touchgfx::Scanline::isReady() const method

@fn int Scanline::isReady(int y) const; Checks if a Scanline is ready for rendering. Checks if a Scanline is ready for rendering. A Scanline is ready for rendering when the y coordinate has changed. Since all the cells are sorted, a change in the y coordinate means that we have moved to the next Scanline and thus the collected data for the Scanline must be rendered before we register cells for the next Scanline.