Scroll so that text cursor remains visible

Closes #165

CHANGELOG.md

@@ -8,27 +8,29 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 ## Unreleased
 
 ### Added ⭐
-*  `Ui::input_mut` to modify how subsequent widgets see the `InputState` and a convenience method `InputState::consume_key` for shortcuts or hotkeys ([#1212](https://github.com/emilk/egui/pull/1212)). 
 * Much improved font selection ([#1154](https://github.com/emilk/egui/pull/1154)):
   * You can now select any font size and family using `RichText::size` amd `RichText::family` and the new `FontId`.
   * Easily change text styles with `Style::text_styles`.
   * Added `Ui::text_style_height`.
   * Added `TextStyle::resolve`.
-* Made v-align and scale of user fonts tweakable ([#1241](https://github.com/emilk/egui/pull/1027)).
+  * Made v-align and scale of user fonts tweakable ([#1241](https://github.com/emilk/egui/pull/1027)).
+* Plot:
+  * Added `Plot::x_axis_formatter` and `Plot::y_axis_formatter` for custom axis labels ([#1130](https://github.com/emilk/egui/pull/1130)).
+  * Added `Plot::allow_boxed_zoom()`, `Plot::boxed_zoom_pointer()` for boxed zooming on plots ([#1188](https://github.com/emilk/egui/pull/1188)).
+  * Added plot pointer coordinates with `Plot::coordinates_formatter`. ([#1235](https://github.com/emilk/egui/pull/1235)).
+  * Added linked axis support for plots via `plot::LinkedAxisGroup` ([#1184](https://github.com/emilk/egui/pull/1184)).
 * `Context::load_texture` to convert an image into a texture which can be displayed using e.g. `ui.image(texture, size)` ([#1110](https://github.com/emilk/egui/pull/1110)).
+* `Ui::input_mut` to modify how subsequent widgets see the `InputState` and a convenience method `InputState::consume_key` for shortcuts or hotkeys ([#1212](https://github.com/emilk/egui/pull/1212)).
 * Added `Ui::add_visible` and `Ui::add_visible_ui`.
 * Opt-in dependency on `tracing` crate for logging warnings ([#1192](https://github.com/emilk/egui/pull/1192)).
 * Added `CollapsingHeader::icon` to override the default open/close icon using a custom function. ([1147](https://github.com/emilk/egui/pull/1147)).
-* Added `Plot::x_axis_formatter` and `Plot::y_axis_formatter` for custom axis labels ([#1130](https://github.com/emilk/egui/pull/1130)).
 * Added `ui.data()`, `ctx.data()`, `ctx.options()` and `ctx.tessellation_options()` ([#1175](https://github.com/emilk/egui/pull/1175)).
-* Added `Plot::allow_boxed_zoom()`, `Plot::boxed_zoom_pointer()` for boxed zooming on plots ([#1188](https://github.com/emilk/egui/pull/1188)).
-* Added linked axis support for plots via `plot::LinkedAxisGroup` ([#1184](https://github.com/emilk/egui/pull/1184)).
 * Added `Response::on_hover_text_at_pointer` as a convenience akin to `Response::on_hover_text` ([1179](https://github.com/emilk/egui/pull/1179)).
 * Added `ui.weak(text)`.
 * Added `Context::move_to_top` and `Context::top_most_layer` for managing the layer on the top ([#1242](https://github.com/emilk/egui/pull/1242)).
-* Added plot pointer coordinates with `Plot::coordinates_formatter`. ([#1235](https://github.com/emilk/egui/pull/1235)).
-* Added `Slider::step_by` ([1255](https://github.com/emilk/egui/pull/1225)).
+* Added `Slider::step_by` ([1225](https://github.com/emilk/egui/pull/1225)).
 * Added ability to scroll an UI into view without specifying an alignment ([1247](https://github.com/emilk/egui/pull/1247)).
+* Added `Ui::scroll_to_rect` ([1252](https://github.com/emilk/egui/pull/1252)).
 
 ### Changed 🔧
 * ⚠️ `Context::input` and `Ui::input` now locks a mutex. This can lead to a dead-lock is used in an `if let` binding!
@@ -60,6 +62,7 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 * Fixed `enable_drag` for Windows ([#1108](https://github.com/emilk/egui/pull/1108)).
 * Calling `Context::set_pixels_per_point` before the first frame will now work.
 * Tooltips that don't fit the window don't flicker anymore ([#1240](https://github.com/emilk/egui/pull/1240)).
+* Scroll areas now follow text cursor ([1252](https://github.com/emilk/egui/pull/1252)).
 
 ### Contributors 🙏
 * [AlexxxRu](https://github.com/alexxxru): [#1108](https://github.com/emilk/egui/pull/1108).

egui/src/containers/scroll_area.rs

@@ -498,7 +498,7 @@ impl Prepared {
                     let clip_end = clip_rect.max[d];
                     let mut spacing = ui.spacing().item_spacing[d];
 
-                    if let Some(align) = align {
+                    let delta = if let Some(align) = align {
                         let center_factor = align.to_factor();
 
                         let offset =
@@ -507,19 +507,20 @@ impl Prepared {
                         // Depending on the alignment we need to add or subtract the spacing
                         spacing *= remap(center_factor, 0.0..=1.0, -1.0..=1.0);
 
-                        state.offset[d] = offset + spacing;
+                        offset + spacing
                     } else if start < clip_start && end < clip_end {
-                        let min_adjust =
-                            (clip_start - start + spacing).min(clip_end - end - spacing);
-                        state.offset[d] -= min_adjust;
+                        -(clip_start - start + spacing).min(clip_end - end - spacing)
                     } else if end > clip_end && start > clip_start {
-                        let min_adjust =
-                            (end - clip_end + spacing).min(start - clip_start - spacing);
-                        state.offset[d] += min_adjust;
+                        (end - clip_end + spacing).min(start - clip_start - spacing)
                     } else {
                         // Ui is already in view, no need to adjust scroll.
-                        continue;
+                        0.0
                     };
+
+                    if delta != 0.0 {
+                        state.offset[d] += delta;
+                        ui.ctx().request_repaint();
+                    }
                 }
             }
         }

egui/src/response.rs

@@ -443,10 +443,11 @@ impl Response {
         )
     }
 
-    /// Adjust the scroll position until this UI becomes visible. If `align` is not provided, it'll scroll enough to
-    /// bring the UI into view.
+    /// Adjust the scroll position until this UI becomes visible.
     ///
-    /// See also [`Ui::scroll_to_cursor`]
+    /// If `align` is `None`, it'll scroll enough to bring the UI into view.
+    ///
+    /// See also: [`Ui::scroll_to_cursor`], [`Ui::scroll_to`].
     ///
     /// ```
     /// # egui::__run_test_ui(|ui| {

egui/src/ui.rs

@@ -904,10 +904,36 @@ impl Ui {
         (response, painter)
     }
 
-    /// Adjust the scroll position until the cursor becomes visible. If `align` is not provided, it'll scroll enough to
-    /// bring the cursor into view.
+    /// Adjust the scroll position of any parent [`ScrollArea`] so that the given `Rect` becomes visible.
     ///
-    /// See also [`Response::scroll_to_me`]
+    /// If `align` is `None`, it'll scroll enough to bring the cursor into view.
+    ///
+    /// See also: [`Response::scroll_to_me`], [`Ui::scroll_to`].
+    ///
+    /// ```
+    /// # use egui::Align;
+    /// # egui::__run_test_ui(|ui| {
+    /// egui::ScrollArea::vertical().show(ui, |ui| {
+    ///     // …
+    ///     let response = ui.button("Center on me.").clicked();
+    ///     if response.clicked() {
+    ///         ui.scroll_to_rect(response.rect, Some(Align::CENTER));
+    ///     }
+    /// });
+    /// # });
+    /// ```
+    pub fn scroll_to_rect(&self, rect: Rect, align: Option<Align>) {
+        for d in 0..2 {
+            let range = rect.min[d]..=rect.max[d];
+            self.ctx().frame_state().scroll_target[d] = Some((range, align));
+        }
+    }
+
+    /// Adjust the scroll position of any parent [`ScrollArea`] so that the cursor (where the next widget goes) becomes visible.
+    ///
+    /// If `align` is not provided, it'll scroll enough to bring the cursor into view.
+    ///
+    /// See also: [`Response::scroll_to_me`], [`Ui::scroll_to`].
     ///
     /// ```
     /// # use egui::Align;
@@ -924,7 +950,7 @@ impl Ui {
     /// });
     /// # });
     /// ```
-    pub fn scroll_to_cursor(&mut self, align: Option<Align>) {
+    pub fn scroll_to_cursor(&self, align: Option<Align>) {
         let target = self.next_widget_position();
         for d in 0..2 {
             let target = target[d];

egui/src/widgets/text_edit/builder.rs

@@ -561,7 +561,7 @@ impl<'t> TextEdit<'t> {
                     // We paint the cursor on top of the text, in case
                     // the text galley has backgrounds (as e.g. `code` snippets in markup do).
                     paint_cursor_selection(ui, &painter, text_draw_pos, &galley, &cursor_range);
-                    paint_cursor_end(
+                    let cursor_pos = paint_cursor_end(
                         ui,
                         row_height,
                         &painter,
@@ -570,6 +570,8 @@ impl<'t> TextEdit<'t> {
                         &cursor_range.primary,
                     );
 
+                    ui.scroll_to_rect(cursor_pos, None); // keep cursor in view
+
                     if interactive && text.is_mutable() {
                         // egui_web uses `text_cursor_pos` when showing IME,
                         // so only set it when text is editable and visible!
@@ -887,7 +889,7 @@ fn paint_cursor_end(
     pos: Pos2,
     galley: &Galley,
     cursor: &Cursor,
-) {
+) -> Rect {
     let stroke = ui.visuals().selection.stroke;
 
     let mut cursor_pos = galley.pos_from_cursor(cursor).translate(pos.to_vec2());
@@ -915,6 +917,8 @@ fn paint_cursor_end(
             (width, stroke.color),
         );
     }
+
+    cursor_pos
 }
 
 // ----------------------------------------------------------------------------