Cleanup.
Remove CalcSize.
Don't wrap contents. Auto scroll.
Move timer'd invalidation to the render items themselves.
Use DefaultSize instead of setting the size in the constructor.
Un-extract Render.
Move RenderGraph from LigraControl to GraphItem.
Move Render3DGraph from LigraControl to Graph3DItem.
Move RenderMathPaint from LigraControl to MathPaintItem.