class Renderer

This function is responsible for rendering a single batch of Flatland rectangles into a

render target. This function is designed to be called on the render thread, not on any

Flatland instance thread. The specific behavior may differ depending on the specific subclass

implementation, which may also be a null renderer.

This function assumes that clients have already validated their input data by comparing it

against the BufferCollectionMetadata received from calling |Validate| above. This function

will abort if invalid data has been passed in or if |Validate| has never been called.

The size of the arrays |rectangles| and |images| must match or else this function will CHECK.

Entries in each array with the same index will be used together in rendering.

The final argument |render_args| contains optional arguments that affect rendering. See the

doc comments on each field of |struct RenderArgs|.

If any of the |images| use protected memory but the |render_target| is not using protected

memory, the renderer replaces protected content with black solid color.

Values needed to adjust the color of the framebuffer as a postprocessing effect.

Returns the pixel format that the renderer prefers to use for render targets.

TODO(https://fxbug.dev/42065293): Rename this to reflect that it's for a render target.

Returns true if the renderer is capable of switching to protected mode.

Returns true if the renderer has to switch to protected mode to render the given |images|. If

true, the caller is responsible for providing a render target using the protected memory when

calling Render().

TODO(https://fxbug.dev/42062402): The caller should be able to figure out if the images are

protected. Remove this after moving to prunable tokens in the callers.

Implementations which use Vulkan or similar should implement this by generating render passes

and pipelines, so that there is no jank due to lazily generating them later.