Skip to content

Make Postscript renderer deterministic #643

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Shane32 merged 1 commit into from
Oct 6, 2025
Merged

Make Postscript renderer deterministic #643

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
133 changes: 70 additions & 63 deletions QRCoder/PostscriptQRCode.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -101,7 +101,7 @@ public string GetGraphic(Size viewBox, Color darkColor, Color lightColor, bool d
var pointsPerModule = (double)Math.Min(viewBox.Width, viewBox.Height) / (double)drawableModulesCount;

string psFile = string.Format(PS_HEADER, new object[] {
DateTime.Now.ToString("s"), CleanSvgVal(viewBox.Width), CleanSvgVal(pointsPerModule),
CleanSvgVal(viewBox.Width), CleanSvgVal(pointsPerModule),
epsFormat ? "EPSF-3.0" : string.Empty
});
psFile += string.Format(PS_FUNCTIONS, new object[] {
Expand Down Expand Up @@ -130,68 +130,75 @@ public string GetGraphic(Size viewBox, Color darkColor, Color lightColor, bool d
/// <returns>Returns the cleaned string representation of the double value.</returns>
private string CleanSvgVal(double input) => input.ToString(System.Globalization.CultureInfo.InvariantCulture);

private const string PS_HEADER = @"%!PS-Adobe-3.0 {3}
%%Creator: QRCoder.NET
%%Title: QRCode
%%CreationDate: {0}
Copy link
Owner Author

@Shane32 Shane32 Oct 6, 2025 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This "CreationDate" line is the only removed line; the constant is otherwise identical. (although {1} becomes {0} etc)

%%DocumentData: Clean7Bit
%%Origin: 0
%%DocumentMedia: Default {1} {1} 0 () ()
%%BoundingBox: 0 0 {1} {1}
%%LanguageLevel: 2
%%Pages: 1
%%Page: 1 1
%%EndComments
%%BeginConstants
/sz {1} def
/sc {2} def
%%EndConstants
%%BeginFeature: *PageSize Default
<< /PageSize [ sz sz ] /ImagingBBox null >> setpagedevice
%%EndFeature
";

private const string PS_FUNCTIONS = @"%%BeginFunctions
/csquare {{
newpath
0 0 moveto
0 1 rlineto
1 0 rlineto
0 -1 rlineto
closepath
setrgbcolor
fill
}} def
/f {{
{0} {1} {2} csquare
1 0 translate
}} def
/b {{
1 0 translate
}} def
/background {{
{3} {4} {5} csquare
}} def
/nl {{
-{6} -1 translate
}} def
%%EndFunctions
%%BeginBody
0 0 moveto
gsave
sz sz scale
background
grestore
gsave
sc sc scale
0 {6} 1 sub translate
";

private const string PS_FOOTER = @"%%EndBody
grestore
showpage
%%EOF
";
// Note: line terminations here will encode differently based on which platform QRCoder was compiled on (CRLF vs LF);
// however, PostScript interpreters should handle both equally well.
Comment on lines +133 to +134
Copy link
Contributor

@coderabbitai coderabbitai bot Oct 6, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

🛠️ Refactor suggestion | 🟠 Major

🧩 Analysis chain

Verify cross-platform test determinism.

The comment correctly notes that line terminations will differ based on compilation platform (CRLF on Windows, LF on Unix). While PostScript interpreters handle both, this could cause approval test failures when developers compile on different platforms and the tests perform exact string comparisons.

Consider one of these approaches:

  1. Normalize line endings in the generated PostScript to always use LF (more deterministic)
  2. Update approval tests to ignore line ending differences
  3. Document that developers should use consistent line endings in their development environment

Run this script to check how the approval tests handle line ending differences:

🏁 Script executed:

#!/bin/bash
# Check if approval tests normalize line endings

# Search for the ShouldMatchApproved implementation and configuration
rg -n "ShouldMatchApproved|NoDiff" --type cs -A 5 -B 5

# Look for any line ending normalization in test utilities
rg -n "LineEnding|CRLF|\\\\r\\\\n|normalize" --type cs

Length of output: 66105

Ensure deterministic LF line endings in PostScript output
Approval tests use exact NoDiff comparisons, so CRLF vs LF variations break on different platforms.

  • Normalize GetGraphic to emit LF-only line endings
  • Update PostscriptQRCodeRendererTests to ignore CRLF/LF differences
🤖 Prompt for AI Agents 
In QRCoder/PostscriptQRCode.cs around lines 133-134, the PostScript output
currently may contain platform-dependent CRLF line endings; modify GetGraphic so
it deterministically returns LF-only line endings by normalizing the final
string (replace "\r\n" and any lone "\r" with "\n") before returning; also
update PostscriptQRCodeRendererTests to either compare normalized strings
(replace CRLF with LF on both expected and actual) or use a test helper that
normalizes line endings so comparisons ignore CRLF vs LF differences.

private const string PS_HEADER = """
%!PS-Adobe-3.0 {2}
%%Creator: QRCoder.NET
%%Title: QRCode
%%DocumentData: Clean7Bit
%%Origin: 0
%%DocumentMedia: Default {0} {0} 0 () ()
%%BoundingBox: 0 0 {0} {0}
%%LanguageLevel: 2
%%Pages: 1
%%Page: 1 1
%%EndComments
%%BeginConstants
/sz {0} def
/sc {1} def
%%EndConstants
%%BeginFeature: *PageSize Default
<< /PageSize [ sz sz ] /ImagingBBox null >> setpagedevice
%%EndFeature

""";

private const string PS_FUNCTIONS = """
%%BeginFunctions
/csquare {{
newpath
0 0 moveto
0 1 rlineto
1 0 rlineto
0 -1 rlineto
closepath
setrgbcolor
fill
}} def
/f {{
{0} {1} {2} csquare
1 0 translate
}} def
/b {{
1 0 translate
}} def
/background {{
{3} {4} {5} csquare
}} def
/nl {{
-{6} -1 translate
}} def
%%EndFunctions
%%BeginBody
0 0 moveto
gsave
sz sz scale
background
grestore
gsave
sc sc scale
0 {6} 1 sub translate

""";

private const string PS_FOOTER = """
%%EndBody
grestore
showpage
%%EOF

""";
}

/// <summary>
Expand Down
19 changes: 5 additions & 14 deletions QRCoderTests/PostscriptQRCodeRendererTests.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ public void can_render_postscript_qrcode_simple()
var gen = new QRCodeGenerator();
var data = gen.CreateQrCode("This is a quick test! 123#?", QRCodeGenerator.ECCLevel.L);
var ps = new PostscriptQRCode(data).GetGraphic(5);
RemoveCreationDate(ps).ShouldMatchApproved(x => x.NoDiff());
ps.ShouldMatchApproved(x => x.NoDiff());
Copy link
Owner Author

@Shane32 Shane32 Oct 6, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Tests previously removed the creation date from the verified files. So all tests continue to match with no change to test result data.

}

[Fact]
Expand All @@ -19,7 +19,7 @@ public void can_render_postscript_qrcode_eps()
var gen = new QRCodeGenerator();
var data = gen.CreateQrCode("This is a quick test! 123#?", QRCodeGenerator.ECCLevel.L);
var ps = new PostscriptQRCode(data).GetGraphic(5, true);
RemoveCreationDate(ps).ShouldMatchApproved(x => x.NoDiff());
ps.ShouldMatchApproved(x => x.NoDiff());
}

[Fact]
Expand All @@ -29,7 +29,7 @@ public void can_render_postscript_qrcode_size()
var gen = new QRCodeGenerator();
var data = gen.CreateQrCode("This is a quick test! 123#?", QRCodeGenerator.ECCLevel.L);
var ps = new PostscriptQRCode(data).GetGraphic(new Size(33, 33));
RemoveCreationDate(ps).ShouldMatchApproved(x => x.NoDiff());
ps.ShouldMatchApproved(x => x.NoDiff());
}

[Fact]
Expand All @@ -39,7 +39,7 @@ public void can_render_postscript_qrcode_size_no_quiet_zones()
var gen = new QRCodeGenerator();
var data = gen.CreateQrCode("This is a quick test! 123#?", QRCodeGenerator.ECCLevel.L);
var ps = new PostscriptQRCode(data).GetGraphic(new Size(50, 50), false);
RemoveCreationDate(ps).ShouldMatchApproved(x => x.NoDiff());
ps.ShouldMatchApproved(x => x.NoDiff());
}

[Fact]
Expand All @@ -49,15 +49,6 @@ public void can_render_postscript_qrcode_colors()
var gen = new QRCodeGenerator();
var data = gen.CreateQrCode("This is a quick test! 123#?", QRCodeGenerator.ECCLevel.L);
var ps = new PostscriptQRCode(data).GetGraphic(5, Color.Red, Color.Blue);
RemoveCreationDate(ps).ShouldMatchApproved(x => x.NoDiff());
}

private static string RemoveCreationDate(string text)
{
// Regex pattern to match lines that start with %%CreationDate: followed by any characters until the end of the line
string pattern = @"%%CreationDate:.*\r?\n?";

// Use Regex.Replace to remove matching lines
return Regex.Replace(text, pattern, string.Empty, RegexOptions.Multiline);
ps.ShouldMatchApproved(x => x.NoDiff());
}
}