Better text selection

lib/ui/src/platform.rs

@@ -69,6 +69,10 @@ pub enum PlatformEvent {
         window_id: WindowId,
         event: KeyboardEvent,
     },
+    ClipboardText {
+        window_id: WindowId,
+        text: String,
+    },
     PrimarySelectionText {
         window_id: WindowId,
         text: String,
@@ -107,6 +111,13 @@ pub enum PlatformRequest {
         window_id: WindowId,
         scene: SceneSnapshot,
     },
+    SetClipboardText {
+        window_id: WindowId,
+        text: String,
+    },
+    RequestClipboardText {
+        window_id: WindowId,
+    },
     SetPrimarySelectionText {
         window_id: WindowId,
         text: String,
@@ -254,6 +265,21 @@ impl PlatformProxy {
         self.send(PlatformRequest::RequestPrimarySelectionText { window_id })
     }
 
+    pub fn set_clipboard_text(
+        &self,
+        window_id: WindowId,
+        text: impl Into<String>,
+    ) -> Result<(), PlatformClosed> {
+        self.send(PlatformRequest::SetClipboardText {
+            window_id,
+            text: text.into(),
+        })
+    }
+
+    pub fn request_clipboard_text(&self, window_id: WindowId) -> Result<(), PlatformClosed> {
+        self.send(PlatformRequest::RequestClipboardText { window_id })
+    }
+
     pub fn set_cursor_icon(
         &self,
         window_id: WindowId,
@@ -328,6 +354,8 @@ pub fn start_headless() -> PlatformRuntime {
                             PlatformRequest::ReplaceScene { window_id, scene } => {
                                 handle_replace_scene(&state, window_id, scene);
                             }
+                            PlatformRequest::SetClipboardText { .. } => {}
+                            PlatformRequest::RequestClipboardText { .. } => {}
                             PlatformRequest::SetPrimarySelectionText { .. } => {}
                             PlatformRequest::RequestPrimarySelectionText { .. } => {}
                             PlatformRequest::SetCursorIcon { .. } => {}

lib/ui/src/runtime.rs

@@ -117,6 +117,16 @@ impl WindowController {
         self.proxy.set_primary_selection_text(self.id, text)
     }
 
+    /// Copies plain text to the platform clipboard for this window.
+    pub fn set_clipboard_text(&self, text: impl Into<String>) -> Result<(), PlatformClosed> {
+        self.proxy.set_clipboard_text(self.id, text)
+    }
+
+    /// Requests the current plain-text clipboard contents from the platform.
+    pub fn request_clipboard_text(&self) -> Result<(), PlatformClosed> {
+        self.proxy.request_clipboard_text(self.id)
+    }
+
     /// Requests the current plain-text primary selection contents from the platform.
     pub fn request_primary_selection_text(&self) -> Result<(), PlatformClosed> {
         self.proxy.request_primary_selection_text(self.id)

lib/ui/src/scene.rs

@@ -240,6 +240,77 @@ impl PreparedText {
         ))
     }
 
+    pub fn previous_char_boundary(&self, offset: usize) -> usize {
+        let offset = offset.min(self.text.len());
+        self.text[..offset]
+            .char_indices()
+            .last()
+            .map(|(index, _)| index)
+            .unwrap_or(0)
+    }
+
+    pub fn next_char_boundary(&self, offset: usize) -> usize {
+        let offset = offset.min(self.text.len());
+        if offset >= self.text.len() {
+            return self.text.len();
+        }
+        self.text
+            .char_indices()
+            .find_map(|(index, _)| (index > offset).then_some(index))
+            .unwrap_or(self.text.len())
+    }
+
+    pub fn line_start_offset(&self, offset: usize) -> Option<usize> {
+        Some(self.line_for_offset(offset)?.text_start)
+    }
+
+    pub fn line_end_offset(&self, offset: usize) -> Option<usize> {
+        Some(self.line_for_offset(offset)?.text_end)
+    }
+
+    pub fn vertical_offset(&self, offset: usize, line_delta: isize) -> Option<usize> {
+        if line_delta == 0 {
+            return Some(offset.min(self.text.len()));
+        }
+        let offset = offset.min(self.text.len());
+        let line = self.line_for_offset(offset)?;
+        let current_index = self.lines.iter().position(|candidate| candidate == line)?;
+        let next_index = current_index.checked_add_signed(line_delta)?;
+        let next_line = self.lines.get(next_index)?;
+        let target_x = self.caret_x_for_line_offset(line, offset);
+        Some(self.byte_offset_for_line_position(next_line, target_x))
+    }
+
+    pub fn word_range_for_offset(&self, offset: usize) -> Range<usize> {
+        if self.text.is_empty() {
+            return 0..0;
+        }
+        let offset = offset.min(self.text.len());
+        let target = self.word_class_offset(offset);
+        let Some((target_start, target_ch)) = self.char_at(target) else {
+            return 0..self.text.len();
+        };
+        let target_class = classify_word_char(target_ch);
+
+        let mut start = target_start;
+        while let Some((previous_start, previous_ch)) = self.char_before(start) {
+            if classify_word_char(previous_ch) != target_class {
+                break;
+            }
+            start = previous_start;
+        }
+
+        let mut end = target_start + target_ch.len_utf8();
+        while let Some((next_start, next_ch)) = self.char_at(end) {
+            if classify_word_char(next_ch) != target_class {
+                break;
+            }
+            end = next_start + next_ch.len_utf8();
+        }
+
+        start..end
+    }
+
     pub fn apply_selected_text_color(&mut self, start: usize, end: usize) {
         let Some(selected_color) = self.selection_style.text_color else {
             return;
@@ -336,6 +407,50 @@ impl PreparedText {
             .map(|glyph| glyph.position.x + glyph.advance.max(0.0))
             .unwrap_or(line.rect.origin.x)
     }
+
+    fn char_at(&self, offset: usize) -> Option<(usize, char)> {
+        if offset >= self.text.len() {
+            return None;
+        }
+        self.text[offset..].chars().next().map(|ch| (offset, ch))
+    }
+
+    fn char_before(&self, offset: usize) -> Option<(usize, char)> {
+        let offset = offset.min(self.text.len());
+        self.text[..offset].char_indices().last()
+    }
+
+    fn word_class_offset(&self, offset: usize) -> usize {
+        if offset >= self.text.len() {
+            return self.previous_char_boundary(offset);
+        }
+        if offset > 0
+            && let (Some((_, previous)), Some((_, current))) =
+                (self.char_before(offset), self.char_at(offset))
+            && classify_word_char(current) == WordClass::Whitespace
+            && classify_word_char(previous) == WordClass::Word
+        {
+            return self.previous_char_boundary(offset);
+        }
+        offset
+    }
+}
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+enum WordClass {
+    Word,
+    Whitespace,
+    Punctuation,
+}
+
+fn classify_word_char(ch: char) -> WordClass {
+    if ch.is_whitespace() {
+        WordClass::Whitespace
+    } else if ch.is_alphanumeric() || ch == '_' {
+        WordClass::Word
+    } else {
+        WordClass::Punctuation
+    }
 }
 
 #[derive(Clone, Debug, PartialEq)]
@@ -484,4 +599,58 @@ mod tests {
             Some(Rect::new(42.0, 20.0, 2.0, 16.0))
         );
     }
+
+    #[test]
+    fn prepared_text_word_range_tracks_words_and_punctuation() {
+        let text = PreparedText::monospace(
+            "alpha beta, gamma",
+            Point::new(10.0, 20.0),
+            16.0,
+            8.0,
+            Color::rgb(0xFF, 0xFF, 0xFF),
+        );
+
+        assert_eq!(text.word_range_for_offset(1), 0..5);
+        assert_eq!(text.word_range_for_offset(6), 6..10);
+        assert_eq!(text.word_range_for_offset(10), 10..11);
+        assert_eq!(text.word_range_for_offset(text.text.len()), 12..17);
+    }
+
+    #[test]
+    fn prepared_text_vertical_offset_moves_between_lines() {
+        let mut text = PreparedText::monospace(
+            "abcdwxyz",
+            Point::new(10.0, 20.0),
+            16.0,
+            8.0,
+            Color::rgb(0xFF, 0xFF, 0xFF),
+        );
+        text.lines = vec![
+            super::PreparedTextLine {
+                rect: Rect::new(10.0, 20.0, 32.0, 16.0),
+                text_start: 0,
+                text_end: 4,
+                glyph_start: 0,
+                glyph_end: 4,
+            },
+            super::PreparedTextLine {
+                rect: Rect::new(10.0, 36.0, 32.0, 16.0),
+                text_start: 4,
+                text_end: 8,
+                glyph_start: 4,
+                glyph_end: 8,
+            },
+        ];
+        for (index, glyph) in text.glyphs.iter_mut().enumerate() {
+            if index >= 4 {
+                glyph.position.y = 36.0;
+                glyph.position.x = 10.0 + ((index - 4) as f32 * 8.0);
+            }
+        }
+
+        assert_eq!(text.vertical_offset(2, 1), Some(6));
+        assert_eq!(text.vertical_offset(6, -1), Some(2));
+        assert_eq!(text.line_start_offset(6), Some(4));
+        assert_eq!(text.line_end_offset(2), Some(4));
+    }
 }