Add indents change for multiline selection (#1195)

lib/src/models/documents/document.dart

@@ -170,6 +170,12 @@ class Document {
     return (res.node as Line).collectAllStyles(res.offset, len);
   }
 
+  /// Returns all styles for any character within the specified text range.
+  List<OffsetValue<Style>> collectAllStylesWithOffset(int index, int len) {
+    final res = queryChild(index);
+    return (res.node as Line).collectAllStylesWithOffsets(res.offset, len);
+  }
+
   /// Returns plain text within the specified text range.
   String getPlainText(int index, int len) {
     final res = queryChild(index);

lib/src/models/documents/nodes/line.dart

@@ -458,6 +458,44 @@ class Line extends Container<Leaf?> {
     return result;
   }
 
+  /// Returns all styles for any character within the specified text range.
+  List<OffsetValue<Style>> collectAllStylesWithOffsets(
+    int offset,
+    int len, {
+    int beg = 0,
+  }) {
+    final local = math.min(length - offset, len);
+    final result = <OffsetValue<Style>>[];
+
+    final data = queryChild(offset, true);
+    var node = data.node as Leaf?;
+    if (node != null) {
+      var pos = 0;
+      pos = node.length - data.offset;
+      result.add(OffsetValue(node.documentOffset, node.style, node.length));
+      while (!node!.isLast && pos < local) {
+        node = node.next as Leaf;
+        result.add(OffsetValue(node.documentOffset, node.style, node.length));
+        pos += node.length;
+      }
+    }
+
+    result.add(OffsetValue(documentOffset, style, length));
+    if (parent is Block) {
+      final block = parent as Block;
+      result.add(OffsetValue(block.documentOffset, block.style, block.length));
+    }
+
+    final remaining = len - local;
+    if (remaining > 0 && nextLine != null) {
+      final rest =
+      nextLine!.collectAllStylesWithOffsets(0, remaining, beg: local);
+      result.addAll(rest);
+    }
+
+    return result;
+  }
+
   /// Returns plain text within the specified text range.
   String getPlainText(int offset, int len) {
     final plainText = StringBuffer();

lib/src/models/structs/offset_value.dart

@@ -1,5 +1,6 @@
 class OffsetValue<T> {
-  OffsetValue(this.offset, this.value);
+  OffsetValue(this.offset, this.value, [this.length]);
   final int offset;
+  final int? length;
   final T value;
 }

lib/src/widgets/controller.dart

@@ -101,6 +101,14 @@ class QuillController extends ChangeNotifier {
 
   // Increases or decreases the indent of the current selection by 1.
   void indentSelection(bool isIncrease) {
+    if (selection.isCollapsed) {
+      _indentSelectionFormat(isIncrease);
+    } else {
+      _indentSelectionEachLine(isIncrease);
+    }
+  }
+
+  void _indentSelectionFormat(bool isIncrease) {
     final indent = getSelectionStyle().attributes[Attribute.indent.key];
     if (indent == null) {
       if (isIncrease) {
@@ -119,6 +127,37 @@ class QuillController extends ChangeNotifier {
     formatSelection(Attribute.getIndentLevel(indent.value - 1));
   }
 
+  void _indentSelectionEachLine(bool isIncrease) {
+    final styles = document.collectAllStylesWithOffset(
+      selection.start,
+      selection.end - selection.start,
+    );
+    for (final style in styles) {
+      final indent = style.value.attributes[Attribute.indent.key];
+      final formatIndex = math.max(style.offset, selection.start);
+      final formatLength = math.min(
+        style.offset + (style.length ?? 0),
+        selection.end,
+      ) - style.offset;
+      Attribute? formatAttribute;
+      if (indent == null) {
+        if (isIncrease) {
+          formatAttribute = Attribute.indentL1;
+        }
+      } else if (indent.value == 1 && !isIncrease) {
+        formatAttribute = Attribute.clone(Attribute.indentL1, null);
+      } else if (isIncrease) {
+        formatAttribute = Attribute.getIndentLevel(indent.value + 1);
+      } else {
+        formatAttribute = Attribute.getIndentLevel(indent.value - 1);
+      }
+      if (formatAttribute != null) {
+        document.format(formatIndex, formatLength, formatAttribute);
+      }
+    }
+    notifyListeners();
+  }
+
   /// Returns all styles for each node within selection
   List<OffsetValue<Style>> getAllIndividualSelectionStyles() {
     final styles = document.collectAllIndividualStyles(