Use bleed area for page’s painting area

Also use border box for canvas.

Fix #1943.

tests/draw/test_background.py

@@ -1054,13 +1054,14 @@ def test_background_size_clip(assert_pixels):
 
 @assert_no_logs
 def test_bleed_background_size_clip(assert_pixels):
+    # Regression test for https://github.com/Kozea/WeasyPrint/issues/1943
     assert_pixels('''
-        RRRRRR
-        RBBBBR
-        RBRBBR
-        RBBBBR
-        RBBBBR
-        RRRRRR
+        BBBBBB
+        BBBBBB
+        BBRBBB
+        BBBBBB
+        BBBBBB
+        BBBBBB
     ''', '''
       <style>
          @page { size: 4px; bleed: 1px; margin: 1px;

weasyprint/draw.py

@@ -55,14 +55,11 @@ def lighten(color):
 
 def draw_page(page, stream):
     """Draw the given PageBox."""
-    bleed = {
-        side: page.style[f'bleed_{side}'].value
-        for side in ('top', 'right', 'bottom', 'left')}
     marks = page.style['marks']
     stacking_context = StackingContext.from_page(page)
     draw_background(
-        stream, stacking_context.box.background, clip_box=False, bleed=bleed,
-        marks=marks)
+        stream, stacking_context.box.background, clip_box=False,
+        bleed=page.bleed, marks=marks)
     draw_background(stream, page.canvas_background, clip_box=False)
     draw_border(stream, page)
     draw_stacking_context(stream, stacking_context)
@@ -249,26 +246,14 @@ def draw_background(stream, bg, clip_box=True, bleed=None, marks=()):
                 stream.set_color_rgb(*bg.color[:3])
                 stream.set_alpha(bg.color.alpha)
                 painting_area = bg.layers[-1].painting_area
-                if painting_area:
-                    if bleed:
-                        # Painting area is the PDF BleedBox
-                        x, y, width, height = painting_area
-                        painting_area = (
-                            x - bleed['left'], y - bleed['top'],
-                            width + bleed['left'] + bleed['right'],
-                            height + bleed['top'] + bleed['bottom'])
-                    stream.rectangle(*painting_area)
-                    stream.clip()
-                    stream.end()
+                stream.rectangle(*painting_area)
+                stream.clip()
+                stream.end()
                 stream.rectangle(*painting_area)
                 stream.fill()
 
         if bleed and marks:
             x, y, width, height = bg.layers[-1].painting_area
-            x -= bleed['left']
-            y -= bleed['top']
-            width += bleed['left'] + bleed['right']
-            height += bleed['top'] + bleed['bottom']
             half_bleed = {key: value * 0.5 for key, value in bleed.items()}
             svg = f'''
               <svg height="{height}" width="{width}"

weasyprint/formatting_structure/boxes.py

@@ -722,6 +722,19 @@ def __init__(self, page_type, style):
     def __repr__(self):
         return f'<{type(self).__name__} {self.page_type}>'
 
+    @property
+    def bleed(self):
+        return {
+            side: self.style[f'bleed_{side}'].value
+            for side in ('top', 'right', 'bottom', 'left')}
+
+    @property
+    def bleed_area(self):
+        return (
+            -self.bleed['left'], -self.bleed['top'],
+            self.margin_width() + self.bleed['left'] + self.bleed['right'],
+            self.margin_height() + self.bleed['top'] + self.bleed['bottom'])
+
 
 class MarginBox(BlockContainerBox):
     """Box in page margins, as defined in CSS3 Paged Media"""

weasyprint/layout/background.py

@@ -82,9 +82,11 @@ def layout_background_layer(box, page, resolution, image, size, clip, repeat,
     clipped_boxes = []
     painting_area = 0, 0, 0, 0
     if box is page:
-        painting_area = 0, 0, page.margin_width(), page.margin_height()
-        # XXX: how does border-radius work on pages?
-        clipped_boxes = [box.rounded_border_box()]
+        # [The page’s] background painting area is the bleed area […]
+        # regardless of background-clip.
+        # https://drafts.csswg.org/css-page-3/#painting
+        painting_area = page.bleed_area
+        clipped_boxes = []
     elif isinstance(box, boxes.TableRowGroupBox):
         clipped_boxes = []
         total_height = 0
@@ -215,13 +217,13 @@ def layout_backgrounds(page, get_image_from_uri):
                 break
 
     if chosen_box.background:
-        painting_area = box_rectangle(page, 'padding-box')
+        painting_area = box_rectangle(page, 'border-box')
         original_background = page.background
         layout_box_backgrounds(
             page, page, get_image_from_uri, layout_children=False,
             style=chosen_box.style)
         page.canvas_background = page.background._replace(
-            # TODO: shouldn’t background-clip be considered here?
+            # TODO: background-clip should be updated
             layers=[
                 layer._replace(painting_area=painting_area)
                 for layer in page.background.layers])