For some cases, like driving a full screen fragment shader, it is sometimes convenient to not have to create and upload a mesh because the necessary vertices are simple to synthesize in the vertex shader. Bevy's existing pipeline compiler assumes that there will always be a vertex buffer. This PR changes that such that vertex buffer descriptor is only added to the pipeline layout if there are vertex attributes in the shader.
Before, when deriving `SystemLabel` for a type without `Clone`, the error message was:
```
the trait `SystemLabel` is not implemented for `&TransformSystem`
```
Now it is
```
the trait `Clone` is not implemented for `TransformSystem`
```
which directly shows what's needed to fix the problem.
In this case, the previous section header linked to in second badge in `plugins_guidelines` didn't actually exist, so I just linked to the same section as the first badge
Also I need to check that github handles the relative links correctly
* Simple Implementation to address #1327 by adding a focused field to the window and related system
* Changing Window update function from bevy_window to bevy_winit.
* Removing unused imports.
the mailbox option doesn't do framelimiting on some devices. we need to rely on vsync for framelimiting until bevy supports framelimiting internally. #1343
The existing snippet fails to compile with:
```
no method named `system` found for fn item `fn(bevy::prelude::Commands) {example_system}` in the current scope
```
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.
* Fix Interaction getting stuck when pressing and releasing mouse button in one frame
* Fix Interaction not resetting in some cases with FocusPolicy::Pass
* use `length_squared` for visible entities
* ortho projection 2d/3d different depth calculation
* use ScalingMode::FixedVertical for 3d ortho
* new example: 3d orthographic
* add normalized orthographic projection
* custom scale for ScaledOrthographicProjection
* allow choosing base axis for ScaledOrthographicProjection
* cargo fmt
* add general (scaled) orthographic camera bundle
FIXME: does the same "far" trick from Camera2DBundle make any sense here?
* fixes
* camera bundles: rename and new ortho constructors
* unify orthographic projections
* give PerspectiveCameraBundle constructors like those of OrthographicCameraBundle
* update examples with new camera bundle syntax
* rename CameraUiBundle to UiCameraBundle
* update examples
* ScalingMode::None
* remove extra blank lines
* sane default bounds for orthographic projection
* fix alien_cake_addict example
* reorder ScalingMode enum variants
* ios example fix
