newEnd.y || (begin.y == newEnd.y && begin.x < newEnd.x)) {
+      return BufferRangeShift(begin, newEnd);
+    } else {
+      return BufferRangeShift(newEnd, begin);
+    }
+  }
+}

lib/src/ui/controller.dart

@@ -6,6 +6,7 @@ import 'package:xterm/src/core/buffer/line.dart';
 import 'package:xterm/src/core/buffer/range.dart';
 import 'package:xterm/src/core/buffer/range_block.dart';
 import 'package:xterm/src/core/buffer/range_line.dart';
+import 'package:xterm/src/core/buffer/range_shift.dart';
 import 'package:xterm/src/ui/pointer_input.dart';
 import 'package:xterm/src/ui/selection_mode.dart';
 
@@ -73,6 +74,8 @@ class TerminalController with ChangeNotifier {
         return BufferRangeLine(begin, end);
       case SelectionMode.block:
         return BufferRangeBlock(begin, end);
+      case SelectionMode.shift:
+        return BufferRangeShift(begin, end);
     }
   }