Set color to a single point in Cairo

[Basile B. via Digitalmars-d-learn]

On Saturday, 19 December 2015 at 14:16:23 UTC, TheDGuy wrote:
> is it possible to set the color of a single pixel with Cairo?

Not like you would do with a classic canvas (2d grid), because 
colors are applied with `cairo_fill()` and `cairo_stroke()` on a 
particular path.

but you can define a path that represents a single pixel and fill 
it:

```
cairo_rectangle (cr, x, y, 1, 1); // 1 pix rectangle
cairo_set_source_rgba (cr, 0, 0, 0, 1); // color
cairo_fill (cr); // fill the rectangle with source rgba

```

However cairo is node made to be used like this. The workflow is 
usually more based on stacked layers (1 layer = 1 path) with 
different filling, different transparency.