Bug 1856755 - Implement an internal zoom: document value that forces effective zoom to 1. r=jfkthame

The name matches the value that webkit (but not blink) exposes to the
web. We don't expose it.

Filed w3c/csswg-drafts#9435 for this.

Differential Revision: https://phabricator.services.mozilla.com/D190025

UltraBlame original commit: 3203468939abba2f75ed2c29203b6caa1b50e9ad

Author: marco-c

layout/style/res/scrollbars.css

@@ -262,6 +262,28 @@ collapse
 :
 initial
 ;
+/
+*
+We
+don
+'
+t
+want
+zoom
+on
+our
+ancestors
+to
+affect
+our
+styles
+.
+*
+/
+zoom
+:
+document
+;
 math
 -
 depth

servo/components/style/properties/cascade.rs

@@ -3965,7 +3965,9 @@ builder
 inherited_effective_zoom
 (
 )
-*
+.
+compute_effective
+(
 self
 .
 context
@@ -3975,6 +3977,7 @@ builder
 specified_zoom
 (
 )
+)
 ;
 }
 fn

servo/components/style/properties/longhands/box.mako.rs

@@ -4077,5 +4077,10 @@ affects
 "
 layout
 "
+enabled_in
+=
+"
+ua
+"
 )
 }

servo/components/style/values/computed/box.rs

@@ -1339,82 +1339,6 @@ ZoomFixedPoint
 )
 ;
 impl
-std
-:
-:
-ops
-:
-:
-Mul
-for
-Zoom
-{
-type
-Output
-=
-Zoom
-;
-fn
-mul
-(
-self
-rhs
-:
-Self
-)
--
->
-Self
-{
-if
-self
-=
-=
-Self
-:
-:
-ONE
-{
-return
-rhs
-;
-}
-if
-rhs
-=
-=
-Self
-:
-:
-ONE
-{
-return
-self
-;
-}
-Zoom
-(
-ZoomFixedPoint
-:
-:
-from_float
-(
-self
-.
-value
-(
-)
-*
-rhs
-.
-value
-(
-)
-)
-)
-}
-}
-impl
 ToComputedValue
 for
 specified
@@ -1469,6 +1393,17 @@ ONE
 Self
 :
 :
+Document
+=
+>
+return
+Zoom
+:
+:
+DOCUMENT
+Self
+:
+:
 Value
 (
 ref
@@ -1583,6 +1518,36 @@ fmt
 :
 Write
 {
+use
+std
+:
+:
+fmt
+:
+:
+Write
+;
+if
+*
+self
+=
+=
+Self
+:
+:
+DOCUMENT
+{
+return
+dest
+.
+write_str
+(
+"
+document
+"
+)
+;
+}
 self
 .
 value
@@ -1686,6 +1651,22 @@ ZOOM_FRACTION_BITS
 }
 )
 ;
+pub
+const
+DOCUMENT
+:
+Zoom
+=
+Zoom
+(
+ZoomFixedPoint
+{
+value
+:
+0
+}
+)
+;
 #
 [
 inline
@@ -1731,6 +1712,72 @@ to_float
 (
 )
 }
+pub
+fn
+compute_effective
+(
+self
+specified
+:
+Self
+)
+-
+>
+Self
+{
+if
+specified
+=
+=
+Self
+:
+:
+DOCUMENT
+{
+return
+Self
+:
+:
+ONE
+;
+}
+if
+self
+=
+=
+Self
+:
+:
+ONE
+{
+return
+specified
+;
+}
+if
+specified
+=
+=
+Self
+:
+:
+ONE
+{
+return
+self
+;
+}
+Zoom
+(
+self
+.
+0
+*
+specified
+.
+0
+)
+}
 #
 [
 inline

servo/components/style/values/specified/box.rs

@@ -10316,6 +10316,21 @@ enum
 Zoom
 {
 Normal
+#
+[
+parse
+(
+condition
+=
+"
+ParserContext
+:
+:
+in_ua_sheet
+"
+)
+]
+Document
 Value
 (
 NonNegativeNumberOrPercentage

testing/web-platform/tests/css/zoom/tentative/scroll-corner-crash.html

@@ -0,0 +1,28 @@
+<
+style
+>
+*
+{
+overflow
+:
+scroll
+scroll
+;
+}
+<
+/
+style
+>
+<
+h4
+style
+=
+"
+zoom
+:
+3
+"
+>
+<
+figure
+>