Fix scroll_with_delta only scrolling if the ScrollArea is focussed

crates/egui/src/containers/scroll_area.rs

@@ -851,7 +851,8 @@ impl Prepared {
 
         let max_offset = content_size - inner_rect.size();
         let is_hovering_outer_rect = ui.rect_contains_pointer(outer_rect);
-        if scrolling_enabled && is_hovering_outer_rect {
+        let force_current_scroll_area = ui.input(|i| i.force_current_scroll_area);
+        if scrolling_enabled && is_hovering_outer_rect || force_current_scroll_area {
             let always_scroll_enabled_direction = ui.style().always_scroll_the_only_direction
                 && scroll_enabled[0] != scroll_enabled[1];
             for d in 0..2 {
@@ -879,6 +880,7 @@ impl Prepared {
                             } else {
                                 input.smooth_scroll_delta[d] = 0.0;
                             }
+                            input.force_current_scroll_area = false;
                         });
 
                         state.scroll_stuck_to_end[d] = false;

crates/egui/src/input_state.rs

@@ -70,6 +70,10 @@ pub struct InputState {
     /// at the end of the frame this will be zero if a scroll-area consumed the delta.
     pub smooth_scroll_delta: Vec2,
 
+    /// Force the current scroll area to consume the [Self::smooth_scroll_delta], independent of the focus / mouse position.
+    /// This is used when using [crate::Ui::scroll_with_delta] to scroll the current scroll area.
+    pub(crate) force_current_scroll_area: bool,
+
     /// Zoom scale factor this frame (e.g. from ctrl-scroll or pinch gesture).
     ///
     /// * `zoom = 1`: no change.
@@ -154,6 +158,7 @@ impl Default for InputState {
             unprocessed_scroll_delta: Vec2::ZERO,
             raw_scroll_delta: Vec2::ZERO,
             smooth_scroll_delta: Vec2::ZERO,
+            force_current_scroll_area: false,
             zoom_factor_delta: 1.0,
             screen_rect: Rect::from_min_size(Default::default(), vec2(10_000.0, 10_000.0)),
             pixels_per_point: 1.0,
@@ -255,6 +260,7 @@ impl InputState {
             unprocessed_scroll_delta,
             raw_scroll_delta,
             smooth_scroll_delta,
+            force_current_scroll_area: false,
             zoom_factor_delta,
             screen_rect,
             pixels_per_point,
@@ -1113,6 +1119,7 @@ impl InputState {
             unprocessed_scroll_delta,
             raw_scroll_delta,
             smooth_scroll_delta,
+            force_current_scroll_area,
 
             zoom_factor_delta,
             screen_rect,
@@ -1157,6 +1164,9 @@ impl InputState {
         ui.label(format!(
             "smooth_scroll_delta: {smooth_scroll_delta:?} points"
         ));
+        ui.label(format!(
+            "force_current_scroll_area: {force_current_scroll_area}"
+        ));
         ui.label(format!("zoom_factor_delta: {zoom_factor_delta:4.2}x"));
         ui.label(format!("screen_rect: {screen_rect:?} points"));
         ui.label(format!(

crates/egui/src/ui.rs

@@ -1091,8 +1091,10 @@ impl Ui {
     /// # });
     /// ```
     pub fn scroll_with_delta(&self, delta: Vec2) {
-        self.ctx()
-            .input_mut(|input| input.smooth_scroll_delta += delta);
+        self.ctx().input_mut(|input| {
+            input.smooth_scroll_delta += delta;
+            input.force_current_scroll_area = true;
+        });
     }
 }
 

crates/egui_demo_lib/src/demo/scrolling.rs

@@ -258,6 +258,7 @@ impl super::View for ScrollTo {
         let mut go_to_scroll_offset = false;
         let mut scroll_top = false;
         let mut scroll_bottom = false;
+        let mut scroll_delta = None;
 
         ui.horizontal(|ui| {
             ui.label("Scroll to a specific item index:");
@@ -292,6 +293,9 @@ impl super::View for ScrollTo {
         ui.horizontal(|ui| {
             scroll_top |= ui.button("Scroll to top").clicked();
             scroll_bottom |= ui.button("Scroll to bottom").clicked();
+            if ui.button("Scroll down by 64px").clicked() {
+                scroll_delta = Some(Vec2::new(0.0, -64.0));
+            }
         });
 
         let mut scroll_area = ScrollArea::vertical().max_height(200.0).auto_shrink(false);
@@ -305,6 +309,10 @@ impl super::View for ScrollTo {
                 if scroll_top {
                     ui.scroll_to_cursor(Some(Align::TOP));
                 }
+                if let Some(scroll_delta) = scroll_delta {
+                    ui.scroll_with_delta(scroll_delta);
+                }
+
                 ui.vertical(|ui| {
                     for item in 1..=num_items {
                         if track_item && item == self.track_item {