Fix debug-assert hit in panel sizing code

Author: emilk

crates/egui/src/containers/panel.rs

@@ -262,9 +262,7 @@ impl SidePanel {
         let frame = frame.unwrap_or_else(|| Frame::side_top_panel(ui.style()));
         let inner_response = frame.show(&mut panel_ui, |ui| {
             ui.set_min_height(ui.max_rect().height()); // Make sure the frame fills the full height
-            ui.set_min_width(
-                width_range.min - (frame.inner_margin.left + frame.inner_margin.right),
-            );
+            ui.set_min_width((width_range.min - frame.inner_margin.sum().x).at_least(0.0));
             add_contents(ui)
         });
 
@@ -730,9 +728,7 @@ impl TopBottomPanel {
         let frame = frame.unwrap_or_else(|| Frame::side_top_panel(ui.style()));
         let inner_response = frame.show(&mut panel_ui, |ui| {
             ui.set_min_width(ui.max_rect().width()); // Make the frame fill full width
-            ui.set_min_height(
-                height_range.min - (frame.inner_margin.top + frame.inner_margin.bottom),
-            );
+            ui.set_min_height((height_range.min - frame.inner_margin.sum().y).at_least(0.0));
             add_contents(ui)
         });
 

crates/egui/src/placer.rs

@@ -248,6 +248,9 @@ impl Placer {
     /// Set the minimum width of the ui.
     /// This can't shrink the ui, only make it larger.
     pub(crate) fn set_min_width(&mut self, width: f32) {
+        if width <= 0.0 {
+            return;
+        }
         let rect = self.next_widget_space_ignore_wrap_justify(vec2(width, 0.0));
         self.region.expand_to_include_x(rect.min.x);
         self.region.expand_to_include_x(rect.max.x);
@@ -256,6 +259,9 @@ impl Placer {
     /// Set the minimum height of the ui.
     /// This can't shrink the ui, only make it larger.
     pub(crate) fn set_min_height(&mut self, height: f32) {
+        if height <= 0.0 {
+            return;
+        }
         let rect = self.next_widget_space_ignore_wrap_justify(vec2(0.0, height));
         self.region.expand_to_include_y(rect.min.y);
         self.region.expand_to_include_y(rect.max.y);

crates/egui/src/ui.rs

@@ -530,12 +530,14 @@ impl Ui {
     /// Set the minimum width of the ui.
     /// This can't shrink the ui, only make it larger.
     pub fn set_min_width(&mut self, width: f32) {
+        egui_assert!(0.0 <= width);
         self.placer.set_min_width(width);
     }
 
     /// Set the minimum height of the ui.
     /// This can't shrink the ui, only make it larger.
     pub fn set_min_height(&mut self, height: f32) {
+        egui_assert!(0.0 <= height);
         self.placer.set_min_height(height);
     }