What is font autohinting, and when should it be used with custom fonts?

Font autohinting is a technique used to improve the rendering of fonts at small sizes or low resolutions by automatically adding hints to the font outlines. These hints provide instructions to the rendering engine on how to adjust the glyph shapes to align with the pixel grid more accurately, resulting in clearer and sharper text rendering.

Here's when font autohinting should be considered with custom fonts:

1. **Low-resolution Displays**: Font autohinting is particularly useful for improving the legibility of text on low-resolution displays, such as older monitors, mobile devices with lower pixel densities, or certain types of printers. It helps mitigate issues like blurry or jagged text by aligning glyph edges with the pixel grid.

2. **Small Font Sizes**: Text rendered at small font sizes can suffer from readability issues due to the limited number of pixels available to represent each glyph. Autohinting helps optimize glyph shapes for small sizes, ensuring that characters remain distinct and legible even when rendered at tiny sizes.

3. **Custom Fonts with Limited Hinting**: Some custom fonts may lack manual hinting instructions, especially if they were designed primarily for display purposes or for high-resolution environments. In such cases, autohinting can be used to add hints automatically, improving the font's rendering quality at smaller sizes or on lower-resolution screens.

4. **Cross-platform Compatibility**: Autohinting can enhance cross-platform compatibility by providing consistent text rendering across different operating systems and rendering environments. It helps ensure that custom fonts appear as intended, regardless of the platform or device used for viewing.

5. **Accessibility**: Improved text legibility benefits users with visual impairments or those who rely on screen readers or assistive technologies. Autohinting can contribute to better accessibility by making text easier to read and comprehend, especially at smaller sizes.

However, it's worth noting that autohinting is not always necessary or desirable, especially for high-resolution displays or when using fonts specifically designed for modern digital environments. In some cases, autohinting can distort the original design intent of the font or result in overly rigid glyph shapes. Therefore, whether to use autohinting with custom fonts depends on factors such as the intended use case, target devices, and design considerations.