Merge pull request #178 from AvaloniaUI/feature/cell-selection

MVP of cell selection

docs/column-types.md

@@ -20,6 +20,24 @@ This is the signature of the `TextColumn` constructor. There are two most import
 **Note**:               
 The sample above is taken from [this article](https://github.com/AvaloniaUI/Avalonia.Controls.TreeDataGrid/blob/master/docs/get-started-flat.md). If you feel like you need more examples feel free to check it, there is a sample that shows how to use TextColumns and how to run a whole `TreeDataGrid` using them. 
 
+## CheckBoxColumn
+
+As its name suggests, `CheckBoxColumn` displays a `CheckBox` in its cells. For a readonly checkbox:
+
+```csharp
+new CheckColumn<Person>("Firstborn", x => x.IsFirstborn)
+```
+
+The first parameter defines the column header. The second parameter is an expression which gets the value of the property from the model.
+
+For a read/write checkbox:
+
+```csharp
+new CheckColumn<Person>("Firstborn", x => x.IsFirstborn, (o, v) => o.IsFirstborn = v)
+```
+
+This overload adds a second paramter which is the expression used to set the property in the model.
+
 ## HierarchicalExpanderColumn
 `HierarchicalExpanderColumn` can be used only with `HierarchicalTreeDataGrid` (a.k.a TreeView) thats what Hierarchical stands for in its name, also it can be used only with `HierarchicalTreeDataGridSource`. This type of columns can be useful when you want cells to show an expander to reveal nested data.
 

docs/selection.md

@@ -0,0 +1,92 @@
+# Selection
+
+Two selection modes are supported:
+
+- Row selection allows the user to select whole rows
+- Cell selection allows the user to select individial cells
+
+Both selection types support either single or multiple selection. The default selection type is single row selection.
+
+## Index Paths
+
+Because `TreeDataGrid` supports hierarchical data, using a simple index to identify a row in the data source isn't enough. Instead indexes are represented using the `IndexPath` struct.
+
+An `IndexPath` is essentially an array of indexes, each element of which specifies the index at a succesively deeper level in the hierarchy of the data.
+
+Consider the following data source:
+
+```
+|- A
+|  |- B
+|  |- C
+|     |- D
+|- E
+```
+
+- `A` has an index path of `0` as it's the first item at the root of the hierarchy
+- `B` has an index path of `0,0` as it's the first child of the first item
+- `C` has an index path of `0,1` as it's the second child of the first item
+- `D` has an index path of `0,1,0` as it's the first child of `C`
+- `E` has an index path of `1` as it's the second item in the root
+
+`IndexPath` is an immutable struct which is constructed with an array of integers, e.g.: `new ItemPath(0, 1, 0)`. There is also an implicit conversion from `int` for when working with a flat data source.
+
+## Row Selection
+
+Row selection is the default and is exposed via the `RowSelection` property on the `FlatTreeDataGridSource<TModel>` and `HierarchicalTreeDataGridSource<TModel>` classes when enabled. Row selection is stored in an instance of the `TreeDataGridRowSelectionModel<TModel>` class.
+
+By default is single selection. To enable multiple selection set the the `SingleSelect` property to `false`, e.g.:
+
+```csharp
+Source = new FlatTreeDataGridSource<Person>(_people)
+{
+    Columns =
+    {
+        new TextColumn<Person, string>("First Name", x => x.FirstName),
+        new TextColumn<Person, string>("Last Name", x => x.LastName),
+        new TextColumn<Person, int>("Age", x => x.Age),
+    },
+};
+
+Source.RowSelection!.SingleSelect = false;
+```
+
+The properties on `ITreeDataGridRowSelectionModel<TModel>` can be used to manipulate the selection, e.g.:
+
+```csharp
+Source.RowSelection!.SelectedIndex = 1;
+```
+
+Or
+
+```csharp
+Source.RowSelection!.SelectedIndex = new IndexPath(0, 1);
+```
+
+## Cell Selection
+
+To enable cell selection for a `TreeDataGridSource`, assign an instance of `TreeDataGridCellSelectionModel<TModel>` to the source's `Selection` property:
+
+```csharp
+Source = new FlatTreeDataGridSource<Person>(_people)
+{
+    Columns =
+    {
+        new TextColumn<Person, string>("First Name", x => x.FirstName),
+        new TextColumn<Person, string>("Last Name", x => x.LastName),
+        new TextColumn<Person, int>("Age", x => x.Age),
+    },
+};
+
+Source.Selection = new TreeDataGridCellSelectionModel<Person>(Source);
+```
+
+Or for multiple cell selection:
+
+```csharp
+Source.Selection = new TreeDataGridCellSelectionModel<Person>(Source) { SingleSelect = false };
+```
+
+Cell selection is is exposed via the `CellSelection` property on the `FlatTreeDataGridSource<TModel>` and `HierarchicalTreeDataGridSource<TModel>` classes when enabled.
+
+The `CellIndex` struct indentifies an individual cell with by combination of an integer column index and an `IndexPath` row index.

readme.md

@@ -32,3 +32,4 @@ We accept issues and pull requests but we answer and review only pull requests a
 - [Creating a flat `TreeDataGrid`](docs/get-started-flat.md)
 - [Creating a hierarchical `TreeDataGrid`](docs/get-started-hierarchical.md)
 - [Supported column types](docs/column-types.md)
+- [Selection](docs/selection.md)

samples/TreeDataGridDemo/MainWindow.axaml

@@ -11,7 +11,8 @@
     <TabItem Header="Countries">
       <DockPanel>
         <TextBlock Classes="realized-count" DockPanel.Dock="Bottom"/>
-        <StackPanel DockPanel.Dock="Right" Spacing="4">
+        <StackPanel DockPanel.Dock="Right" Spacing="4" Margin="4 0 0 0">
+          <CheckBox IsChecked="{Binding Countries.CellSelection}">Cell Selection</CheckBox>
           <Label Target="countryTextBox">_Country</Label>
           <TextBox Name="countryTextBox">Sealand</TextBox>
           <Label Target="regionTextBox">_Region</Label>
@@ -48,6 +49,11 @@
           <ComboBox ItemsSource="{Binding Files.Drives}"
                     SelectedItem="{Binding Files.SelectedDrive}"
                     DockPanel.Dock="Left"/>
+          <CheckBox IsChecked="{Binding Files.CellSelection}"
+                    Margin="4 0 0 0"
+                    DockPanel.Dock="Right">
+            Cell Selection
+          </CheckBox>
           <TextBox Text="{Binding Files.SelectedPath, Mode=OneWay}"
                    Margin="4 0 0 0"
                    VerticalContentAlignment="Center"

samples/TreeDataGridDemo/ViewModels/CountriesPageViewModel.cs

@@ -3,13 +3,15 @@
 using Avalonia.Controls;
 using Avalonia.Controls.Models.TreeDataGrid;
 using Avalonia.Controls.Selection;
+using ReactiveUI;
 using TreeDataGridDemo.Models;
 
 namespace TreeDataGridDemo.ViewModels
 {
-    internal class CountriesPageViewModel
+    internal class CountriesPageViewModel : ReactiveObject
     {
         private readonly ObservableCollection<Country> _data;
+        private bool _cellSelection;
 
         public CountriesPageViewModel()
         {
@@ -20,8 +22,8 @@ public CountriesPageViewModel()
                 Columns =
                 {
                     new TextColumn<Country, string>("Country", x => x.Name, (r, v) => r.Name = v, new GridLength(6, GridUnitType.Star), new()
-                    { 
-                        IsTextSearchEnabled = true 
+                    {
+                        IsTextSearchEnabled = true
                     }),
                     new TextColumn<Country, string>("Region", x => x.Region, new GridLength(4, GridUnitType.Star)),
                     new TextColumn<Country, int>("Population", x => x.Population, new GridLength(3, GridUnitType.Star)),
@@ -35,6 +37,23 @@ public CountriesPageViewModel()
             Source.RowSelection!.SingleSelect = false;
         }
 
+        public bool CellSelection
+        {
+            get => _cellSelection;
+            set
+            {
+                if (_cellSelection != value)
+                {
+                    _cellSelection = value;
+                    if (_cellSelection)
+                        Source.Selection = new TreeDataGridCellSelectionModel<Country>(Source) { SingleSelect = false };
+                    else
+                        Source.Selection = new TreeDataGridRowSelectionModel<Country>(Source) { SingleSelect = false };
+                    this.RaisePropertyChanged();
+                }
+            }
+        }
+
         public FlatTreeDataGridSource<Country> Source { get; }
 
         public void AddCountry(Country country) => _data.Add(country);

samples/TreeDataGridDemo/ViewModels/FilesPageViewModel.cs

@@ -20,6 +20,7 @@ namespace TreeDataGridDemo.ViewModels
     public class FilesPageViewModel : ReactiveObject
     {
         private static IconConverter? s_iconConverter;
+        private bool _cellSelection;
         private FileTreeNodeModel? _root;
         private string _selectedDrive;
         private string? _selectedPath;
@@ -94,6 +95,23 @@ public FilesPageViewModel()
                 });
         }
 
+        public bool CellSelection
+        {
+            get => _cellSelection;
+            set
+            {
+                if (_cellSelection != value)
+                {
+                    _cellSelection = value;
+                    if (_cellSelection)
+                        Source.Selection = new TreeDataGridCellSelectionModel<FileTreeNodeModel>(Source) { SingleSelect = false };
+                    else
+                        Source.Selection = new TreeDataGridRowSelectionModel<FileTreeNodeModel>(Source) { SingleSelect = false };
+                    this.RaisePropertyChanged();
+                }
+            }
+        }
+
         public IList<string> Drives { get; }
 
         public string SelectedDrive

src/Avalonia.Controls.TreeDataGrid/Avalonia.Controls.TreeDataGrid.csproj

@@ -2,6 +2,7 @@
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
     <IsPackable>True</IsPackable>
+    <LangVersion>10</LangVersion>
     <RootNamespace>Avalonia.Controls</RootNamespace>
   </PropertyGroup>
   <PropertyGroup>

src/Avalonia.Controls.TreeDataGrid/CellIndex.cs

@@ -0,0 +1,13 @@
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// Represents a cell in a <see cref="TreeDataGrid"/>.
+    /// </summary>
+    /// <param name="ColumnIndex">
+    /// The index of the cell in the <see cref="TreeDataGrid.Columns"/> collection.
+    /// </param>
+    /// <param name="RowIndex">
+    /// The hierarchical index of the row model in the data source.
+    /// </param>
+    public readonly record struct CellIndex(int ColumnIndex, IndexPath RowIndex);
+}

src/Avalonia.Controls.TreeDataGrid/FlatTreeDataGridSource.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Linq;
+using Avalonia.Controls.Models;
 using Avalonia.Controls.Models.TreeDataGrid;
 using Avalonia.Controls.Selection;
 using Avalonia.Input;
@@ -12,8 +13,10 @@ namespace Avalonia.Controls
     /// A data source for a <see cref="TreeDataGrid"/> which displays a flat grid.
     /// </summary>
     /// <typeparam name="TModel">The model type.</typeparam>
-    public class FlatTreeDataGridSource<TModel> : ITreeDataGridSource<TModel>, IDisposable
-        where TModel: class
+    public class FlatTreeDataGridSource<TModel> : NotifyingBase,
+        ITreeDataGridSource<TModel>,
+        IDisposable
+            where TModel: class
     {
         private IEnumerable<TModel> _items;
         private TreeDataGridItemsSourceView<TModel> _itemsView;
@@ -45,6 +48,7 @@ public IEnumerable<TModel> Items
                     _rows?.SetItems(_itemsView);
                     if (_selection is object)
                         _selection.Source = value;
+                    RaisePropertyChanged();
                 }
             }
         }
@@ -59,13 +63,18 @@ public ITreeDataGridSelection? Selection
             }
             set
             {
-                if (_selection is object)
-                    throw new InvalidOperationException("Selection is already initialized.");
-                _selection = value;
-                _isSelectionSet = true;
+                if (_selection != value)
+                {
+                    if (value?.Source != _items)
+                        throw new InvalidOperationException("Selection source must be set to Items.");
+                    _selection = value;
+                    _isSelectionSet = true;
+                    RaisePropertyChanged();
+                }
             }
         }
 
+        public ITreeDataGridCellSelectionModel<TModel>? CellSelection => Selection as ITreeDataGridCellSelectionModel<TModel>;
         public ITreeDataGridRowSelectionModel<TModel>? RowSelection => Selection as ITreeDataGridRowSelectionModel<TModel>;
         public bool IsHierarchical => false;
         public bool IsSorted => _comparer is not null;

src/Avalonia.Controls.TreeDataGrid/HierarchicalTreeDataGridSource.cs

@@ -4,6 +4,7 @@
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using Avalonia.Controls.Models;
 using Avalonia.Controls.Models.TreeDataGrid;
 using Avalonia.Controls.Selection;
 using Avalonia.Input;
@@ -15,7 +16,8 @@ namespace Avalonia.Controls
     /// row may have multiple columns.
     /// </summary>
     /// <typeparam name="TModel">The model type.</typeparam>
-    public class HierarchicalTreeDataGridSource<TModel> : ITreeDataGridSource<TModel>,
+    public class HierarchicalTreeDataGridSource<TModel> : NotifyingBase,
+        ITreeDataGridSource<TModel>,
         IDisposable,
         IExpanderRowController<TModel>
         where TModel: class
@@ -70,13 +72,18 @@ public ITreeDataGridSelection? Selection
             }
             set
             {
-                if (_selection is object)
-                    throw new InvalidOperationException("Selection is already initialized.");
-                _selection = value;
-                _isSelectionSet = true;
+                if (_selection != value)
+                {
+                    if (value?.Source != _items)
+                        throw new InvalidOperationException("Selection source must be set to Items.");
+                    _selection = value;
+                    _isSelectionSet = true;
+                    RaisePropertyChanged();
+                }
             }
         }
 
+        public ITreeDataGridCellSelectionModel<TModel>? CellSelection => Selection as ITreeDataGridCellSelectionModel<TModel>;
         public ITreeDataGridRowSelectionModel<TModel>? RowSelection => Selection as ITreeDataGridRowSelectionModel<TModel>;
         public bool IsHierarchical => true;
         public bool IsSorted => _comparison is not null;

src/Avalonia.Controls.TreeDataGrid/ITreeDataGridSource.cs

@@ -10,7 +10,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// Represents a data source for a <see cref="TreeDataGrid"/> control.
     /// </summary>
-    public interface ITreeDataGridSource
+    public interface ITreeDataGridSource : INotifyPropertyChanged
     {
         /// <summary>
         /// Gets the columns to be displayed.

src/Avalonia.Controls.TreeDataGrid/Primitives/ITreeDataGridCell.cs

@@ -1,12 +1,19 @@
 using Avalonia.Controls.Models.TreeDataGrid;
+using Avalonia.Controls.Selection;
 
 namespace Avalonia.Controls.Primitives
 {
     internal interface ITreeDataGridCell
     {
         int ColumnIndex { get; }
 
-        void Realize(TreeDataGridElementFactory factory, ICell model, int columnIndex, int rowIndex);
+        void Realize(
+            TreeDataGridElementFactory factory,
+            ITreeDataGridSelectionInteraction? selection,
+            ICell model,
+            int columnIndex,
+            int rowIndex);
+
         void Unrealize();
     }
 }