Blurred borders in Cairo

Question

What is proper way to draw a blurred rectangular border using the Cairo API? I am writing a patch for Shotwell to add a blurred shadow to the thumbnails in the thumbnail view.

For now I am experimenting with manual blurring.

Answer 1

I ended up drawing the border with linear and radial gradients.

Here is a small visualization. The lines symbolize the linear grandients and the 0 the radial gradients.

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 0------0