Bug 1540093 - Refactor some enabledness checks. r=mats

There are some common checks that could get some easy-to-use aliases.

Differential Revision: https://phabricator.services.mozilla.com/D25117

--HG--
extra : moz-landing-system : lando

servo/components/style/media_queries/media_feature_expression.rs

@@ -17,7 +17,6 @@ use crate::parser::{Parse, ParserContext};
 #[cfg(feature = "servo")]
 use crate::servo::media_queries::MEDIA_FEATURES;
 use crate::str::{starts_with_ignore_ascii_case, string_as_ascii_lowercase};
-use crate::stylesheets::Origin;
 use crate::values::computed::{self, ToComputedValue};
 use crate::values::specified::{Integer, Length, Number, Resolution};
 use crate::values::{serialize_atom_identifier, CSSFloat};
@@ -290,7 +289,7 @@ impl MediaFeatureExpression {
 
             let mut requirements = ParsingRequirements::empty();
 
-            if context.chrome_rules_enabled() || context.stylesheet_origin == Origin::UserAgent {
+            if context.in_ua_or_chrome_sheet() {
                 requirements.insert(ParsingRequirements::CHROME_AND_UA_ONLY);
             }
 

servo/components/style/parser.rs

@@ -146,10 +146,23 @@ impl<'a> ParserContext<'a> {
         error_reporter.report_error(self.url_data, location, error)
     }
 
+    /// Whether we're in a user-agent stylesheet.
+    #[inline]
+    pub fn in_ua_sheet(&self) -> bool {
+        self.stylesheet_origin == Origin::UserAgent
+    }
+
     /// Returns whether chrome-only rules should be parsed.
+    #[inline]
     pub fn chrome_rules_enabled(&self) -> bool {
         self.url_data.is_chrome() || self.stylesheet_origin == Origin::User
     }
+
+    /// Whether we're in a user-agent stylesheet or chrome rules are enabled.
+    #[inline]
+    pub fn in_ua_or_chrome_sheet(&self) -> bool {
+        self.in_ua_sheet() || self.chrome_rules_enabled()
+    }
 }
 
 /// A trait to abstract parsing of a specified value given a `ParserContext` and

servo/components/style/stylesheets/supports_rule.rs

@@ -223,8 +223,7 @@ impl SupportsCondition {
 #[cfg(feature = "gecko")]
 fn eval_moz_bool_pref(name: &CStr, cx: &ParserContext) -> bool {
     use crate::gecko_bindings::bindings;
-    use crate::stylesheets::Origin;
-    if cx.stylesheet_origin != Origin::UserAgent && !cx.chrome_rules_enabled() {
+    if !cx.in_ua_or_chrome_sheet() {
         return false;
     }
     unsafe { bindings::Gecko_GetBoolPrefValue(name.as_ptr()) }

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

@@ -21,22 +21,17 @@ use std::fmt::{self, Write};
 use style_traits::{CssWriter, KeywordsCollectFn, ParseError};
 use style_traits::{SpecifiedValueInfo, StyleParseErrorKind, ToCss};
 
-fn in_ua_or_chrome_sheet(context: &ParserContext) -> bool {
-    use crate::stylesheets::Origin;
-    context.stylesheet_origin == Origin::UserAgent || context.chrome_rules_enabled()
-}
-
 #[cfg(feature = "gecko")]
 fn moz_display_values_enabled(context: &ParserContext) -> bool {
     use crate::gecko_bindings::structs;
-    in_ua_or_chrome_sheet(context) ||
+    context.in_ua_or_chrome_sheet() ||
         unsafe { structs::StaticPrefs_sVarCache_layout_css_xul_display_values_content_enabled }
 }
 
 #[cfg(feature = "gecko")]
 fn moz_box_display_values_enabled(context: &ParserContext) -> bool {
     use crate::gecko_bindings::structs;
-    in_ua_or_chrome_sheet(context) ||
+    context.in_ua_or_chrome_sheet() ||
         unsafe {
             structs::StaticPrefs_sVarCache_layout_css_xul_box_display_values_content_enabled
         }
@@ -988,27 +983,27 @@ pub enum Appearance {
     /// A typical dialog button.
     Button,
     /// Various arrows that go in buttons
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ButtonArrowDown,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ButtonArrowNext,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ButtonArrowPrevious,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ButtonArrowUp,
     /// A rectangular button that contains complex content
     /// like images (e.g. HTML <button> elements)
     ButtonBevel,
     /// The focus outline box inside of a button.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ButtonFocus,
     /// The caret of a text area
     Caret,
     /// A dual toolbar button (e.g., a Back button with a dropdown)
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Dualbutton,
     /// A groupbox.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Groupbox,
     /// A inner-spin button.
     InnerSpinButton,
@@ -1017,17 +1012,17 @@ pub enum Appearance {
     /// A listbox item.
     Listitem,
     /// Menu Bar background
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menubar,
     /// <menu> and <menuitem> appearances
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menuitem,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Checkmenuitem,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Radiomenuitem,
     /// For text on non-iconic menuitems only
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menuitemtext,
     /// A dropdown list.
     Menulist,
@@ -1038,28 +1033,28 @@ pub enum Appearance {
     /// An editable textfield with a dropdown list (a combobox).
     MenulistTextfield,
     /// Menu Popup background.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menupopup,
     /// menu checkbox/radio appearances
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menucheckbox,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menuradio,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menuseparator,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menuarrow,
     /// An image in the menu gutter, like in bookmarks or history.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Menuimage,
     /// A horizontal meter bar.
     #[parse(aliases = "meterbar")]
     Meter,
     /// The meter bar's meter indicator.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Meterchunk,
     /// The "arrowed" part of the dropdown button that open up a dropdown list.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMenulistButton,
     /// For HTML's <input type=number>
     NumberInput,
@@ -1067,7 +1062,7 @@ pub enum Appearance {
     #[parse(aliases = "progressbar")]
     ProgressBar,
     /// The progress bar's progress indicator
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Progresschunk,
     /// A vertical progress bar.
     ProgressbarVertical,
@@ -1077,25 +1072,25 @@ pub enum Appearance {
     Radio,
     /// A generic container that always repaints on state changes. This is a
     /// hack to make XUL checkboxes and radio buttons work.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     CheckboxContainer,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     RadioContainer,
     /// The label part of a checkbox or radio button, used for painting a focus
     /// outline.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     CheckboxLabel,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     RadioLabel,
     /// nsRangeFrame and its subparts
     Range,
     RangeThumb,
     /// The resizer background area in a status bar for the resizer widget in
     /// the corner of a window.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Resizerpanel,
     /// The resizer itself.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Resizer,
     /// A slider.
     ScaleHorizontal,
@@ -1109,26 +1104,26 @@ pub enum Appearance {
     /// The ticks for a slider.
     Scalethumbtick,
     /// A scrollbar.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Scrollbar,
     /// A small scrollbar.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ScrollbarSmall,
     /// The scrollbar slider
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ScrollbarHorizontal,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ScrollbarVertical,
     /// A scrollbar button (up/down/left/right).
     /// Keep these in order (some code casts these values to `int` in order to
     /// compare them against each other).
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ScrollbarbuttonUp,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ScrollbarbuttonDown,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ScrollbarbuttonLeft,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ScrollbarbuttonRight,
     /// The scrollbar thumb.
     ScrollbarthumbHorizontal,
@@ -1137,47 +1132,47 @@ pub enum Appearance {
     ScrollbartrackHorizontal,
     ScrollbartrackVertical,
     /// The scroll corner
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Scrollcorner,
     /// A searchfield.
     Searchfield,
     /// A separator.  Can be horizontal or vertical.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Separator,
     /// A spin control (up/down control for time/date pickers).
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Spinner,
     /// The up button of a spin control.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     SpinnerUpbutton,
     /// The down button of a spin control.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     SpinnerDownbutton,
     /// The textfield of a spin control
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     SpinnerTextfield,
     /// A splitter.  Can be horizontal or vertical.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Splitter,
     /// A status bar in a main application window.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Statusbar,
     /// A single pane of a status bar.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Statusbarpanel,
     /// A single tab in a tab widget.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Tab,
     /// A single pane (inside the tabpanels container).
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Tabpanel,
     /// The tab panels container.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Tabpanels,
     /// The tabs scroll arrows (left/right).
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     TabScrollArrowBack,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     TabScrollArrowForward,
     /// A multi-line text field, e.g. HTML <textarea>.
     #[parse(aliases = "textfield-multiline")]
@@ -1185,119 +1180,119 @@ pub enum Appearance {
     /// A single-line text field, e.g. HTML <input type=text>.
     Textfield,
     /// A toolbar in an application window.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Toolbar,
     /// A single toolbar button (with no associated dropdown).
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Toolbarbutton,
     /// The dropdown portion of a toolbar button
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     ToolbarbuttonDropdown,
     /// The gripper for a toolbar.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Toolbargripper,
     /// The toolbox that contains the toolbars.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Toolbox,
     /// A tooltip.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Tooltip,
     /// A listbox or tree widget header
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Treeheader,
     /// An individual header cell
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Treeheadercell,
     /// The sort arrow for a header.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Treeheadersortarrow,
     /// A tree item.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Treeitem,
     /// A tree widget branch line
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Treeline,
     /// A tree widget twisty.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Treetwisty,
     /// Open tree widget twisty.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Treetwistyopen,
     /// A tree widget.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Treeview,
     /// Window and dialog backgrounds.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Window,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     Dialog,
 
     /// Vista Rebars.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWinCommunicationsToolbox,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWinMediaToolbox,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWinBrowsertabbarToolbox,
     /// Vista glass.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWinGlass,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWinBorderlessGlass,
     /// -moz-apperance style used in setting proper glass margins.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWinExcludeGlass,
 
     /// Titlebar elements on the Mac.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacFullscreenButton,
     /// Mac help button.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacHelpButton,
 
     /// Windows themed window frame elements.
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowButtonBox,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowButtonBoxMaximized,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowButtonClose,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowButtonMaximize,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowButtonMinimize,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowButtonRestore,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowFrameBottom,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowFrameLeft,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowFrameRight,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowTitlebar,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowTitlebarMaximized,
 
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozGtkInfoBar,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacActiveSourceListSelection,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacDisclosureButtonClosed,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacDisclosureButtonOpen,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacSourceList,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacSourceListSelection,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacVibrancyDark,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacVibrancyLight,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacVibrantTitlebarDark,
-    #[parse(condition = "in_ua_or_chrome_sheet")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacVibrantTitlebarLight,
 
     /// A non-disappearing scrollbar.