Remove borders from flex containers when split between pages

Related to #2066.

tests/layout/test_flex.py

@@ -447,6 +447,42 @@ def test_flex_direction_column_break():
     assert div.height == 2
 
 
+@assert_no_logs
+def test_flex_direction_column_break_border():
+    page1, page2 = render_pages('''
+      <style>
+        @page { size: 8px 7px }
+        article, div { border: 1px solid black }
+      </style>
+      <article style="display: flex; flex-direction: column; font: 2px weasyprint">
+        <div>A B C</div>
+      </article>
+    ''')
+    html, = page1.children
+    body, = html.children
+    article, = body.children
+    assert article.border_height() == 7
+    assert article.border_top_width == 1
+    assert article.border_bottom_width == 0
+    div, = article.children
+    assert div.children[0].children[0].text == 'A'
+    assert div.children[1].children[0].text == 'B'
+    assert div.border_height() == 6
+    assert div.border_top_width == 1
+    assert div.border_bottom_width == 0
+    html, = page2.children
+    body, = html.children
+    article, = body.children
+    assert article.border_height() == 4
+    assert article.border_top_width == 0
+    assert article.border_bottom_width == 1
+    div, = article.children
+    assert div.children[0].children[0].text == 'C'
+    assert div.border_height() == 3
+    assert div.border_top_width == 0
+    assert div.border_bottom_width == 1
+
+
 @assert_no_logs
 def test_flex_item_min_width():
     page, = render_pages('''

weasyprint/layout/absolute.py

@@ -205,7 +205,7 @@ def absolute_block(context, box, containing_block, fixed_boxes, bottom_space,
         new_box, resume_at, _, _, _ = flex_layout(
             context, box, bottom_space, skip_stack, containing_block,
             page_is_empty=True, absolute_boxes=absolute_boxes,
-            fixed_boxes=fixed_boxes)
+            fixed_boxes=fixed_boxes, discard=False)
     elif isinstance(box, (boxes.GridContainerBox)):
         new_box, resume_at, _, _, _ = grid_layout(
             context, box, bottom_space, skip_stack, containing_block,

weasyprint/layout/block.py

@@ -81,7 +81,7 @@ def block_level_layout_switch(context, box, bottom_space, skip_stack,
     elif isinstance(box, boxes.FlexBox):
         result = flex_layout(
             context, box, bottom_space, skip_stack, containing_block,
-            page_is_empty, absolute_boxes, fixed_boxes)
+            page_is_empty, absolute_boxes, fixed_boxes, discard)
     elif isinstance(box, boxes.GridBox):
         result = grid_layout(
             context, box, bottom_space, skip_stack, containing_block,

weasyprint/layout/flex.py

@@ -16,12 +16,23 @@ class FlexLine(list):
 
 
 def flex_layout(context, box, bottom_space, skip_stack, containing_block,
-                page_is_empty, absolute_boxes, fixed_boxes):
+                page_is_empty, absolute_boxes, fixed_boxes, discard):
     from . import block, preferred
 
     context.create_block_formatting_context()
     resume_at = None
 
+    is_start = skip_stack is None
+    box.remove_decoration(start=not is_start, end=False)
+
+    discard |= box.style['continue'] == 'discard'
+    draw_bottom_decoration = (
+        discard or box.style['box_decoration_break'] == 'clone')
+
+    if draw_bottom_decoration:
+        bottom_space += (
+            box.padding_bottom + box.border_bottom_width + box.margin_bottom)
+
     if box.style['position'] == 'relative':
         # New containing block, use a new absolute list
         absolute_boxes = []
@@ -294,10 +305,7 @@ def flex_layout(context, box, bottom_space, skip_stack, containing_block,
             for index, child in enumerate(children):
                 if not child.is_flex_item:
                     continue
-                child_height = (
-                    child.hypothetical_main_size +
-                    child.border_top_width + child.border_bottom_width +
-                    child.padding_top + child.padding_bottom)
+                child_height = child.hypothetical_main_size
                 if getattr(box, axis) == 'auto' and (
                         child_height + box.height > available_main_space):
                     resume_at = {index: None}
@@ -557,7 +565,7 @@ def flex_layout(context, box, bottom_space, skip_stack, containing_block,
                 block.block_level_layout_switch(
                     context, child_copy, -inf, child_skip_stack, parent_box,
                     page_is_empty, absolute_boxes, fixed_boxes,
-                    [], False, None))
+                    [], discard, None))
 
             child._baseline = find_in_flow_baseline(new_child) or 0
             if cross == 'height':
@@ -1023,7 +1031,7 @@ def flex_layout(context, box, bottom_space, skip_stack, containing_block,
                 new_child, child_resume_at = block.block_level_layout_switch(
                     context, child, bottom_space, child_skip_stack, box,
                     page_is_empty, absolute_boxes, fixed_boxes,
-                    adjoining_margins=[], discard=False, max_lines=None)[:2]
+                    adjoining_margins=[], discard=discard, max_lines=None)[:2]
                 if new_child is None:
                     if resume_at:
                         resume_index, = resume_at
@@ -1072,6 +1080,8 @@ def flex_layout(context, box, bottom_space, skip_stack, containing_block,
             else:
                 box.baseline = 0
 
+    box.remove_decoration(start=False, end=resume_at and not discard)
+
     context.finish_block_formatting_context(box)
 
     # TODO: Check these returned values.

weasyprint/layout/float.py

@@ -68,7 +68,7 @@ def float_layout(context, box, containing_block, absolute_boxes, fixed_boxes,
             context, box, bottom_space=bottom_space,
             skip_stack=skip_stack, containing_block=containing_block,
             page_is_empty=True, absolute_boxes=absolute_boxes,
-            fixed_boxes=fixed_boxes)
+            fixed_boxes=fixed_boxes, discard=False)
     elif isinstance(box, boxes.GridContainerBox):
         box, resume_at, _, _, _ = grid_layout(
             context, box, bottom_space=bottom_space,

weasyprint/layout/inline.py

@@ -513,7 +513,7 @@ def split_inline_level(context, box, position_x, max_x, bottom_space,
                 setattr(box, f'margin_{side}', 0)
         new_box, resume_at, _, _, _ = flex_layout(
             context, box, -inf, skip_stack, containing_block, False,
-            absolute_boxes, fixed_boxes)
+            absolute_boxes, fixed_boxes, False)
         preserved_line_break = False
         first_letter = '\u2e80'
         last_letter = '\u2e80'