Fix glitches when scrolling

crates/egui/src/layers.rs

@@ -158,6 +158,11 @@ impl PaintList {
         self.0[idx.0].shape = Shape::Noop;
     }
 
+    /// Mutate the shape at the given index, if any.
+    pub fn mutate_shape(&mut self, idx: ShapeIdx, f: impl FnOnce(&mut ClippedShape)) {
+        self.0.get_mut(idx.0).map(f);
+    }
+
     /// Transform each [`Shape`] and clip rectangle by this much, in-place
     pub fn transform(&mut self, transform: TSTransform) {
         for ClippedShape { clip_rect, shape } in &mut self.0 {

crates/egui/src/text_selection/label_text_selection.rs

@@ -6,7 +6,9 @@ use crate::{
 };
 
 use super::{
-    text_cursor_state::cursor_rect, visuals::paint_text_selection, CursorRange, TextCursorState,
+    text_cursor_state::cursor_rect,
+    visuals::{paint_text_selection, RowVertexIndices},
+    CursorRange, TextCursorState,
 };
 
 /// Turn on to help debug this
@@ -92,7 +94,9 @@ pub struct LabelSelectionState {
     last_copied_galley_rect: Option<Rect>,
 
     /// Painted selections this frame.
-    painted_shape_idx: Vec<ShapeIdx>,
+    ///
+    /// Kept so we can undo a bad selection visualization if we don't see both ends of the selection this frame.
+    painted_selections: Vec<(ShapeIdx, Vec<RowVertexIndices>)>,
 }
 
 impl Default for LabelSelectionState {
@@ -107,7 +111,7 @@ impl Default for LabelSelectionState {
             has_reached_secondary: Default::default(),
             text_to_copy: Default::default(),
             last_copied_galley_rect: Default::default(),
-            painted_shape_idx: Default::default(),
+            painted_selections: Default::default(),
         }
     }
 }
@@ -150,7 +154,7 @@ impl LabelSelectionState {
         state.has_reached_secondary = false;
         state.text_to_copy.clear();
         state.last_copied_galley_rect = None;
-        state.painted_shape_idx.clear();
+        state.painted_selections.clear();
 
         state.store(ctx);
     }
@@ -173,8 +177,26 @@ impl LabelSelectionState {
                 // glitching by removing all painted selections:
                 ctx.graphics_mut(|layers| {
                     if let Some(list) = layers.get_mut(selection.layer_id) {
-                        for shape_idx in state.painted_shape_idx.drain(..) {
-                            list.reset_shape(shape_idx);
+                        for (shape_idx, row_selections) in state.painted_selections.drain(..) {
+                            list.mutate_shape(shape_idx, |shape| {
+                                if let epaint::Shape::Text(text_shape) = &mut shape.shape {
+                                    let galley = Arc::make_mut(&mut text_shape.galley);
+                                    for row_selection in row_selections {
+                                        if let Some(row) = galley.rows.get_mut(row_selection.row) {
+                                            for vertex_index in row_selection.vertex_indices {
+                                                if let Some(vertex) = row
+                                                    .visuals
+                                                    .mesh
+                                                    .vertices
+                                                    .get_mut(vertex_index as usize)
+                                                {
+                                                    vertex.color = epaint::Color32::TRANSPARENT;
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            });
                         }
                     }
                 });
@@ -260,16 +282,28 @@ impl LabelSelectionState {
     ///
     /// Make sure the widget senses clicks and drags.
     ///
-    /// This should be called before painting the text, because this will
-    /// add the text selection (if any) to the galley.
+    /// This also takes care of painting the galley.
     pub fn label_text_selection(
         ui: &Ui,
         response: &Response,
         galley_pos: Pos2,
-        galley: &mut Arc<Galley>,
+        mut galley: Arc<Galley>,
+        fallback_color: epaint::Color32,
+        underline: epaint::Stroke,
     ) {
         let mut state = Self::load(ui.ctx());
-        state.on_label(ui, response, galley_pos, galley);
+        let new_vertex_indices = state.on_label(ui, response, galley_pos, &mut galley);
+
+        let shape_idx = ui.painter().add(
+            epaint::TextShape::new(galley_pos, galley, fallback_color).with_underline(underline),
+        );
+
+        if !new_vertex_indices.is_empty() {
+            state
+                .painted_selections
+                .push((shape_idx, new_vertex_indices));
+        }
+
         state.store(ui.ctx());
     }
 
@@ -443,13 +477,14 @@ impl LabelSelectionState {
         }
     }
 
+    /// Returns indices of new vertices in the galley, if any.
     fn on_label(
         &mut self,
         ui: &Ui,
         response: &Response,
         galley_pos: Pos2,
         galley: &mut Arc<Galley>,
-    ) {
+    ) -> Vec<RowVertexIndices> {
         let widget_id = response.id;
 
         if response.hovered {
@@ -557,12 +592,14 @@ impl LabelSelectionState {
 
         let cursor_range = cursor_state.range(galley);
 
+        let mut new_vertex_indices = vec![];
+
         if let Some(cursor_range) = cursor_range {
             paint_text_selection(
                 galley,
                 ui.visuals(),
                 &cursor_range,
-                Some(&mut self.painted_shape_idx),
+                Some(&mut new_vertex_indices),
             );
         }
 
@@ -575,6 +612,8 @@ impl LabelSelectionState {
             galley_pos,
             galley,
         );
+
+        new_vertex_indices
     }
 }
 

crates/egui/src/text_selection/visuals.rs

@@ -2,16 +2,20 @@ use std::sync::Arc;
 
 use crate::*;
 
-use self::layers::ShapeIdx;
-
 use super::CursorRange;
 
+#[derive(Clone, Debug)]
+pub struct RowVertexIndices {
+    pub row: usize,
+    pub vertex_indices: [u32; 6],
+}
+
 /// Adds text selection rectangles to the galley.
 pub fn paint_text_selection(
     galley: &mut Arc<Galley>,
     visuals: &Visuals,
     cursor_range: &CursorRange,
-    mut out_shaped_idx: Option<&mut Vec<ShapeIdx>>,
+    mut new_vertex_indices: Option<&mut Vec<RowVertexIndices>>,
 ) {
     if cursor_range.is_empty() {
         return;
@@ -75,8 +79,11 @@ pub fn paint_text_selection(
         mesh.indices[glyph_index_start..glyph_index_start + 6]
             .clone_from_slice(&selection_triangles);
 
-        if let Some(out_shaped_idx) = &mut out_shaped_idx {
-            // TODO
+        if let Some(new_vertex_indices) = &mut new_vertex_indices {
+            new_vertex_indices.push(RowVertexIndices {
+                row: ri,
+                vertex_indices: selection_triangles,
+            });
         }
     }
 }

crates/egui/src/widgets/hyperlink.rs

@@ -36,7 +36,7 @@ impl Widget for Link {
         let Self { text } = self;
         let label = Label::new(text).sense(Sense::click());
 
-        let (galley_pos, mut galley, response) = label.layout_in_ui(ui);
+        let (galley_pos, galley, response) = label.layout_in_ui(ui);
         response
             .widget_info(|| WidgetInfo::labeled(WidgetType::Link, ui.is_enabled(), galley.text()));
 
@@ -52,12 +52,15 @@ impl Widget for Link {
 
             let selectable = ui.style().interaction.selectable_labels;
             if selectable {
-                LabelSelectionState::label_text_selection(ui, &response, galley_pos, &mut galley);
+                LabelSelectionState::label_text_selection(
+                    ui, &response, galley_pos, galley, color, underline,
+                );
+            } else {
+                ui.painter().add(
+                    epaint::TextShape::new(galley_pos, galley, color).with_underline(underline),
+                );
             }
 
-            ui.painter()
-                .add(epaint::TextShape::new(galley_pos, galley, color).with_underline(underline));
-
             if response.hovered() {
                 ui.ctx().set_cursor_icon(CursorIcon::PointingHand);
             }

crates/egui/src/widgets/label.rs

@@ -245,7 +245,7 @@ impl Widget for Label {
 
         let selectable = self.selectable;
 
-        let (galley_pos, mut galley, mut response) = self.layout_in_ui(ui);
+        let (galley_pos, galley, mut response) = self.layout_in_ui(ui);
         response
             .widget_info(|| WidgetInfo::labeled(WidgetType::Label, ui.is_enabled(), galley.text()));
 
@@ -269,13 +269,20 @@ impl Widget for Label {
 
             let selectable = selectable.unwrap_or_else(|| ui.style().interaction.selectable_labels);
             if selectable {
-                LabelSelectionState::label_text_selection(ui, &response, galley_pos, &mut galley);
+                LabelSelectionState::label_text_selection(
+                    ui,
+                    &response,
+                    galley_pos,
+                    galley,
+                    response_color,
+                    underline,
+                );
+            } else {
+                ui.painter().add(
+                    epaint::TextShape::new(galley_pos, galley, response_color)
+                        .with_underline(underline),
+                );
             }
-
-            ui.painter().add(
-                epaint::TextShape::new(galley_pos, galley, response_color)
-                    .with_underline(underline),
-            );
         }
 
         response