Freeze scroll area (#472)

* added ScrollArea::enable_scrolling

* also freeze dragging and scroll-bar

* fixed styling of inactive scrollbar

* fixed docs (backtick-quoted TextEdit)

Co-authored-by: edko99 <edko@jouzz.com>

CHANGELOG.md

@@ -21,6 +21,7 @@ NOTE: [`eframe`](eframe/CHANGELOG.md), [`egui_web`](egui_web/CHANGELOG.md) and [
 * Add features `extra_asserts` and `extra_debug_asserts` to enable additional checks.
 * `TextEdit` now supports edits on a generic buffer using `TextBuffer`.
 * Add `Context::set_debug_on_hover` and `egui::trace!(ui)`
+* Add `ScrollArea::enable_scrolling` to allow freezing scrolling when editing TextEdit widgets within it
 
 ### Changed 🔧
 * Plot: Changed `Curve` to `Line`.

egui/src/containers/scroll_area.rs

@@ -36,6 +36,7 @@ pub struct ScrollArea {
     always_show_scroll: bool,
     id_source: Option<Id>,
     offset: Option<Vec2>,
+    scrolling_enabled: bool,
 }
 
 impl ScrollArea {
@@ -51,6 +52,7 @@ impl ScrollArea {
             always_show_scroll: false,
             id_source: None,
             offset: None,
+            scrolling_enabled: true,
         }
     }
 
@@ -75,6 +77,17 @@ impl ScrollArea {
         self.offset = Some(Vec2::new(0.0, offset));
         self
     }
+
+    /// Control the scrolling behavior
+    /// If `true` (default), the scroll area will respond to user scrolling
+    /// If `false`, the scroll area will not respond to user scrolling
+    ///
+    /// This can be used, for example, to optionally freeze scrolling while the user
+    /// is inputing text in a `TextEdit` widget contained within the scroll area
+    pub fn enable_scrolling(mut self, enable: bool) -> Self {
+        self.scrolling_enabled = enable;
+        self
+    }
 }
 
 struct Prepared {
@@ -87,6 +100,7 @@ struct Prepared {
     /// Relative coordinates: the offset and size of the view of the inner UI.
     /// `viewport.min == ZERO` means we scrolled to the top.
     viewport: Rect,
+    scrolling_enabled: bool,
 }
 
 impl ScrollArea {
@@ -96,6 +110,7 @@ impl ScrollArea {
             always_show_scroll,
             id_source,
             offset,
+            scrolling_enabled,
         } = self;
 
         let ctx = ui.ctx().clone();
@@ -152,6 +167,7 @@ impl ScrollArea {
             inner_rect,
             content_ui,
             viewport,
+            scrolling_enabled,
         }
     }
 
@@ -229,6 +245,7 @@ impl Prepared {
             mut current_scroll_bar_width,
             content_ui,
             viewport: _,
+            scrolling_enabled,
         } = self;
 
         let content_size = content_ui.min_size();
@@ -268,7 +285,12 @@ impl Prepared {
 
         if content_is_too_small {
             // Drag contents to scroll (for touch screens mostly):
-            let content_response = ui.interact(inner_rect, id.with("area"), Sense::drag());
+            let sense = if self.scrolling_enabled {
+                Sense::drag()
+            } else {
+                Sense::hover()
+            };
+            let content_response = ui.interact(inner_rect, id.with("area"), sense);
 
             let input = ui.input();
             if content_response.dragged() {
@@ -293,7 +315,7 @@ impl Prepared {
         }
 
         let max_offset = content_size.y - inner_rect.height();
-        if ui.rect_contains_pointer(outer_rect) {
+        if scrolling_enabled && ui.rect_contains_pointer(outer_rect) {
             let mut frame_state = ui.ctx().frame_state();
             let scroll_delta = frame_state.scroll_delta;
 
@@ -340,7 +362,12 @@ impl Prepared {
             );
 
             let interact_id = id.with("vertical");
-            let response = ui.interact(outer_scroll_rect, interact_id, Sense::click_and_drag());
+            let sense = if self.scrolling_enabled {
+                Sense::click_and_drag()
+            } else {
+                Sense::hover()
+            };
+            let response = ui.interact(outer_scroll_rect, interact_id, sense);
 
             if let Some(pointer_pos) = response.interact_pointer_pos() {
                 let scroll_start_offset_from_top =
@@ -383,7 +410,11 @@ impl Prepared {
                 );
             }
 
-            let visuals = ui.style().interact(&response);
+            let visuals = if scrolling_enabled {
+                ui.style().interact(&response)
+            } else {
+                &ui.style().visuals.widgets.inactive
+            };
 
             ui.painter().add(epaint::Shape::Rect {
                 rect: outer_scroll_rect,