com.google.fonts/check/042 Add rationale
Fixes
@@ -3315,12 +3315,24 @@ def com_google_fonts_check_040(ttFont, vmetrics):
@check(
id = 'com.google.fonts/check/042'
+ rationale = """When OS/2 and hhea vertical metrics match, the same
+ linespacing results on macOS, GNU+Linux and Windows. Unfortunately as of 2018,
+ Google Fonts has released many fonts with vertical metrics that don't match
+ in this way. When we fix this issue in these existing families, we will
+ create a visible change in line/paragraph layout for either Windows or macOS
+ users, which will upset some of them.
+
+ But we have a duty to fix broken stuff, and inconsistent paragraph layout is
+ unacceptably broken when it is possible to avoid it.
+
+ If users complain and prefer the old broken version, they are libre to take
+ care of their own situation."""
)
def com_google_fonts_check_042(ttFont):
"""Checking OS/2 Metrics match hhea Metrics.
OS/2 and hhea vertical metric values should match. This will produce
- the same linespacing on Mac, GNU/Linux and Windows.
+ the same linespacing on Mac, GNU+Linux and Windows.
Mac OS X uses the hhea values.
Windows uses OS/2 or Win, depending on the OS or fsSelection bit value.
