GridSplitter.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using System.Reflection;
using Microsoft.Toolkit.Uwp.Extensions;
using Windows.ApplicationModel.Resources;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Automation;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Input;

namespace Microsoft.Toolkit.Uwp.UI.Controls
{
    /// <summary>
    /// Represents the control that redistributes space between columns or rows of a Grid control.
    /// </summary>
    public partial class GridSplitter : Control
    {
        internal const int GripperCustomCursorDefaultResource = -1;
        internal static readonly CoreCursor ColumnsSplitterCursor = new CoreCursor(CoreCursorType.SizeWestEast, 1);
        internal static readonly CoreCursor RowSplitterCursor = new CoreCursor(CoreCursorType.SizeNorthSouth, 1);

        internal CoreCursor PreviousCursor { get; set; }

        private GridResizeDirection _resizeDirection;
        private GridResizeBehavior _resizeBehavior;
        private GripperHoverWrapper _hoverWrapper;
        private TextBlock _gripperDisplay;

        private bool _pressed = false;
        private bool _dragging = false;
        private bool _pointerEntered = false;

        /// <summary>
        /// Gets the target parent grid from level
        /// </summary>
        private FrameworkElement TargetControl
        {
            get
            {
                if (ParentLevel == 0)
                {
                    return this;
                }

                var parent = Parent;
                for (int i = 2; i < ParentLevel; i++)
                {
                    var frameworkElement = parent as FrameworkElement;
                    if (frameworkElement != null)
                    {
                        parent = frameworkElement.Parent;
                    }
                }

                return parent as FrameworkElement;
            }
        }

        /// <summary>
        /// Gets GridSplitter Container Grid
        /// </summary>
        private Grid Resizable => TargetControl?.Parent as Grid;

        /// <summary>
        /// Gets the current Column definition of the parent Grid
        /// </summary>
        private ColumnDefinition CurrentColumn
        {
            get
            {
                if (Resizable == null)
                {
                    return null;
                }

                var gridSplitterTargetedColumnIndex = GetTargetedColumn();

                if ((gridSplitterTargetedColumnIndex >= 0)
                    && (gridSplitterTargetedColumnIndex < Resizable.ColumnDefinitions.Count))
                {
                    return Resizable.ColumnDefinitions[gridSplitterTargetedColumnIndex];
                }

                return null;
            }
        }

        /// <summary>
        /// Gets the Sibling Column definition of the parent Grid
        /// </summary>
        private ColumnDefinition SiblingColumn
        {
            get
            {
                if (Resizable == null)
                {
                    return null;
                }

                var gridSplitterSiblingColumnIndex = GetSiblingColumn();

                if ((gridSplitterSiblingColumnIndex >= 0)
                    && (gridSplitterSiblingColumnIndex < Resizable.ColumnDefinitions.Count))
                {
                    return Resizable.ColumnDefinitions[gridSplitterSiblingColumnIndex];
                }

                return null;
            }
        }

        /// <summary>
        /// Gets the current Row definition of the parent Grid
        /// </summary>
        private RowDefinition CurrentRow
        {
            get
            {
                if (Resizable == null)
                {
                    return null;
                }

                var gridSplitterTargetedRowIndex = GetTargetedRow();

                if ((gridSplitterTargetedRowIndex >= 0)
                    && (gridSplitterTargetedRowIndex < Resizable.RowDefinitions.Count))
                {
                    return Resizable.RowDefinitions[gridSplitterTargetedRowIndex];
                }

                return null;
            }
        }

        /// <summary>
        /// Gets the Sibling Row definition of the parent Grid
        /// </summary>
        private RowDefinition SiblingRow
        {
            get
            {
                if (Resizable == null)
                {
                    return null;
                }

                var gridSplitterSiblingRowIndex = GetSiblingRow();

                if ((gridSplitterSiblingRowIndex >= 0)
                    && (gridSplitterSiblingRowIndex < Resizable.RowDefinitions.Count))
                {
                    return Resizable.RowDefinitions[gridSplitterSiblingRowIndex];
                }

                return null;
            }
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="GridSplitter"/> class.
        /// </summary>
        public GridSplitter()
        {
            DefaultStyleKey = typeof(GridSplitter);
            Loaded += GridSplitter_Loaded;
            string automationName = "WCT_GridSplitter_AutomationName".GetLocalized("Microsoft.Toolkit.Uwp.UI.Controls/Resources");
            AutomationProperties.SetName(this, automationName);
        }

        /// <inheritdoc />
        protected override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            // Unhook registered events
            Loaded -= GridSplitter_Loaded;
            PointerEntered -= GridSplitter_PointerEntered;
            PointerExited -= GridSplitter_PointerExited;
            PointerPressed -= GridSplitter_PointerPressed;
            PointerReleased -= GridSplitter_PointerReleased;
            ManipulationStarted -= GridSplitter_ManipulationStarted;
            ManipulationCompleted -= GridSplitter_ManipulationCompleted;

            _hoverWrapper?.UnhookEvents();

            // Register Events
            Loaded += GridSplitter_Loaded;
            PointerEntered += GridSplitter_PointerEntered;
            PointerExited += GridSplitter_PointerExited;
            PointerPressed += GridSplitter_PointerPressed;
            PointerReleased += GridSplitter_PointerReleased;
            ManipulationStarted += GridSplitter_ManipulationStarted;
            ManipulationCompleted += GridSplitter_ManipulationCompleted;

            _hoverWrapper?.UpdateHoverElement(Element);

            ManipulationMode = ManipulationModes.TranslateX | ManipulationModes.TranslateY;
        }

        private void GridSplitter_PointerReleased(object sender, PointerRoutedEventArgs e)
        {
            _pressed = false;
            VisualStateManager.GoToState(this, _pointerEntered ? "PointerOver" : "Normal", true);
        }

        private void GridSplitter_PointerPressed(object sender, PointerRoutedEventArgs e)
        {
            _pressed = true;
            VisualStateManager.GoToState(this, "Pressed", true);
        }

        private void GridSplitter_PointerExited(object sender, PointerRoutedEventArgs e)
        {
            _pointerEntered = false;

            if (!_pressed && !_dragging)
            {
                VisualStateManager.GoToState(this, "Normal", true);
            }
        }

        private void GridSplitter_PointerEntered(object sender, PointerRoutedEventArgs e)
        {
            _pointerEntered = true;

            if (!_pressed && !_dragging)
            {
                VisualStateManager.GoToState(this, "PointerOver", true);
            }
        }

        private void GridSplitter_ManipulationCompleted(object sender, ManipulationCompletedRoutedEventArgs e)
        {
            _dragging = false;
            _pressed = false;
            VisualStateManager.GoToState(this, _pointerEntered ? "PointerOver" : "Normal", true);
        }

        private void GridSplitter_ManipulationStarted(object sender, ManipulationStartedRoutedEventArgs e)
        {
            _dragging = true;
            VisualStateManager.GoToState(this, "Pressed", true);
        }
    }
}