Use normalize_point helper method in widgets (#24020)

# Objective

Closes #23909

## Solution

A simple refactoring.

## Testing

Ran `examples/ui/widgets/vertical_slider.rs` and
`examples/ui/widgets/feathers_gallery.rs` to see whether color plane and
scrollbar still work as intended

Author: agluszak

crates/bevy_feathers/src/controls/color_plane.rs

@@ -289,6 +289,30 @@ fn update_plane_color(
     }
 }
 
+fn emit_color_plane_value_change(
+    commands: &mut Commands,
+    source: Entity,
+    node: &ComputedNode,
+    node_target: &ComputedUiRenderTargetInfo,
+    transform: &UiGlobalTransform,
+    pointer_position: Vec2,
+    ui_scale: f32,
+    is_final: bool,
+) {
+    let Some(pos) = node.normalize_point(
+        *transform,
+        pointer_position * node_target.scale_factor() / ui_scale,
+    ) else {
+        return;
+    };
+
+    commands.trigger(ValueChange {
+        source,
+        value: (pos + Vec2::splat(0.5)).clamp(Vec2::ZERO, Vec2::ONE),
+        is_final,
+    });
+}
+
 fn on_pointer_press(
     mut press: On<Pointer<Press>>,
     q_color_planes: Query<Has<InteractionDisabled>, With<ColorPlane>>,
@@ -309,16 +333,16 @@ fn on_pointer_press(
     {
         press.propagate(false);
         if !disabled {
-            let local_pos = transform.try_inverse().unwrap().transform_point2(
-                press.pointer_location.position * node_target.scale_factor() / ui_scale.0,
+            emit_color_plane_value_change(
+                &mut commands,
+                parent.0,
+                node,
+                node_target,
+                transform,
+                press.pointer_location.position,
+                ui_scale.0,
+                false,
             );
-            let pos = local_pos / node.size() + Vec2::splat(0.5);
-            let new_value = pos.clamp(Vec2::ZERO, Vec2::ONE);
-            commands.trigger(ValueChange {
-                source: parent.0,
-                value: new_value,
-                is_final: false,
-            });
         }
     }
 }
@@ -361,16 +385,16 @@ fn on_drag(
     {
         drag.propagate(false);
         if state.0 && !disabled {
-            let local_pos = transform.try_inverse().unwrap().transform_point2(
-                drag.pointer_location.position * node_target.scale_factor() / ui_scale.0,
+            emit_color_plane_value_change(
+                &mut commands,
+                parent.0,
+                node,
+                node_target,
+                transform,
+                drag.pointer_location.position,
+                ui_scale.0,
+                false,
             );
-            let pos = local_pos / node.size() + Vec2::splat(0.5);
-            let new_value = pos.clamp(Vec2::ZERO, Vec2::ONE);
-            commands.trigger(ValueChange {
-                source: parent.0,
-                value: new_value,
-                is_final: false,
-            });
         }
     }
 }
@@ -398,16 +422,16 @@ fn on_drag_end(
     {
         drag_end.propagate(false);
         if state.0 && !disabled {
-            let local_pos = transform.try_inverse().unwrap().transform_point2(
-                drag_end.pointer_location.position * node_target.scale_factor() / ui_scale.0,
+            emit_color_plane_value_change(
+                &mut commands,
+                parent.0,
+                node,
+                node_target,
+                transform,
+                drag_end.pointer_location.position,
+                ui_scale.0,
+                true,
             );
-            let pos = local_pos / node.size() + Vec2::splat(0.5);
-            let new_value = pos.clamp(Vec2::ZERO, Vec2::ONE);
-            commands.trigger(ValueChange {
-                source: parent.0,
-                value: new_value,
-                is_final: true,
-            });
         }
         state.0 = false;
     }

crates/bevy_ui_widgets/src/scrollbar.rs

@@ -145,10 +145,12 @@ fn scrollbar_on_pointer_down(
         // If they click on the scrollbar track, page up or down.
         ev.propagate(false);
 
-        // Convert to widget-local coordinates.
-        let local_pos = transform.try_inverse().unwrap().transform_point2(
+        let Some(normalized_pos) = node.normalize_point(
+            *transform,
             ev.event().pointer_location.position * node_target.scale_factor() / ui_scale.0,
-        ) + node.size() * 0.5;
+        ) else {
+            return;
+        };
 
         // Bail if we don't find the target entity.
         let Ok((mut scroll_pos, scroll_content)) = q_scroll_pos.get_mut(scrollbar.target) else {
@@ -170,16 +172,12 @@ fn scrollbar_on_pointer_down(
 
         match scrollbar.orientation {
             ControlOrientation::Horizontal => {
-                if node.size().x > 0. {
-                    let click_pos = local_pos.x * content_size.x / node.size().x;
-                    adjust_scroll_pos(&mut scroll_pos.x, click_pos, visible_size.x, max_range.x);
-                }
+                let click_pos = (normalized_pos.x + 0.5) * content_size.x;
+                adjust_scroll_pos(&mut scroll_pos.x, click_pos, visible_size.x, max_range.x);
             }
             ControlOrientation::Vertical => {
-                if node.size().y > 0. {
-                    let click_pos = local_pos.y * content_size.y / node.size().y;
-                    adjust_scroll_pos(&mut scroll_pos.y, click_pos, visible_size.y, max_range.y);
-                }
+                let click_pos = (normalized_pos.y + 0.5) * content_size.y;
+                adjust_scroll_pos(&mut scroll_pos.y, click_pos, visible_size.y, max_range.y);
             }
         }
     }

crates/bevy_ui_widgets/src/slider.rs

@@ -306,9 +306,12 @@ pub(crate) fn slider_on_pointer_down(
             .unwrap_or(0.0);
 
         // Detect track click.
-        let local_pos = transform.try_inverse().unwrap().transform_point2(
+        let Some(normalized_pos) = node.normalize_point(
+            *transform,
             press.pointer_location.position * node_target.scale_factor() / ui_scale.0,
-        );
+        ) else {
+            return;
+        };
         let track_size = if is_vertical {
             node.size().y - thumb_size
         } else {
@@ -319,13 +322,13 @@ pub(crate) fn slider_on_pointer_down(
         let click_val = if track_size > 0. {
             if is_vertical {
                 // For vertical sliders: bottom-to-top (0 at bottom, max at top)
-                // local_pos.y ranges from -height/2 (top) to +height/2 (bottom)
-                let y_from_bottom = (node.size().y / 2.0) - local_pos.y;
+                // normalized_pos.y ranges from -0.5 (top) to +0.5 (bottom)
+                let y_from_bottom = (0.5 - normalized_pos.y) * node.size().y;
                 let adjusted_y = y_from_bottom - thumb_size / 2.0;
                 adjusted_y * range.span() / track_size + range.start()
             } else {
                 // For horizontal sliders: convert from center-origin to left-origin
-                let x_from_left = local_pos.x + node.size().x / 2.0;
+                let x_from_left = (normalized_pos.x + 0.5) * node.size().x;
                 let adjusted_x = x_from_left - thumb_size / 2.0;
                 adjusted_x * range.span() / track_size + range.start()
             }