From e102e89c6ade6fa5bb9a716a1d836a636dcf2918 Mon Sep 17 00:00:00 2001
From: lufte <javier@lufte.net>
Date: Fri, 10 May 2024 18:50:10 -0300
Subject: Implement `scroll_by` operation for `scrollable`

`scroll_by` allows scrolling an absolute offset
that is applied to the current scrolling position.
---
 core/src/widget/operation.rs            | 46 +++++++++++++++++++++++++++++----
 core/src/widget/operation/scrollable.rs | 45 ++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+), 5 deletions(-)

(limited to 'core/src/widget')

diff --git a/core/src/widget/operation.rs b/core/src/widget/operation.rs
index 4ee4b4a7..097c3601 100644
--- a/core/src/widget/operation.rs
+++ b/core/src/widget/operation.rs
@@ -38,6 +38,7 @@ pub trait Operation<T = ()>: Send {
         _state: &mut dyn Scrollable,
         _id: Option<&Id>,
         _bounds: Rectangle,
+        _content_bounds: Rectangle,
         _translation: Vector,
     ) {
     }
@@ -76,9 +77,16 @@ where
         state: &mut dyn Scrollable,
         id: Option<&Id>,
         bounds: Rectangle,
+        content_bounds: Rectangle,
         translation: Vector,
     ) {
-        self.as_mut().scrollable(state, id, bounds, translation);
+        self.as_mut().scrollable(
+            state,
+            id,
+            bounds,
+            content_bounds,
+            translation,
+        );
     }
 
     fn text_input(&mut self, state: &mut dyn TextInput, id: Option<&Id>) {
@@ -151,9 +159,16 @@ where
             state: &mut dyn Scrollable,
             id: Option<&Id>,
             bounds: Rectangle,
+            content_bounds: Rectangle,
             translation: Vector,
         ) {
-            self.operation.scrollable(state, id, bounds, translation);
+            self.operation.scrollable(
+                state,
+                id,
+                bounds,
+                content_bounds,
+                translation,
+            );
         }
 
         fn text_input(&mut self, state: &mut dyn TextInput, id: Option<&Id>) {
@@ -222,9 +237,16 @@ where
                     state: &mut dyn Scrollable,
                     id: Option<&Id>,
                     bounds: Rectangle,
+                    content_bounds: Rectangle,
                     translation: Vector,
                 ) {
-                    self.operation.scrollable(state, id, bounds, translation);
+                    self.operation.scrollable(
+                        state,
+                        id,
+                        bounds,
+                        content_bounds,
+                        translation,
+                    );
                 }
 
                 fn focusable(
@@ -262,9 +284,16 @@ where
             state: &mut dyn Scrollable,
             id: Option<&Id>,
             bounds: Rectangle,
+            content_bounds: Rectangle,
             translation: Vector,
         ) {
-            self.operation.scrollable(state, id, bounds, translation);
+            self.operation.scrollable(
+                state,
+                id,
+                bounds,
+                content_bounds,
+                translation,
+            );
         }
 
         fn text_input(&mut self, state: &mut dyn TextInput, id: Option<&Id>) {
@@ -341,9 +370,16 @@ where
             state: &mut dyn Scrollable,
             id: Option<&Id>,
             bounds: Rectangle,
+            content_bounds: Rectangle,
             translation: crate::Vector,
         ) {
-            self.operation.scrollable(state, id, bounds, translation);
+            self.operation.scrollable(
+                state,
+                id,
+                bounds,
+                content_bounds,
+                translation,
+            );
         }
 
         fn text_input(&mut self, state: &mut dyn TextInput, id: Option<&Id>) {
diff --git a/core/src/widget/operation/scrollable.rs b/core/src/widget/operation/scrollable.rs
index 12161255..c2fecf56 100644
--- a/core/src/widget/operation/scrollable.rs
+++ b/core/src/widget/operation/scrollable.rs
@@ -9,6 +9,14 @@ pub trait Scrollable {
 
     /// Scroll the widget to the given [`AbsoluteOffset`] along the horizontal & vertical axis.
     fn scroll_to(&mut self, offset: AbsoluteOffset);
+
+    /// Scroll the widget by the given [`AbsoluteOffset`] along the horizontal & vertical axis.
+    fn scroll_by(
+        &mut self,
+        offset: AbsoluteOffset,
+        bounds: Rectangle,
+        content_bounds: Rectangle,
+    );
 }
 
 /// Produces an [`Operation`] that snaps the widget with the given [`Id`] to
@@ -34,6 +42,7 @@ pub fn snap_to<T>(target: Id, offset: RelativeOffset) -> impl Operation<T> {
             state: &mut dyn Scrollable,
             id: Option<&Id>,
             _bounds: Rectangle,
+            _content_bounds: Rectangle,
             _translation: Vector,
         ) {
             if Some(&self.target) == id {
@@ -68,6 +77,7 @@ pub fn scroll_to<T>(target: Id, offset: AbsoluteOffset) -> impl Operation<T> {
             state: &mut dyn Scrollable,
             id: Option<&Id>,
             _bounds: Rectangle,
+            _content_bounds: Rectangle,
             _translation: Vector,
         ) {
             if Some(&self.target) == id {
@@ -79,6 +89,41 @@ pub fn scroll_to<T>(target: Id, offset: AbsoluteOffset) -> impl Operation<T> {
     ScrollTo { target, offset }
 }
 
+/// Produces an [`Operation`] that scrolls the widget with the given [`Id`] by
+/// the provided [`AbsoluteOffset`].
+pub fn scroll_by<T>(target: Id, offset: AbsoluteOffset) -> impl Operation<T> {
+    struct ScrollBy {
+        target: Id,
+        offset: AbsoluteOffset,
+    }
+
+    impl<T> Operation<T> for ScrollBy {
+        fn container(
+            &mut self,
+            _id: Option<&Id>,
+            _bounds: Rectangle,
+            operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
+        ) {
+            operate_on_children(self);
+        }
+
+        fn scrollable(
+            &mut self,
+            state: &mut dyn Scrollable,
+            id: Option<&Id>,
+            bounds: Rectangle,
+            content_bounds: Rectangle,
+            _translation: Vector,
+        ) {
+            if Some(&self.target) == id {
+                state.scroll_by(self.offset, bounds, content_bounds);
+            }
+        }
+    }
+
+    ScrollBy { target, offset }
+}
+
 /// The amount of absolute offset in each direction of a [`Scrollable`].
 #[derive(Debug, Clone, Copy, PartialEq, Default)]
 pub struct AbsoluteOffset {
-- 
cgit