Use of Cairo

Overview

Cairo draws into a virtual plane. To identify points on that plane, we use a coordinate system that associates every point of the plane with an unique pair of numbers.

Along the x-axis, the values increase from left to right, along the y-axis, the values increase from the top downwards.

The following drawing shows the default coordinate system used by Cairo:

Cairo uses a drawing tool, called context, to draw on a surface. The most commonly used surface is the interior of a DrawingArea. It is however also possible to draw into a bitmap.

The context offers a lot of facilities to

• draw lines, polylines, arcs, Bézier curves and arbitrary paths
• fill rect angles, arc segments, arc sectors and regions bordered by arbitrary paths
• draw text
• use various strike widths and stroke styles
• use both opaque and translucent colours
• use colour gradients and fill patterns
• use a clip mask
• use coordinate transformations

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