Fix "pages" counter in non-root absolute boxes

These boxes were not available through the "descendants" function, because they
are represented by placeholders. They are also not available in the list of
absolute boxes of the page, because they’re not relative to the root page.

The new "placeholders" parameter of "descendants" goes through placeholders and
gets all the absolute children.

Putting "descendants" and "children" in all boxes, not just parents, avoids
useless checks and special cases.

Fix #2029.

tests/layout/test_inline.py

@@ -62,10 +62,9 @@ def test_breaking_linebox():
         for child in line.children:
             assert child.element_tag in ('em', 'p')
             assert child.style['font_size'] == 13
-            if isinstance(child, boxes.ParentBox):
-                for child_child in child.children:
-                    assert child.element_tag in ('em', 'strong', 'span')
-                    assert child.style['font_size'] == 13
+            for child_child in child.children:
+                assert child.element_tag in ('em', 'strong', 'span')
+                assert child.style['font_size'] == 13
 
 
 @assert_no_logs

tests/test_target.py

@@ -167,7 +167,7 @@ def test_target_absolute():
           content: target-counter('#h', page);
         }
         div {
-           position: absolute;
+          position: absolute;
         }
       </style>
       <div><a id="span">link</a></div>
@@ -182,3 +182,32 @@ def test_target_absolute():
     text_box, after = inline.children
     assert text_box.text == 'link'
     assert after.children[0].text == '1'
+
+
+@assert_no_logs
+def test_target_absolute_non_root():
+    document = FakeHTML(string='''
+      <style>
+        a::after {
+          content: target-counter('#h', page);
+        }
+        section {
+          position: relative;
+        }
+        div {
+          position: absolute;
+        }
+      </style>
+      <section><div><a id="span">link</a></div></section>
+      <h1 id="h">abc</h1>
+    ''')
+    page, = document.render().pages
+    html, = page._page_box.children
+    body, = html.children
+    section, h1 = body.children
+    div, = section.children
+    line, = div.children
+    inline, = line.children
+    text_box, after = inline.children
+    assert text_box.text == 'link'
+    assert after.children[0].text == '1'

weasyprint/draw.py

@@ -810,10 +810,9 @@ def draw_outlines(stream, box):
                     stream, outline_box, 4 * (width,), style,
                     styled_color(style, color, side))
 
-    if isinstance(box, boxes.ParentBox):
-        for child in box.children:
-            if isinstance(child, boxes.Box):
-                draw_outlines(stream, child)
+    for child in box.children:
+        if isinstance(child, boxes.Box):
+            draw_outlines(stream, child)
 
 
 def draw_table(stream, table):

weasyprint/formatting_structure/boxes.py

@@ -82,13 +82,23 @@ class Box:
 
     # Default, overriden on some subclasses
     def all_children(self):
-        return ()
+        return self.children
+
+    def descendants(self, placeholders=False):
+        """A flat generator for a box, its children and descendants."""
+        yield self
+        for child in self.children:
+            if placeholders or isinstance(child, Box):
+                yield from child.descendants(placeholders)
+            else:
+                yield child
 
     def __init__(self, element_tag, style, element):
         self.element_tag = element_tag
         self.element = element
         self.style = style
         self.remove_decoration_sides = set()
+        self.children = []
 
     def __repr__(self):
         return f'<{type(self).__name__} {self.element_tag}>'
@@ -332,9 +342,6 @@ class ParentBox(Box):
         super().__init__(element_tag, style, element)
         self.children = tuple(children)
 
-    def all_children(self):
-        return self.children
-
     def _reset_spacing(self, side):
         """Set to 0 the margin, padding and border of ``side``."""
         self.remove_decoration_sides.add(side)
@@ -353,7 +360,7 @@ class ParentBox(Box):
     def copy_with_children(self, new_children):
         """Create a new equivalent box with given ``new_children``."""
         new_box = self.copy()
-        new_box.children = list(new_children)
+        new_box.children = new_children
 
         # Clear and reset removed decorations as we don't want to keep the
         # previous data, for example when a box is split between two pages.
@@ -363,19 +370,9 @@ class ParentBox(Box):
 
     def deepcopy(self):
         result = self.copy()
-        result.children = tuple(child.deepcopy() for child in self.children)
+        result.children = list(child.deepcopy() for child in self.children)
         return result
 
-    def descendants(self):
-        """A flat generator for a box, its children and descendants."""
-        yield self
-        for child in self.children:
-            if isinstance(child, ParentBox):
-                for grand_child in child.descendants():
-                    yield grand_child
-            else:
-                yield child
-
     def get_wrapped_table(self):
         """Get the table wrapped by the box."""
         assert self.is_table_wrapper

weasyprint/formatting_structure/build.py

@@ -1231,7 +1231,7 @@ def process_whitespace(box, following_collapsible_space=False):
 
         box.text = text
 
-    elif isinstance(box, boxes.ParentBox):
+    else:
         for child in box.children:
             if isinstance(child, (boxes.TextBox, boxes.InlineBox)):
                 child_collapsible_space = process_whitespace(
@@ -1257,7 +1257,7 @@ def process_text_transform(box):
         if box.style['hyphens'] == 'none':
             box.text = box.text.replace('\u00AD', '')  # U+00AD is soft hyphen
 
-    elif isinstance(box, boxes.ParentBox) and not box.is_running():
+    elif not box.is_running():
         for child in box.children:
             if isinstance(child, (boxes.TextBox, boxes.InlineBox)):
                 process_text_transform(child)
@@ -1316,7 +1316,7 @@ def inline_in_block(box):
         ]
 
     """
-    if not isinstance(box, boxes.ParentBox) or box.is_running():
+    if not box.children or box.is_running():
         return box
 
     box_children = list(box.children)
@@ -1451,7 +1451,7 @@ def block_in_inline(box):
         ]
 
     """
-    if not isinstance(box, boxes.ParentBox) or box.is_running():
+    if not box.children or box.is_running():
         return box
 
     new_children = []

weasyprint/layout/__init__.py

@@ -316,10 +316,9 @@ class LayoutContext:
                         for (string_name, _) in element.style['string_set']:
                             if string_name == name:
                                 return first_string
-                    if isinstance(element, boxes.ParentBox):
-                        if element.children:
-                            element = element.children[0]
-                            continue
+                    if element.children:
+                        element = element.children[0]
+                        continue
                     break
             elif keyword == 'last':
                 return last_string

weasyprint/layout/block.py

@@ -917,7 +917,7 @@ def block_level_page_break(sibling_before, sibling_after):
     box = sibling_before
     while isinstance(box, block_parallel_box_types):
         values.append(box.style['break_after'])
-        if not (isinstance(box, boxes.ParentBox) and box.children):
+        if not box.children:
             break
         box = box.children[-1]
     values.reverse()  # Have them in tree order
@@ -925,7 +925,7 @@ def block_level_page_break(sibling_before, sibling_after):
     box = sibling_after
     while isinstance(box, block_parallel_box_types):
         values.append(box.style['break_before'])
-        if not (isinstance(box, boxes.ParentBox) and box.children):
+        if not box.children:
             break
         box = box.children[0]
 

weasyprint/layout/page.py

@@ -1,7 +1,6 @@
 """Layout for pages and CSS3 margin boxes."""
 
 import copy
-from itertools import chain
 from math import inf
 
 from ..css import PageType, computed_from_cascaded
@@ -666,9 +665,6 @@ def make_page(context, root_box, page_type, resume_at, page_number,
     context.finish_block_formatting_context(root_box)
 
     page.children = [root_box, footnote_area]
-    descendants = chain(page.descendants(), *(
-        child.descendants() if hasattr(child, 'descendants') else (child,)
-        for child in positioned_boxes))
 
     # Update page counter values
     _standardize_page_based_counters(style, None)
@@ -692,7 +688,7 @@ def make_page(context, root_box, page_type, resume_at, page_number,
         cached_anchors.extend(x_remake_state.get('anchors', []))
         cached_lookups.extend(x_remake_state.get('content_lookups', []))
 
-    for child in descendants:
+    for child in page.descendants(placeholders=True):
         # Cache target's page counters
         anchor = child.style['anchor']
         if anchor and anchor not in cached_anchors:

weasyprint/layout/table.py

@@ -845,14 +845,14 @@ def find_in_flow_baseline(box, last=False, baseline_types=(boxes.LineBox,)):
     # See https://www.w3.org/TR/css-align-3/#synthesize-baseline
     if isinstance(box, baseline_types):
         return box.position_y + box.baseline
-    if isinstance(box, boxes.ParentBox) and not isinstance(
-            box, boxes.TableCaptionBox):
-        children = reversed(box.children) if last else box.children
-        for child in children:
-            if child.is_in_normal_flow():
-                result = find_in_flow_baseline(child, last, baseline_types)
-                if result is not None:
-                    return result
+    elif isinstance(box, boxes.TableCaptionBox):
+        return
+    children = reversed(box.children) if last else box.children
+    for child in children:
+        if child.is_in_normal_flow():
+            result = find_in_flow_baseline(child, last, baseline_types)
+            if result is not None:
+                return result
 
 
 def distribute_excess_width(context, grid, excess_width, column_widths,