upd: fix container layout size error when children count is 0.

examples/remove_demo/remove_widget.rs

@@ -35,23 +35,33 @@ impl ObjectImpl for RemoveWidget {
         self.parent_construct();
 
         self.bottom.set_margin_top(5);
+        self.bottom.set_background(Color::GREY_LIGHT);
 
         self.set_hexpand(true);
         self.set_vexpand(true);
+        let mut button_0 = Button::new(Some("Remove 1th"));
         let mut button_1 = Button::new(Some("Remove Left"));
         let mut button_2 = Button::new(Some("Remove Right"));
         let mut button_3 = Button::new(Some("Remove Stack"));
         let mut button_4 = Button::new(Some("Remove SplitPane Left"));
         let mut button_5 = Button::new(Some("Remove SplitPane RightTop"));
         let mut button_6 = Button::new(Some("Remove SplitPane RightBottomLeft"));
         let mut button_7 = Button::new(Some("Remove SplitPane RightBottomRight"));
+        button_0.width_request(100);
+        button_1.width_request(100);
         button_1.width_request(100);
         button_2.width_request(100);
         button_3.width_request(100);
         button_4.width_request(200);
         button_5.width_request(200);
         button_6.width_request(200);
         button_7.width_request(200);
+        connect!(
+            button_0,
+            mouse_pressed(),
+            self,
+            remove_0th_pressed(MouseEvent)
+        );
         connect!(
             button_1,
             mouse_pressed(),
@@ -94,6 +104,7 @@ impl ObjectImpl for RemoveWidget {
             self,
             remove_split_pane_right_bottom_right(MouseEvent)
         );
+        self.top.add_child(button_0);
         self.top.add_child(button_1);
         self.top.add_child(button_2);
         self.top.add_child(button_3);
@@ -123,6 +134,13 @@ impl RemoveWidget {
         Self::new_alloc()
     }
 
+    pub fn remove_0th_pressed(&mut self, _: MouseEvent) {
+        let id = self.bottom.children().first().map(|c| c.id());
+        if let Some(id) = id {
+            self.bottom.remove_children(id);
+        }
+    }
+
     pub fn remove_left_pressed(&mut self, _: MouseEvent) {
         self.bottom.remove_children(self.to_remove);
     }

tmui/src/layout.rs

@@ -383,6 +383,8 @@ impl SizeCalculation for dyn WidgetImpl {
             } else {
                 if self.detecting_width() != 0 {
                     self.set_fixed_width(self.detecting_width())
+                } else {
+                    self.set_fixed_width(0);
                 }
             }
         }
@@ -442,6 +444,8 @@ impl SizeCalculation for dyn WidgetImpl {
             } else {
                 if self.detecting_height() != 0 {
                     self.set_fixed_height(self.detecting_height())
+                } else {
+                    self.set_fixed_height(0);
                 }
             }
         }