box model fixes and tests

sandbox/align.css

@@ -10,27 +10,27 @@ Widget {
 }
 
 #thing {
+
     width: auto;
-    height: auto;
-    
+    height: 10;
     background:magenta;
     margin: 3;
-    padding: 1;
-    border: solid white;
-    box-sizing: content-box;
-    /* border: solid white; */
+    padding: 1; 
+    border: solid white; 
+    box-sizing: border-box;
+    border: solid white; 
     align-horizontal: center;    
 }
 
 
 #thing2 {
-    width: auto;
-    height: 10;
-    /* border: solid white; */
-     outline: heavy blue; 
-
+    border: solid white;
+    /* outline: heavy blue;  */
+    
     padding: 1 2;
-    box-sizing: content-box;
+    box-sizing: border-box;
+
+    max-height: 100vh;
 
     background:green;
     align-horizontal: center;
@@ -39,8 +39,7 @@ Widget {
 
 
 #thing3 {
-    width: 20;
-    height: 10;
+
     margin: 1;
     background:blue;
     align-horizontal: center;

sandbox/basic.css

@@ -201,7 +201,8 @@ Warning {
 
 Success {
   max-width: 80;
-  height:3;
+  height:3;  
+  box-sizing: border-box;
   background: $success-lighten-3;
   color: $text-success-lighten-3-fade-1;
   border-top: hkey $success;

src/textual/box_model.py

@@ -1,4 +1,5 @@
 from __future__ import annotations
+from operator import is_
 
 
 from typing import Callable, NamedTuple, TYPE_CHECKING
@@ -18,8 +19,8 @@ def get_box_model(
     styles: StylesBase,
     container_size: Size,
     parent_size: Size,
-    get_auto_width: Callable[[Size, Size, Spacing], int],
-    get_auto_height: Callable[[Size, Size, Spacing], int],
+    get_content_width: Callable[[Size, Size], int],
+    get_content_height: Callable[[Size, Size], int],
 ) -> BoxModel:
     """Resolve the box model for this Styles.
 
@@ -36,23 +37,30 @@ def get_box_model(
 
     has_rule = styles.has_rule
     width, height = container_size
+    is_content_box = styles.box_sizing == "content-box"
+    gutter = styles.padding + styles.border.spacing
 
-    gutter = Spacing(0, 0, 0, 0)
-    if styles.box_sizing == "content-box":
-        if has_rule("padding"):
-            gutter += styles.padding
-        gutter += styles.border.spacing
-
-    else:  # border-box
-        gutter -= styles.border.spacing
-
-    if has_rule("width"):
-        if styles.width.is_auto:
-            width = get_auto_width(container_size, parent_size, gutter)
-        else:
-            width = styles.width.resolve_dimension(container_size, parent_size)
+    if not has_rule("width") or styles.width.is_auto:
+        # When width is auto, we want enough space to always fit the content
+        width = get_content_width(container_size, parent_size)
+        if not is_content_box:
+            # If box sizing is border box we want to enlarge the width so that it
+            # can accommodate padding + border
+            width += gutter.width
     else:
-        width = max(0, width - styles.margin.width)
+        width = styles.width.resolve_dimension(container_size, parent_size)
+
+    if not has_rule("height") or styles.height.is_auto:
+        height = get_content_height(container_size, parent_size)
+        if not is_content_box:
+            height += gutter.height
+    else:
+        height = styles.height.resolve_dimension(container_size, parent_size)
+
+    if is_content_box:
+        gutter_width, gutter_height = gutter.totals
+        width += gutter_width
+        height += gutter_height
 
     if has_rule("min_width"):
         min_width = styles.min_width.resolve_dimension(container_size, parent_size)
@@ -62,23 +70,15 @@ def get_box_model(
         max_width = styles.max_width.resolve_dimension(container_size, parent_size)
         width = min(width, max_width)
 
-    if has_rule("height"):
-        if styles.height.is_auto:
-            height = get_auto_height(container_size, parent_size, gutter)
-        else:
-            height = styles.height.resolve_dimension(container_size, parent_size)
-    else:
-        height = max(0, height - styles.margin.height)
-
     if has_rule("min_height"):
         min_height = styles.min_height.resolve_dimension(container_size, parent_size)
         height = max(height, min_height)
 
     if has_rule("max_height"):
         max_height = styles.max_height.resolve_dimension(container_size, parent_size)
-        height = min(width, max_height)
+        height = min(height, max_height)
 
-    size = Size(width, height) + gutter.totals
-    margin = styles.margin if has_rule("margin") else Spacing(0, 0, 0, 0)
+    size = Size(width, height)
+    margin = styles.margin
 
     return BoxModel(size, margin)

src/textual/css/_style_properties.py

@@ -8,7 +8,6 @@ when setting and getting.
 """
 
 from __future__ import annotations
-from tkinter.tix import AUTO
 
 from typing import Iterable, NamedTuple, TYPE_CHECKING, cast
 

src/textual/layouts/horizontal.py

@@ -34,9 +34,10 @@ class HorizontalLayout(Layout):
             max((box1.margin.right, box2.margin.left))
             for box1, box2 in zip(box_models, box_models[1:])
         ]
-        margins.append(box_models[-1].margin.right)
+        if box_models:
+            margins.append(box_models[-1].margin.right)
 
-        x = box_models[0].margin.left
+        x = box_models[0].margin.left if box_models else 0
 
         for widget, box_model, margin in zip(parent.children, box_models, margins):
             content_width, content_height = box_model.size
@@ -47,7 +48,7 @@ class HorizontalLayout(Layout):
             x += region.width + margin
             max_width = x
 
-        max_width += margins[-1]
+        max_width += margins[-1] if margins else 0
 
         total_region = Region(0, 0, max_width, max_height)
         add_placement(WidgetPlacement(total_region, None, 0))

src/textual/layouts/vertical.py

@@ -35,9 +35,10 @@ class VerticalLayout(Layout):
             max((box1.margin.bottom, box2.margin.top))
             for box1, box2 in zip(box_models, box_models[1:])
         ]
-        margins.append(box_models[-1].margin.bottom)
+        if box_models:
+            margins.append(box_models[-1].margin.bottom)
 
-        y = box_models[0].margin.top
+        y = box_models[0].margin.top if box_models else 0
 
         for widget, box_model, margin in zip(parent.children, box_models, margins):
             content_width, content_height = box_model.size
@@ -48,7 +49,7 @@ class VerticalLayout(Layout):
             y += region.height + margin
             max_height = y
 
-        max_height += margins[-1]
+        max_height += margins[-1] if margins else 0
 
         total_region = Region(0, 0, max_width, max_height)
         add_placement(WidgetPlacement(total_region, None, 0))

src/textual/screen.py

@@ -131,7 +131,8 @@ class Screen(Widget):
                         )
                     )
         except Exception as error:
-            self.app.panic(error)
+            self.app.on_exception(error)
+            return
         self.app.refresh()
         self._dirty_widgets.clear()
 

src/textual/widget.py

@@ -115,21 +115,16 @@ class Widget(DOMNode):
             self.get_content_width,
             self.get_content_height,
         )
-        self.log(self, self.styles.padding, self.styles.border.spacing)
         return box_model
 
-    def get_content_width(
-        self, container_size: Size, parent_size: Size, gutter: Spacing
-    ) -> int:
+    def get_content_width(self, container_size: Size, parent_size: Size) -> int:
         console = self.app.console
         renderable = self.render()
         measurement = Measurement.get(console, console.options, renderable)
         return measurement.maximum
 
-    def get_content_height(
-        self, container_size: Size, parent_size: Size, gutter: Spacing
-    ) -> int:
-        return container_size.height - gutter.height
+    def get_content_height(self, container_size: Size, parent_size: Size) -> int:
+        return container_size.height
 
     async def watch_scroll_x(self, new_value: float) -> None:
         self.horizontal_scrollbar.position = int(new_value)