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[API Proposal]: Add ReadOnlySpan<char> overloads to System.Drawing.Graphics

See original GitHub issue

Background and motivation

When drawing strings manually in WinForms, new text is frequently created. Since the methods System.Drawing.Graphics and System.Drawing.GraphicsPath only accept strings String allocations occur frequently.

It would be better to add an overload that accepts ReadOnlySpan<char> so that the buffer can be passed directly.

API Proposal

namespace System.Drawing
{
    public sealed partial class Graphics : System.MarshalByRefObject, System.Drawing.IDeviceContext, System.IDisposable
    {
        // Existing:
        public void DrawString(string? s, System.Drawing.Font font, System.Drawing.Brush brush, System.Drawing.PointF point) { }
        public void DrawString(string? s, System.Drawing.Font font, System.Drawing.Brush brush, System.Drawing.PointF point, System.Drawing.StringFormat? format) { }
        public void DrawString(string? s, System.Drawing.Font font, System.Drawing.Brush brush, System.Drawing.RectangleF layoutRectangle) { }
        public void DrawString(string? s, System.Drawing.Font font, System.Drawing.Brush brush, System.Drawing.RectangleF layoutRectangle, System.Drawing.StringFormat? format) { }
        public void DrawString(string? s, System.Drawing.Font font, System.Drawing.Brush brush, float x, float y) { }
        public void DrawString(string? s, System.Drawing.Font font, System.Drawing.Brush brush, float x, float y, System.Drawing.StringFormat? format) { }
        public System.Drawing.Region[] MeasureCharacterRanges(string? text, System.Drawing.Font font, System.Drawing.RectangleF layoutRect, System.Drawing.StringFormat? stringFormat) { throw null; }
        public System.Drawing.SizeF MeasureString(string? text, System.Drawing.Font font) { throw null; }
        public System.Drawing.SizeF MeasureString(string? text, System.Drawing.Font font, System.Drawing.PointF origin, System.Drawing.StringFormat? stringFormat) { throw null; }
        public System.Drawing.SizeF MeasureString(string? text, System.Drawing.Font font, System.Drawing.SizeF layoutArea) { throw null; }
        public System.Drawing.SizeF MeasureString(string? text, System.Drawing.Font font, System.Drawing.SizeF layoutArea, System.Drawing.StringFormat? stringFormat) { throw null; }
        public System.Drawing.SizeF MeasureString(string? text, System.Drawing.Font font, System.Drawing.SizeF layoutArea, System.Drawing.StringFormat? stringFormat, out int charactersFitted, out int linesFilled) { throw null; }
        public System.Drawing.SizeF MeasureString(string? text, System.Drawing.Font font, int width) { throw null; }
        public System.Drawing.SizeF MeasureString(string? text, System.Drawing.Font font, int width, System.Drawing.StringFormat? format) { throw null; }

        // Proposal
        public void DrawString(ReadOnlySpan<char> s, System.Drawing.Font font, System.Drawing.Brush brush, System.Drawing.PointF point) { }
        public void DrawString(ReadOnlySpan<char> s, System.Drawing.Font font, System.Drawing.Brush brush, System.Drawing.PointF point, System.Drawing.StringFormat? format) { }
        public void DrawString(ReadOnlySpan<char> s, System.Drawing.Font font, System.Drawing.Brush brush, System.Drawing.RectangleF layoutRectangle) { }
        public void DrawString(ReadOnlySpan<char> s, System.Drawing.Font font, System.Drawing.Brush brush, System.Drawing.RectangleF layoutRectangle, System.Drawing.StringFormat? format) { }
        public void DrawString(ReadOnlySpan<char> s, System.Drawing.Font font, System.Drawing.Brush brush, float x, float y) { }
        public void DrawString(ReadOnlySpan<char> s, System.Drawing.Font font, System.Drawing.Brush brush, float x, float y, System.Drawing.StringFormat? format) { }
        public System.Drawing.Region[] MeasureCharacterRanges(ReadOnlySpan<char> text, System.Drawing.Font font, System.Drawing.RectangleF layoutRect, System.Drawing.StringFormat? stringFormat) { throw null; }
        public System.Drawing.SizeF MeasureString(ReadOnlySpan<char> text, System.Drawing.Font font) { throw null; }
        public System.Drawing.SizeF MeasureString(ReadOnlySpan<char> text, System.Drawing.Font font, System.Drawing.PointF origin, System.Drawing.StringFormat? stringFormat) { throw null; }
        public System.Drawing.SizeF MeasureString(ReadOnlySpan<char> text, System.Drawing.Font font, System.Drawing.SizeF layoutArea) { throw null; }
        public System.Drawing.SizeF MeasureString(ReadOnlySpan<char> text, System.Drawing.Font font, System.Drawing.SizeF layoutArea, System.Drawing.StringFormat? stringFormat) { throw null; }
        public System.Drawing.SizeF MeasureString(ReadOnlySpan<char> text, System.Drawing.Font font, System.Drawing.SizeF layoutArea, System.Drawing.StringFormat? stringFormat, out int charactersFitted, out int linesFilled) { throw null; }
        public System.Drawing.SizeF MeasureString(ReadOnlySpan<char> text, System.Drawing.Font font, int width) { throw null; }
        public System.Drawing.SizeF MeasureString(ReadOnlySpan<char> text, System.Drawing.Font font, int width, System.Drawing.StringFormat? format) { throw null; }
    }

    public sealed partial class GraphicsPath : System.MarshalByRefObject, System.ICloneable, System.IDisposable
    {
        // Existing:
        public void AddString(string s, System.Drawing.FontFamily family, int style, float emSize, System.Drawing.Point origin, System.Drawing.StringFormat? format) { }
        public void AddString(string s, System.Drawing.FontFamily family, int style, float emSize, System.Drawing.PointF origin, System.Drawing.StringFormat? format) { }
        public void AddString(string s, System.Drawing.FontFamily family, int style, float emSize, System.Drawing.Rectangle layoutRect, System.Drawing.StringFormat? format) { }
        public void AddString(string s, System.Drawing.FontFamily family, int style, float emSize, System.Drawing.RectangleF layoutRect, System.Drawing.StringFormat? format) { }

        // Proposal
        public void AddString(ReadOnlySpan<char> s, System.Drawing.FontFamily family, int style, float emSize, System.Drawing.Point origin, System.Drawing.StringFormat? format) { }
        public void AddString(ReadOnlySpan<char> s, System.Drawing.FontFamily family, int style, float emSize, System.Drawing.PointF origin, System.Drawing.StringFormat? format) { }
        public void AddString(ReadOnlySpan<char> s, System.Drawing.FontFamily family, int style, float emSize, System.Drawing.Rectangle layoutRect, System.Drawing.StringFormat? format) { }
        public void AddString(ReadOnlySpan<char> s, System.Drawing.FontFamily family, int style, float emSize, System.Drawing.RectangleF layoutRect, System.Drawing.StringFormat? format) { }
    }
}

API Usage

It is possible to pass buffers on the stack.

GraphicsPath gp = new GraphicsPath();
...
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    var g = e.Graphics;
    Span<char> buf = stackalloc char[512];
    DateTime.Now.TryFormat(buf, out var writtern);
    g.DrawString(buf, ...);

    gp.AddString(buf, ...);
}

Alternative Designs

I can’t think of any.

Risks

I can’t think of any.

Issue Analytics

State:
Created a year ago
Reactions:4
Comments:9 (7 by maintainers)

Top GitHub Comments

2reactions

JeremyKuhnecommented, Jun 2, 2022

Seems rational. Would just need to double check that the underlying GDI+ APIs all take a length (and not a null-terminated string). I believe that is the case…

0reactions

Philip-Wang01commented, Mar 30, 2023

Verified this on .NET 8.0 latest build: 8.0.100-preview.4.23179.4, has been added ReadOnlySpan<char> overloads to Graphics.DrawString.

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