Fix x position of RTL characters with trailing space

When a line has an unwanted trailing space, the space is removed and the
textbox’ width (and its ancestor’s) is recalculated.

If the line characters have a main RTL Unicode direction (not the CSS box
direction, the text direction), the trailing space is at the left of the
box. Recalculating the width is not enough, we also need to fix the x position.

Testing would be better with Arabic characters, but none is included in
Ahem. Forcing the text direction works well too.

Fix #1111.

weasyprint/layout/inlines.py

@@ -246,6 +246,13 @@ def remove_last_whitespace(context, box):
         assert resume is None
         space_width = box.width - new_box.width
         box.width = new_box.width
+        if new_box.pango_layout.first_line_direction % 2:
+            # RTL line, the trailing space is at the left of the box. We have
+            # to translate the box to align the stripped text with the right
+            # edge of the box.
+            box.position_x -= space_width
+            for ancestor in ancestors:
+                ancestor.position_x -= space_width
     else:
         space_width = box.width
         box.width = 0

weasyprint/tests/test_draw/test_text.py

@@ -88,3 +88,29 @@ def test_text_overflow_ellipsis():
       <div><div style="text-overflow: clip">abcde</div></div>
       <div><div style="overflow: visible">abcde</div></div>
 ''')
+
+
+def test_text_align_rtl_trailing_whitespace():
+    # Test text alignment for rtl text with trailing space.
+    # Test regression: https://github.com/Kozea/WeasyPrint/issues/1111
+    assert_pixels('text_overflow', 9, 9, '''
+        _________
+        _rrrrBBB_
+        _________
+        _rrrrBBB_
+        _________
+        _________
+        _________
+        _________
+        _________
+    ''', '''
+      <style>
+        @font-face {src: url(AHEM____.TTF); font-family: ahem}
+        @page { background: white; size: 9px }
+        body { font-family: ahem; color: blue; font-size: 1px }
+        p { background: red; line-height: 1; width: 7em; margin: 1em }
+      </style>
+      <p style="direction: rtl"> abc </p>
+      <!-- &#8207 forces Unicode RTL direction for the following chars -->
+      <p style="direction: rtl"> &#8207;abc </p>
+    ''')

weasyprint/text.py

@@ -110,7 +110,9 @@
         PangoLayout *layout;
         gint         start_index;
         gint         length;
-        /* ... */
+        void        *runs;
+        guint        is_paragraph_start : 1;
+        guint        resolved_dir : 3;
     } PangoLayoutLine;
 
     typedef struct  {
@@ -654,6 +656,7 @@ def setup(self, context, font_size, style):
 
         self.context = context
         self.style = style
+        self.first_line_direction = 0
 
         # Cairo crashes with font-size: 0 when using Win32 API
         # See https://github.com/Kozea/WeasyPrint/pull/599
@@ -739,6 +742,7 @@ def get_first_line(self):
             index = second_line.start_index
         else:
             index = None
+        self.first_line_direction = first_line.resolved_dir
         return first_line, index
 
     def set_text(self, text, justify=False):