Always set font size when font is changed in line

In setting the font size also sets the font family, and that’s useful when we
have different fonts in the same text block. It happens for example when
characters are missing from a font and are replaced by a fallback font’s
character.

Fix #1748.

tests/draw/test_text.py

@@ -827,6 +827,30 @@ def test_font_size_very_small(assert_pixels):
     ''')
 
 
+def test_missing_glyph_fallback(assert_pixels):
+    # The apostrophe is not included in weasyprint.otf
+    assert_pixels('''
+        zzzzzzzzzzzzzzzzz___
+        zzzzzzzzzzzzzzzzzRR_
+        zzzzzzzzzzzzzzzzzRR_
+        zzzzzzzzzzzzzzzzz___
+    ''', '''
+      <style>
+        @font-face {src: url(weasyprint.otf); font-family: weasyprint}
+        @page {
+          size: 20px 4px;
+        }
+        body {
+          color: red;
+          font-family: weasyprint;
+          font-size: 2px;
+          line-height: 0;
+          margin: 2px 1px;
+          text-align: right;
+        }
+      </style>'a''')
+
+
 def test_tabulation_character(assert_pixels):
     # Test regression: https://github.com/Kozea/WeasyPrint/issues/1515
     assert_pixels('''

weasyprint/draw.py

@@ -1135,9 +1135,7 @@ def draw_first_line(stream, textbox, text_overflow, block_ellipsis, x, y,
             if string:
                 stream.show_text(string)
             string = ''
-            if last_font is None or font.bitmap != last_font.bitmap:
-                stream.set_font_size(
-                    font.hash, 1 if font.bitmap else font_size)
+            stream.set_font_size(font.hash, 1 if font.bitmap else font_size)
             last_font = font
         string += '<'
         for i in range(num_glyphs):