Rearrange layouting contexts ♻

1 files changed, 41 insertions, 14 deletions

diff --git a/src/layout/stacked.rs b/src/layout/stacked.rs
index 3a29f722..0b7bfd4f 100644
--- a/src/layout/stacked.rs
+++ b/src/layout/stacked.rs
@@ -17,10 +17,37 @@ pub struct StackLayouter {
 }
 
 /// The context for stack layouting.
+///
+/// See [`LayoutContext`] for details about the fields.
 #[derive(Debug, Copy, Clone)]
 pub struct StackContext {
+    pub alignment: Alignment,
     pub space: LayoutSpace,
-    pub extra_space: Option<LayoutSpace>,
+    pub followup_spaces: Option<LayoutSpace>,
+    pub shrink_to_fit: bool,
+}
+
+macro_rules! reuse {
+    ($ctx:expr) => {
+        StackContext {
+            alignment: $ctx.alignment,
+            space: $ctx.space,
+            followup_spaces: $ctx.followup_spaces,
+            shrink_to_fit: $ctx.shrink_to_fit
+        }
+    };
+}
+
+impl StackContext {
+    /// Create a stack context from a generic layout context.
+    pub fn from_layout_ctx(ctx: LayoutContext) -> StackContext {
+        reuse!(ctx)
+    }
+
+    /// Create a stack context from a flex context.
+    pub fn from_flex_ctx(ctx: FlexContext) -> StackContext {
+        reuse!(ctx)
+    }
 }
 
 impl StackLayouter {
@@ -33,8 +60,8 @@ impl StackLayouter {
 
             space: ctx.space,
             usable: ctx.space.usable(),
-            dimensions: start_dimensions(ctx.space),
-            cursor: start_cursor(ctx.space),
+            dimensions: start_dimensions(ctx.alignment, ctx.space),
+            cursor: start_cursor(ctx.alignment, ctx.space),
             in_extra_space: false,
             started: true,
         }
@@ -57,7 +84,7 @@ impl StackLayouter {
         };
 
         if self.overflows(new_dimensions) {
-            if self.ctx.extra_space.is_some() &&
+            if self.ctx.followup_spaces.is_some() &&
                 !(self.in_extra_space && self.overflows(layout.dimensions))
             {
                 self.finish_layout(true)?;
@@ -70,7 +97,7 @@ impl StackLayouter {
         // Determine where to put the box. When we right-align it, we want the
         // cursor to point to the top-right corner of the box. Therefore, the
         // position has to be moved to the left by the width of the box.
-        let position = match self.space.alignment {
+        let position = match self.ctx.alignment {
             Alignment::Left => self.cursor,
             Alignment::Right => self.cursor - Size2D::with_x(layout.dimensions.x),
             Alignment::Center => self.cursor - Size2D::with_x(layout.dimensions.x / 2),
@@ -101,7 +128,7 @@ impl StackLayouter {
         let new_dimensions = self.dimensions + Size2D::with_y(space);
 
         if self.overflows(new_dimensions) {
-            if self.ctx.extra_space.is_some() {
+            if self.ctx.followup_spaces.is_some() {
                 self.finish_layout(false)?;
             } else {
                 return Err(LayoutError::NotEnoughSpace("cannot fit space into stack"));
@@ -133,7 +160,7 @@ impl StackLayouter {
     pub fn finish_layout(&mut self, start_new_empty: bool) -> LayoutResult<()> {
         let actions = std::mem::replace(&mut self.actions, LayoutActionList::new());
         self.layouts.add(Layout {
-            dimensions: if self.space.shrink_to_fit {
+            dimensions: if self.ctx.shrink_to_fit {
                 self.dimensions.padded(self.space.padding)
             } else {
                 self.space.dimensions
@@ -152,12 +179,12 @@ impl StackLayouter {
     }
 
     pub fn start_new_space(&mut self) -> LayoutResult<()> {
-        if let Some(space) = self.ctx.extra_space {
+        if let Some(space) = self.ctx.followup_spaces {
             self.started = true;
             self.space = space;
             self.usable = space.usable();
-            self.dimensions = start_dimensions(space);
-            self.cursor = start_cursor(space);
+            self.dimensions = start_dimensions(self.ctx.alignment, space);
+            self.cursor = start_cursor(self.ctx.alignment, space);
             self.in_extra_space = true;
             Ok(())
         } else {
@@ -183,19 +210,19 @@ impl StackLayouter {
     }
 }
 
-fn start_dimensions(space: LayoutSpace) -> Size2D {
-    match space.alignment {
+fn start_dimensions(alignment: Alignment, space: LayoutSpace) -> Size2D {
+    match alignment {
         Alignment::Left => Size2D::zero(),
         Alignment::Right | Alignment::Center => Size2D::with_x(space.usable().x),
     }
 }
 
-fn start_cursor(space: LayoutSpace) -> Size2D {
+fn start_cursor(alignment: Alignment, space: LayoutSpace) -> Size2D {
     Size2D {
         // If left-align, the cursor points to the top-left corner of
         // each box. If we right-align, it points to the top-right
         // corner.
-        x: match space.alignment {
+        x: match alignment {
             Alignment::Left => space.padding.left,
             Alignment::Right => space.dimensions.x - space.padding.right,
             Alignment::Center => space.padding.left + (space.usable().x / 2),