Over the past two years, I have regularly come across articles and libraries that attempt to improve how underline text decorations are rendered on the web. The same problem exist on Android: underline text decorations cross descenders. Compare how Android draws underlined text (top) and how it could be drawn instead (bottom):

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Which do you prefer?

While I wholeheartedly approve of these efforts, I have never been fond of the solutions made publicly available. The current state of the art — admittedly forced upon developers by the limitations of CSS — seems to rely on drawing linear gradients and multiple shadows (I have seen up to 12!). These solutions have the undeniable quality of working but the idea of drawing so many shadows, even without blurring them, makes the graphics programmer in me cringe. …

Efficient text rendering with OpenGL ES

Any developer with a few years of experience writing client-side applications is acutely aware of how complicated text rendering can be. At least that’s what I thought until 2010 when I started writing libhwui, an OpenGL backend for Android 3.0’s 2D drawing API. I then realized that text gets even more complicated when you’re trying to use a GPU to draw it on screen.

Text and Android

Android’s hardware accelerated font renderer was originally written by a co-worker on the Renderscript team and was then improved upon and optimized by several engineers including my good friend Chet Haase and I. You can easily find many tutorials on how to render text with OpenGL but most — if not all — articles focus on games and conveniently avoid dealing with difficult issues.
The approach described here is by no means novel but I thought it would be convenient for some developers to get a high-level overview of how a complete GPU-based text rendering system can be implemented. …


Romain Guy

Working on awesome stuff at Google

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