Top-down Rendering

[qiumuyang]

Current Implementation renders nested objects from children to parents. The parent's size cannot be determined until all children are rendered except for the FixedContainer object.

If we organize the parent-child relationship in a tree, we now render the tree from children to parents, i.e. bottom-up rendering. It works well until we need to render the root object to any size. Under such circumstances, we need to render the tree from parents to children, i.e. top-down rendering. Parents determine the desired size of children, and children render themselves to the desired size.

To support top-down rendering, we maybe need to add a new method to RenderObject:

def render_to(self, width: int, height: int) -> RenderImage:
    """Render the object to a specific size.
    
    Default implementation is to render the object as usual and resize the
    result to the desired size.
    """
    return self.render().resize(width, height)

Further details are to be discussed.