Triangle rasterization under the hood (the old-school approach)

I didn't find a single source which would gave me a complete and clear picture of how to rasterize a triangle in a simplest way.

So, here's my attempt to put everything in order.

Consider, that we know how to draw a line and nothing more. Here's the corresponding method declaration for it:

void drawLine(int x0, int y0, int x1, int y1, Color color);

We need to implement a method which will draw a triangle and fill it with a specified color. Here's the corresponding method declaration:

void drawTriangle(Vec2 v0, Vec2 v1, Vec2 v2, Color color);

Here's the visual representation of what this method should do:

Initial vertices

Rasterized triangle

drawTriangle(v0, v1, v2, Color.BLACK)

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