Graphics/Text: add optional rounding for letter and line spacing by Praful-Joshi · Pull Request #3638 · SFML/SFML

Praful-Joshi · 2026-01-14T18:32:30Z

This pull request introduces optional pixel rounding for text letter spacing and line spacing in sf::Text.

When using fractional spacing factors (e.g. setLetterSpacing(1.1f)), glyph positions may fall on sub-pixel coordinates, which can lead to blurred text due to texture filtering and rasterization behavior. This PR adds a way to opt into pixel-aligned spacing without changing the existing default behavior.

What’s new:

Added setLetterSpacingRounding(bool) / getLetterSpacingRounding()
Added setLineSpacingRounding(bool) / getLineSpacingRounding()
When enabled, rounding is applied during geometry generation only
Default behavior remains unchanged (rounding disabled)

This allows users to choose between:

Exact mathematical spacing (current default)
Sharper text rendering when using fractional spacing values

Related issue:
Fixes #3595

Checklist:

Has this change been discussed in an issue before: Yes
Does the code follow the SFML Code Style Guide: Yes
Have you provided example/test code for your changes: Yes

Tasks:

Tested on macOS

How to test this PR?
The effect is most visible when using fractional spacing values.

Minimal example:
#include <SFML/Graphics.hpp>

int main()
{
sf::RenderWindow window(sf::VideoMode({800, 600}), "Text spacing rounding test");
window.setFramerateLimit(60);

sf::Font font;
font.openFromFile("font.ttf");

sf::Text text(font);
text.setString("SFML TEXT SPACING TEST\nThe quick brown fox jumps over the lazy dog");
text.setCharacterSize(24);
text.setLetterSpacing(1.1f);
text.setLineSpacing(1.1f);

// New API
text.setLetterSpacingRounding(true);
text.setLineSpacingRounding(true);

text.setPosition({50.f, 50.f});

while (window.isOpen())
{
    while (const auto event = window.pollEvent())
    {
        if (event->is<sf::Event::Closed>())
            window.close();
    }

    window.clear(sf::Color(36, 36, 71));
    window.draw(text);
    window.display();
}

}

Without Rounding:

With Rounding:

Compare the output with rounding enabled vs disabled to clearly see the difference in sharpness.

Marioalexsan · 2026-01-14T21:36:19Z

+    const float letterSpacingFactor = m_roundLetterSpacing ? roundToPixel(m_letterSpacingFactor) : m_letterSpacingFactor;
+    const float letterSpacing = (whitespaceWidth / 3.0f) * (letterSpacingFactor - 1.0f);
+    const float lineSpacingFactor = m_roundLineSpacing ? roundToPixel(m_lineSpacingFactor) : m_lineSpacingFactor;
+    const float lineSpacing = m_font->getLineSpacing(m_characterSize) * lineSpacingFactor;
+


Why is rounding applied to letterSpacingFactor and lineSpacingFactor instead of letterSpacing and lineSpacing, i.e. the final values used to adjust spacing?

I wasn't sure if I should mess with letterSpacing and lineSpacing as they are also dependent on whitespaceWidth so I just decided to round m_letterSpacingFactor and m_lineSpacingFactor instead. But you're right, rounding should be applied to the final spacing values to avoid changing their semantic meaning. I’ll move the rounding accordingly.

Marioalexsan · 2026-01-14T21:41:38Z

+    ////////////////////////////////////////////////////////////
+    /// \brief Round a value to the nearest pixel coordinate
+    ///
+    /// This function rounds the given floating-point value to
+    /// the nearest integer value, which corresponds to a pixel
+    /// boundary in window coordinates.
+    ///
+    /// \param value Value to round
+    ///
+    /// \return Rounded value
+    ////////////////////////////////////////////////////////////
+    float roundToPixel(float value) const;


I don't see why this method is needed as part of the public interface, or even as a helper method. It has nothing to do with an sf::Text instance, being just a wrapper around std::round. You can just use that directly in the implementation.

Agreed. I was contemplating real hard on this one. roundToPixel doesn’t belong in the public interface and doesn’t add value over std::round. I’ll remove it and apply rounding directly in the implementation.

Marioalexsan · 2026-01-14T21:43:06Z

+////////////////////////////////////////////////////////////
+void Text::setLetterSpacingRounding(bool enabled)
+{
+    if(m_roundLetterSpacing != enabled)
+    {
+        m_roundLetterSpacing = enabled;
+    }
+}
+
+
+////////////////////////////////////////////////////////////
+void Text::setLineSpacingRounding(bool enabled)
+{
+    if(m_roundLineSpacing != enabled)
+    {
+        m_roundLineSpacing = enabled;
+    }
+}


Changing these settings affect the geometry, so you do need to set m_geometryNeedUpdate = true; if the values have changed.

Good catch! this was an oversight. I’ll make sure toggling the rounding mode properly invalidates geometry by setting m_geometryNeedUpdate = true.

Marioalexsan · 2026-01-14T21:44:59Z

+    ////////////////////////////////////////////////////////////
+    /// \brief Tell whether letter spacing rounding is enabled
+    ///
+    /// \return True if letter spacing rounding is enabled, false otherwise
+    ///
+    /// \see `setLetterSpacingRounding`
+    ///
+    ////////////////////////////////////////////////////////////
+    [[nodiscard]] bool getLetterSpacingRounding() const;
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Tell whether line spacing rounding is enabled
+    ///
+    /// \return True if line spacing rounding is enabled, false otherwise
+    ///
+    /// \see `setLineSpacingRounding`
+    ///
+    ////////////////////////////////////////////////////////////
+    [[nodiscard]] bool getLineSpacingRounding() const;


What is the use case of separating the rounding mode vertically and horizontally, instead of using a single setting for it?

Yaah I was wondering this too. I just moved ahead with the separate implementation to be on the safer side. I’ll consolidate this into one spacing-rounding setting applied consistently to both directions.

Praful-Joshi · 2026-01-15T03:46:50Z

@Marioalexsan Done. I made a commit with the fixes.

Graphics/Text: add optional rounding for letter and line spacing

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Marioalexsan reviewed Jan 14, 2026

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Graphics/Text: add optional pixel rounding for text spacing

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Graphics/Text: add optional rounding for letter and line spacing#3638

Graphics/Text: add optional rounding for letter and line spacing#3638
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Praful-Joshi:TextSpacingRoudingIssue#3595

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