# Objective
In this PR I added the ability to opt-out graphical backends. Closes#3155.
## Solution
I turned backends into `Option` ~~and removed panicking sub app API to force users handle the error (was suggested by `@cart`)~~.
This makes the [New Bevy Renderer](#2535) the default (and only) renderer. The new renderer isn't _quite_ ready for the final release yet, but I want as many people as possible to start testing it so we can identify bugs and address feedback prior to release.
The examples are all ported over and operational with a few exceptions:
* I removed a good portion of the examples in the `shader` folder. We still have some work to do in order to make these examples possible / ergonomic / worthwhile: #3120 and "high level shader material plugins" are the big ones. This is a temporary measure.
* Temporarily removed the multiple_windows example: doing this properly in the new renderer will require the upcoming "render targets" changes. Same goes for the render_to_texture example.
* Removed z_sort_debug: entity visibility sort info is no longer available in app logic. we could do this on the "render app" side, but i dont consider it a priority.
The `Texture::convert` function previously was only compiled when
one of the image format features (`png`, `jpeg` etc.) were enabled.
The `bevy_sprite` crate needs this function though, which led
to compilation errors when using `cargo check --no-default-features
--features render`.
Now the `convert` function has no features and the `texture_to_image`
and `image_to_texture` utilites functions are in an unconditionally
compiled module.
This adds support for PNG images only for now. More formats can be added
relatively easily.
Images with various pixel formats are supported (such as RGB-16bit or
R-8bit).
