HtmlContainer.cs

// "Therefore those skilled at the unorthodox
// are infinite as heaven and earth,
// inexhaustible as the great rivers.
// When they come to an end,
// they begin again,
// like the days and months;
// they die and are reborn,
// like the four seasons."
// 
// - Sun Tsu,
// "The Art of War"

using System;
using System.Collections.Generic;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Html;
using Avalonia.Input;
using Avalonia.Media;
using TheArtOfDev.HtmlRenderer.Adapters.Entities;
using TheArtOfDev.HtmlRenderer.Core;
using TheArtOfDev.HtmlRenderer.Core.Entities;
using TheArtOfDev.HtmlRenderer.Core.Parse;
using TheArtOfDev.HtmlRenderer.Core.Utils;
using TheArtOfDev.HtmlRenderer.Avalonia.Adapters;
using TheArtOfDev.HtmlRenderer.Avalonia.Utilities;

namespace TheArtOfDev.HtmlRenderer.Avalonia
{
    /// <summary>
    /// Low level handling of Html Renderer logic, this class is used by <see cref="HtmlParser"/>, 
    /// <see cref="HtmlLabel"/>, <see cref="HtmlToolTip"/> and <see cref="HtmlRender"/>.<br/>
    /// </summary>
    /// <seealso cref="HtmlContainerInt"/>
    public sealed class HtmlContainer : IDisposable
    {
        #region Fields and Consts

        /// <summary>
        /// The internal core html container
        /// </summary>
        private readonly HtmlContainerInt _htmlContainerInt;

        #endregion


        /// <summary>
        /// Init.
        /// </summary>
        public HtmlContainer()
        {
            _htmlContainerInt = new HtmlContainerInt(AvaloniaAdapter.Instance);
        }

        /// <summary>
        /// Raised when the set html document has been fully loaded.<br/>
        /// Allows manipulation of the html dom, scroll position, etc.
        /// </summary>
        public event EventHandler LoadComplete
        {
            add { _htmlContainerInt.LoadComplete += value; }
            remove { _htmlContainerInt.LoadComplete -= value; }
        }

        /// <summary>
        /// Raised when the user clicks on a link in the html.<br/>
        /// Allows canceling the execution of the link.
        /// </summary>
        public event EventHandler<HtmlLinkClickedEventArgs> LinkClicked
        {
            add { _htmlContainerInt.LinkClicked += value; }
            remove { _htmlContainerInt.LinkClicked -= value; }
        }

        /// <summary>
        /// Raised when html renderer requires refresh of the control hosting (invalidation and re-layout).
        /// </summary>
        /// <remarks>
        /// There is no guarantee that the event will be raised on the main thread, it can be raised on thread-pool thread.
        /// </remarks>
        public event EventHandler<HtmlRefreshEventArgs> Refresh
        {
            add { _htmlContainerInt.Refresh += value; }
            remove { _htmlContainerInt.Refresh -= value; }
        }

        /// <summary>
        /// Raised when Html Renderer request scroll to specific location.<br/>
        /// This can occur on document anchor click.
        /// </summary>
        public event EventHandler<HtmlScrollEventArgs> ScrollChange
        {
            add { _htmlContainerInt.ScrollChange += value; }
            remove { _htmlContainerInt.ScrollChange -= value; }
        }

        /// <summary>
        /// Raised when an error occurred during html rendering.<br/>
        /// </summary>
        /// <remarks>
        /// There is no guarantee that the event will be raised on the main thread, it can be raised on thread-pool thread.
        /// </remarks>
        public event EventHandler<HtmlRenderErrorEventArgs> RenderError
        {
            add { _htmlContainerInt.RenderError += value; }
            remove { _htmlContainerInt.RenderError -= value; }
        }

        /// <summary>
        /// Raised when a stylesheet is about to be loaded by file path or URI by link element.<br/>
        /// This event allows to provide the stylesheet manually or provide new source (file or Uri) to load from.<br/>
        /// If no alternative data is provided the original source will be used.<br/>
        /// </summary>
        public event EventHandler<HtmlStylesheetLoadEventArgs> StylesheetLoad
        {
            add { _htmlContainerInt.StylesheetLoad += value; }
            remove { _htmlContainerInt.StylesheetLoad -= value; }
        }

        /// <summary>
        /// Raised when an image is about to be loaded by file path or URI.<br/>
        /// This event allows to provide the image manually, if not handled the image will be loaded from file or download from URI.
        /// </summary>
        public event EventHandler<HtmlImageLoadEventArgs> ImageLoad
        {
            add { _htmlContainerInt.ImageLoad += value; }
            remove { _htmlContainerInt.ImageLoad -= value; }
        }

        /// <summary>
        /// The internal core html container
        /// </summary>
        internal HtmlContainerInt HtmlContainerInt
        {
            get { return _htmlContainerInt; }
        }

        /// <summary>
        /// the parsed stylesheet data used for handling the html
        /// </summary>
        public CssData CssData
        {
            get { return _htmlContainerInt.CssData; }
        }

        /// <summary>
        /// Gets or sets a value indicating if image asynchronous loading should be avoided (default - false).<br/>
        /// True - images are loaded synchronously during html parsing.<br/>
        /// False - images are loaded asynchronously to html parsing when downloaded from URL or loaded from disk.<br/>
        /// </summary>
        /// <remarks>
        /// Asynchronously image loading allows to unblock html rendering while image is downloaded or loaded from disk using IO 
        /// ports to achieve better performance.<br/>
        /// Asynchronously image loading should be avoided when the full html content must be available during render, like render to image.
        /// </remarks>
        public bool AvoidAsyncImagesLoading
        {
            get { return _htmlContainerInt.AvoidAsyncImagesLoading; }
            set { _htmlContainerInt.AvoidAsyncImagesLoading = value; }
        }

        /// <summary>
        /// Gets or sets a value indicating if image loading only when visible should be avoided (default - false).<br/>
        /// True - images are loaded as soon as the html is parsed.<br/>
        /// False - images that are not visible because of scroll location are not loaded until they are scrolled to.
        /// </summary>
        /// <remarks>
        /// Images late loading improve performance if the page contains image outside the visible scroll area, especially if there is large 
        /// amount of images, as all image loading is delayed (downloading and loading into memory).<br/>
        /// Late image loading may effect the layout and actual size as image without set size will not have actual size until they are loaded
        /// resulting in layout change during user scroll.<br/>
        /// Early image loading may also effect the layout if image without known size above the current scroll location are loaded as they
        /// will push the html elements down.
        /// </remarks>
        public bool AvoidImagesLateLoading
        {
            get { return _htmlContainerInt.AvoidImagesLateLoading; }
            set { _htmlContainerInt.AvoidImagesLateLoading = value; }
        }

        /// <summary>
        /// Is content selection is enabled for the rendered html (default - true).<br/>
        /// If set to 'false' the rendered html will be static only with ability to click on links.
        /// </summary>
        public bool IsSelectionEnabled
        {
            get { return _htmlContainerInt.IsSelectionEnabled; }
            set { _htmlContainerInt.IsSelectionEnabled = value; }
        }

        /// <summary>
        /// Is the build-in context menu enabled and will be shown on mouse right click (default - true)
        /// </summary>
        public bool IsContextMenuEnabled
        {
            get { return _htmlContainerInt.IsContextMenuEnabled; }
            set { _htmlContainerInt.IsContextMenuEnabled = value; }
        }

        /// <summary>
        /// The scroll offset of the html.<br/>
        /// This will adjust the rendered html by the given offset so the content will be "scrolled".<br/>
        /// </summary>
        /// <example>
        /// Element that is rendered at location (50,100) with offset of (0,200) will not be rendered as it
        /// will be at -100 therefore outside the client Rect.
        /// </example>
        public Point ScrollOffset
        {
            get { return Util.Convert(_htmlContainerInt.ScrollOffset); }
            set { _htmlContainerInt.ScrollOffset = Util.Convert(value); }
        }

        /// <summary>
        /// The top-left most location of the rendered html.<br/>
        /// This will offset the top-left corner of the rendered html.
        /// </summary>
        public Point Location
        {
            get { return Util.Convert(_htmlContainerInt.Location); }
            set { _htmlContainerInt.Location = Util.Convert(value); }
        }

        /// <summary>
        /// The max width and height of the rendered html.<br/>
        /// The max width will effect the html layout wrapping lines, resize images and tables where possible.<br/>
        /// The max height does NOT effect layout, but will not render outside it (clip).<br/>
        /// <see cref="ActualSize"/> can be exceed the max size by layout restrictions (unwrappable line, set image size, etc.).<br/>
        /// Set zero for unlimited (width\height separately).<br/>
        /// </summary>
        public Size MaxSize
        {
            get { return Util.Convert(_htmlContainerInt.MaxSize); }
            set { _htmlContainerInt.MaxSize = Util.Convert(value); }
        }

        /// <summary>
        /// The actual size of the rendered html (after layout)
        /// </summary>
        public Size ActualSize
        {
            get { return Util.Convert(_htmlContainerInt.ActualSize); }
            internal set { _htmlContainerInt.ActualSize = Util.Convert(value); }
        }

        /// <summary>
        /// Get the currently selected text segment in the html.
        /// </summary>
        public string SelectedText
        {
            get { return _htmlContainerInt.SelectedText; }
        }

        /// <summary>
        /// Copy the currently selected html segment with style.
        /// </summary>
        public string SelectedHtml
        {
            get { return _htmlContainerInt.SelectedHtml; }
        }

        /// <summary>
        /// Clear the current selection.
        /// </summary>
        public void ClearSelection()
        {
            HtmlContainerInt.ClearSelection();
        }

        /// <summary>
        /// Init with optional document and stylesheet.
        /// </summary>
        /// <param name="htmlSource">the html to init with, init empty if not given</param>
        /// <param name="baseCssData">optional: the stylesheet to init with, init default if not given</param>
        public void SetHtml(string htmlSource, CssData baseCssData = null)
        {
            _htmlContainerInt.SetHtml(htmlSource, baseCssData);
        }

        /// <summary>
        /// Clear the content of the HTML container releasing any resources used to render previously existing content.
        /// </summary>
        public void Clear()
        {
            _htmlContainerInt.Clear();
        }

        /// <summary>
        /// Get html from the current DOM tree with style if requested.
        /// </summary>
        /// <param name="styleGen">Optional: controls the way styles are generated when html is generated (default: <see cref="HtmlGenerationStyle.Inline"/>)</param>
        /// <returns>generated html</returns>
        public string GetHtml(HtmlGenerationStyle styleGen = HtmlGenerationStyle.Inline)
        {
            return _htmlContainerInt.GetHtml(styleGen);
        }

        /// <summary>
        /// Get attribute value of element at the given x,y location by given key.<br/>
        /// If more than one element exist with the attribute at the location the inner most is returned.
        /// </summary>
        /// <param name="location">the location to find the attribute at</param>
        /// <param name="attribute">the attribute key to get value by</param>
        /// <returns>found attribute value or null if not found</returns>
        public string GetAttributeAt(Point location, string attribute)
        {
            return _htmlContainerInt.GetAttributeAt(Util.Convert(location), attribute);
        }

        /// <summary>
        /// Get all the links in the HTML with the element Rect and href data.
        /// </summary>
        /// <returns>collection of all the links in the HTML</returns>
        public List<LinkElementData<Rect>> GetLinks()
        {
            var linkElements = new List<LinkElementData<Rect>>();
            foreach (var link in HtmlContainerInt.GetLinks())
            {
                linkElements.Add(new LinkElementData<Rect>(link.Id, link.Href, Util.Convert(link.Rectangle)));
            }
            return linkElements;
        }

        /// <summary>
        /// Get css link href at the given x,y location.
        /// </summary>
        /// <param name="location">the location to find the link at</param>
        /// <returns>css link href if exists or null</returns>
        public string GetLinkAt(Point location)
        {
            return _htmlContainerInt.GetLinkAt(Util.Convert(location));
        }

        /// <summary>
        /// Get the Rect of html element as calculated by html layout.<br/>
        /// Element if found by id (id attribute on the html element).<br/>
        /// Note: to get the screen Rect you need to adjust by the hosting control.<br/>
        /// </summary>
        /// <param name="elementId">the id of the element to get its Rect</param>
        /// <returns>the Rect of the element or null if not found</returns>
        public Rect? GetElementRectangle(string elementId)
        {
            var r = _htmlContainerInt.GetElementRectangle(elementId);
            return r.HasValue ? Util.Convert(r.Value) : (Rect?)null;
        }

        /// <summary>
        /// Measures the bounds of box and children, recursively.
        /// </summary>
        public void PerformLayout()
        {
            using (var ig = new GraphicsAdapter())
            {
                _htmlContainerInt.PerformLayout(ig);
            }
        }

        /// <summary>
        /// Render the html using the given device.
        /// </summary>
        /// <param name="g">the device to use to render</param>
        /// <param name="clip">the clip rectangle of the html container</param>
        public void PerformPaint(DrawingContext g, Rect clip)
        {
            ArgChecker.AssertArgNotNull(g, "g");

            using (var ig = new GraphicsAdapter(g, Util.Convert(clip)))
            {
                _htmlContainerInt.PerformPaint(ig);
            }
        }

        /// <summary>
        /// Handle mouse down to handle selection.
        /// </summary>
        /// <param name="parent">the control hosting the html to invalidate</param>
        /// <param name="e">the mouse event args</param>
        public void HandleLeftMouseDown(Control parent, PointerEventArgs e)
        {
            ArgChecker.AssertArgNotNull(parent, "parent");
            ArgChecker.AssertArgNotNull(e, "e");
            
            _htmlContainerInt.HandleMouseDown(new ControlAdapter(parent), Util.Convert(e.GetPosition(parent)));
        }

        /// <summary>
        /// Handle mouse up to handle selection and link click.
        /// </summary>
        /// <param name="parent">the control hosting the html to invalidate</param>
        /// <param name="e">the mouse event args</param>
        public void HandleLeftMouseUp(Control parent, PointerEventArgs e)
        {
            ArgChecker.AssertArgNotNull(parent, "parent");
            ArgChecker.AssertArgNotNull(e, "e");

            var mouseEvent = new RMouseEvent(true);
            _htmlContainerInt.HandleMouseUp(new ControlAdapter(parent), Util.Convert(e.GetPosition(parent)), mouseEvent);
        }

        /// <summary>
        /// Handle mouse double click to select word under the mouse.
        /// </summary>
        /// <param name="parent">the control hosting the html to set cursor and invalidate</param>
        /// <param name="e">mouse event args</param>
        public void HandleMouseDoubleClick(Control parent, PointerEventArgs e)
        {
            ArgChecker.AssertArgNotNull(parent, "parent");
            ArgChecker.AssertArgNotNull(e, "e");

            _htmlContainerInt.HandleMouseDoubleClick(new ControlAdapter(parent), Util.Convert(e.GetPosition(parent)));
        }

        /// <summary>
        /// Handle mouse move to handle hover cursor and text selection.
        /// </summary>
        /// <param name="parent">the control hosting the html to set cursor and invalidate</param>
        /// <param name="mousePos">the mouse event args</param>
        public void HandleMouseMove(Control parent, Point mousePos)
        {
            ArgChecker.AssertArgNotNull(parent, "parent");

            _htmlContainerInt.HandleMouseMove(new ControlAdapter(parent), Util.Convert(mousePos));
        }

        /// <summary>
        /// Handle mouse leave to handle hover cursor.
        /// </summary>
        /// <param name="parent">the control hosting the html to set cursor and invalidate</param>
        public void HandleMouseLeave(Control parent)
        {
            ArgChecker.AssertArgNotNull(parent, "parent");

            _htmlContainerInt.HandleMouseLeave(new ControlAdapter(parent));
        }

        /// <summary>
        /// Handle key down event for selection and copy.
        /// </summary>
        /// <param name="parent">the control hosting the html to invalidate</param>
        /// <param name="e">the pressed key</param>
        public void HandleKeyDown(Control parent, KeyEventArgs e)
        {
            ArgChecker.AssertArgNotNull(parent, "parent");
            ArgChecker.AssertArgNotNull(e, "e");

            _htmlContainerInt.HandleKeyDown(new ControlAdapter(parent), CreateKeyEevent(e));
        }

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            _htmlContainerInt.Dispose();
        }


        #region Private methods

        /// <summary>
        /// Create HtmlRenderer key event from Avalonia key event.
        /// </summary>
        private static RKeyEvent CreateKeyEevent(KeyEventArgs e)
        {
            var control = (e.Modifiers & InputModifiers.Control) == InputModifiers.Control;
            return new RKeyEvent(control, e.Key == Key.A, e.Key == Key.C);
        }

        #endregion
    }
}