Fix same_broken_child

The old code assumed that both skip stacks were absolute, but for the second
one previous children have already been skipped. We now check that we're in
the first child at each level, meaning that we're still breaking the same
child.

Related to #923.

weasyprint/layout/inlines.py

@@ -1294,12 +1294,17 @@ def can_break_inside(box):
     return False
 
 
-def same_broken_child(skip_stack_1, skip_stack_2):
+def same_broken_child(original_skip_stack, relative_skip_stack):
     """Check that the skip stacks design the same text box."""
-    while isinstance(skip_stack_1, tuple) and isinstance(skip_stack_2, tuple):
-        if skip_stack_1[1] is None and skip_stack_2[1] is None:
+    while (isinstance(original_skip_stack, tuple) and
+            isinstance(relative_skip_stack, tuple)):
+        if original_skip_stack[1] is None and relative_skip_stack[1] is None:
+            # The last levels of the two skip_stack are the same
             return True
-        if skip_stack_1[0] != skip_stack_2[0]:
+        if relative_skip_stack[0] != 0:
+            # If at the current level the skip_stack is not 0, it means that
+            # it is not the first child that has been cut
             return False
-        skip_stack_1, skip_stack_2 = skip_stack_1[1], skip_stack_2[1]
+        original_skip_stack = original_skip_stack[1]
+        relative_skip_stack = relative_skip_stack[1]
     return False

weasyprint/tests/test_layout/test_inline.py

@@ -361,6 +361,27 @@ def test_breaking_linebox_regression_9():
     assert line2.children[1].text == 'ddd'
 
 
+@assert_no_logs
+def test_breaking_linebox_regression_10():
+    # Regression test for https://github.com/Kozea/WeasyPrint/issues/923
+    page, = parse(
+        '<style>@font-face {src: url(AHEM____.TTF); font-family: ahem}</style>'
+        '<p style="width:195px; font-family: ahem">'
+        '  <span>'
+        '    <span>xxxxxx YYY yyyyyy yyy</span>'
+        '    ZZZZZZ zzzzz'
+        '  </span> )x '
+        '</p>')
+    html, = page.children
+    body, = html.children
+    p, = body.children
+    line1, line2, line3, line4 = p.children
+    assert line1.children[0].children[0].children[0].text == 'xxxxxx YYY'
+    assert line2.children[0].children[0].children[0].text == 'yyyyyy yyy'
+    assert line3.children[0].children[0].text == 'ZZZZZZ zzzzz'
+    assert line4.children[0].text == ')x'
+
+
 @assert_no_logs
 def test_linebox_text():
     page, = parse('''