Augment slide with horizontal layout info

def horizontal_layout(self, draw, slide):
        """ Augment slide with horizontal layout info """
        padding = self.padding
        heading = slide['heading']

        top = padding
        left = padding

        top += heading['height'] + padding

        rows = slide['rows']

        for row in rows:

            images = row.get('images', 0)

            items = row['items']
            
            used_width = sum(x.get('width', 0) for x in items)

            available_width = WIDTH - (
                used_width + ((1 + len(items)) * padding))

            if images:
                image_width = available_width // images

            # OK, now set left for all items and image_width for images
            left = padding
            for item in row['items']:

                if item.get('image'):
                    item['width'] = image_width

                item['left'] = left    

                left += item['width'] + padding

        return