From 8e981a1b287f5594904b8cf319b21d4bbbbf9125 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 3 Feb 2023 10:23:23 -0700
Subject: [PATCH] [transform] Change the DecomposedTransform skewX sign to
 match Transform

Unfortunate but for consistency's sake.

This deviates from VarComposite convention.

https://github.com/fonttools/fonttools/pull/2958#issuecomment-1416155600
---
 Lib/fontTools/misc/transform.py        | 6 +++---
 Lib/fontTools/ttLib/tables/_g_l_y_f.py | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Lib/fontTools/misc/transform.py b/Lib/fontTools/misc/transform.py
index 786df84b4..9ceee0a20 100644
--- a/Lib/fontTools/misc/transform.py
+++ b/Lib/fontTools/misc/transform.py
@@ -418,7 +418,7 @@ class DecomposedTransform:
     rotation: float = 0  # in degrees, counter-clockwise
     scaleX: float = 1
     scaleY: float = 1
-    skewX: float = 0  # in degrees, counter-clockwise
+    skewX: float = 0  # in degrees, clockwise
     skewY: float = 0  # in degrees, counter-clockwise
     tCenterX: float = 0
     tCenterY: float = 0
@@ -455,7 +455,7 @@ class DecomposedTransform:
             math.degrees(rotation),
             scaleX,
             scaleY,
-            -math.degrees(skewX),
+            math.degrees(skewX),
             math.degrees(skewY),
             0,
             0,
@@ -475,7 +475,7 @@ class DecomposedTransform:
         )
         t = t.rotate(math.radians(self.rotation))
         t = t.scale(self.scaleX, self.scaleY)
-        t = t.skew(-math.radians(self.skewX), math.radians(self.skewY))
+        t = t.skew(math.radians(self.skewX), math.radians(self.skewY))
         t = t.translate(-self.tCenterX, -self.tCenterY)
         return t
 
diff --git a/Lib/fontTools/ttLib/tables/_g_l_y_f.py b/Lib/fontTools/ttLib/tables/_g_l_y_f.py
index af7670bc0..4d2221631 100644
--- a/Lib/fontTools/ttLib/tables/_g_l_y_f.py
+++ b/Lib/fontTools/ttLib/tables/_g_l_y_f.py
@@ -1734,7 +1734,7 @@ VAR_COMPONENT_TRANSFORM_MAPPING = {
         VarComponentFlags.HAVE_SCALE_Y, 10, 1, 1
     ),
     "skewX": VarComponentTransformMappingValues(
-        VarComponentFlags.HAVE_SKEW_X, 12, 180, 0
+        VarComponentFlags.HAVE_SKEW_X, 12, -180, 0
     ),
     "skewY": VarComponentTransformMappingValues(
         VarComponentFlags.HAVE_SKEW_Y, 12, 180, 0
@@ -1988,7 +1988,7 @@ class GlyphVarComponent(object):
             controls.append("skew")
             coords.append(
                 (
-                    fl2fi(self.transform.skewX / 180, 12),
+                    fl2fi(self.transform.skewX / -180, 12),
                     fl2fi(self.transform.skewY / 180, 12),
                 )
             )
@@ -2027,7 +2027,7 @@ class GlyphVarComponent(object):
             i += 1
         if self.flags & (VarComponentFlags.HAVE_SKEW_X | VarComponentFlags.HAVE_SKEW_Y):
             self.transform.skewX, self.transform.skewY = (
-                fi2fl(coords[i][0], 12) * 180,
+                fi2fl(coords[i][0], 12) * -180,
                 fi2fl(coords[i][1], 12) * 180,
             )
             i += 1