Allow scroll_to and snap_to to operate on a single axis

Co-authored-by: Rizzen Yazston <rizzen.yazston@gmail.com>

core/src/widget/operation/scrollable.rs

@@ -5,10 +5,10 @@ use crate::{Rectangle, Vector};
 /// The internal state of a widget that can be scrolled.
 pub trait Scrollable {
     /// Snaps the scroll of the widget to the given `percentage` along the horizontal & vertical axis.
-    fn snap_to(&mut self, offset: RelativeOffset);
+    fn snap_to(&mut self, offset: RelativeOffset<Option<f32>>);
 
     /// Scroll the widget to the given [`AbsoluteOffset`] along the horizontal & vertical axis.
-    fn scroll_to(&mut self, offset: AbsoluteOffset);
+    fn scroll_to(&mut self, offset: AbsoluteOffset<Option<f32>>);
 
     /// Scroll the widget by the given [`AbsoluteOffset`] along the horizontal & vertical axis.
     fn scroll_by(
@@ -21,10 +21,13 @@ pub trait Scrollable {
 
 /// Produces an [`Operation`] that snaps the widget with the given [`Id`] to
 /// the provided `percentage`.
-pub fn snap_to<T>(target: Id, offset: RelativeOffset) -> impl Operation<T> {
+pub fn snap_to<T>(
+    target: Id,
+    offset: RelativeOffset<Option<f32>>,
+) -> impl Operation<T> {
     struct SnapTo {
         target: Id,
-        offset: RelativeOffset,
+        offset: RelativeOffset<Option<f32>>,
     }
 
     impl<T> Operation<T> for SnapTo {
@@ -51,10 +54,13 @@ pub fn snap_to<T>(target: Id, offset: RelativeOffset) -> impl Operation<T> {
 
 /// Produces an [`Operation`] that scrolls the widget with the given [`Id`] to
 /// the provided [`AbsoluteOffset`].
-pub fn scroll_to<T>(target: Id, offset: AbsoluteOffset) -> impl Operation<T> {
+pub fn scroll_to<T>(
+    target: Id,
+    offset: AbsoluteOffset<Option<f32>>,
+) -> impl Operation<T> {
     struct ScrollTo {
         target: Id,
-        offset: AbsoluteOffset,
+        offset: AbsoluteOffset<Option<f32>>,
     }
 
     impl<T> Operation<T> for ScrollTo {
@@ -111,22 +117,31 @@ pub fn scroll_by<T>(target: Id, offset: AbsoluteOffset) -> impl Operation<T> {
 
 /// The amount of absolute offset in each direction of a [`Scrollable`].
 #[derive(Debug, Clone, Copy, PartialEq, Default)]
-pub struct AbsoluteOffset {
+pub struct AbsoluteOffset<T = f32> {
     /// The amount of horizontal offset
-    pub x: f32,
+    pub x: T,
     /// The amount of vertical offset
-    pub y: f32,
+    pub y: T,
+}
+
+impl From<AbsoluteOffset> for AbsoluteOffset<Option<f32>> {
+    fn from(offset: AbsoluteOffset) -> Self {
+        Self {
+            x: Some(offset.x),
+            y: Some(offset.y),
+        }
+    }
 }
 
 /// The amount of relative offset in each direction of a [`Scrollable`].
 ///
 /// A value of `0.0` means start, while `1.0` means end.
 #[derive(Debug, Clone, Copy, PartialEq, Default)]
-pub struct RelativeOffset {
+pub struct RelativeOffset<T = f32> {
     /// The amount of horizontal offset
-    pub x: f32,
+    pub x: T,
     /// The amount of vertical offset
-    pub y: f32,
+    pub y: T,
 }
 
 impl RelativeOffset {
@@ -136,3 +151,12 @@ impl RelativeOffset {
     /// A relative offset that points to the bottom-right of a [`Scrollable`].
     pub const END: Self = Self { x: 1.0, y: 1.0 };
 }
+
+impl From<RelativeOffset> for RelativeOffset<Option<f32>> {
+    fn from(offset: RelativeOffset) -> Self {
+        Self {
+            x: Some(offset.x),
+            y: Some(offset.y),
+        }
+    }
+}

runtime/src/widget/operation.rs

@@ -9,10 +9,13 @@ pub use crate::core::widget::operation::scrollable::{
 };
 
 /// Snaps the scrollable with the given [`Id`] to the provided [`RelativeOffset`].
-pub fn snap_to<T>(id: impl Into<Id>, offset: RelativeOffset) -> Task<T> {
+pub fn snap_to<T>(
+    id: impl Into<Id>,
+    offset: impl Into<RelativeOffset<Option<f32>>>,
+) -> Task<T> {
     task::effect(Action::widget(operation::scrollable::snap_to(
         id.into(),
-        offset,
+        offset.into(),
     )))
 }
 
@@ -20,15 +23,18 @@ pub fn snap_to<T>(id: impl Into<Id>, offset: RelativeOffset) -> Task<T> {
 pub fn snap_to_end<T>(id: impl Into<Id>) -> Task<T> {
     task::effect(Action::widget(operation::scrollable::snap_to(
         id.into(),
-        RelativeOffset::END,
+        RelativeOffset::END.into(),
     )))
 }
 
 /// Scrolls the scrollable with the given [`Id`] to the provided [`AbsoluteOffset`].
-pub fn scroll_to<T>(id: impl Into<Id>, offset: AbsoluteOffset) -> Task<T> {
+pub fn scroll_to<T>(
+    id: impl Into<Id>,
+    offset: impl Into<AbsoluteOffset<Option<f32>>>,
+) -> Task<T> {
     task::effect(Action::widget(operation::scrollable::scroll_to(
         id.into(),
-        offset,
+        offset.into(),
     )))
 }
 

widget/src/scrollable.rs

@@ -1673,11 +1673,11 @@ impl Default for State {
 }
 
 impl operation::Scrollable for State {
-    fn snap_to(&mut self, offset: RelativeOffset) {
+    fn snap_to(&mut self, offset: RelativeOffset<Option<f32>>) {
         State::snap_to(self, offset);
     }
 
-    fn scroll_to(&mut self, offset: AbsoluteOffset) {
+    fn scroll_to(&mut self, offset: AbsoluteOffset<Option<f32>>) {
         State::scroll_to(self, offset);
     }
 
@@ -1829,18 +1829,28 @@ impl State {
         self.unsnap(bounds, content_bounds);
     }
 
-    fn snap_to(&mut self, offset: RelativeOffset) {
-        self.offset_x = Offset::Relative(offset.x.clamp(0.0, 1.0));
-        self.offset_y = Offset::Relative(offset.y.clamp(0.0, 1.0));
+    fn snap_to(&mut self, offset: RelativeOffset<Option<f32>>) {
+        if let Some(x) = offset.x {
+            self.offset_x = Offset::Relative(x.clamp(0.0, 1.0));
+        }
+
+        if let Some(y) = offset.y {
+            self.offset_y = Offset::Relative(y.clamp(0.0, 1.0));
+        }
     }
 
-    fn scroll_to(&mut self, offset: AbsoluteOffset) {
-        self.offset_x = Offset::Absolute(offset.x.max(0.0));
-        self.offset_y = Offset::Absolute(offset.y.max(0.0));
+    fn scroll_to(&mut self, offset: AbsoluteOffset<Option<f32>>) {
+        if let Some(x) = offset.x {
+            self.offset_x = Offset::Absolute(x.max(0.0));
+        }
+
+        if let Some(y) = offset.y {
+            self.offset_y = Offset::Absolute(y.max(0.0));
+        }
     }
 
     /// Scroll by the provided [`AbsoluteOffset`].
-    pub fn scroll_by(
+    fn scroll_by(
         &mut self,
         offset: AbsoluteOffset,
         bounds: Rectangle,
@@ -1851,7 +1861,7 @@ impl State {
 
     /// Unsnaps the current scroll position, if snapped, given the bounds of the
     /// [`Scrollable`] and its contents.
-    pub fn unsnap(&mut self, bounds: Rectangle, content_bounds: Rectangle) {
+    fn unsnap(&mut self, bounds: Rectangle, content_bounds: Rectangle) {
         self.offset_x = Offset::Absolute(
             self.offset_x.absolute(bounds.width, content_bounds.width),
         );