diff --git a/egui/src/containers/collapsing_header.rs b/egui/src/containers/collapsing_header.rs
index 12d0e798..afa4d416 100644
--- a/egui/src/containers/collapsing_header.rs
+++ b/egui/src/containers/collapsing_header.rs
@@ -63,18 +63,15 @@ impl State {
         add_contents: impl FnOnce(&mut Ui) -> R,
     ) -> Option<(R, Response)> {
         let openness = self.openness(ui.ctx(), id);
-        let animate = 0.0 < openness && openness < 1.0;
-        if animate {
+        if openness <= 0.0 {
+            None
+        } else if openness < 1.0 {
             Some(ui.wrap(|child_ui| {
-                let max_height = if self.open {
-                    if let Some(full_height) = self.open_height {
-                        remap_clamp(openness, 0.0..=1.0, 0.0..=full_height)
-                    } else {
-                        // First frame of expansion.
-                        // We don't know full height yet, but we will next frame.
-                        // Just use a placeholder value that shows some movement:
-                        10.0
-                    }
+                let max_height = if self.open && self.open_height.is_none() {
+                    // First frame of expansion.
+                    // We don't know full height yet, but we will next frame.
+                    // Just use a placeholder value that shows some movement:
+                    10.0
                 } else {
                     let full_height = self.open_height.unwrap_or_default();
                     remap_clamp(openness, 0.0..=1.0, 0.0..=full_height)
@@ -84,23 +81,21 @@ impl State {
                 clip_rect.max.y = clip_rect.max.y.min(child_ui.max_rect().top() + max_height);
                 child_ui.set_clip_rect(clip_rect);
 
-                let r = add_contents(child_ui);
+                let ret = add_contents(child_ui);
 
-                self.open_height = Some(child_ui.min_size().y);
-
-                // Pretend children took up less space:
                 let mut min_rect = child_ui.min_rect();
-                min_rect.max.y = min_rect.max.y.min(min_rect.top() + max_height);
+                self.open_height = Some(min_rect.height());
+
+                // Pretend children took up at most `max_height` space:
+                min_rect.max.y = min_rect.max.y.at_most(min_rect.top() + max_height);
                 child_ui.force_set_min_rect(min_rect);
-                r
+                ret
             }))
-        } else if self.open || ui.memory().all_collpasing_are_open {
+        } else {
             let (ret, response) = ui.wrap(add_contents);
             let full_size = response.rect.size();
             self.open_height = Some(full_size.y);
             Some((ret, response))
-        } else {
-            None
         }
     }
 }
diff --git a/egui/src/containers/window.rs b/egui/src/containers/window.rs
index 835c2047..6e26957a 100644
--- a/egui/src/containers/window.rs
+++ b/egui/src/containers/window.rs
@@ -25,7 +25,7 @@ pub struct Window<'open> {
 }
 
 impl<'open> Window<'open> {
-    // TODO: Into<Label>
+    /// The winodw title must be unique, and should not change.
     pub fn new(title: impl Into<String>) -> Self {
         let title = title.into();
         let area = Area::new(&title);
@@ -40,7 +40,7 @@ impl<'open> Window<'open> {
             resize: Resize::default()
                 .with_stroke(false)
                 .min_size([96.0, 32.0])
-                .default_size([420.0, 420.0]),
+                .default_size([420.0, 420.0]), // Default inner size of a winodw
             scroll: None,
             collapsible: true,
         }
@@ -219,10 +219,6 @@ impl<'open> Window<'open> {
         // First interact (move etc) to avoid frame delay:
         let last_frame_outer_rect = area.state().rect();
         let interaction = if possible.movable || possible.resizable {
-            let title_bar_height = title_label.font_height(ctx.fonts(), &ctx.style())
-                + 1.0 * ctx.style().spacing.item_spacing.y; // this could be better
-            let margins = 2.0 * frame.margin + vec2(0.0, title_bar_height);
-
             window_interaction(
                 ctx,
                 possible,
@@ -231,6 +227,11 @@ impl<'open> Window<'open> {
                 last_frame_outer_rect,
             )
             .and_then(|window_interaction| {
+                // Calculate roughly how much larger the window size is compared to the inner rect
+                let title_bar_height = title_label.font_height(ctx.fonts(), &ctx.style())
+                    + 1.0 * ctx.style().spacing.item_spacing.y; // this could be better
+                let margins = 2.0 * frame.margin + vec2(0.0, title_bar_height);
+
                 interact(
                     window_interaction,
                     ctx,
@@ -276,9 +277,9 @@ impl<'open> Window<'open> {
                         ui.allocate_space(ui.style().spacing.item_spacing);
 
                         if let Some(scroll) = scroll {
-                            scroll.show(ui, add_contents)
+                            scroll.show(ui, add_contents);
                         } else {
-                            add_contents(ui)
+                            add_contents(ui);
                         }
                     })
                 })
@@ -685,6 +686,7 @@ impl TitleBar {
             let left = outer_rect.left();
             let right = outer_rect.right();
             let y = content_response.rect.top() + ui.style().spacing.item_spacing.y * 0.5;
+            // let y = lerp(self.rect.bottom()..=content_response.rect.top(), 0.5);
             ui.painter().line_segment(
                 [pos2(left, y), pos2(right, y)],
                 ui.style().visuals.widgets.inactive.bg_stroke,
diff --git a/egui/src/paint/tessellator.rs b/egui/src/paint/tessellator.rs
index e10a5ec3..de69bec0 100644
--- a/egui/src/paint/tessellator.rs
+++ b/egui/src/paint/tessellator.rs
@@ -673,10 +673,10 @@ fn mul_color(color: Srgba, factor: f32) -> Srgba {
 /// * `scratchpad_path`: if you plan to run `tessellate_paint_command`
 ///    many times, pass it a reference to the same `Path` to avoid excessive allocations.
 fn tessellate_paint_command(
-    clip_rect: Rect,
-    command: PaintCmd,
     options: TesselationOptions,
     fonts: &Fonts,
+    clip_rect: Rect,
+    command: PaintCmd,
     out: &mut Triangles,
     scratchpad_points: &mut Vec<Pos2>,
     scratchpad_path: &mut Path,
@@ -773,63 +773,77 @@ fn tessellate_paint_command(
             text_style,
             color,
         } => {
-            if color == TRANSPARENT {
-                return;
-            }
-            galley.sanity_check();
-
-            let num_chars = galley.text.chars().count();
-            out.reserve_triangles(num_chars * 2);
-            out.reserve_vertices(num_chars * 4);
-
-            let tex_w = fonts.texture().width as f32;
-            let tex_h = fonts.texture().height as f32;
-
-            let text_offset = vec2(0.0, 1.0); // Eye-balled for buttons. TODO: why is this needed?
-
-            let clip_rect = clip_rect.expand(2.0); // Some fudge to handle letters that are slightly larger than expected.
-
-            let font = &fonts[text_style];
-            let mut chars = galley.text.chars();
-            for line in &galley.rows {
-                let line_min_y = pos.y + line.y_min + text_offset.x;
-                let line_max_y = line_min_y + font.row_height();
-                let is_line_visible =
-                    line_max_y >= clip_rect.min.y && line_min_y <= clip_rect.max.y;
-
-                for x_offset in line.x_offsets.iter().take(line.x_offsets.len() - 1) {
-                    let c = chars.next().unwrap();
-
-                    if options.coarse_tessellation_culling && !is_line_visible {
-                        // culling individual lines of text is important, since a single `PaintCmd::Text`
-                        // can span hundreds of lines.
-                        continue;
-                    }
-
-                    if let Some(glyph) = font.uv_rect(c) {
-                        let mut left_top =
-                            pos + glyph.offset + vec2(*x_offset, line.y_min) + text_offset;
-                        left_top.x = font.round_to_pixel(left_top.x); // Pixel-perfection.
-                        left_top.y = font.round_to_pixel(left_top.y); // Pixel-perfection.
-
-                        let pos = Rect::from_min_max(left_top, left_top + glyph.size);
-                        let uv = Rect::from_min_max(
-                            pos2(glyph.min.0 as f32 / tex_w, glyph.min.1 as f32 / tex_h),
-                            pos2(glyph.max.0 as f32 / tex_w, glyph.max.1 as f32 / tex_h),
-                        );
-                        out.add_rect_with_uv(pos, uv, color);
-                    }
-                }
-                if line.ends_with_newline {
-                    let newline = chars.next().unwrap();
-                    debug_assert_eq!(newline, '\n');
-                }
-            }
-            assert_eq!(chars.next(), None);
+            tesselate_text(
+                options, fonts, clip_rect, pos, &galley, text_style, color, out,
+            );
         }
     }
 }
 
+#[allow(clippy::too_many_arguments)]
+fn tesselate_text(
+    options: TesselationOptions,
+    fonts: &Fonts,
+    clip_rect: Rect,
+    pos: Pos2,
+    galley: &super::Galley,
+    text_style: super::TextStyle,
+    color: Srgba,
+    out: &mut Triangles,
+) {
+    if color == TRANSPARENT {
+        return;
+    }
+    galley.sanity_check();
+
+    let num_chars = galley.text.chars().count();
+    out.reserve_triangles(num_chars * 2);
+    out.reserve_vertices(num_chars * 4);
+
+    let tex_w = fonts.texture().width as f32;
+    let tex_h = fonts.texture().height as f32;
+
+    let text_offset = vec2(0.0, 1.0); // Eye-balled for buttons. TODO: why is this needed?
+
+    let clip_rect = clip_rect.expand(2.0); // Some fudge to handle letters that are slightly larger than expected.
+
+    let font = &fonts[text_style];
+    let mut chars = galley.text.chars();
+    for line in &galley.rows {
+        let line_min_y = pos.y + line.y_min + text_offset.x;
+        let line_max_y = line_min_y + font.row_height();
+        let is_line_visible = line_max_y >= clip_rect.min.y && line_min_y <= clip_rect.max.y;
+
+        for x_offset in line.x_offsets.iter().take(line.x_offsets.len() - 1) {
+            let c = chars.next().unwrap();
+
+            if options.coarse_tessellation_culling && !is_line_visible {
+                // culling individual lines of text is important, since a single `PaintCmd::Text`
+                // can span hundreds of lines.
+                continue;
+            }
+
+            if let Some(glyph) = font.uv_rect(c) {
+                let mut left_top = pos + glyph.offset + vec2(*x_offset, line.y_min) + text_offset;
+                left_top.x = font.round_to_pixel(left_top.x); // Pixel-perfection.
+                left_top.y = font.round_to_pixel(left_top.y); // Pixel-perfection.
+
+                let pos = Rect::from_min_max(left_top, left_top + glyph.size);
+                let uv = Rect::from_min_max(
+                    pos2(glyph.min.0 as f32 / tex_w, glyph.min.1 as f32 / tex_h),
+                    pos2(glyph.max.0 as f32 / tex_w, glyph.max.1 as f32 / tex_h),
+                );
+                out.add_rect_with_uv(pos, uv, color);
+            }
+        }
+        if line.ends_with_newline {
+            let newline = chars.next().unwrap();
+            debug_assert_eq!(newline, '\n');
+        }
+    }
+    assert_eq!(chars.next(), None);
+}
+
 /// Turns `PaintCmd`:s into sets of triangles.
 ///
 /// The given commands will be painted back-to-front (painters algorithm).
@@ -862,10 +876,10 @@ pub fn tessellate_paint_commands(
 
         let out = &mut jobs.last_mut().unwrap().1;
         tessellate_paint_command(
-            clip_rect,
-            cmd,
             options,
             fonts,
+            clip_rect,
+            cmd,
             out,
             &mut scratchpad_points,
             &mut scratchpad_path,
@@ -875,6 +889,8 @@ pub fn tessellate_paint_commands(
     if options.debug_paint_clip_rects {
         for (clip_rect, triangles) in &mut jobs {
             tessellate_paint_command(
+                options,
+                fonts,
                 Rect::everything(),
                 PaintCmd::Rect {
                     rect: *clip_rect,
@@ -882,8 +898,6 @@ pub fn tessellate_paint_commands(
                     fill: Default::default(),
                     stroke: Stroke::new(2.0, srgba(150, 255, 150, 255)),
                 },
-                options,
-                fonts,
                 triangles,
                 &mut scratchpad_points,
                 &mut scratchpad_path,