Overhaul the Keyboard API

Overhaul the keyboard API in winit to mimic the W3C specification
to achieve better crossplatform parity. The `KeyboardInput` event
is now uses `KeyEvent` which consists of:

  - `physical_key` - a cross platform way to refer to scancodes;
  - `logical_key`  - keysym value, which shows your key respecting the
                     layout;
  - `text`         - the text produced by this keypress;
  - `location`     - the location of the key on the keyboard;
  - `repeat`       - whether the key was produced by the repeat.

And also a `platform_specific` field which encapsulates extra
information on desktop platforms, like key without modifiers
and text with all modifiers.

The `Modifiers` were also slightly reworked as in, the information
whether the left or right modifier is pressed is now also exposed
on platforms where it could be queried reliably. The support was
also added for the web and orbital platforms finishing the API
change.

This change made the `OptionAsAlt` API on macOS redundant thus it
was removed all together.

Co-authored-by: Artúr Kovács <kovacs.artur.barnabas@gmail.com>
Co-authored-by: Kirill Chibisov <contact@kchibisov.com>
Co-authored-by: daxpedda <daxpedda@gmail.com>
Fixes: #2631.
Fixes: #2055.
Fixes: #2032.
Fixes: #1904.
Fixes: #1810.
Fixes: #1700.
Fixes: #1443.
Fixes: #1343.
Fixes: #1208.
Fixes: #1151.
Fixes: #812.
Fixes: #600.
Fixes: #361.
Fixes: #343.

src/platform_impl/linux/mod.rs

@@ -18,6 +18,7 @@ use std::{
 #[cfg(x11_platform)]
 use once_cell::sync::Lazy;
 use raw_window_handle::{RawDisplayHandle, RawWindowHandle};
+use smol_str::SmolStr;
 
 #[cfg(x11_platform)]
 pub use self::x11::XNotSupported;
@@ -28,11 +29,13 @@ use crate::platform::x11::XlibErrorHook;
 use crate::{
     dpi::{PhysicalPosition, PhysicalSize, Position, Size},
     error::{ExternalError, NotSupportedError, OsError as RootOsError},
-    event::Event,
+    event::{Event, KeyEvent},
     event_loop::{
         ControlFlow, DeviceEventFilter, EventLoopClosed, EventLoopWindowTarget as RootELW,
     },
     icon::Icon,
+    keyboard::{Key, KeyCode},
+    platform::{modifier_supplement::KeyEventExtModifierSupplement, scancode::KeyCodeExtScancode},
     window::{
         CursorGrabMode, CursorIcon, ImePurpose, ResizeDirection, Theme, UserAttentionType,
         WindowAttributes, WindowButtons, WindowLevel,
@@ -42,6 +45,7 @@ use crate::{
 pub(crate) use crate::icon::RgbaIcon as PlatformIcon;
 pub(self) use crate::platform_impl::Fullscreen;
 
+pub mod common;
 #[cfg(wayland_platform)]
 pub mod wayland;
 #[cfg(x11_platform)]
@@ -514,6 +518,11 @@ impl Window {
         x11_or_wayland!(match self; Window(w) => w.set_ime_position(position))
     }
 
+    #[inline]
+    pub fn reset_dead_keys(&self) {
+        common::xkb_state::reset_dead_keys()
+    }
+
     #[inline]
     pub fn set_ime_allowed(&self, allowed: bool) {
         x11_or_wayland!(match self; Window(w) => w.set_ime_allowed(allowed))
@@ -624,6 +633,37 @@ impl Window {
     }
 }
 
+#[derive(Debug, Clone, Eq, PartialEq, Hash)]
+pub struct KeyEventExtra {
+    pub key_without_modifiers: Key,
+    pub text_with_all_modifiers: Option<SmolStr>,
+}
+
+impl KeyEventExtModifierSupplement for KeyEvent {
+    #[inline]
+    fn text_with_all_modifiers(&self) -> Option<&str> {
+        self.platform_specific
+            .text_with_all_modifiers
+            .as_ref()
+            .map(|s| s.as_str())
+    }
+
+    #[inline]
+    fn key_without_modifiers(&self) -> Key {
+        self.platform_specific.key_without_modifiers.clone()
+    }
+}
+
+impl KeyCodeExtScancode for KeyCode {
+    fn from_scancode(scancode: u32) -> KeyCode {
+        common::keymap::raw_keycode_to_keycode(scancode)
+    }
+
+    fn to_scancode(self) -> Option<u32> {
+        common::keymap::keycode_to_raw(self)
+    }
+}
+
 /// Hooks for X11 errors.
 #[cfg(x11_platform)]
 pub(crate) static mut XLIB_ERROR_HOOKS: Lazy<Mutex<Vec<XlibErrorHook>>> =