Add documentation comments to bevy_window (#4333)

# Objective
- Add documentation comments and `#![warn(missing_docs)]` to `bevy_window`.
- Part of #3492

crates/bevy_window/src/cursor.rs

@@ -1,39 +1,81 @@
-/// The icon to display for a window's cursor
+/// The icon to display for a window's cursor.
+///
+/// Examples of all of these cursors can be found [here](https://www.w3schools.com/cssref/playit.asp?filename=playcss_cursor).
+/// This `enum` is simply a copy of a similar `enum` found in [`winit`](https://docs.rs/winit/latest/winit/window/enum.CursorIcon.html).
+/// `winit`, in turn, mostly copied cursor types avilable in the browser.
 #[derive(Debug, Hash, PartialEq, Eq, Clone, Copy)]
 pub enum CursorIcon {
+    /// The platform-dependent default cursor.
     Default,
+    /// A simple crosshair.   
     Crosshair,
+    /// A hand (often used to indicate links in web browsers).    
     Hand,
+    /// An arrow. This is the default cursor on most systems.    
     Arrow,
+    /// Indicates something is to be moved.    
     Move,
+    /// Indicates text that may be selected or edited.    
     Text,
+    /// Program busy indicator.    
     Wait,
+    /// Help indicator (often rendered as a "?")    
     Help,
+    /// Progress indicator. Shows that processing is being done.
+    ///
+    /// But in contrast with "Wait" the user may still interact with the program.
+    /// Often rendered as a spinning beach ball, or an arrow with a watch or hourglass.    
     Progress,
+    /// Cursor showing that something cannot be done.    
     NotAllowed,
+    /// Indicates that a context menu is available.
     ContextMenu,
+    /// Indicates that a cell (or set of cells) may be selected.
     Cell,
+    /// Indicates vertical text that may be selected or edited.
     VerticalText,
+    /// Indicates that an alias of something is to be created.
     Alias,
+    /// Indicates something is to be copied.
     Copy,
+    /// Indicates that the dragged item cannot be dropped here.
     NoDrop,
+    /// Indicates that something can be grabbed.
     Grab,
+    /// Indicates that something is grabbed.
     Grabbing,
+    /// Indicates that the user can scroll by dragging the mouse.
     AllScroll,
+    /// Indicates that the user can zoom in.
     ZoomIn,
+    /// Indicates that the user can zoom out.
     ZoomOut,
+    /// Indicates that an edge of a box is to be moved right (east).
     EResize,
+    /// Indicates that an edge of a box is to be moved up (north).
     NResize,
+    /// Indicates that an edge of a box is to be moved up and right (north/east).
     NeResize,
+    /// indicates that an edge of a box is to be moved up and left (north/west).
     NwResize,
+    /// Indicates that an edge of a box is to be moved down (south).
     SResize,
+    /// The cursor indicates that an edge of a box is to be moved down and right (south/east).
     SeResize,
+    /// The cursor indicates that an edge of a box is to be moved down and left (south/west).
     SwResize,
+    /// Indicates that an edge of a box is to be moved left (west).
     WResize,
+    /// Indicates a bidirectional resize cursor.
     EwResize,
+    /// Indicates a bidirectional resize cursor.
     NsResize,
+    /// Indicates a bidirectional resize cursor.
     NeswResize,
+    /// Indicates a bidirectional resize cursor.
     NwseResize,
+    /// Indicates that a column can be resized horizontally.
     ColResize,
+    /// Indicates that the row can be resized vertically.
     RowResize,
 }

crates/bevy_window/src/event.rs

@@ -3,13 +3,13 @@ use std::path::PathBuf;
 use super::{WindowDescriptor, WindowId};
 use bevy_math::{IVec2, Vec2};
 
-/// A window event that is sent whenever a windows logical size has changed
+/// A window event that is sent whenever a window's logical size has changed.
 #[derive(Debug, Clone)]
 pub struct WindowResized {
     pub id: WindowId,
-    /// The new logical width of the window
+    /// The new logical width of the window.
     pub width: f32,
-    /// The new logical height of the window
+    /// The new logical height of the window.
     pub height: f32,
 }
 
@@ -58,18 +58,18 @@ pub struct WindowCloseRequested {
 pub struct WindowClosed {
     pub id: WindowId,
 }
-
+/// An event that is sent whenenver the user's cursor moves.
 #[derive(Debug, Clone)]
 pub struct CursorMoved {
     pub id: WindowId,
     pub position: Vec2,
 }
-
+/// An event that is sent whenever the user's cursor enters a window.
 #[derive(Debug, Clone)]
 pub struct CursorEntered {
     pub id: WindowId,
 }
-
+/// An event that is sent whenever the user's cursor leaves a window.
 #[derive(Debug, Clone)]
 pub struct CursorLeft {
     pub id: WindowId,

crates/bevy_window/src/lib.rs

@@ -1,3 +1,4 @@
+#[warn(missing_docs)]
 mod cursor;
 mod event;
 mod raw_window_handle;
@@ -23,13 +24,15 @@ pub mod prelude {
 use bevy_app::prelude::*;
 use bevy_ecs::{event::Events, schedule::SystemLabel};
 
+/// A [`Plugin`] that defines an interface for windowing support in Bevy.
 pub struct WindowPlugin {
     /// Whether to create a window when added.
     ///
     /// Note that if there are no windows, by default the App will exit,
     /// due to [`exit_on_all_closed`].
     pub add_primary_window: bool,
     /// Whether to exit the app when there are no open windows.
+    ///
     /// If disabling this, ensure that you send the [`bevy_app::AppExit`]
     /// event when the app should exit. If this does not occur, you will
     /// create 'headless' processes (processes without windows), which may
@@ -38,7 +41,7 @@ pub struct WindowPlugin {
     /// If true, this plugin will add [`exit_on_all_closed`] to [`CoreStage::Update`].
     pub exit_on_all_closed: bool,
     /// Whether to close windows when they are requested to be closed (i.e.
-    /// when the close button is pressed)
+    /// when the close button is pressed).
     ///
     /// If true, this plugin will add [`close_when_requested`] to [`CoreStage::Update`].
     /// If this system (or a replacement) is not running, the close button will have no effect.