refactored percent metrics calculations to take into account metrics approach used in the font, added support for Google and Adobe metrics approaches

Author: chrissimpkins

lib/fontline/app.py

@@ -18,9 +18,8 @@
 from fontline.utilities import file_exists, is_supported_filetype
 
 # TODO: support integer addition and subtraction to the metrics values through new sub-commands
-# TODO: support .woff and .woff2 file types?
 # TODO: JSON formatted metrics output
-# TODO: autocorrect command?
+# TODO: add report line items for 'exceeds ymax/ymin values' across each of the three metrics
 
 
 def main():

lib/fontline/commands.py

@@ -81,23 +81,58 @@ def modify_linegap_percent(fontpath, percent):
         # get observed start values from the font
         os2_typo_ascender = tt['OS/2'].__dict__['sTypoAscender']
         os2_typo_descender = tt['OS/2'].__dict__['sTypoDescender']
+        os2_typo_linegap = tt['OS/2'].__dict__['sTypoLineGap']
+        hhea_ascent = tt['hhea'].__dict__['ascent']
+        hhea_descent = tt['hhea'].__dict__['descent']
+        units_per_em = tt['head'].__dict__['unitsPerEm']
 
-        # redefine hhea linegap to 0
-        hhea_linegap = 0
+        # calculate necessary delta values
+        os2_typo_ascdesc_delta = os2_typo_ascender + -(os2_typo_descender)
+        hhea_ascdesc_delta = hhea_ascent + -(hhea_descent)
 
+        # define percent UPM from command line request
         factor = 1.0 * int(percent) / 100
 
-        os2_typo_linegap = int(factor * (os2_typo_ascender + -(os2_typo_descender)))
-        total_height = os2_typo_ascender + -(os2_typo_descender) + os2_typo_linegap
+        # define line spacing units
+        line_spacing_units = int(factor * units_per_em)
+
+        # define total height as UPM + line spacing units
+        total_height = line_spacing_units + units_per_em
 
-        hhea_ascent = int(os2_typo_ascender + 0.5 * os2_typo_linegap)
-        hhea_descent = -(total_height - hhea_ascent)
+        # height calculations for adjustments
+        delta_height = total_height - hhea_ascdesc_delta
+        upper_lower_add_units = int(0.5 * delta_height)
 
-        os2_win_ascent = hhea_ascent
-        os2_win_descent = -hhea_descent
+        # redefine hhea linegap to 0 in all cases
+        hhea_linegap = 0
 
-        # define updated values
+        # Define metrics based upon original design approach in the font
+        # Google metrics approach
+        if os2_typo_linegap == 0 and (os2_typo_ascdesc_delta > units_per_em):
+            # define values
+            os2_typo_ascender += upper_lower_add_units
+            os2_typo_descender -= upper_lower_add_units
+            hhea_ascent += upper_lower_add_units
+            hhea_descent -= upper_lower_add_units
+            os2_win_ascent = hhea_ascent
+            os2_win_descent = -hhea_descent
+        # Adobe metrics approach
+        elif os2_typo_linegap == 0 and (os2_typo_ascdesc_delta == units_per_em):
+            hhea_ascent += upper_lower_add_units
+            hhea_descent -= upper_lower_add_units
+            os2_win_ascent = hhea_ascent
+            os2_win_descent = -hhea_descent
+        else:
+            os2_typo_linegap = line_spacing_units
+            hhea_ascent = int(os2_typo_ascender + 0.5 * os2_typo_linegap)
+            hhea_descent = -(total_height - hhea_ascent)
+            os2_win_ascent = hhea_ascent
+            os2_win_descent = -hhea_descent
+
+        # define updated values from above calculations
         tt['hhea'].__dict__['lineGap'] = hhea_linegap
+        tt['OS/2'].__dict__['sTypoAscender'] = os2_typo_ascender
+        tt['OS/2'].__dict__['sTypoDescender'] = os2_typo_descender
         tt['OS/2'].__dict__['sTypoLineGap'] = os2_typo_linegap
         tt['OS/2'].__dict__['usWinAscent'] = os2_win_ascent
         tt['OS/2'].__dict__['usWinDescent'] = os2_win_descent

tests/test_percent_cmd.py

@@ -103,7 +103,9 @@ def test_percent_cmd_font_file_wrong_filetype(capsys):
 #
 # ///////////////////////////////////////////////////////
 
-def test_percent_cmd_ttf_file_10_percent(capsys):
+# Default approach with TypoLinegap > 0 and TypoAscender + TypoDescender set to UPM height
+
+def test_percent_cmd_ttf_file_10_percent_default_approach(capsys):
     try:
         from fontline.app import main
         fontpath = os.path.join('tests', 'testingfiles', 'Hack-Regular.ttf')
@@ -149,7 +151,7 @@ def test_percent_cmd_ttf_file_10_percent(capsys):
         raise e
 
 
-def test_percent_cmd_otf_file_10_percent(capsys):
+def test_percent_cmd_otf_file_10_percent_default_approach(capsys):
     try:
         from fontline.app import main
         fontpath = os.path.join('tests', 'testingfiles', 'Hack-Regular.otf')
@@ -192,4 +194,239 @@ def test_percent_cmd_otf_file_10_percent(capsys):
             erase_test_file(testpath)
         if file_exists(newfont_path):
             erase_test_file(newfont_path)
-        raise e
+        raise e
+
+
+def test_percent_cmd_ttf_file_30_percent_default_approach(capsys):
+    try:
+        from fontline.app import main
+        fontpath = os.path.join('tests', 'testingfiles', 'Hack-Regular.ttf')
+        testpath = os.path.join('tests', 'testingfiles', 'Hack-Regular-test.ttf')
+        newfont_path = os.path.join('tests', 'testingfiles', 'Hack-Regular-test-linegap30.ttf')
+        create_test_file(fontpath)
+        assert file_exists(testpath) is True
+        sys.argv = ['font-line', 'percent', '30', testpath]
+        main()
+
+        assert file_exists(newfont_path)
+
+        tt = ttLib.TTFont(newfont_path)
+
+        os2_typo_ascender = tt['OS/2'].__dict__['sTypoAscender']
+        os2_typo_descender = tt['OS/2'].__dict__['sTypoDescender']
+        os2_win_ascent = tt['OS/2'].__dict__['usWinAscent']
+        os2_win_descent = tt['OS/2'].__dict__['usWinDescent']
+        os2_typo_linegap = tt['OS/2'].__dict__['sTypoLineGap']
+        hhea_ascent = tt['hhea'].__dict__['ascent']
+        hhea_descent = tt['hhea'].__dict__['descent']
+        hhea_linegap = tt['hhea'].__dict__['lineGap']
+        units_per_em = tt['head'].__dict__['unitsPerEm']
+
+        assert os2_typo_ascender == 1556
+        assert os2_typo_descender == -492
+        assert os2_win_ascent == 1863
+        assert os2_win_descent == 799
+        assert units_per_em == 2048
+        assert os2_typo_linegap == 614
+        assert hhea_ascent == 1863
+        assert hhea_descent == -799
+        assert hhea_linegap == 0
+
+        erase_test_file(testpath)
+        erase_test_file(newfont_path)
+    except Exception as e:
+        # cleanup test files
+        if file_exists(testpath):
+            erase_test_file(testpath)
+        if file_exists(newfont_path):
+            erase_test_file(newfont_path)
+        raise e
+
+
+# Google metrics approach with TypoLinegap & hhea linegap = 0, all other metrics set to same values of internal leading
+
+def test_percent_cmd_ttf_file_10_percent_google_approach(capsys):
+    try:
+        from fontline.app import main
+        fontpath = os.path.join('tests', 'testingfiles', 'FiraMono-Regular.ttf')
+        testpath = os.path.join('tests', 'testingfiles', 'FiraMono-Regular-test.ttf')
+        newfont_path = os.path.join('tests', 'testingfiles', 'FiraMono-Regular-test-linegap10.ttf')
+        create_test_file(fontpath)
+        assert file_exists(testpath) is True
+        sys.argv = ['font-line', 'percent', '10', testpath]
+        main()
+
+        assert file_exists(newfont_path)
+
+        tt = ttLib.TTFont(newfont_path)
+
+        os2_typo_ascender = tt['OS/2'].__dict__['sTypoAscender']
+        os2_typo_descender = tt['OS/2'].__dict__['sTypoDescender']
+        os2_win_ascent = tt['OS/2'].__dict__['usWinAscent']
+        os2_win_descent = tt['OS/2'].__dict__['usWinDescent']
+        os2_typo_linegap = tt['OS/2'].__dict__['sTypoLineGap']
+        hhea_ascent = tt['hhea'].__dict__['ascent']
+        hhea_descent = tt['hhea'].__dict__['descent']
+        hhea_linegap = tt['hhea'].__dict__['lineGap']
+        units_per_em = tt['head'].__dict__['unitsPerEm']
+
+        assert os2_typo_ascender == 885
+        assert os2_typo_descender == -215
+        assert os2_win_ascent == 885
+        assert os2_win_descent == 215
+        assert units_per_em == 1000
+        assert os2_typo_linegap == 0
+        assert hhea_ascent == 885
+        assert hhea_descent == -215
+        assert hhea_linegap == 0
+
+        erase_test_file(testpath)
+        erase_test_file(newfont_path)
+    except Exception as e:
+        # cleanup test files
+        if file_exists(testpath):
+            erase_test_file(testpath)
+        if file_exists(newfont_path):
+            erase_test_file(newfont_path)
+        raise e
+
+
+def test_percent_cmd_ttf_file_30_percent_google_approach(capsys):
+    try:
+        from fontline.app import main
+        fontpath = os.path.join('tests', 'testingfiles', 'FiraMono-Regular.ttf')
+        testpath = os.path.join('tests', 'testingfiles', 'FiraMono-Regular-test.ttf')
+        newfont_path = os.path.join('tests', 'testingfiles', 'FiraMono-Regular-test-linegap30.ttf')
+        create_test_file(fontpath)
+        assert file_exists(testpath) is True
+        sys.argv = ['font-line', 'percent', '30', testpath]
+        main()
+
+        assert file_exists(newfont_path)
+
+        tt = ttLib.TTFont(newfont_path)
+
+        os2_typo_ascender = tt['OS/2'].__dict__['sTypoAscender']
+        os2_typo_descender = tt['OS/2'].__dict__['sTypoDescender']
+        os2_win_ascent = tt['OS/2'].__dict__['usWinAscent']
+        os2_win_descent = tt['OS/2'].__dict__['usWinDescent']
+        os2_typo_linegap = tt['OS/2'].__dict__['sTypoLineGap']
+        hhea_ascent = tt['hhea'].__dict__['ascent']
+        hhea_descent = tt['hhea'].__dict__['descent']
+        hhea_linegap = tt['hhea'].__dict__['lineGap']
+        units_per_em = tt['head'].__dict__['unitsPerEm']
+
+        assert os2_typo_ascender == 985
+        assert os2_typo_descender == -315
+        assert os2_win_ascent == 985
+        assert os2_win_descent == 315
+        assert units_per_em == 1000
+        assert os2_typo_linegap == 0
+        assert hhea_ascent == 985
+        assert hhea_descent == -315
+        assert hhea_linegap == 0
+
+        erase_test_file(testpath)
+        erase_test_file(newfont_path)
+    except Exception as e:
+        # cleanup test files
+        if file_exists(testpath):
+            erase_test_file(testpath)
+        if file_exists(newfont_path):
+            erase_test_file(newfont_path)
+        raise e
+
+
+# Adobe metrics approach with TypoLinegap and hhea linegap = 0, TypoAscender + TypoDescender = UPM &
+# internal leading added to winAsc/winDesc & hhea Asc/hhea Desc metrics
+
+def test_percent_cmd_ttf_file_10_percent_adobe_approach(capsys):
+    try:
+        from fontline.app import main
+        fontpath = os.path.join('tests', 'testingfiles', 'SourceCodePro-Regular.ttf')
+        testpath = os.path.join('tests', 'testingfiles', 'SourceCodePro-Regular-test.ttf')
+        newfont_path = os.path.join('tests', 'testingfiles', 'SourceCodePro-Regular-test-linegap10.ttf')
+        create_test_file(fontpath)
+        assert file_exists(testpath) is True
+        sys.argv = ['font-line', 'percent', '10', testpath]
+        main()
+
+        assert file_exists(newfont_path)
+
+        tt = ttLib.TTFont(newfont_path)
+
+        os2_typo_ascender = tt['OS/2'].__dict__['sTypoAscender']
+        os2_typo_descender = tt['OS/2'].__dict__['sTypoDescender']
+        os2_win_ascent = tt['OS/2'].__dict__['usWinAscent']
+        os2_win_descent = tt['OS/2'].__dict__['usWinDescent']
+        os2_typo_linegap = tt['OS/2'].__dict__['sTypoLineGap']
+        hhea_ascent = tt['hhea'].__dict__['ascent']
+        hhea_descent = tt['hhea'].__dict__['descent']
+        hhea_linegap = tt['hhea'].__dict__['lineGap']
+        units_per_em = tt['head'].__dict__['unitsPerEm']
+
+        assert os2_typo_ascender == 750
+        assert os2_typo_descender == -250
+        assert os2_win_ascent == 906
+        assert os2_win_descent == 195
+        assert units_per_em == 1000
+        assert os2_typo_linegap == 0
+        assert hhea_ascent == 906
+        assert hhea_descent == -195
+        assert hhea_linegap == 0
+
+        erase_test_file(testpath)
+        erase_test_file(newfont_path)
+    except Exception as e:
+        # cleanup test files
+        if file_exists(testpath):
+            erase_test_file(testpath)
+        if file_exists(newfont_path):
+            erase_test_file(newfont_path)
+        raise e
+
+
+def test_percent_cmd_ttf_file_30_percent_adobe_approach(capsys):
+    try:
+        from fontline.app import main
+        fontpath = os.path.join('tests', 'testingfiles', 'SourceCodePro-Regular.ttf')
+        testpath = os.path.join('tests', 'testingfiles', 'SourceCodePro-Regular-test.ttf')
+        newfont_path = os.path.join('tests', 'testingfiles', 'SourceCodePro-Regular-test-linegap30.ttf')
+        create_test_file(fontpath)
+        assert file_exists(testpath) is True
+        sys.argv = ['font-line', 'percent', '30', testpath]
+        main()
+
+        assert file_exists(newfont_path)
+
+        tt = ttLib.TTFont(newfont_path)
+
+        os2_typo_ascender = tt['OS/2'].__dict__['sTypoAscender']
+        os2_typo_descender = tt['OS/2'].__dict__['sTypoDescender']
+        os2_win_ascent = tt['OS/2'].__dict__['usWinAscent']
+        os2_win_descent = tt['OS/2'].__dict__['usWinDescent']
+        os2_typo_linegap = tt['OS/2'].__dict__['sTypoLineGap']
+        hhea_ascent = tt['hhea'].__dict__['ascent']
+        hhea_descent = tt['hhea'].__dict__['descent']
+        hhea_linegap = tt['hhea'].__dict__['lineGap']
+        units_per_em = tt['head'].__dict__['unitsPerEm']
+
+        assert os2_typo_ascender == 750
+        assert os2_typo_descender == -250
+        assert os2_win_ascent == 1005
+        assert os2_win_descent == 294
+        assert units_per_em == 1000
+        assert os2_typo_linegap == 0
+        assert hhea_ascent == 1005
+        assert hhea_descent == -294
+        assert hhea_linegap == 0
+
+        erase_test_file(testpath)
+        erase_test_file(newfont_path)
+    except Exception as e:
+        # cleanup test files
+        if file_exists(testpath):
+            erase_test_file(testpath)
+        if file_exists(newfont_path):
+            erase_test_file(newfont_path)
+        raise e