Merge pull request #1856 from jhff/pane_grid_split_with_dragged_pane

[Feature] Enhance PaneGrid to split panes by drag & drop

style/src/pane_grid.rs

@@ -1,16 +1,17 @@
 //! Change the appearance of a pane grid.
-use iced_core::Color;
+use iced_core::{Background, Color};
 
-/// A set of rules that dictate the style of a container.
-pub trait StyleSheet {
-    /// The supported style of the [`StyleSheet`].
-    type Style: Default;
-
-    /// The [`Line`] to draw when a split is picked.
-    fn picked_split(&self, style: &Self::Style) -> Option<Line>;
-
-    /// The [`Line`] to draw when a split is hovered.
-    fn hovered_split(&self, style: &Self::Style) -> Option<Line>;
+/// The appearance of the hovered region of a pane grid.
+#[derive(Debug, Clone, Copy)]
+pub struct Appearance {
+    /// The [`Background`] of the hovered pane region.
+    pub background: Background,
+    /// The border width of the hovered pane region.
+    pub border_width: f32,
+    /// The border [`Color`] of the hovered pane region.
+    pub border_color: Color,
+    /// The border radius of the hovered pane region.
+    pub border_radius: f32,
 }
 
 /// A line.
@@ -24,3 +25,18 @@ pub struct Line {
     /// The width of the [`Line`].
     pub width: f32,
 }
+
+/// A set of rules that dictate the style of a container.
+pub trait StyleSheet {
+    /// The supported style of the [`StyleSheet`].
+    type Style: Default;
+
+    /// The [`Region`] to draw when a pane is hovered.
+    fn hovered_region(&self, style: &Self::Style) -> Appearance;
+
+    /// The [`Line`] to draw when a split is picked.
+    fn picked_split(&self, style: &Self::Style) -> Option<Line>;
+
+    /// The [`Line`] to draw when a split is hovered.
+    fn hovered_split(&self, style: &Self::Style) -> Option<Line>;
+}

style/src/theme.rs

@@ -715,6 +715,25 @@ pub enum PaneGrid {
 impl pane_grid::StyleSheet for Theme {
     type Style = PaneGrid;
 
+    fn hovered_region(&self, style: &Self::Style) -> pane_grid::Appearance {
+        match style {
+            PaneGrid::Default => {
+                let palette = self.extended_palette();
+
+                pane_grid::Appearance {
+                    background: Background::Color(Color {
+                        a: 0.5,
+                        ..palette.primary.base.color
+                    }),
+                    border_width: 2.0,
+                    border_color: palette.primary.strong.color,
+                    border_radius: 0.0,
+                }
+            }
+            PaneGrid::Custom(custom) => custom.hovered_region(self),
+        }
+    }
+
     fn picked_split(&self, style: &Self::Style) -> Option<pane_grid::Line> {
         match style {
             PaneGrid::Default => {