support placeholder for empty content

app/lib/pages/home_page.dart

@@ -103,6 +103,7 @@ class _HomePageState extends State<HomePage> {
               focusNode: _focusNode,
               autoFocus: false,
               readOnly: false,
+              placeholder: 'Add content',
               enableInteractiveSelection: true,
               expands: false,
               padding: EdgeInsets.zero,

lib/models/documents/attribute.dart

@@ -24,6 +24,7 @@ class Attribute<T> {
     Attribute.link.key: Attribute.link,
     Attribute.color.key: Attribute.color,
     Attribute.background.key: Attribute.background,
+    Attribute.placeholder.key: Attribute.placeholder,
     Attribute.header.key: Attribute.header,
     Attribute.indent.key: Attribute.indent,
     Attribute.align.key: Attribute.align,
@@ -53,6 +54,8 @@ class Attribute<T> {
 
   static final BackgroundAttribute background = BackgroundAttribute(null);
 
+  static final PlaceholderAttribute placeholder = PlaceholderAttribute();
+
   static final HeaderAttribute header = HeaderAttribute();
 
   static final IndentAttribute indent = IndentAttribute();
@@ -78,7 +81,8 @@ class Attribute<T> {
     Attribute.strikeThrough.key,
     Attribute.link.key,
     Attribute.color.key,
-    Attribute.background.key
+    Attribute.background.key,
+    Attribute.placeholder.key,
   };
 
   static final Set<String> blockKeys = {
@@ -222,6 +226,11 @@ class BackgroundAttribute extends Attribute<String> {
       : super('background', AttributeScope.INLINE, val);
 }
 
+/// This is custom attribute for hint
+class PlaceholderAttribute extends Attribute<bool> {
+  PlaceholderAttribute() : super('placeholder', AttributeScope.INLINE, true);
+}
+
 class HeaderAttribute extends Attribute<int> {
   HeaderAttribute({int level}) : super('header', AttributeScope.BLOCK, level);
 }

lib/models/documents/document.dart

@@ -249,7 +249,7 @@ class Document {
     }
 
     Delta delta = node.toDelta();
-    return delta.length == 1 && delta.first.data == '\n';
+    return delta.length == 1 && delta.first.data == '\n' && delta.first.key == 'insert';
   }
 }
 

lib/widgets/default_styles.dart

@@ -54,6 +54,7 @@ class DefaultStyles {
   final TextStyle sizeLarge; // 'large'
   final TextStyle sizeHuge; // 'huge'
   final TextStyle link;
+  final DefaultTextBlockStyle placeHolder;
   final DefaultTextBlockStyle lists;
   final DefaultTextBlockStyle quote;
   final DefaultTextBlockStyle code;
@@ -70,6 +71,7 @@ class DefaultStyles {
       this.underline,
       this.strikeThrough,
       this.link,
+      this.placeHolder,
       this.lists,
       this.quote,
       this.code,
@@ -144,6 +146,15 @@ class DefaultStyles {
           color: themeData.accentColor,
           decoration: TextDecoration.underline,
         ),
+        placeHolder: DefaultTextBlockStyle(
+            defaultTextStyle.style.copyWith(
+              fontSize: 20.0,
+              height: 1.5,
+              color: Colors.grey.withOpacity(0.6),
+            ),
+            Tuple2(0.0, 0.0),
+            Tuple2(0.0, 0.0),
+            null),
         lists: DefaultTextBlockStyle(
             baseStyle, baseSpacing, Tuple2(0.0, 6.0), null),
         quote: DefaultTextBlockStyle(
@@ -188,6 +199,7 @@ class DefaultStyles {
         underline: other.underline ?? this.underline,
         strikeThrough: other.strikeThrough ?? this.strikeThrough,
         link: other.link ?? this.link,
+        placeHolder: other.placeHolder ?? this.placeHolder,
         lists: other.lists ?? this.lists,
         quote: other.quote ?? this.quote,
         code: other.code ?? this.code,

lib/widgets/editor.dart

@@ -134,6 +134,7 @@ class QuillEditor extends StatefulWidget {
   final bool autoFocus;
   final bool showCursor;
   final bool readOnly;
+  final String placeholder;
   final bool enableInteractiveSelection;
   final double minHeight;
   final double maxHeight;
@@ -154,6 +155,7 @@ class QuillEditor extends StatefulWidget {
       @required this.autoFocus,
       this.showCursor,
       @required this.readOnly,
+      this.placeholder,
       this.enableInteractiveSelection,
       this.minHeight,
       this.maxHeight,
@@ -256,6 +258,7 @@ class _QuillEditorState extends State<QuillEditor>
           widget.scrollable,
           widget.padding,
           widget.readOnly,
+          widget.placeholder,
           widget.onLaunchUrl,
           ToolbarOptions(
             copy: true,
@@ -359,6 +362,9 @@ class _QuillEditorSelectionGestureDetectorBuilder
   }
 
   bool _onTapping(TapUpDetails details) {
+    if (_state.widget.controller.document.isEmpty()) {
+      return false;
+    }
     TextPosition pos =
         getRenderEditor().getPositionForOffset(details.globalPosition);
     containerNode.ChildQuery result =

lib/widgets/raw_editor.dart

@@ -1,3 +1,5 @@
+import 'dart:convert';
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -32,6 +34,7 @@ class RawEditor extends StatefulWidget {
   final bool scrollable;
   final EdgeInsetsGeometry padding;
   final bool readOnly;
+  final String placeholder;
   final ValueChanged<String> onLaunchUrl;
   final ToolbarOptions toolbarOptions;
   final bool showSelectionHandles;
@@ -58,6 +61,7 @@ class RawEditor extends StatefulWidget {
       this.scrollable,
       this.padding,
       this.readOnly,
+      this.placeholder,
       this.onLaunchUrl,
       this.toolbarOptions,
       this.showSelectionHandles,
@@ -504,6 +508,12 @@ class RawEditorState extends EditorState
     super.build(context);
 
     Document _doc = widget.controller.document;
+    if (_doc.isEmpty() &&
+        !widget.focusNode.hasFocus &&
+        widget.placeholder != null) {
+      _doc = Document.fromJson(jsonDecode(
+          '[{"attributes":{"placeholder":true},"insert":"${widget.placeholder}\\n"}]'));
+    }
 
     Widget child = CompositedTransformTarget(
       link: _toolbarLayerLink,

lib/widgets/text_line.dart

@@ -88,6 +88,11 @@ class TextLine extends StatelessWidget {
 
     TextStyle textStyle = TextStyle();
 
+    if (line.style.containsKey(Attribute.placeholder.key)) {
+      textStyle = defaultStyles.placeHolder.style;
+      return TextSpan(children: children, style: textStyle);
+    }
+
     Attribute header = line.style.attributes[Attribute.header.key];
     Map<Attribute, TextStyle> m = {
       Attribute.h1: defaultStyles.h1.style,