Allow for duplicate font variation styles (#9362)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Tests/fonts/LICENSE.txt

@@ -2,7 +2,7 @@
 NotoNastaliqUrdu-Regular.ttf and NotoSansSymbols-Regular.ttf, from https://github.com/googlei18n/noto-fonts
 NotoSans-Regular.ttf, from https://www.google.com/get/noto/
 NotoSansJP-Thin.otf, from https://www.google.com/get/noto/help/cjk/
-AdobeVFPrototype.ttf, from https://github.com/adobe-fonts/adobe-variable-font-prototype
+AdobeVFPrototype.ttf, from https://github.com/adobe-fonts/adobe-variable-font-prototype. AdobeVFPrototypeDuplicates.ttf is a modified version of this
 TINY5x3GX.ttf, from http://velvetyne.fr/fonts/tiny
 ArefRuqaa-Regular.ttf, from https://github.com/google/fonts/tree/master/ofl/arefruqaa
 ter-x20b.pcf, from http://terminus-font.sourceforge.net/

Tests/test_imagefont.py

@@ -702,7 +702,7 @@ def test_variation_get(font: ImageFont.FreeTypeFont) -> None:
         font.get_variation_axes()
 
     font = ImageFont.truetype("Tests/fonts/AdobeVFPrototype.ttf")
-    assert font.get_variation_names(), [
+    assert font.get_variation_names() == [
         b"ExtraLight",
         b"Light",
         b"Regular",
@@ -742,6 +742,21 @@ def test_variation_get(font: ImageFont.FreeTypeFont) -> None:
     ]
 
 
+def test_variation_duplicates() -> None:
+    font = ImageFont.truetype("Tests/fonts/AdobeVFPrototypeDuplicates.ttf")
+    assert font.get_variation_names() == [
+        b"ExtraLight",
+        b"Light",
+        b"Regular",
+        b"Semibold",
+        b"Bold",
+        b"Black",
+        b"Black Medium Contrast",
+        b"Black High Contrast",
+        b"Default",
+    ]
+
+
 def _check_text(font: ImageFont.FreeTypeFont, path: str, epsilon: float) -> None:
     im = Image.new("RGB", (100, 75), "white")
     d = ImageDraw.Draw(im)

src/PIL/ImageFont.py

@@ -675,8 +675,12 @@ class FreeTypeFont:
         :returns: A list of the named styles in a variation font.
         :exception OSError: If the font is not a variation font.
         """
-        names = self.font.getvarnames()
-        return [name.replace(b"\x00", b"") for name in names]
+        names = []
+        for name in self.font.getvarnames():
+            name = name.replace(b"\x00", b"")
+            if name not in names:
+                names.append(name)
+        return names
 
     def set_variation_by_name(self, name: str | bytes) -> None:
         """

src/_imagingft.c

@@ -1287,7 +1287,6 @@ font_getvarnames(FontObject *self) {
                 }
                 PyList_SetItem(list_names, j, list_name);
                 list_names_filled[j] = 1;
-                break;
             }
         }
     }