Fix margin collapsing between caption and table wrapper.

weasyprint/layout/blocks.py

@@ -461,7 +461,6 @@ def block_container_layout(context, box, max_position_y, skip_stack,
             new_containing_block = box
 
             if not new_containing_block.is_table_wrapper:
-                # TODO: there's no collapsing margins inside tables, right?
                 resolve_percentages(child, new_containing_block)
                 if (child.is_in_normal_flow() and
                         last_in_flow_child is None and
@@ -493,7 +492,7 @@ def block_container_layout(context, box, max_position_y, skip_stack,
                         adjoining_margins = []
                         position_y = box.content_box_y()
 
-            if adjoining_margins and isinstance(child, boxes.TableBox):
+            if adjoining_margins and box.is_table_wrapper:
                 collapsed_margin = collapse_margin(adjoining_margins)
                 child.position_y += collapsed_margin
                 position_y += collapsed_margin
@@ -625,8 +624,11 @@ def block_container_layout(context, box, max_position_y, skip_stack,
             # not adjoining. (position_y is not used afterwards.)
             adjoining_margins = []
 
-    if box.border_bottom_width or box.padding_bottom or (
-            establishes_formatting_context(box) or box.is_for_root_element):
+    if (box.border_bottom_width or
+            box.padding_bottom or
+            establishes_formatting_context(box) or
+            box.is_for_root_element or
+            box.is_table_wrapper):
         position_y += collapse_margin(adjoining_margins)
         adjoining_margins = []
 

weasyprint/tests/test_layout/test_table.py

@@ -2075,3 +2075,61 @@ def test_inline_table_baseline(vertical_align, table_position_y):
     assert text1.position_y == text2.position_y == 0
     assert table.height == 10 * 2
     assert table.position_y == table_position_y
+
+
+@assert_no_logs
+def test_table_caption_margin_top():
+    page, = render_pages('''
+      <style>
+        table { margin: 20px; }
+        caption, h1, h2 { margin: 20px; height: 10px }
+        td { height: 10px }
+      </style>
+      <h1></h1>
+      <table>
+        <caption></caption>
+        <tr>
+          <td></td>
+        </tr>
+      </table>
+      <h2></h2>
+    ''')
+    html, = page.children
+    body, = html.children
+    h1, wrapper, h2 = body.children
+    caption, table = wrapper.children
+    tbody, = table.children
+    assert (h1.content_box_x(), h1.content_box_y()) == (20, 20)
+    assert (wrapper.content_box_x(), wrapper.content_box_y()) == (20, 50)
+    assert (caption.content_box_x(), caption.content_box_y()) == (40, 70)
+    assert (tbody.content_box_x(), tbody.content_box_y()) == (20, 100)
+    assert (h2.content_box_x(), h2.content_box_y()) == (20, 130)
+
+
+@assert_no_logs
+def test_table_caption_margin_bottom():
+    page, = render_pages('''
+      <style>
+        table { margin: 20px; }
+        caption, h1, h2 { margin: 20px; height: 10px; caption-side: bottom }
+        td { height: 10px }
+      </style>
+      <h1></h1>
+      <table>
+        <caption></caption>
+        <tr>
+          <td></td>
+        </tr>
+      </table>
+      <h2></h2>
+    ''')
+    html, = page.children
+    body, = html.children
+    h1, wrapper, h2 = body.children
+    table, caption = wrapper.children
+    tbody, = table.children
+    assert (h1.content_box_x(), h1.content_box_y()) == (20, 20)
+    assert (wrapper.content_box_x(), wrapper.content_box_y()) == (20, 50)
+    assert (tbody.content_box_x(), tbody.content_box_y()) == (20, 50)
+    assert (caption.content_box_x(), caption.content_box_y()) == (40, 80)
+    assert (h2.content_box_x(), h2.content_box_y()) == (20, 130)