Bug 1753565 - Default disable smooth scrolls if prefers-reduced-motion. r=botond

If the user has the prefers-reduced-motion system setting enabled, do
not enable smooth scrolls by default.

Differential Revision: https://phabricator.services.mozilla.com/D172446

UltraBlame original commit: a2f066123f3c6b76e43c5f09b154d838f1ba798b

Author: marco-c

gfx/layers/apz/test/gtest/TestBasic.cpp

@@ -1833,6 +1833,16 @@ APZCBasicTester
 MultipleSmoothScrollsSmooth
 )
 {
+SCOPED_GFX_PREF_BOOL
+(
+"
+general
+.
+smoothScroll
+"
+true
+)
+;
 ScrollMetadata
 metadata
 ;
@@ -2627,6 +2637,16 @@ SCOPED_GFX_PREF_BOOL
 general
 .
 smoothScroll
+"
+true
+)
+;
+SCOPED_GFX_PREF_BOOL
+(
+"
+general
+.
+smoothScroll
 .
 msdPhysics
 .
@@ -2652,6 +2672,16 @@ SCOPED_GFX_PREF_BOOL
 general
 .
 smoothScroll
+"
+true
+)
+;
+SCOPED_GFX_PREF_BOOL
+(
+"
+general
+.
+smoothScroll
 .
 msdPhysics
 .

layout/base/nsLayoutUtils.cpp

@@ -726,6 +726,15 @@ include
 "
 mozilla
 /
+StaticPrefs_general
+.
+h
+"
+#
+include
+"
+mozilla
+/
 StaticPrefs_gfx
 .
 h
@@ -40446,6 +40455,63 @@ void
 nsLayoutUtils
 :
 :
+RecomputeSmoothScrollDefault
+(
+)
+{
+Preferences
+:
+:
+SetBool
+(
+"
+general
+.
+smoothScroll
+"
+!
+LookAndFeel
+:
+:
+GetInt
+(
+LookAndFeel
+:
+:
+IntID
+:
+:
+PrefersReducedMotion
+0
+)
+PrefValueKind
+:
+:
+Default
+)
+;
+}
+bool
+nsLayoutUtils
+:
+:
+IsSmoothScrollingEnabled
+(
+)
+{
+return
+StaticPrefs
+:
+:
+general_smoothScroll
+(
+)
+;
+}
+void
+nsLayoutUtils
+:
+:
 Initialize
 (
 )

layout/base/nsLayoutUtils.h

@@ -6847,6 +6847,18 @@ nsIFrame
 aFrame
 )
 ;
+static
+bool
+IsSmoothScrollingEnabled
+(
+)
+;
+static
+void
+RecomputeSmoothScrollDefault
+(
+)
+;
 private
 :
 static

layout/generic/nsGfxScrollFrame.cpp

@@ -10143,23 +10143,6 @@ aCurrentVelocity
 )
 ;
 }
-bool
-nsHTMLScrollFrame
-:
-:
-IsSmoothScrollingEnabled
-(
-)
-{
-return
-StaticPrefs
-:
-:
-general_smoothScroll
-(
-)
-;
-}
 void
 nsHTMLScrollFrame
 :
@@ -11750,6 +11733,9 @@ IsSmooth
 )
 &
 &
+nsLayoutUtils
+:
+:
 IsSmoothScrollingEnabled
 (
 )
@@ -36614,7 +36600,7 @@ Instant
 |
 |
 !
-nsHTMLScrollFrame
+nsLayoutUtils
 :
 :
 IsSmoothScrollingEnabled

layout/generic/nsGfxScrollFrame.h

@@ -2440,12 +2440,6 @@ FireScrolledAreaEvent
 (
 )
 ;
-static
-bool
-IsSmoothScrollingEnabled
-(
-)
-;
 void
 FinishReflowForScrollbar
 (

widget/nsXPLookAndFeel.cpp

@@ -89,6 +89,13 @@ h
 #
 include
 "
+nsLayoutUtils
+.
+h
+"
+#
+include
+"
 Theme
 .
 h
@@ -2954,6 +2961,21 @@ RecomputeColorSchemes
 (
 )
 ;
+if
+(
+XRE_IsParentProcess
+(
+)
+)
+{
+nsLayoutUtils
+:
+:
+RecomputeSmoothScrollDefault
+(
+)
+;
+}
 Preferences
 :
 :
@@ -6150,6 +6172,13 @@ XRE_IsParentProcess
 )
 )
 {
+nsLayoutUtils
+:
+:
+RecomputeSmoothScrollDefault
+(
+)
+;
 widget
 :
 :