Merge pull request #35 from hecrj/feature/scrollables

Scrollable widget

1 files changed, 151 insertions, 0 deletions

diff --git a/core/src/widget/scrollable.rs b/core/src/widget/scrollable.rs
new file mode 100644
index 00000000..31a5abed
--- /dev/null
+++ b/core/src/widget/scrollable.rs
@@ -0,0 +1,151 @@
+use crate::{Align, Column, Length, Point, Rectangle};
+
+#[derive(Debug)]
+pub struct Scrollable<'a, Element> {
+    pub state: &'a mut State,
+    pub height: Length,
+    pub max_height: Length,
+    pub align_self: Option<Align>,
+    pub content: Column<Element>,
+}
+
+impl<'a, Element> Scrollable<'a, Element> {
+    pub fn new(state: &'a mut State) -> Self {
+        Scrollable {
+            state,
+            height: Length::Shrink,
+            max_height: Length::Shrink,
+            align_self: None,
+            content: Column::new(),
+        }
+    }
+
+    /// Sets the vertical spacing _between_ elements.
+    ///
+    /// Custom margins per element do not exist in Iced. You should use this
+    /// method instead! While less flexible, it helps you keep spacing between
+    /// elements consistent.
+    pub fn spacing(mut self, units: u16) -> Self {
+        self.content = self.content.spacing(units);
+        self
+    }
+
+    /// Sets the padding of the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn padding(mut self, units: u16) -> Self {
+        self.content = self.content.padding(units);
+        self
+    }
+
+    /// Sets the width of the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn width(mut self, width: Length) -> Self {
+        self.content = self.content.width(width);
+        self
+    }
+
+    /// Sets the height of the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn height(mut self, height: Length) -> Self {
+        self.height = height;
+        self
+    }
+
+    /// Sets the maximum width of the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn max_width(mut self, max_width: Length) -> Self {
+        self.content = self.content.max_width(max_width);
+        self
+    }
+
+    /// Sets the maximum height of the [`Scrollable`] in pixels.
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn max_height(mut self, max_height: Length) -> Self {
+        self.max_height = max_height;
+        self
+    }
+
+    /// Sets the alignment of the [`Scrollable`] itself.
+    ///
+    /// This is useful if you want to override the default alignment given by
+    /// the parent container.
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn align_self(mut self, align: Align) -> Self {
+        self.align_self = Some(align);
+        self
+    }
+
+    /// Sets the horizontal alignment of the contents of the [`Scrollable`] .
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn align_items(mut self, align_items: Align) -> Self {
+        self.content = self.content.align_items(align_items);
+        self
+    }
+
+    /// Adds an element to the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn push<E>(mut self, child: E) -> Scrollable<'a, Element>
+    where
+        E: Into<Element>,
+    {
+        self.content = self.content.push(child);
+        self
+    }
+}
+
+#[derive(Debug, Clone, Copy, Default)]
+pub struct State {
+    pub scrollbar_grabbed_at: Option<Point>,
+    offset: u32,
+}
+
+impl State {
+    pub fn new() -> Self {
+        State::default()
+    }
+
+    pub fn scroll(
+        &mut self,
+        delta_y: f32,
+        bounds: Rectangle,
+        content_bounds: Rectangle,
+    ) {
+        if bounds.height >= content_bounds.height {
+            return;
+        }
+
+        self.offset = (self.offset as i32 - delta_y.round() as i32)
+            .max(0)
+            .min((content_bounds.height - bounds.height) as i32)
+            as u32;
+    }
+
+    pub fn scroll_to(
+        &mut self,
+        percentage: f32,
+        bounds: Rectangle,
+        content_bounds: Rectangle,
+    ) {
+        self.offset = ((content_bounds.height - bounds.height) * percentage)
+            .max(0.0) as u32;
+    }
+
+    pub fn offset(&self, bounds: Rectangle, content_bounds: Rectangle) -> u32 {
+        let hidden_content =
+            (content_bounds.height - bounds.height).round() as u32;
+
+        self.offset.min(hidden_content).max(0)
+    }
+
+    pub fn is_scrollbar_grabbed(&self) -> bool {
+        self.scrollbar_grabbed_at.is_some()
+    }
+}