Refactor ruin_app, add some README files, minor usability in reactivity

lib/ui/src/layout.rs

@@ -257,6 +257,7 @@ pub fn layout_snapshot_with_cache(
     }
 }
 
+#[allow(clippy::too_many_arguments)]
 fn layout_element(
     element: &Element,
     rect: Rect,
@@ -797,6 +798,7 @@ struct MeasuredChild {
     is_flex: bool,
 }
 
+#[allow(clippy::too_many_arguments)]
 fn layout_container_children(
     element: &Element,
     content: Rect,
@@ -996,8 +998,13 @@ fn intrinsic_container_content_size(
                     .height
                     .map(|h| h + vertical_insets(child_insets))
                     .unwrap_or(content_size.height);
-                let child_size =
-                    intrinsic_size(child, UiSize::new(offered_w, offered_h), text_system, perf_stats, layout_cache);
+                let child_size = intrinsic_size(
+                    child,
+                    UiSize::new(offered_w, offered_h),
+                    text_system,
+                    perf_stats,
+                    layout_cache,
+                );
                 // child_size is always outer; accumulate directly.
                 width = width.max(child_size.width);
                 if !skip_main {
@@ -1030,8 +1037,13 @@ fn intrinsic_container_content_size(
                     .height
                     .map(|h| h + vertical_insets(child_insets))
                     .unwrap_or(content_size.height);
-                let child_size =
-                    intrinsic_size(child, UiSize::new(offered_w, offered_h), text_system, perf_stats, layout_cache);
+                let child_size = intrinsic_size(
+                    child,
+                    UiSize::new(offered_w, offered_h),
+                    text_system,
+                    perf_stats,
+                    layout_cache,
+                );
                 // child_size.width is outer; use directly as the fixed main contribution.
                 let child_main = child_size.width;
                 fixed_main += child_main;

lib/ui/src/scene.rs

@@ -80,6 +80,9 @@ impl Color {
     /// safe to reserve as a sentinel.  No user-facing API sets this value directly.
     pub const SENTINEL: Self = Self::rgba(0, 0, 0, 0);
 
+    pub const BLACK: Self = Self::rgb(0, 0, 0);
+    pub const WHITE: Self = Self::rgb(255, 255, 255);
+
     pub const fn rgba(r: u8, g: u8, b: u8, a: u8) -> Self {
         Self { r, g, b, a }
     }
@@ -219,6 +222,7 @@ impl Deref for PreparedText {
 
 impl PreparedText {
     /// Construct a `PreparedText` from shaped data.  Called by `TextSystem::prepare_spans`.
+    #[allow(clippy::too_many_arguments)]
     pub(crate) fn from_layout(
         element_id: Option<ElementId>,
         text: String,
@@ -623,10 +627,18 @@ impl DisplayItem {
     /// Return a copy of this item with all positions shifted by `offset`.
     pub fn translated(&self, offset: Point) -> Self {
         fn translate_rect(r: Rect, o: Point) -> Rect {
-            Rect::new(r.origin.x + o.x, r.origin.y + o.y, r.size.width, r.size.height)
+            Rect::new(
+                r.origin.x + o.x,
+                r.origin.y + o.y,
+                r.size.width,
+                r.size.height,
+            )
         }
         match self {
-            Self::Quad(q) => Self::Quad(Quad { rect: translate_rect(q.rect, offset), ..*q }),
+            Self::Quad(q) => Self::Quad(Quad {
+                rect: translate_rect(q.rect, offset),
+                ..*q
+            }),
             Self::RoundedRect(r) => Self::RoundedRect(RoundedRect {
                 rect: translate_rect(r.rect, offset),
                 ..*r
@@ -838,8 +850,8 @@ mod tests {
 
     #[test]
     fn prepared_text_vertical_offset_moves_between_lines() {
-        use std::sync::Arc;
         use super::{PreparedTextLine, TextLayoutData};
+        use std::sync::Arc;
 
         let mut text = PreparedText::monospace(
             "abcdwxyz",
@@ -873,7 +885,11 @@ mod tests {
             }
         }
         let orig_size = text.layout.size;
-        text.layout = Arc::new(TextLayoutData { lines, glyphs, size: orig_size });
+        text.layout = Arc::new(TextLayoutData {
+            lines,
+            glyphs,
+            size: orig_size,
+        });
 
         assert_eq!(text.vertical_offset(2, 1), Some(6));
         assert_eq!(text.vertical_offset(6, -1), Some(2));
@@ -892,8 +908,12 @@ mod tests {
         let target_line = &text.lines[1];
         // Lines store LOCAL coords; add text.origin to get absolute window coords for the query.
         let y = text.origin.y + target_line.rect.origin.y + target_line.rect.size.height * 0.5;
-        let start = text.byte_offset_for_position(Point::new(text.origin.x + target_line.rect.origin.x, y));
-        let end = text.byte_offset_for_position(Point::new(text.origin.x + target_line.rect.origin.x + 16.0, y));
+        let start =
+            text.byte_offset_for_position(Point::new(text.origin.x + target_line.rect.origin.x, y));
+        let end = text.byte_offset_for_position(Point::new(
+            text.origin.x + target_line.rect.origin.x + 16.0,
+            y,
+        ));
         let rects = text.selection_rects(start, end);
 
         assert_eq!(rects.len(), 1);