Add inline input method support

This commit adds support for inline IME handling. It also makes the
search bar use underline cursor instead of using '_' character.

Fixes #1613.

7 files changed, 296 insertions, 46 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 85364b8e..3f16e7d2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -27,6 +27,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Escape sequence to set hyperlinks (`OSC 8 ; params ; URI ST`)
 - Config `hints.enabled.hyperlinks` for hyperlink escape sequence hint highlight
 - `window.decorations_theme_variant` to control both Wayland CSD and GTK theme variant on X11
+- Support for inline input method
 
 ### Changed
 
@@ -42,6 +43,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Config option `window.gtk_theme_variant`, you should use `window.decorations_theme_variant` instead
 - `--class` now sets both class part of WM_CLASS property and instance
 - `--class`'s `general` and `instance` options were swapped
+- Search bar is now respecting cursor thickness
+- On X11 the IME popup window is stuck at the bottom of the window due to Xlib limitations
+- IME no longer works in Vi mode when moving around
 
 ### Fixed
 
diff --git a/alacritty/src/display/content.rs b/alacritty/src/display/content.rs
index 478982bb..c062ba9b 100644
--- a/alacritty/src/display/content.rs
+++ b/alacritty/src/display/content.rs
@@ -51,6 +51,7 @@ impl<'a> RenderableContent<'a> {
         let cursor_shape = if terminal_content.cursor.shape == CursorShape::Hidden
             || display.cursor_hidden
             || search_state.regex().is_some()
+            || display.ime.preedit().is_some()
         {
             CursorShape::Hidden
         } else if !term.is_focused && config.terminal_config.cursor.unfocused_hollow {
@@ -394,6 +395,10 @@ impl RenderableCursor {
 }
 
 impl RenderableCursor {
+    pub fn new(point: Point<usize>, shape: CursorShape, cursor_color: Rgb, is_wide: bool) -> Self {
+        Self { shape, cursor_color, text_color: cursor_color, is_wide, point }
+    }
+
     pub fn color(&self) -> Rgb {
         self.cursor_color
     }
diff --git a/alacritty/src/display/mod.rs b/alacritty/src/display/mod.rs
index 7bd50049..e48d2b68 100644
--- a/alacritty/src/display/mod.rs
+++ b/alacritty/src/display/mod.rs
@@ -20,8 +20,9 @@ use serde::{Deserialize, Serialize};
 use wayland_client::EventQueue;
 
 use crossfont::{self, Rasterize, Rasterizer};
+use unicode_width::UnicodeWidthChar;
 
-use alacritty_terminal::ansi::NamedColor;
+use alacritty_terminal::ansi::{CursorShape, NamedColor};
 use alacritty_terminal::config::MAX_SCROLLBACK_LINES;
 use alacritty_terminal::event::{EventListener, OnResize, WindowSize};
 use alacritty_terminal::grid::Dimensions as TermDimensions;
@@ -38,7 +39,7 @@ use crate::config::window::{Dimensions, Identity};
 use crate::config::UiConfig;
 use crate::display::bell::VisualBell;
 use crate::display::color::List;
-use crate::display::content::RenderableContent;
+use crate::display::content::{RenderableContent, RenderableCursor};
 use crate::display::cursor::IntoRects;
 use crate::display::damage::RenderDamageIterator;
 use crate::display::hint::{HintMatch, HintState};
@@ -46,7 +47,7 @@ use crate::display::meter::Meter;
 use crate::display::window::Window;
 use crate::event::{Mouse, SearchState};
 use crate::message_bar::{MessageBuffer, MessageType};
-use crate::renderer::rects::{RenderLines, RenderRect};
+use crate::renderer::rects::{RenderLine, RenderLines, RenderRect};
 use crate::renderer::{self, GlyphCache, Renderer};
 use crate::string::{ShortenDirection, StrShortener};
 
@@ -362,6 +363,9 @@ pub struct Display {
     /// The renderer update that takes place only once before the actual rendering.
     pub pending_renderer_update: Option<RendererUpdate>,
 
+    /// The ime on the given display.
+    pub ime: Ime,
+
     // Mouse point position when highlighting hints.
     hint_mouse_point: Option<Point>,
 
@@ -374,6 +378,77 @@ pub struct Display {
     meter: Meter,
 }
 
+/// Input method state.
+#[derive(Debug, Default)]
+pub struct Ime {
+    /// Whether the IME is enabled.
+    enabled: bool,
+
+    /// Current IME preedit.
+    preedit: Option<Preedit>,
+}
+
+impl Ime {
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    #[inline]
+    pub fn set_enabled(&mut self, is_enabled: bool) {
+        if is_enabled {
+            self.enabled = is_enabled
+        } else {
+            // Clear state when disabling IME.
+            *self = Default::default();
+        }
+    }
+
+    #[inline]
+    pub fn is_enabled(&self) -> bool {
+        self.enabled
+    }
+
+    #[inline]
+    pub fn set_preedit(&mut self, preedit: Option<Preedit>) {
+        self.preedit = preedit;
+    }
+
+    #[inline]
+    pub fn preedit(&self) -> Option<&Preedit> {
+        self.preedit.as_ref()
+    }
+}
+
+#[derive(Debug, Default)]
+pub struct Preedit {
+    /// The preedit text.
+    text: String,
+
+    /// Byte offset for cursor start into the preedit text.
+    ///
+    /// `None` means that the cursor is invisible.
+    cursor_byte_offset: Option<usize>,
+
+    /// The cursor offset from the end of the preedit in char width.
+    cursor_end_offset: Option<usize>,
+}
+
+impl Preedit {
+    pub fn new(text: String, cursor_byte_offset: Option<usize>) -> Self {
+        let cursor_end_offset = if let Some(byte_offset) = cursor_byte_offset {
+            // Convert byte offset into char offset.
+            let cursor_end_offset =
+                text[byte_offset..].chars().fold(0, |acc, ch| acc + ch.width().unwrap_or(1));
+
+            Some(cursor_end_offset)
+        } else {
+            None
+        };
+
+        Self { text, cursor_byte_offset, cursor_end_offset }
+    }
+}
+
 /// Pending renderer updates.
 ///
 /// All renderer updates are cached to be applied just before rendering, to avoid platform-specific
@@ -529,6 +604,7 @@ impl Display {
             hint_state,
             meter: Meter::new(),
             size_info,
+            ime: Ime::new(),
             highlighted_hint: None,
             vi_highlighted_hint: None,
             #[cfg(not(any(target_os = "macos", windows)))]
@@ -750,6 +826,7 @@ impl Display {
             grid_cells.push(cell);
         }
         let selection_range = content.selection_range();
+        let foreground_color = content.color(NamedColor::Foreground as usize);
         let background_color = content.color(NamedColor::Background as usize);
         let display_offset = content.display_offset();
         let cursor = content.cursor();
@@ -835,9 +912,7 @@ impl Display {
         };
 
         // Draw cursor.
-        for rect in cursor.rects(&size_info, config.terminal_config.cursor.thickness()) {
-            rects.push(rect);
-        }
+        rects.extend(cursor.rects(&size_info, config.terminal_config.cursor.thickness()));
 
         // Push visual bell after url/underline/strikeout rects.
         let visual_bell_intensity = self.visual_bell.intensity();
@@ -853,6 +928,55 @@ impl Display {
             rects.push(visual_bell_rect);
         }
 
+        // Handle IME positioning and search bar rendering.
+        let ime_position = match search_state.regex() {
+            Some(regex) => {
+                let search_label = match search_state.direction() {
+                    Direction::Right => FORWARD_SEARCH_LABEL,
+                    Direction::Left => BACKWARD_SEARCH_LABEL,
+                };
+
+                let search_text = Self::format_search(regex, search_label, size_info.columns());
+
+                // Render the search bar.
+                self.draw_search(config, &search_text);
+
+                // Draw search bar cursor.
+                let line = size_info.screen_lines();
+                let column = Column(search_text.chars().count() - 1);
+
+                // Add cursor to search bar if IME is not active.
+                if self.ime.preedit().is_none() {
+                    let fg = config.colors.footer_bar_foreground();
+                    let shape = CursorShape::Underline;
+                    let cursor = RenderableCursor::new(Point::new(line, column), shape, fg, false);
+                    rects.extend(
+                        cursor.rects(&size_info, config.terminal_config.cursor.thickness()),
+                    );
+                }
+
+                Some(Point::new(line, column))
+            },
+            None => {
+                let num_lines = self.size_info.screen_lines();
+                term::point_to_viewport(display_offset, cursor_point)
+                    .filter(|point| point.line < num_lines)
+            },
+        };
+
+        // Handle IME.
+        if self.ime.is_enabled() {
+            if let Some(point) = ime_position {
+                let (fg, bg) = if search_state.regex().is_some() {
+                    (config.colors.footer_bar_foreground(), config.colors.footer_bar_background())
+                } else {
+                    (foreground_color, background_color)
+                };
+
+                self.draw_ime_preview(point, fg, bg, &mut rects, config);
+            }
+        }
+
         if self.debug_damage {
             self.highlight_damage(&mut rects);
         }
@@ -900,34 +1024,11 @@ impl Display {
 
         self.draw_render_timer(config);
 
-        // Handle search and IME positioning.
-        let ime_position = match search_state.regex() {
-            Some(regex) => {
-                let search_label = match search_state.direction() {
-                    Direction::Right => FORWARD_SEARCH_LABEL,
-                    Direction::Left => BACKWARD_SEARCH_LABEL,
-                };
-
-                let search_text = Self::format_search(regex, search_label, size_info.columns());
-
-                // Render the search bar.
-                self.draw_search(config, &search_text);
-
-                // Compute IME position.
-                let line = Line(size_info.screen_lines() as i32 + 1);
-                Point::new(line, Column(search_text.chars().count() - 1))
-            },
-            None => cursor_point,
-        };
-
         // Draw hyperlink uri preview.
         if has_highlighted_hint {
             self.draw_hyperlink_preview(config, vi_cursor_point, display_offset);
         }
 
-        // Update IME position.
-        self.window.update_ime_position(ime_position, &self.size_info);
-
         // Frame event should be requested before swaping buffers, since it requires surface
         // `commit`, which is done by swap buffers under the hood.
         #[cfg(all(feature = "wayland", not(any(target_os = "macos", windows))))]
@@ -1015,6 +1116,95 @@ impl Display {
         dirty
     }
 
+    #[inline(never)]
+    fn draw_ime_preview(
+        &mut self,
+        point: Point<usize>,
+        fg: Rgb,
+        bg: Rgb,
+        rects: &mut Vec<RenderRect>,
+        config: &UiConfig,
+    ) {
+        let preedit = match self.ime.preedit() {
+            Some(preedit) => preedit,
+            None => {
+                // In case we don't have preedit, just set the popup point.
+                self.window.update_ime_position(point, &self.size_info);
+                return;
+            },
+        };
+
+        let num_cols = self.size_info.columns();
+
+        // Get the visible preedit.
+        let visible_text: String = match (preedit.cursor_byte_offset, preedit.cursor_end_offset) {
+            (Some(byte_offset), Some(end_offset)) if end_offset > num_cols => StrShortener::new(
+                &preedit.text[byte_offset..],
+                num_cols,
+                ShortenDirection::Right,
+                Some(SHORTENER),
+            ),
+            _ => {
+                StrShortener::new(&preedit.text, num_cols, ShortenDirection::Left, Some(SHORTENER))
+            },
+        }
+        .collect();
+
+        let visible_len = visible_text.chars().count();
+
+        let end = cmp::min(point.column.0 + visible_len, num_cols);
+        let start = end.saturating_sub(visible_len);
+
+        let start = Point::new(point.line, Column(start));
+        let end = Point::new(point.line, Column(end - 1));
+
+        let glyph_cache = &mut self.glyph_cache;
+        let metrics = glyph_cache.font_metrics();
+
+        self.renderer.draw_string(
+            start,
+            fg,
+            bg,
+            visible_text.chars(),
+            &self.size_info,
+            glyph_cache,
+        );
+
+        if self.collect_damage() {
+            let damage = self.damage_from_point(Point::new(start.line, Column(0)), num_cols as u32);
+            self.damage_rects.push(damage);
+            self.next_frame_damage_rects.push(damage);
+        }
+
+        // Add underline for preedit text.
+        let underline = RenderLine { start, end, color: fg };
+        rects.extend(underline.rects(Flags::UNDERLINE, &metrics, &self.size_info));
+
+        let ime_popup_point = match preedit.cursor_end_offset {
+            Some(cursor_end_offset) if cursor_end_offset != 0 => {
+                let is_wide = preedit.text[preedit.cursor_byte_offset.unwrap_or_default()..]
+                    .chars()
+                    .next()
+                    .map(|ch| ch.width() == Some(2))
+                    .unwrap_or_default();
+
+                let cursor_column = Column(
+                    (end.column.0 as isize - cursor_end_offset as isize + 1).max(0) as usize,
+                );
+                let cursor_point = Point::new(point.line, cursor_column);
+                let cursor =
+                    RenderableCursor::new(cursor_point, CursorShape::HollowBlock, fg, is_wide);
+                rects.extend(
+                    cursor.rects(&self.size_info, config.terminal_config.cursor.thickness()),
+                );
+                cursor_point
+            },
+            _ => end,
+        };
+
+        self.window.update_ime_position(ime_popup_point, &self.size_info);
+    }
+
     /// Format search regex to account for the cursor and fullwidth characters.
     fn format_search(search_regex: &str, search_label: &str, max_width: usize) -> String {
         let label_len = search_label.len();
@@ -1033,7 +1223,8 @@ impl Display {
             Some(SHORTENER),
         ));
 
-        bar_text.push('_');
+        // Add place for cursor.
+        bar_text.push(' ');
 
         bar_text
     }
diff --git a/alacritty/src/display/window.rs b/alacritty/src/display/window.rs
index 3cc00a98..eac12a22 100644
--- a/alacritty/src/display/window.rs
+++ b/alacritty/src/display/window.rs
@@ -460,10 +460,14 @@ impl Window {
         self.wayland_surface.as_ref()
     }
 
+    pub fn set_ime_allowed(&self, allowed: bool) {
+        self.windowed_context.window().set_ime_allowed(allowed);
+    }
+
     /// Adjust the IME editor position according to the new location of the cursor.
-    pub fn update_ime_position(&self, point: Point, size: &SizeInfo) {
+    pub fn update_ime_position(&self, point: Point<usize>, size: &SizeInfo) {
         let nspot_x = f64::from(size.padding_x() + point.column.0 as f32 * size.cell_width());
-        let nspot_y = f64::from(size.padding_y() + (point.line.0 + 1) as f32 * size.cell_height());
+        let nspot_y = f64::from(size.padding_y() + (point.line + 1) as f32 * size.cell_height());
 
         self.window().set_ime_position(PhysicalPosition::new(nspot_x, nspot_y));
     }
diff --git a/alacritty/src/event.rs b/alacritty/src/event.rs
index 3beb5d1e..b4258a03 100644
--- a/alacritty/src/event.rs
+++ b/alacritty/src/event.rs
@@ -47,7 +47,7 @@ use crate::daemon::foreground_process_path;
 use crate::daemon::spawn_daemon;
 use crate::display::hint::HintMatch;
 use crate::display::window::Window;
-use crate::display::{Display, SizeInfo};
+use crate::display::{Display, Preedit, SizeInfo};
 use crate::input::{self, ActionContext as _, FONT_SIZE_STEP};
 use crate::message_bar::{Message, MessageBuffer};
 use crate::scheduler::{Scheduler, TimerId, Topic};
@@ -476,6 +476,9 @@ impl<'a, N: Notify + 'a, T: EventListener> input::ActionContext<T> for ActionCon
             };
         }
 
+        // Enable IME so we can input into the search bar with it if we were in Vi mode.
+        self.window().set_ime_allowed(true);
+
         self.display.pending_update.dirty = true;
     }
 
@@ -786,7 +789,8 @@ impl<'a, N: Notify + 'a, T: EventListener> input::ActionContext<T> for ActionCon
     /// Toggle the vi mode status.
     #[inline]
     fn toggle_vi_mode(&mut self) {
-        if self.terminal.mode().contains(TermMode::VI) {
+        let was_in_vi_mode = self.terminal.mode().contains(TermMode::VI);
+        if was_in_vi_mode {
             // If we had search running when leaving Vi mode we should mark terminal fully damaged
             // to cleanup highlighted results.
             if self.search_state.dfas.take().is_some() {
@@ -803,6 +807,9 @@ impl<'a, N: Notify + 'a, T: EventListener> input::ActionContext<T> for ActionCon
             self.cancel_search();
         }
 
+        // We don't want IME in Vi mode.
+        self.window().set_ime_allowed(was_in_vi_mode);
+
         self.terminal.toggle_vi_mode();
 
         *self.dirty = true;
@@ -936,6 +943,9 @@ impl<'a, N: Notify + 'a, T: EventListener> ActionContext<'a, N, T> {
 
     /// Cleanup the search state.
     fn exit_search(&mut self) {
+        let vi_mode = self.terminal.mode().contains(TermMode::VI);
+        self.window().set_ime_allowed(!vi_mode);
+
         self.display.pending_update.dirty = true;
         self.search_state.history_index = None;
 
@@ -955,7 +965,8 @@ impl<'a, N: Notify + 'a, T: EventListener> ActionContext<'a, N, T> {
         // Check terminal cursor style.
         let terminal_blinking = self.terminal.cursor_style().blinking;
         let mut blinking = cursor_style.blinking_override().unwrap_or(terminal_blinking);
-        blinking &= vi_mode || self.terminal().mode().contains(TermMode::SHOW_CURSOR);
+        blinking &= (vi_mode || self.terminal().mode().contains(TermMode::SHOW_CURSOR))
+            && self.display().ime.preedit().is_none();
 
         // Update cursor blinking state.
         let window_id = self.display.window.id();
@@ -1216,12 +1227,37 @@ impl input::Processor<EventProxy, ActionContext<'_, Notifier, EventProxy>> {
                             *self.ctx.dirty = true;
                         }
                     },
-                    WindowEvent::Ime(ime) => {
-                        if let Ime::Commit(text) = ime {
+                    WindowEvent::Ime(ime) => match ime {
+                        Ime::Commit(text) => {
+                            // Clear preedit.
+                            self.ctx.display.ime.set_preedit(None);
+                            *self.ctx.dirty = true;
+
                             for ch in text.chars() {
-                                self.received_char(ch)
+                                self.received_char(ch);
                             }
-                        }
+
+                            self.ctx.update_cursor_blinking();
+                        },
+                        Ime::Preedit(text, cursor_offset) => {
+                            let preedit = if text.is_empty() {
+                                None
+                            } else {
+                                Some(Preedit::new(text, cursor_offset.map(|offset| offset.0)))
+                            };
+
+                            self.ctx.display.ime.set_preedit(preedit);
+                            self.ctx.update_cursor_blinking();
+                            *self.ctx.dirty = true;
+                        },
+                        Ime::Enabled => {
+                            self.ctx.display.ime.set_enabled(true);
+                            *self.ctx.dirty = true;
+                        },
+                        Ime::Disabled => {
+                            self.ctx.display.ime.set_enabled(false);
+                            *self.ctx.dirty = true;
+                        },
                     },
                     WindowEvent::KeyboardInput { is_synthetic: true, .. }
                     | WindowEvent::TouchpadPressure { .. }
diff --git a/alacritty/src/input.rs b/alacritty/src/input.rs
index 35aaedda..a612db12 100644
--- a/alacritty/src/input.rs
+++ b/alacritty/src/input.rs
@@ -754,6 +754,11 @@ impl<T: EventListener, A: ActionContext<T>> Processor<T, A> {
 
     /// Process key input.
     pub fn key_input(&mut self, input: KeyboardInput) {
+        // IME input will be applied on commit and shouldn't trigger key bindings.
+        if self.ctx.display().ime.preedit().is_some() {
+            return;
+        }
+
         // All key bindings are disabled while a hint is being selected.
         if self.ctx.display().hint_state.active() {
             *self.ctx.suppress_chars() = false;
@@ -801,6 +806,11 @@ impl<T: EventListener, A: ActionContext<T>> Processor<T, A> {
     pub fn received_char(&mut self, c: char) {
         let suppress_chars = *self.ctx.suppress_chars();
 
+        // Don't insert chars when we have IME running.
+        if self.ctx.display().ime.preedit().is_some() {
+            return;
+        }
+
         // Handle hint selection over anything else.
         if self.ctx.display().hint_state.active() && !suppress_chars {
             self.ctx.hint_input(c);
diff --git a/alacritty/src/string.rs b/alacritty/src/string.rs
index 4a758b34..a111166d 100644
--- a/alacritty/src/string.rs
+++ b/alacritty/src/string.rs
@@ -5,7 +5,7 @@ use std::str::Chars;
 use unicode_width::UnicodeWidthChar;
 
 /// The action performed by [`StrShortener`].
-#[derive(Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum TextAction {
     /// Yield a spacer.
     Spacer,
@@ -93,7 +93,7 @@ impl<'a> StrShortener<'a> {
         let num_chars = iter.last().map_or(offset, |(idx, _)| idx + 1);
         let skip_chars = num_chars - offset;
 
-        let text_action = if num_chars <= max_width || shortener.is_none() {
+        let text_action = if current_len < max_width || shortener.is_none() {
             TextAction::Char
         } else {
             TextAction::Shortener
@@ -203,8 +203,8 @@ mod tests {
             &StrShortener::new(s, len * 2, ShortenDirection::Left, Some('.')).collect::<String>()
         );
 
-        let s = "こJんにちはP";
-        let len = 2 + 1 + 2 + 2 + 2 + 2 + 1;
+        let s = "ちはP";
+        let len = 2 + 2 + 1;
         assert_eq!(
             ".",
             &StrShortener::new(s, 1, ShortenDirection::Right, Some('.')).collect::<String>()
@@ -226,7 +226,7 @@ mod tests {
         );
 
         assert_eq!(
-            "こ .",
+            "ち .",
             &StrShortener::new(s, 3, ShortenDirection::Right, Some('.')).collect::<String>()
         );
 
@@ -236,12 +236,12 @@ mod tests {
         );
 
         assert_eq!(
-            "こ Jん に ち は P",
+            "ち は P",
             &StrShortener::new(s, len * 2, ShortenDirection::Left, Some('.')).collect::<String>()
         );
 
         assert_eq!(
-            "こ Jん に ち は P",
+            "ち は P",
             &StrShortener::new(s, len * 2, ShortenDirection::Right, Some('.')).collect::<String>()
         );
     }