ChatDataGridView.cs

ChatDataGridView.cs

namespace AutoSizeGridDemo
{
    using System;
    using System.ComponentModel;
    using System.Drawing;
    using System.Drawing.Drawing2D;
    using System.Reflection;
    using System.Windows.Forms;

    public partial class Form2 : Form
    {
        private const TextFormatFlags textFormatFlags =
                              TextFormatFlags.TextBoxControl |
                              TextFormatFlags.WordBreak;

        private const int chatIndent = 48;
        private const int borderSize = 1;
        private readonly Padding cellPadding = new Padding(8);
        private readonly Padding bubblePadding = new Padding(4);
        private const int bubbleRadius = 8;
        private readonly Color mineTextColor = Color.White;
        private readonly Color mineBubbleColor = Color.DodgerBlue;
        private readonly Color otherTextColor = Color.Black;
        private readonly Color otherBubbleColor = Color.White;
        private readonly Font proposeFont = new Font("Calibri", 12F, FontStyle.Regular);
        private readonly BindingList<Comment> comments
                                = new BindingList<Comment>();

        class Comment
        {
            public string Text { get; private set; }
            [Browsable(false)] public bool IsMine { get; private set; }
            [Browsable(false)] public Size TextSize { get; private set; }

            private Font ProposeFont;
            private int ProposeWidth;

            public Comment(string text, bool isMine) {
                Text = text;
                IsMine = isMine;
            }

            private bool IsChanged(Font font, int width) {
                if (ProposeFont == null || ProposeFont != font) {
                    return true;
                }
                if (ProposeWidth != width) {
                    return true;
                }
                return false;
            }

            public Size MeasureTextSize(Graphics g, Font font, int width) {
                if (IsChanged(font, width)) {
                    TextSize = TextRenderer.MeasureText(
                                g, Text, font,
                                new Size(width, 1), textFormatFlags);
                    ProposeWidth = width;
                    ProposeFont = font;
                }
                return TextSize;
            }
        }

        public Form2() {
            InitializeComponent();
        }

        private void Form2_Load(object sender, EventArgs e) {
            var pi = typeof(DataGridView).GetProperty("DoubleBuffered",
                            BindingFlags.NonPublic | BindingFlags.Instance);
            if (pi != null) {
                pi.SetValue(dataGridView1, true);
            }
            int index = 1;
            for (int i = 0; i < 250; i++) {
                comments.Add(new Comment($"{index++}: I am creating a chat application using C# window form. But I have a challenge on how to load chat messages using pagination like what skype does that is assuming a chat has 1000 chats I need to first load the last like 50 messages on the TableLayoutPanel.", false));
                comments.Add(new Comment($"{index++}: Wait, I was expecting at a few dozen controls. Creating 1000 controls causes performance issues.", true));
                comments.Add(new Comment($"{index++}: Sorry, I should have suggested another method.", true));
                comments.Add(new Comment($"{index++}: Hmm, It is trouble. DataGridView and ListView are suitable for displaying from the top, but not for displaying from the bottom.", true));
            }
            dataGridView1.DataSource = comments;
            dataGridView1.ScrollBars = ScrollBars.Vertical;
            dataGridView1.AllowUserToAddRows = false;
            dataGridView1.RowHeadersVisible = false;
            dataGridView1.ColumnHeadersVisible = false;
            var column0 = dataGridView1.Columns[0];
            if (column0 != null) {
                column0.Resizable = DataGridViewTriState.False;
                column0.AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;
                column0.ReadOnly = true;
            }
        }

        private void Form2_Shown(object sender, EventArgs e) {
            AdjustHeight(dataGridView1.RowCount - 50);
            dataGridView1.FirstDisplayedScrollingRowIndex
                            = dataGridView1.RowCount - 1;
        }

        private int ProposeWidth {
            get {
                return
                    dataGridView1.ClientSize.Width -
                    SystemInformation.VerticalScrollBarWidth -
                    chatIndent -
                    cellPadding.Horizontal;
            }
        }

        private Font ProposeFont {
            get {
                return proposeFont;
            }
        }

        private void DataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e) {
            if (e.RowIndex > -1 && e.ColumnIndex == 0) {
                DrawCell(e, comments[e.RowIndex]);
                e.Handled = true;
            }
        }

        private void DataGridView1_SizeChanged(object sender, EventArgs e) {
            AdjustDisplay();
        }

        private void DataGridView1_Scroll(object sender, ScrollEventArgs e) {
            AdjustDisplay();
        }

        private void AdjustDisplay() {
            int start = dataGridView1.FirstDisplayedScrollingRowIndex;
            int end = dataGridView1.Rows.GetLastRow(DataGridViewElementStates.Displayed);
            AdjustHeight(start - 10, end + 50);
        }

        private void AdjustHeight(int start) {
            AdjustHeight(start, dataGridView1.RowCount - 1);
        }

        private void AdjustHeight(int start, int end) {
            start = Math.Max(start, 0);
            end = Math.Min(end, dataGridView1.RowCount - 1);
            using (var g = dataGridView1.CreateGraphics()) {
                for (int rowIndex = start; rowIndex <= end; rowIndex++) {
                    var comment = comments[rowIndex];
                    var row = dataGridView1.Rows[rowIndex];
                    var textSize = comment.MeasureTextSize(g, ProposeFont, ProposeWidth);
                    int height = textSize.Height +
                                 cellPadding.Vertical +
                                 bubblePadding.Vertical +
                                 borderSize * 2;
                    if (row.Height != height) {
                        row.Height = height;
                    }
                }
            }
        }

        private void DrawCell(DataGridViewCellPaintingEventArgs e, Comment comment) {
            var text = comment.Text;
            var isMine = comment.IsMine;
            using (var brush = new SolidBrush(dataGridView1.BackgroundColor)) {
                e.Graphics.FillRectangle(brush, e.CellBounds);
            }
            var textSize = comment.TextSize;
            var bubbleSize = new Size(textSize.Width + bubblePadding.Horizontal,
                                      textSize.Height + bubblePadding.Vertical);
            Point bubbleLocation;
            Color bubbleColor;
            Color textColor;
            if (isMine) {
                bubbleLocation = new Point(e.CellBounds.Right - bubbleSize.Width - cellPadding.Right,
                                           e.CellBounds.Top + cellPadding.Top);
                textColor = mineTextColor;
                bubbleColor = mineBubbleColor;
            } else {
                bubbleLocation = new Point(e.CellBounds.Left + cellPadding.Left,
                                           e.CellBounds.Top + cellPadding.Top);
                textColor = otherTextColor;
                bubbleColor = otherBubbleColor;
            }
            Rectangle bubbleArea = new Rectangle(bubbleLocation, bubbleSize);
            FillRoundRectangle(e.Graphics, bubbleArea, bubbleColor);

            Point textLocation = new Point(bubbleLocation.X + bubblePadding.Left,
                                           bubbleLocation.Y + bubblePadding.Top);
            Rectangle textArea = new Rectangle(textLocation, textSize);
            TextRenderer.DrawText(
                        e.Graphics, text, ProposeFont,
                        textArea, textColor, textFormatFlags);
        }

        private static void FillRoundRectangle(Graphics g, Rectangle bounds, Color color) {
            using (var path = GetRoundedRectangle(bounds))
            using (var brush = new SolidBrush(color)) {
                g.FillPath(brush, path);
            }
        }

        private static GraphicsPath GetRoundedRectangle(Rectangle bounds) {
            GraphicsPath path = new GraphicsPath();
            path.AddArc(bounds.X, bounds.Y, bubbleRadius * 2, bubbleRadius * 2, 180, 90);
            path.AddArc(bounds.Right - bubbleRadius * 2, bounds.Y, bubbleRadius * 2, bubbleRadius * 2, 270, 90);
            path.AddArc(bounds.Right - bubbleRadius * 2, bounds.Bottom - bubbleRadius * 2, bubbleRadius * 2, bubbleRadius * 2, 0, 90);
            path.AddArc(bounds.X, bounds.Bottom - bubbleRadius * 2, bubbleRadius * 2, bubbleRadius * 2, 90, 90);
            path.CloseFigure();
            return path;
        }
    }
}