C# DataGridView: Long Text Truncated with “…” on the Left Side When the Column is Right-Aligned

Question

I have a question about the cell truncation (replaced with \"...\"):

How to display the replacement \"...\" on the left side of a cell when the column is right-align

Answer 1

I've ended up implementing this by creating my own DataGridViewLeftCropTextBoxCell. Unfortunately DataGridViewTextBoxCell::Paint is bit a complicated method Reference Source .NET Framework 4.5.2 which uses many .NETs internal methods.

But at first I let base class draw background and borders (and if there's no sensible foreground, just leave it).

Then measure text and shrink it until it fits value bounds.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing;

namespace Project
{
    public class DataGridViewLeftCropTextBoxCell : DataGridViewTextBoxCell
    {

        /// 

        /// Paints contents
        /// 
        /// 
        /// 
        /// 
        /// 
        /// 
        /// 
        /// 
        /// 
        /// 
        /// 
        /// 
        protected override void Paint( Graphics graphics, Rectangle clipBounds, Rectangle cellBounds, int rowIndex, DataGridViewElementStates cellState, object value, object formattedValue, string errorText, DataGridViewCellStyle cellStyle, DataGridViewAdvancedBorderStyle advancedBorderStyle, DataGridViewPaintParts paintParts )
        {
            string formattedString = formattedValue as string;

            // Nothing to draw
            if (String.IsNullOrEmpty( formattedString )) {
                base.Paint( graphics, clipBounds, cellBounds, rowIndex, cellState, value, formattedValue, errorText, cellStyle, advancedBorderStyle, paintParts );
                return;
            }

            // Draw parently without foreground
            base.Paint( graphics, clipBounds, cellBounds, rowIndex, cellState, value, formattedValue, errorText, cellStyle, advancedBorderStyle, paintParts & ~DataGridViewPaintParts.ContentForeground );

            // No foreground?
            if ((paintParts & DataGridViewPaintParts.ContentForeground) == DataGridViewPaintParts.None) {
                return;
            }

            // Calculate value bounds
            Rectangle borderWidths = BorderWidths( advancedBorderStyle );
            Rectangle valBounds = cellBounds;
            valBounds.Offset( borderWidths.X, borderWidths.Y );
            valBounds.Width -= borderWidths.Right;
            valBounds.Height -= borderWidths.Bottom;

            bool cellSelected = (cellState & DataGridViewElementStates.Selected) != 0;

            // Prepare text flags
            TextFormatFlags flags = ComputeTextFormatFlagsForCellStyleAlignment( this.DataGridView.RightToLeft == RightToLeft.Yes, cellStyle.Alignment, cellStyle.WrapMode );
            if ((flags & TextFormatFlags.SingleLine) != 0) {
                flags |= TextFormatFlags.EndEllipsis;
            }

            // Prepare size of text
            Size s = TextRenderer.MeasureText( graphics,
                formattedString,
                cellStyle.Font
            );

            // Text fits into bounds, just append
            if (s.Width < valBounds.Width) {
                TextRenderer.DrawText( graphics,
                    formattedString,
                    cellStyle.Font,
                    valBounds,
                    cellSelected ? cellStyle.SelectionForeColor : cellStyle.ForeColor,
                    flags );
                return;
            }

            // Prepare 
            StringBuilder truncated = new StringBuilder( formattedString );
            truncated.Insert( 0, "..." );

            // Truncate the string until it's small enough 
            while ((s.Width > valBounds.Width) && (truncated.Length > 5)) {
                truncated.Remove( 3, 1 );
                formattedString = truncated.ToString();
                s = TextRenderer.MeasureText( graphics,
                    formattedString,
                    cellStyle.Font
                );
            }

            TextRenderer.DrawText( graphics,
                formattedString,
                cellStyle.Font,
                valBounds,
                cellSelected ? cellStyle.SelectionForeColor : cellStyle.ForeColor,
                flags
            );
        }
    }
}

And you can also create your own column type:

class DataGridViewLeftCropTextBoxColumn : DataGridViewTextBoxColumn
{
    public override DataGridViewCell CellTemplate
    {
        get { return new DataGridViewLeftCropTextBoxCell(); }
        set { base.CellTemplate = value; }
    }
}

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I've borrowed text shrinking from steinar's answer and TextFormatFlags ComputeTextFormatFlagsForCellStyleAlignment from .NET Framework Reference Source.