Split blocks in blocks when possible

Related to #1476.

tests/layout/test_block.py

@@ -833,3 +833,46 @@ def test_continue_discard_children():
     assert div_2.position_y == 2 + 25
     assert div_3.position_y == 2 + 25 * 2
     assert article.border_bottom_width == 1
+
+
+@assert_no_logs
+def test_block_in_block_with_bottom_padding():
+    # Test regression: https://github.com/Kozea/WeasyPrint/issues/1476
+    page_1, page_2 = render_pages('''
+      <style>
+        @font-face { src: url(weasyprint.otf); font-family: weasyprint }
+        @page { size: 8em 3.5em }
+        body { line-height: 1; orphans: 1; widows: 1; font-family: weasyprint }
+        div { padding-bottom: 1em }
+      </style>
+      abc def
+      <div>
+        <p>
+          ghi jkl
+          mno pqr
+        </p>
+      </div>
+      stu vwx''')
+
+    html, = page_1.children
+    body, = html.children
+    anon_body, div = body.children
+    line, = anon_body.children
+    assert line.height == 16
+    assert line.children[0].text == 'abc def'
+    p, = div.children
+    line, = p.children
+    assert line.height == 16
+    assert line.children[0].text == 'ghi jkl'
+
+    html, = page_2.children
+    body, = html.children
+    div, anon_body = body.children
+    p, = div.children
+    line, = p.children
+    assert line.height == 16
+    assert line.children[0].text == 'mno pqr'
+    line, = anon_body.children
+    assert line.height == 16
+    assert line.content_box_y() == 16 + 16  # p content + div padding
+    assert line.children[0].text == 'stu vwx'

weasyprint/layout/block.py

@@ -411,7 +411,6 @@ def _in_flow_layout(context, box, index, child, new_children, page_is_empty,
          context, child, max_position_y, skip_stack, new_containing_block,
          page_is_empty_with_no_children, absolute_boxes, fixed_boxes,
          adjoining_margins, discard)
-    skip_stack = None
 
     if new_child is not None:
         # index in its non-laid-out parent, not in future new parent
@@ -425,28 +424,47 @@ def _in_flow_layout(context, box, index, child, new_children, page_is_empty,
             offset_y = (
                 collapse_margin(adjoining_margins) - new_child.margin_top)
             new_child.translate(0, offset_y)
-            adjoining_margins = []
         # else: blocks handle that themselves.
 
-        adjoining_margins = next_adjoining_margins
-        adjoining_margins.append(new_child.margin_bottom)
-
         if not collapsing_through:
+            new_content_position_y = (
+                new_child.content_box_y() + new_child.height)
             new_position_y = (
                 new_child.border_box_y() + new_child.border_height())
 
-            if (new_position_y > allowed_max_position_y and
+            if (new_content_position_y > allowed_max_position_y and
                     not page_is_empty_with_no_children):
-                # The child overflows the page area, put it on the
-                # next page. (But don’t delay whole blocks if eg.
-                # only the bottom border overflows.)
+                # The child content overflows the page area, display it on the
+                # next page.
+                remove_placeholders([new_child], absolute_boxes, fixed_boxes)
                 new_child = None
+            elif (new_position_y > allowed_max_position_y and
+                    not page_is_empty_with_no_children):
+                # The child border/padding overflows the page area, do the
+                # layout again with a lower max_y value.
+                remove_placeholders([new_child], absolute_boxes, fixed_boxes)
+                max_position_y -= (
+                    new_child.padding_bottom + new_child.border_bottom_width)
+                (new_child, resume_at, next_page, next_adjoining_margins,
+                 collapsing_through) = block_level_layout(
+                     context, child, max_position_y, skip_stack,
+                     new_containing_block, page_is_empty_with_no_children,
+                     absolute_boxes, fixed_boxes, adjoining_margins, discard)
+                if new_child:
+                    position_y = (
+                        new_child.border_box_y() + new_child.border_height())
             else:
                 position_y = new_position_y
 
-        if new_child is not None and new_child.clearance is not None:
+        adjoining_margins = next_adjoining_margins
+        if new_child:
+            adjoining_margins.append(new_child.margin_bottom)
+
+        if new_child and new_child.clearance:
             position_y = new_child.border_box_y() + new_child.border_height()
 
+    skip_stack = None
+
     if new_child is None:
         # Nothing fits in the remaining space of this page: break
         if page_break in ('avoid', 'avoid-page'):