winit-core/ime: add more purposes and content hints

Also move IME example into `ime.rs` thus making IME integrations more
easily comprehendible.

Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

examples

@@ -0,0 +1 @@
+winit/examples

winit-core/src/window.rs

@@ -1136,9 +1136,9 @@ pub trait Window: AsAny + Send + Sync + fmt::Debug {
         let action = if allowed {
             let position = LogicalPosition::new(0, 0);
             let size = LogicalSize::new(0, 0);
-            let ime_caps = ImeCapabilities::new().with_purpose().with_cursor_area();
+            let ime_caps = ImeCapabilities::new().without_hint_and_purpose().with_cursor_area();
             let request_data = ImeRequestData {
-                purpose: Some(ImePurpose::Normal),
+                hint_and_purpose: Some((ImeHint::NONE, ImePurpose::Normal)),
                 // WARNING: there's nothing sensible to use here by default.
                 cursor_area: Some((position.into(), size.into())),
                 ..ImeRequestData::default()
@@ -1160,9 +1160,9 @@ pub trait Window: AsAny + Send + Sync + fmt::Debug {
     /// - **iOS / Android / Web / Windows / X11 / macOS / Orbital:** Unsupported.
     #[deprecated = "use Window::request_ime_update instead"]
     fn set_ime_purpose(&self, purpose: ImePurpose) {
-        if self.ime_capabilities().map(|caps| caps.purpose()).unwrap_or(false) {
+        if self.ime_capabilities().map(|caps| caps.hint_and_purpose()).unwrap_or(false) {
             let _ = self.request_ime_update(ImeRequest::Update(ImeRequestData {
-                purpose: Some(purpose),
+                hint_and_purpose: Some((ImeHint::NONE, purpose)),
                 ..ImeRequestData::default()
             }));
         }
@@ -1186,14 +1186,14 @@ pub trait Window: AsAny + Send + Sync + fmt::Debug {
     ///
     /// ```no_run
     /// # use dpi::{Position, Size};
-    /// # use winit_core::window::{Window, ImePurpose, ImeRequest, ImeCapabilities, ImeRequestData, ImeEnableRequest};
+    /// # use winit_core::window::{Window, ImeHint, ImePurpose, ImeRequest, ImeCapabilities, ImeRequestData, ImeEnableRequest};
     /// # fn scope(window: &dyn Window, cursor_pos: Position, cursor_size: Size) {
     /// // Clear previous state by switching off IME
     /// window.request_ime_update(ImeRequest::Disable).expect("Disable cannot fail");
     ///
-    /// let ime_caps = ImeCapabilities::new().with_cursor_area().with_purpose();
+    /// let ime_caps = ImeCapabilities::new().with_cursor_area().with_hint_and_purpose();
     /// let request_data = ImeRequestData::default()
-    ///                          .with_purpose(ImePurpose::Normal)
+    ///                          .with_hint_and_purpose(ImeHint::NONE, ImePurpose::Normal)
     ///                          .with_cursor_area(cursor_pos, cursor_size);
     /// let enable_ime = ImeEnableRequest::new(ime_caps, request_data.clone()).unwrap();
     /// window.request_ime_update(ImeRequest::Enable(enable_ime)).expect("Enabling may fail if IME is not supported");
@@ -1598,7 +1598,10 @@ pub enum WindowLevel {
 
 /// Generic IME purposes for use in [`Window::set_ime_purpose`].
 ///
+/// The purpose should reflect the kind of data to be entered.
 /// The purpose may improve UX by optimizing the IME for the specific use case,
+/// for example showing relevant characters and hiding unneeded ones,
+/// or changing the icon of the confrirmation button,
 /// if winit can express the purpose to the platform and the platform reacts accordingly.
 ///
 /// ## Platform-specific
@@ -1608,14 +1611,31 @@ pub enum WindowLevel {
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum ImePurpose {
-    /// No special hints for the IME (default).
+    /// No special purpose for the IME (default).
     Normal,
     /// The IME is used for password input.
+    /// The IME will treat the contents as sensitive.
     Password,
     /// The IME is used to input into a terminal.
     ///
     /// For example, that could alter OSK on Wayland to show extra buttons.
     Terminal,
+    /// Number (including decimal separator and sign)
+    Number,
+    /// Phone number
+    Phone,
+    /// URL
+    Url,
+    /// Email address
+    Email,
+    /// Password composed only of digits (treated as sensitive data)
+    Pin,
+    /// Date
+    Date,
+    /// Time
+    Time,
+    /// Date and time
+    DateTime,
 }
 
 impl Default for ImePurpose {
@@ -1624,6 +1644,48 @@ impl Default for ImePurpose {
     }
 }
 
+bitflags! {
+    /// IME hints
+    ///
+    /// The hint should reflect the desired behaviour of the IME
+    /// while entering text.
+    /// The purpose may improve UX by optimizing the IME for the specific use case,
+    /// beyond just the general data type specified in `ImePurpose`.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS / Android / Web / Windows / X11 / macOS / Orbital:** Unsupported.
+    #[non_exhaustive]
+    #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
+    pub struct ImeHint: u32 {
+        /// No special behaviour.
+        const NONE = 0;
+        /// Suggest word completions.
+        const COMPLETION = 0x1;
+        /// Suggest word corrections.
+        const SPELLCHECK = 0x2;
+        /// Switch to uppercase letters at the start of a sentence.
+        const AUTO_CAPITALIZATION = 0x4;
+        /// Prefer lowercase letters.
+        const LOWERCASE = 0x8;
+        /// Prefer uppercase letters.
+        const UPPERCASE = 0x10;
+        /// Prefer casing for titles and headings (can be language dependent).
+        const TITLECASE = 0x20;
+        /// Characters should be hidden.
+        ///
+        /// This may prevent e.g. layout switching with some IMEs, unless hint is disabled.
+        const HIDDEN_TEXT = 0x40;
+        /// Typed text should not be stored.
+        const SENSITIVE_DATA = 0x80;
+        /// Just Latin characters should be entered.
+        const LATIN = 0x100;
+        /// The text input is multiline.
+        const MULTILINE = 0x200;
+    }
+}
+
 #[derive(Debug, PartialEq, Eq, Clone, Hash)]
 pub enum ImeSurroundingTextError {
     /// Text exceeds 4000 bytes
@@ -1759,7 +1821,7 @@ impl ImeEnableRequest {
             return None;
         }
 
-        if capabilities.purpose() ^ request_data.purpose.is_some() {
+        if capabilities.hint_and_purpose() ^ request_data.hint_and_purpose.is_some() {
             return None;
         }
 
@@ -1804,23 +1866,23 @@ impl ImeCapabilities {
         Self::default()
     }
 
-    /// Marks `purpose` as supported.
+    /// Marks `hint and purpose` as supported.
     ///
-    /// For more details see [`ImeRequestData::with_purpose`].
-    pub const fn with_purpose(self) -> Self {
-        Self(self.0.union(ImeCapabilitiesFlags::PURPOSE))
+    /// For more details see [`ImeRequestData::with_hint_and_purpose`].
+    pub const fn with_hint_and_purpose(self) -> Self {
+        Self(self.0.union(ImeCapabilitiesFlags::HINT_AND_PURPOSE))
     }
 
-    /// Marks `purpose` as unsupported.
+    /// Marks `hint and purpose` as unsupported.
     ///
-    /// For more details see [`ImeRequestData::with_purpose`].
-    pub const fn without_purpose(self) -> Self {
-        Self(self.0.difference(ImeCapabilitiesFlags::PURPOSE))
+    /// For more details see [`ImeRequestData::with_hint_and_purpose`].
+    pub const fn without_hint_and_purpose(self) -> Self {
+        Self(self.0.difference(ImeCapabilitiesFlags::HINT_AND_PURPOSE))
     }
 
-    /// Returns `true` if `purpose` is supported.
-    pub const fn purpose(&self) -> bool {
-        self.0.contains(ImeCapabilitiesFlags::PURPOSE)
+    /// Returns `true` if `hint and purpose` is supported.
+    pub const fn hint_and_purpose(&self) -> bool {
+        self.0.contains(ImeCapabilitiesFlags::HINT_AND_PURPOSE)
     }
 
     /// Marks `cursor_area` as supported.
@@ -1865,8 +1927,8 @@ impl ImeCapabilities {
 bitflags! {
     #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
     pub(crate) struct ImeCapabilitiesFlags : u8 {
-        /// Client supports setting IME purpose.
-        const PURPOSE = 1 << 0;
+        /// Client supports setting IME hint and purpose.
+        const HINT_AND_PURPOSE = 1 << 0;
         /// Client supports reporting cursor area for IME popup to
         /// appear.
         const CURSOR_AREA = 1 << 1;
@@ -1884,10 +1946,10 @@ bitflags! {
 #[derive(Debug, PartialEq, Clone, Default)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct ImeRequestData {
-    /// Text input purpose.
+    /// Text input hint and purpose.
     ///
-    /// To support updating it, enable [`ImeCapabilities::PURPOSE`].
-    pub purpose: Option<ImePurpose>,
+    /// To support updating it, enable [`ImeCapabilities::HINT_AND_PURPOSE`].
+    pub hint_and_purpose: Option<(ImeHint, ImePurpose)>,
     /// The IME cursor area which should not be covered by the input method popup.
     ///
     /// To support updating it, enable [`ImeCapabilities::CURSOR_AREA`].
@@ -1899,9 +1961,9 @@ pub struct ImeRequestData {
 }
 
 impl ImeRequestData {
-    /// Sets the purpose hint of the current text input.
-    pub fn with_purpose(self, purpose: ImePurpose) -> Self {
-        Self { purpose: Some(purpose), ..self }
+    /// Sets the hint and purpose of the current text input content.
+    pub fn with_hint_and_purpose(self, hint: ImeHint, purpose: ImePurpose) -> Self {
+        Self { hint_and_purpose: Some((hint, purpose)), ..self }
     }
 
     /// Sets the IME cursor editing area.
@@ -2027,7 +2089,7 @@ mod tests {
         ImeCapabilities, ImeEnableRequest, ImeRequestData, ImeSurroundingText,
         ImeSurroundingTextError,
     };
-    use crate::window::ImePurpose;
+    use crate::window::{ImeHint, ImePurpose};
 
     #[test]
     fn ime_initial_request_caps_match() {
@@ -2040,21 +2102,21 @@ mod tests {
         )
         .is_none());
         assert!(ImeEnableRequest::new(
-            ImeCapabilities::new().with_purpose(),
+            ImeCapabilities::new().with_hint_and_purpose(),
             ImeRequestData::default()
         )
         .is_none());
 
         assert!(ImeEnableRequest::new(
             ImeCapabilities::new().with_cursor_area(),
-            ImeRequestData::default().with_purpose(ImePurpose::Normal)
+            ImeRequestData::default().with_hint_and_purpose(ImeHint::NONE, ImePurpose::Normal)
         )
         .is_none());
 
         assert!(ImeEnableRequest::new(
             ImeCapabilities::new(),
             ImeRequestData::default()
-                .with_purpose(ImePurpose::Normal)
+                .with_hint_and_purpose(ImeHint::NONE, ImePurpose::Normal)
                 .with_cursor_area(position, size)
         )
         .is_none());
@@ -2062,7 +2124,7 @@ mod tests {
         assert!(ImeEnableRequest::new(
             ImeCapabilities::new().with_cursor_area(),
             ImeRequestData::default()
-                .with_purpose(ImePurpose::Normal)
+                .with_hint_and_purpose(ImeHint::NONE, ImePurpose::Normal)
                 .with_cursor_area(position, size)
         )
         .is_none());
@@ -2074,9 +2136,9 @@ mod tests {
         .is_some());
 
         assert!(ImeEnableRequest::new(
-            ImeCapabilities::new().with_purpose().with_cursor_area(),
+            ImeCapabilities::new().with_hint_and_purpose().with_cursor_area(),
             ImeRequestData::default()
-                .with_purpose(ImePurpose::Normal)
+                .with_hint_and_purpose(ImeHint::NONE, ImePurpose::Normal)
                 .with_cursor_area(position, size)
         )
         .is_some());

winit-wayland/src/seat/text_input/mod.rs

@@ -11,7 +11,9 @@ use sctk::reexports::protocols::wp::text_input::zv3::client::zwp_text_input_v3::
 };
 use tracing::warn;
 use winit_core::event::{Ime, WindowEvent};
-use winit_core::window::{ImeCapabilities, ImePurpose, ImeRequestData, ImeSurroundingText};
+use winit_core::window::{
+    ImeCapabilities, ImeHint, ImePurpose, ImeRequestData, ImeSurroundingText,
+};
 
 use crate::state::WinitState;
 
@@ -278,9 +280,7 @@ struct DeleteSurroundingText {
 #[derive(Debug, PartialEq, Clone)]
 pub struct ClientState {
     capabilities: ImeCapabilities,
-
     content_type: ContentType,
-
     /// The IME cursor area which should not be covered by the input method popup.
     cursor_area: (LogicalPosition<u32>, LogicalSize<u32>),
 
@@ -302,8 +302,10 @@ impl ClientState {
             surrounding_text: ImeSurroundingText::new(String::new(), 0, 0).unwrap(),
         };
 
-        let unsupported_flags =
-            capabilities.without_purpose().without_cursor_area().without_surrounding_text();
+        let unsupported_flags = capabilities
+            .without_hint_and_purpose()
+            .without_cursor_area()
+            .without_surrounding_text();
 
         if unsupported_flags != ImeCapabilities::new() {
             warn!(
@@ -322,12 +324,10 @@ impl ClientState {
 
     /// Updates the fields of the state which are present in update_fields.
     pub fn update(&mut self, request_data: ImeRequestData, scale_factor: f64) {
-        if let Some(purpose) = request_data.purpose {
-            if self.capabilities.purpose() {
-                self.content_type = purpose.into();
-            } else {
-                warn!("discarding ImePurpose update without capability enabled.");
-            }
+        if let Some((hint, purpose)) =
+            request_data.hint_and_purpose.filter(|_| self.capabilities.hint_and_purpose())
+        {
+            self.content_type = (hint, purpose).into();
         }
 
         if let Some((position, size)) = request_data.cursor_area {
@@ -350,7 +350,7 @@ impl ClientState {
     }
 
     pub fn content_type(&self) -> Option<ContentType> {
-        self.capabilities.purpose().then_some(self.content_type)
+        self.capabilities.hint_and_purpose().then_some(self.content_type)
     }
 
     pub fn cursor_area(&self) -> Option<(LogicalPosition<u32>, LogicalSize<u32>)> {
@@ -365,20 +365,69 @@ impl ClientState {
 /// Arguments to content_type
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct ContentType {
-    /// Text input purpose
-    purpose: ContentPurpose,
+    /// Text input hint.
     hint: ContentHint,
+    /// Text input purpose.
+    purpose: ContentPurpose,
 }
 
-impl From<ImePurpose> for ContentType {
-    fn from(purpose: ImePurpose) -> Self {
-        let (hint, purpose) = match purpose {
-            ImePurpose::Password => (ContentHint::SensitiveData, ContentPurpose::Password),
-            ImePurpose::Terminal => (ContentHint::None, ContentPurpose::Terminal),
-            _ => return Default::default(),
+/// The two options influence each other, so they must be converted together.
+impl From<(ImeHint, ImePurpose)> for ContentType {
+    fn from((hint, purpose): (ImeHint, ImePurpose)) -> Self {
+        let purpose = match purpose {
+            ImePurpose::Password => ContentPurpose::Password,
+            ImePurpose::Terminal => ContentPurpose::Terminal,
+            ImePurpose::Phone => ContentPurpose::Phone,
+            ImePurpose::Number => ContentPurpose::Number,
+            ImePurpose::Url => ContentPurpose::Url,
+            ImePurpose::Email => ContentPurpose::Email,
+            ImePurpose::Pin => ContentPurpose::Pin,
+            ImePurpose::Date => ContentPurpose::Date,
+            ImePurpose::Time => ContentPurpose::Time,
+            ImePurpose::DateTime => ContentPurpose::Datetime,
+            _ => ContentPurpose::Normal,
         };
 
-        Self { hint, purpose }
+        let base_hint = match purpose {
+            // Before the hint API was introduced, password  purpose guaranteed the
+            // sensitive hint. Keep this behaviour for the sake of backwards compatibility.
+            ContentPurpose::Password | ContentPurpose::Pin => ContentHint::SensitiveData,
+            _ => ContentHint::None,
+        };
+
+        let mut new_hint = base_hint;
+        if hint.contains(ImeHint::COMPLETION) {
+            new_hint |= ContentHint::Completion;
+        }
+        if hint.contains(ImeHint::SPELLCHECK) {
+            new_hint |= ContentHint::Spellcheck;
+        }
+        if hint.contains(ImeHint::AUTO_CAPITALIZATION) {
+            new_hint |= ContentHint::AutoCapitalization;
+        }
+        if hint.contains(ImeHint::LOWERCASE) {
+            new_hint |= ContentHint::Lowercase;
+        }
+        if hint.contains(ImeHint::UPPERCASE) {
+            new_hint |= ContentHint::Uppercase;
+        }
+        if hint.contains(ImeHint::TITLECASE) {
+            new_hint |= ContentHint::Titlecase;
+        }
+        if hint.contains(ImeHint::HIDDEN_TEXT) {
+            new_hint |= ContentHint::HiddenText;
+        }
+        if hint.contains(ImeHint::SENSITIVE_DATA) {
+            new_hint |= ContentHint::SensitiveData;
+        }
+        if hint.contains(ImeHint::LATIN) {
+            new_hint |= ContentHint::Latin;
+        }
+        if hint.contains(ImeHint::MULTILINE) {
+            new_hint |= ContentHint::Multiline;
+        }
+
+        Self { hint: new_hint, purpose }
     }
 }
 

winit/examples

@@ -1 +0,0 @@
-../examples

winit/examples/application.rs

@@ -1,4 +1,7 @@
 //! Simple winit application.
+//!
+//! Note that a real application accepting text input **should** support
+//! the IME interface. See the `ime` example.
 
 use std::collections::HashMap;
 use std::error::Error;
@@ -9,22 +12,21 @@ use std::sync::mpsc::{self, Receiver, Sender};
 use std::sync::Arc;
 #[cfg(all(not(android_platform), not(web_platform)))]
 use std::time::Instant;
-use std::{cmp, fmt, mem};
+use std::{fmt, mem};
 
-use ::tracing::{error, info};
 use cursor_icon::CursorIcon;
-use dpi::LogicalPosition;
 #[cfg(not(android_platform))]
 use rwh_06::{DisplayHandle, HasDisplayHandle};
 #[cfg(not(android_platform))]
 use softbuffer::{Context, Surface};
+use tracing::{error, info};
 #[cfg(all(web_platform, not(android_platform)))]
 use web_time::Instant;
 use winit::application::ApplicationHandler;
 use winit::cursor::{Cursor, CustomCursor, CustomCursorSource};
 use winit::dpi::{LogicalSize, PhysicalPosition, PhysicalSize};
 use winit::error::RequestError;
-use winit::event::{DeviceEvent, DeviceId, Ime, MouseButton, MouseScrollDelta, WindowEvent};
+use winit::event::{DeviceEvent, DeviceId, MouseButton, MouseScrollDelta, WindowEvent};
 use winit::event_loop::{ActiveEventLoop, EventLoop};
 use winit::icon::{Icon, RgbaIcon};
 use winit::keyboard::{Key, ModifiersState};
@@ -39,28 +41,23 @@ use winit::platform::wayland::{ActiveEventLoopExtWayland, WindowAttributesWaylan
 use winit::platform::web::{ActiveEventLoopExtWeb, WindowAttributesWeb};
 #[cfg(x11_platform)]
 use winit::platform::x11::{ActiveEventLoopExtX11, WindowAttributesX11};
-use winit::window::{
-    CursorGrabMode, ImeCapabilities, ImeEnableRequest, ImePurpose, ImeRequestData,
-    ImeSurroundingText, ResizeDirection, Theme, Window, WindowAttributes, WindowId,
-};
+use winit::window::{CursorGrabMode, ResizeDirection, Theme, Window, WindowAttributes, WindowId};
 use winit_core::application::macos::ApplicationHandlerExtMacOS;
-use winit_core::window::ImeRequest;
 
 #[path = "util/tracing.rs"]
-mod tracing;
+mod tracing_init;
 
 #[path = "util/fill.rs"]
 mod fill;
 
 /// The amount of points to around the window for drag resize direction calculations.
 const BORDER_SIZE: f64 = 20.;
-const IME_CURSOR_SIZE: PhysicalSize<u32> = PhysicalSize::new(20, 20);
 
 fn main() -> Result<(), Box<dyn Error>> {
     #[cfg(web_platform)]
     console_error_panic_hook::set_once();
 
-    tracing::init();
+    tracing_init::init();
 
     let event_loop = EventLoop::new()?;
     let (sender, receiver) = mpsc::channel();
@@ -245,7 +242,6 @@ impl Application {
                 window.window.set_simple_fullscreen(!window.window.simple_fullscreen());
             },
             Action::ToggleMaximize => window.toggle_maximize(),
-            Action::ToggleImeInput => window.toggle_ime(),
             Action::Minimize => window.minimize(),
             Action::NextCursor => window.next_cursor(),
             Action::NextCustomCursor => {
@@ -512,41 +508,6 @@ impl ApplicationHandler for Application {
                     }
                 }
             },
-            WindowEvent::Ime(event) => match event {
-                Ime::Enabled => info!("IME enabled for Window={window_id:?}"),
-                Ime::Preedit(text, caret_pos) => {
-                    info!("Preedit: {}, with caret at {:?}", text, caret_pos);
-                },
-                Ime::Commit(text) => {
-                    window.text_field_contents.0.push_str(&text);
-                    window.text_field_contents.1 += text.len();
-
-                    info!("Committed: {}", text);
-                    let request_data = window.get_ime_update();
-                    window.window.request_ime_update(ImeRequest::Update(request_data)).unwrap();
-                },
-                Ime::DeleteSurrounding { before_bytes, after_bytes } => {
-                    let (text, cursor) = &window.text_field_contents;
-
-                    // To anyone copying this, keep in mind that this doesn't take text selection
-                    // into account. The deletion happens *around* the pre-edit,
-                    // and may remove the whole selection or a part of it.
-                    let delete_start = cursor.saturating_sub(before_bytes);
-                    let delete_end = cmp::min(cursor.saturating_add(after_bytes), text.len());
-                    if text.is_char_boundary(delete_start) && text.is_char_boundary(delete_end) {
-                        let new_text = {
-                            let mut t = String::from(&text[..delete_start]);
-                            t.push_str(&text[delete_end..]);
-                            t
-                        };
-                        window.text_field_contents = (new_text, delete_start);
-                        info!("IME deleted bytes: {before_bytes}, {after_bytes}");
-                    } else {
-                        error!("Buggy IME tried to delete with indices not on char boundary.");
-                    }
-                },
-                Ime::Disabled => info!("IME disabled for Window={window_id:?}"),
-            },
             WindowEvent::PinchGesture { delta, .. } => {
                 window.zoom += delta;
                 let zoom = window.zoom;
@@ -581,6 +542,7 @@ impl ApplicationHandler for Application {
             | WindowEvent::DragMoved { .. }
             | WindowEvent::DragDropped { .. }
             | WindowEvent::Destroyed
+            | WindowEvent::Ime(_)
             | WindowEvent::Moved(_) => (),
         }
     }
@@ -635,10 +597,6 @@ impl ApplicationHandlerExtMacOS for Application {
 
 /// State of the window.
 struct WindowState {
-    ime_enabled: bool,
-    /// The contents of the emulated text field for IME purposes (not displayed).
-    /// (text, cursor position in bytes).
-    text_field_contents: (String, usize),
     /// Render surface.
     ///
     /// NOTE: This surface must be dropped before the `Window`.
@@ -693,21 +651,6 @@ impl WindowState {
         let named_idx = 0;
         window.set_cursor(CURSORS[named_idx].into());
 
-        // Allow IME out of the box.
-        let request_data = ImeRequestData::default()
-            .with_purpose(ImePurpose::Normal)
-            .with_cursor_area(LogicalPosition { x: 0, y: 0 }.into(), IME_CURSOR_SIZE.into())
-            .with_surrounding_text(ImeSurroundingText::new(String::new(), 0, 0).unwrap());
-        let enable_request = ImeEnableRequest::new(
-            ImeCapabilities::new().with_purpose().with_cursor_area().with_surrounding_text(),
-            request_data,
-        )
-        .unwrap();
-        let enable_ime = ImeRequest::Enable(enable_request);
-
-        // Initial update
-        window.request_ime_update(enable_ime).unwrap();
-
         let size = window.surface_size();
         let mut state = Self {
             #[cfg(macos_platform)]
@@ -723,8 +666,6 @@ impl WindowState {
             continuous_redraw: false,
             #[cfg(not(android_platform))]
             start_time: Instant::now(),
-            ime_enabled: true,
-            text_field_contents: (String::new(), 0),
             cursor_position: Default::default(),
             cursor_hidden: Default::default(),
             modifiers: Default::default(),
@@ -738,65 +679,12 @@ impl WindowState {
         Ok(state)
     }
 
-    pub fn get_ime_update(&self) -> ImeRequestData {
-        let (text, cursor) = &self.text_field_contents;
-        // A rudimentary text field emulation: the caret moves right by a constant amount for each
-        // code point.
-
-        let text_before_caret = if text.is_char_boundary(*cursor) { &text[..*cursor] } else { "" };
-        let chars_before_caret = text_before_caret.chars().count();
-        let cursor_pos = LogicalPosition { x: 10 * chars_before_caret as u32, y: 0 }.into();
-
-        // Limit text field size
-        const MAX_BYTES: usize = ImeSurroundingText::MAX_TEXT_BYTES;
-        let minimal_offset = cursor / MAX_BYTES * MAX_BYTES;
-        let first_char_boundary =
-            (minimal_offset..*cursor).find(|off| text.is_char_boundary(*off)).unwrap_or(*cursor);
-        let last_char_boundary = (*cursor..(first_char_boundary + MAX_BYTES))
-            .rev()
-            .find(|off| text.is_char_boundary(*off))
-            .unwrap_or(*cursor);
-        let surrounding_text = &text[first_char_boundary..last_char_boundary];
-        let relative_cursor = cursor - first_char_boundary;
-        let surrounding_text =
-            ImeSurroundingText::new(surrounding_text.into(), relative_cursor, relative_cursor)
-                .expect("Bug in example: bad byte calculations");
-        ImeRequestData::default()
-            .with_purpose(ImePurpose::Normal)
-            .with_cursor_area(cursor_pos, IME_CURSOR_SIZE.into())
-            .with_surrounding_text(surrounding_text)
-    }
-
-    pub fn toggle_ime(&mut self) {
-        if self.ime_enabled {
-            self.window.request_ime_update(ImeRequest::Disable).expect("disable can not fail");
-        } else {
-            let enable_request = ImeEnableRequest::new(
-                ImeCapabilities::new().with_purpose().with_cursor_area().with_surrounding_text(),
-                self.get_ime_update(),
-            )
-            .unwrap();
-            self.window.request_ime_update(ImeRequest::Enable(enable_request)).unwrap();
-        };
-
-        self.ime_enabled = !self.ime_enabled;
-    }
-
     pub fn minimize(&mut self) {
         self.window.set_minimized(true);
     }
 
     pub fn cursor_moved(&mut self, position: PhysicalPosition<f64>) {
-        // the IME really cares about the caret,
-        // but there's nothing else to demonstrate a position
         self.cursor_position = Some(position);
-        if self.ime_enabled {
-            let request_data =
-                ImeRequestData::default().with_cursor_area(position.into(), IME_CURSOR_SIZE.into());
-            self.window
-                .request_ime_update(ImeRequest::Update(request_data))
-                .expect("A capability was not initially declared");
-        }
     }
 
     pub fn cursor_left(&mut self) {
@@ -1113,7 +1001,6 @@ enum Action {
     ToggleCursorVisibility,
     CreateNewWindow,
     ToggleResizeIncrements,
-    ToggleImeInput,
     ToggleDecorations,
     ToggleResizable,
     ToggleFullscreen,
@@ -1150,7 +1037,6 @@ impl Action {
             Action::CloseWindow => "Close window",
             Action::ToggleCursorVisibility => "Hide cursor",
             Action::CreateNewWindow => "Create new window",
-            Action::ToggleImeInput => "Toggle IME input",
             Action::ToggleDecorations => "Toggle decorations",
             Action::ToggleResizable => "Toggle window resizable state",
             Action::ToggleFullscreen => "Toggle fullscreen",
@@ -1370,7 +1256,6 @@ const KEY_BINDINGS: &[Binding<&'static str>] = &[
     #[cfg(macos_platform)]
     Binding::new("F", ModifiersState::ALT, Action::ToggleSimpleFullscreen),
     Binding::new("D", ModifiersState::CONTROL, Action::ToggleDecorations),
-    Binding::new("I", ModifiersState::CONTROL, Action::ToggleImeInput),
     Binding::new("L", ModifiersState::CONTROL, Action::CycleCursorGrab),
     Binding::new("P", ModifiersState::CONTROL, Action::ToggleResizeIncrements),
     Binding::new("R", ModifiersState::CONTROL, Action::ToggleResizable),

winit/examples/ime.rs

@@ -0,0 +1,374 @@
+//! Showcases the use of an input method engine (IME)
+//! by emulating a text edit field.
+//!
+//! Use CTRL+i to toggle IME support.
+//! Use CTRL+p to cycle content purpose values.
+//! Use CTRL+h to cycle content hint permutations.
+
+use std::cmp;
+use std::error::Error;
+
+use dpi::{LogicalPosition, PhysicalSize};
+use tracing::{error, info};
+use winit::application::ApplicationHandler;
+use winit::event::{Ime, WindowEvent};
+use winit::event_loop::{ActiveEventLoop, EventLoop};
+use winit::keyboard::{Key, ModifiersState, NamedKey};
+#[cfg(web_platform)]
+use winit::platform::web::WindowAttributesWeb;
+use winit::window::{
+    ImeCapabilities, ImeEnableRequest, ImeHint, ImePurpose, ImeRequest, ImeRequestData,
+    ImeSurroundingText, Window, WindowAttributes, WindowId,
+};
+
+#[path = "util/fill.rs"]
+mod fill;
+#[path = "util/tracing.rs"]
+mod tracing_init;
+
+const IME_CURSOR_SIZE: PhysicalSize<u32> = PhysicalSize::new(20, 20);
+
+#[derive(Debug)]
+struct App {
+    window: Option<Box<dyn Window>>,
+    input_state: TextInputState,
+    modifiers: ModifiersState,
+}
+
+/// State of the undisplayed text input field.
+#[derive(Debug)]
+struct TextInputState {
+    ime_enabled: bool,
+    /// The contents of the emulated text field for IME purposes (not displayed).
+    /// (text, cursor position in bytes).
+    contents: String,
+    /// The purpose of the contents the emulated text field expects
+    purpose: ImePurpose,
+    /// The behaviour hints for the IME regarding the emulated text field
+    hint: ImeHint,
+}
+
+impl TextInputState {
+    fn text_and_cursor(&self) -> (&str, usize) {
+        (&self.contents, self.contents.len())
+    }
+
+    fn append_text(&mut self, text: &str) {
+        self.contents.push_str(text);
+    }
+
+    fn set_text(&mut self, text: String) {
+        self.contents = text;
+    }
+
+    fn pop(&mut self) {
+        self.contents.pop();
+    }
+}
+
+impl ApplicationHandler for App {
+    fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
+        #[cfg(not(web_platform))]
+        let window_attributes = WindowAttributes::default();
+        #[cfg(web_platform)]
+        let window_attributes = WindowAttributes::default()
+            .with_platform_attributes(Box::new(WindowAttributesWeb::default().with_append(true)));
+        self.window = match event_loop.create_window(window_attributes) {
+            Ok(window) => Some(window),
+            Err(err) => {
+                eprintln!("error creating window: {err}");
+                event_loop.exit();
+                return;
+            },
+        };
+
+        // Allow IME out of the box.
+        let enable_request = ImeEnableRequest::new(
+            ImeCapabilities::new()
+                .with_hint_and_purpose()
+                .with_cursor_area()
+                .with_surrounding_text(),
+            self.get_ime_update(),
+        )
+        .unwrap();
+        let enable_ime = ImeRequest::Enable(enable_request);
+
+        // Initial update
+        self.window().request_ime_update(enable_ime).unwrap();
+    }
+
+    fn window_event(&mut self, event_loop: &dyn ActiveEventLoop, _: WindowId, event: WindowEvent) {
+        match event {
+            WindowEvent::CloseRequested => {
+                info!("Close was requested; stopping");
+                self.window = None;
+                event_loop.exit();
+            },
+            WindowEvent::SurfaceResized(_) => {
+                self.window.as_ref().expect("resize event without a window").request_redraw();
+            },
+            WindowEvent::RedrawRequested => {
+                // Redraw the application.
+                //
+                // It's preferable for applications that do not render continuously to render in
+                // this event rather than in AboutToWait, since rendering in here allows
+                // the program to gracefully handle redraws requested by the OS.
+
+                let window = self.window.as_ref().expect("redraw request without a window");
+
+                // Notify that you're about to draw.
+                window.pre_present_notify();
+
+                // Draw.
+                fill::fill_window(window.as_ref());
+
+                // For contiguous redraw loop you can request a redraw from here.
+                // window.request_redraw();
+            },
+            WindowEvent::Ime(event) => {
+                self.handle_ime_event(event);
+            },
+            WindowEvent::ModifiersChanged(modifiers) => {
+                self.modifiers = modifiers.state();
+                info!("Modifiers changed to {:?}", self.modifiers);
+            },
+            WindowEvent::KeyboardInput { event, is_synthetic: false, .. } => {
+                let mods = self.modifiers;
+
+                // Dispatch actions only on press.
+                if event.state.is_pressed() {
+                    self.handle_key_pressed(event, mods);
+                }
+            },
+            _ => (),
+        }
+    }
+}
+
+impl App {
+    fn handle_key_pressed(&mut self, event: winit::event::KeyEvent, mods: ModifiersState) {
+        match event.key_without_modifiers.as_ref() {
+            Key::Character("i") if mods == ModifiersState::CONTROL => self.toggle_ime(),
+            Key::Character("p") if mods == ModifiersState::CONTROL => {
+                self.input_state.purpose = match self.input_state.purpose {
+                    ImePurpose::Normal => ImePurpose::Password,
+                    ImePurpose::Password => ImePurpose::Terminal,
+                    ImePurpose::Terminal => ImePurpose::Number,
+                    ImePurpose::Number => ImePurpose::Phone,
+                    ImePurpose::Phone => ImePurpose::Url,
+                    ImePurpose::Url => ImePurpose::Email,
+                    ImePurpose::Email => ImePurpose::Pin,
+                    ImePurpose::Pin => ImePurpose::Date,
+                    ImePurpose::Date => ImePurpose::Time,
+                    ImePurpose::Time => ImePurpose::DateTime,
+                    ImePurpose::DateTime => ImePurpose::Normal,
+                    _ => ImePurpose::Normal,
+                };
+                if self.input_state.ime_enabled {
+                    self.window()
+                        .request_ime_update(ImeRequest::Update(self.get_ime_update()))
+                        .unwrap();
+                }
+                info!("text input purpose now {:?}", self.input_state.purpose);
+            },
+            Key::Character("h") if mods == ModifiersState::CONTROL => {
+                let bump = |hint: ImeHint| {
+                    if hint.is_all() {
+                        ImeHint::NONE
+                    } else {
+                        // Go through all integers. We'll skip invalid ones
+                        ImeHint::from_bits_retain(hint.bits().wrapping_add(1))
+                    }
+                };
+                let mut new_hint = bump(self.input_state.hint);
+
+                while !ImeHint::all().contains(new_hint) {
+                    new_hint = bump(new_hint);
+                }
+
+                self.input_state.hint = new_hint;
+
+                if self.input_state.ime_enabled {
+                    self.window()
+                        .request_ime_update(ImeRequest::Update(self.get_ime_update()))
+                        .unwrap();
+                }
+                info!("text input IME hint now {:?}", self.input_state.hint);
+            },
+            Key::Named(NamedKey::Backspace) => {
+                self.input_state.pop();
+                self.print_input_state();
+            },
+            _ => {
+                if let Some(text) = event.text_with_all_modifiers {
+                    self.input_state.append_text(&text);
+                    if self.input_state.ime_enabled {
+                        self.window()
+                            .request_ime_update(ImeRequest::Update(self.get_ime_update()))
+                            .unwrap();
+                    }
+                    self.print_input_state();
+                }
+            },
+        }
+    }
+
+    fn handle_ime_event(&mut self, event: Ime) {
+        let window = self.window.as_ref().expect("IME request without a window");
+        match event {
+            Ime::Enabled => info!("IME enabled for Window={:?}", window.id()),
+            Ime::Preedit(text, caret_pos) => info!("Preedit: {text}, with caret at {caret_pos:?}"),
+            Ime::Commit(text) => {
+                self.input_state.append_text(&text);
+                let request_data = self.get_ime_update();
+                window.request_ime_update(ImeRequest::Update(request_data)).unwrap();
+                self.print_input_state();
+            },
+            Ime::DeleteSurrounding { before_bytes, after_bytes } => {
+                let (text, cursor) = &self.input_state.text_and_cursor();
+
+                // To anyone copying this, keep in mind that this doesn't take text
+                // selection into account. The deletion happens
+                // *around* the pre-edit, and may remove the whole
+                // selection or a part of it.
+                let delete_start = cursor.saturating_sub(before_bytes);
+                let delete_end = cmp::min(cursor.saturating_add(after_bytes), text.len());
+                if text.is_char_boundary(delete_start) && text.is_char_boundary(delete_end) {
+                    let new_text = {
+                        let mut t = String::from(&text[..delete_start]);
+                        t.push_str(&text[delete_end..]);
+                        t
+                    };
+                    self.input_state.set_text(new_text);
+                    info!("IME deleted bytes: {before_bytes}, {after_bytes}");
+                    self.print_input_state();
+                } else {
+                    error!("Buggy IME tried to delete with indices not on char boundary.");
+                }
+            },
+            Ime::Disabled => info!("IME disabled for Window={:?}", window.id()),
+        }
+    }
+
+    fn toggle_ime(&mut self) {
+        let enable = !self.input_state.ime_enabled;
+
+        if enable {
+            let enable_request = ImeEnableRequest::new(
+                ImeCapabilities::new()
+                    .with_hint_and_purpose()
+                    .with_cursor_area()
+                    .with_surrounding_text(),
+                self.get_ime_update(),
+            )
+            .unwrap();
+            self.window().request_ime_update(ImeRequest::Enable(enable_request)).unwrap();
+        } else {
+            self.window().request_ime_update(ImeRequest::Disable).expect("disable can not fail");
+        };
+
+        self.input_state.ime_enabled = enable;
+
+        info!("IME enabled now {}", self.input_state.ime_enabled);
+    }
+
+    fn get_ime_update(&self) -> ImeRequestData {
+        let text = &self.input_state.contents;
+        let cursor = text.len();
+        // A rudimentary text field emulation: the caret moves right by a constant amount for each
+        // code point.
+
+        let text_before_caret = if text.is_char_boundary(cursor) { &text[..cursor] } else { "" };
+        let chars_before_caret = text_before_caret.chars().count();
+        let cursor_pos = LogicalPosition::<u32> { x: 10 * chars_before_caret as u32, y: 0 };
+
+        // Limit text field size
+        const MAX_BYTES: usize = ImeSurroundingText::MAX_TEXT_BYTES;
+        let minimal_offset = cursor / MAX_BYTES * MAX_BYTES;
+        let first_char_boundary =
+            (minimal_offset..cursor).find(|off| text.is_char_boundary(*off)).unwrap_or(cursor);
+        let last_char_boundary = (cursor..(first_char_boundary + MAX_BYTES))
+            .rev()
+            .find(|off| text.is_char_boundary(*off))
+            .unwrap_or(cursor);
+        let surrounding_text = &text[first_char_boundary..last_char_boundary];
+        let relative_cursor = cursor - first_char_boundary;
+        let surrounding_text =
+            ImeSurroundingText::new(surrounding_text.into(), relative_cursor, relative_cursor)
+                .expect("Bug in example: bad byte calculations");
+
+        ImeRequestData::default()
+            .with_hint_and_purpose(self.input_state.hint, self.input_state.purpose)
+            .with_cursor_area(cursor_pos.into(), IME_CURSOR_SIZE.into())
+            .with_surrounding_text(surrounding_text)
+    }
+
+    fn print_input_state(&self) {
+        let (text, cursor) = &self.input_state.text_and_cursor();
+        // Representing a selection with the cursor and anchor as ends is not
+        // supported yet. Using the same position for anchor to mark no
+        // selection.
+        info!("{}", preedit_with_cursor(text, *cursor, *cursor));
+    }
+
+    fn window(&self) -> &dyn Window {
+        self.window.as_ref().unwrap().as_ref()
+    }
+}
+
+/// Prints text of the text field, highlighting cursor position
+fn preedit_with_cursor(text: &str, cursor: usize, anchor: usize) -> String {
+    preedit_with_cursor_checked(text, cursor, anchor).unwrap_or_else(|e| format!("INVALID: {e}"))
+}
+
+fn preedit_with_cursor_checked(text: &str, cursor: usize, anchor: usize) -> Result<String, &str> {
+    let first = cmp::min(cursor, anchor);
+    let before = text.get(0..first).ok_or("first segment ends not on char boundary")?;
+    let second = cmp::max(cursor, anchor);
+    let mid = if second == first {
+        None
+    } else {
+        Some(text.get(first..second).ok_or("second segment ends not on char boundary")?)
+    };
+    let end = text.get(second..).unwrap();
+    Ok(match (first == cursor, before, mid, end) {
+        (_, before, None, end) => format!("{before}|{end}"),
+        (true, before, Some(mid), end) => format!("{before}|{mid}_{end}"),
+        (false, before, Some(mid), end) => format!("{before}_{mid}|{end}"),
+    })
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    #[cfg(web_platform)]
+    console_error_panic_hook::set_once();
+
+    tracing_init::init();
+
+    let event_loop = EventLoop::new()?;
+
+    println!(
+        r#"This showcases the use of an input method engine (IME) by emulating a text edit field.
+Use CTRL+i to toggle IME support.
+Use CTRL+p to cycle content purpose values.
+Use CTRL+h to cycle content hint permutations.
+"#
+    );
+
+    let app = App {
+        window: None,
+        input_state: TextInputState {
+            ime_enabled: true,
+            contents: String::new(),
+            purpose: ImePurpose::Normal,
+            // While we don't show text and thus we use ImeHint::HIDDEN
+            // it may cause the IME to not do layout switch, etc at all.
+            hint: ImeHint::NONE,
+        },
+        modifiers: ModifiersState::default(),
+    };
+
+    // For alternative loop run options see `pump_events` and `run_on_demand` examples.
+    event_loop.run_app(app)?;
+
+    Ok(())
+}

winit/src/changelog/unreleased.md

@@ -84,6 +84,8 @@ changelog entry.
 - On Wayland, added implementation for `Window::set_window_icon`
 - Add `Window::request_ime_update` to atomically apply set of IME changes.
 - Add `Ime::DeleteSurrounding` to let the input method delete text.
+- Add more `ImePurpose` values.
+- Add `ImeHints` to request particular IME behaviour.
 
 ### Changed