style: Rework -x-text-zoom to allow disabling text zoom and min-font-size separately

And use it instead of explicit document checks. This centralizes where
we check for it.

IsChromeDoc is relatively cheap, but this bug wants to also check for
PDF.js which is a bit more expensive.

No behavior change.

Differential Revision: https://phabricator.services.mozilla.com/D176940

10 files changed, 46 insertions, 65 deletions

diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index 0e4dca33a1f..b5bcaa8242a 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -1596,10 +1596,9 @@ impl<'le> TElement for GeckoElement<'le> {
         V: Push<ApplicableDeclarationBlock>,
     {
         use crate::properties::longhands::_x_lang::SpecifiedValue as SpecifiedLang;
-        use crate::properties::longhands::_x_text_zoom::SpecifiedValue as SpecifiedZoom;
         use crate::properties::longhands::color::SpecifiedValue as SpecifiedColor;
         use crate::stylesheets::layer_rule::LayerOrder;
-        use crate::values::specified::color::Color;
+        use crate::values::specified::{color::Color, font::XTextScale};
         lazy_static! {
             static ref TABLE_COLOR_RULE: ApplicableDeclarationBlock = {
                 let global_style_data = &*GLOBAL_STYLE_DATA;
@@ -1627,10 +1626,10 @@ impl<'le> TElement for GeckoElement<'le> {
                     LayerOrder::root(),
                 )
             };
-            static ref SVG_TEXT_DISABLE_ZOOM_RULE: ApplicableDeclarationBlock = {
+            static ref SVG_TEXT_DISABLE_SCALE_RULE: ApplicableDeclarationBlock = {
                 let global_style_data = &*GLOBAL_STYLE_DATA;
                 let pdb = PropertyDeclarationBlock::with_one(
-                    PropertyDeclaration::XTextZoom(SpecifiedZoom(false)),
+                    PropertyDeclaration::XTextScale(XTextScale::None),
                     Importance::Normal,
                 );
                 let arc = Arc::new_leaked(global_style_data.shared_lock.wrap(pdb));
@@ -1653,7 +1652,7 @@ impl<'le> TElement for GeckoElement<'le> {
         }
         if ns == structs::kNameSpaceID_SVG as i32 {
             if self.local_name().as_ptr() == atom!("text").as_ptr() {
-                hints.push(SVG_TEXT_DISABLE_ZOOM_RULE.clone());
+                hints.push(SVG_TEXT_DISABLE_SCALE_RULE.clone());
             }
         }
         let declarations =
diff --git a/components/style/properties/cascade.rs b/components/style/properties/cascade.rs
index 441aadfafe4..dab60dcba2f 100644
--- a/components/style/properties/cascade.rs
+++ b/components/style/properties/cascade.rs
@@ -1028,28 +1028,31 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
         builder.mutate_font().gecko_mut().mFont.size = min_font_size;
     }
 
-    /// <svg:text> is not affected by text zoom, and it uses a preshint
-    /// to disable it. We fix up the struct when this happens by
-    /// unzooming its contained font values, which will have been zoomed
-    /// in the parent.
+    /// <svg:text> is not affected by text zoom, and it uses a preshint to disable it. We fix up
+    /// the struct when this happens by unzooming its contained font values, which will have been
+    /// zoomed in the parent.
     ///
-    /// FIXME(emilio): Also, why doing this _before_ handling font-size? That
-    /// sounds wrong.
+    /// FIXME(emilio): Why doing this _before_ handling font-size? That sounds wrong.
     #[cfg(feature = "gecko")]
     fn unzoom_fonts_if_needed(&mut self) {
-        if !self.seen.contains(LonghandId::XTextZoom) {
+        if !self.seen.contains(LonghandId::XTextScale) {
             return;
         }
 
         let builder = &mut self.context.builder;
 
-        let parent_zoom = builder.get_parent_font().gecko().mAllowZoomAndMinSize;
-        let zoom = builder.get_font().gecko().mAllowZoomAndMinSize;
-        if zoom == parent_zoom {
+        let parent_text_scale = builder.get_parent_font().clone__x_text_scale();
+        let text_scale = builder.get_font().clone__x_text_scale();
+        if parent_text_scale == text_scale {
             return;
         }
+        debug_assert_ne!(
+            parent_text_scale.text_zoom_enabled(),
+            text_scale.text_zoom_enabled(),
+            "There's only one value that disables it"
+        );
         debug_assert!(
-            !zoom,
+            !text_scale.text_zoom_enabled(),
             "We only ever disable text zoom (in svg:text), never enable it"
         );
         let device = builder.device;
@@ -1140,7 +1143,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
             }
 
             let mut min = parent_font.mScriptMinSize;
-            if font.mAllowZoomAndMinSize {
+            if font.mXTextScale.text_zoom_enabled() {
                 min = builder.device.zoom_text(min);
             }
 
diff --git a/components/style/properties/data.py b/components/style/properties/data.py
index 109689fb5de..195b773ca8d 100644
--- a/components/style/properties/data.py
+++ b/components/style/properties/data.py
@@ -503,7 +503,7 @@ class Longhand(Property):
                 "UserSelect",
                 "WordBreak",
                 "XSpan",
-                "XTextZoom",
+                "XTextScale",
                 "ZIndex",
             }
         if self.name == "overflow-y":
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index ebd58d3bc91..6391b357200 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -841,8 +841,7 @@ fn static_assert() {
                             font-variant-alternates font-variant-east-asian
                             font-variant-ligatures font-variant-numeric
                             font-language-override font-feature-settings
-                            font-variation-settings -moz-min-font-size-ratio
-                            -x-text-zoom""" %>
+                            font-variation-settings -moz-min-font-size-ratio""" %>
 <%self:impl_trait style_struct_name="Font"
     skip_longhands="${skip_font_longhands}">
 
@@ -943,27 +942,8 @@ fn static_assert() {
         })
     }
 
-    #[allow(non_snake_case)]
-    pub fn set__x_text_zoom(&mut self, v: longhands::_x_text_zoom::computed_value::T) {
-        self.gecko.mAllowZoomAndMinSize = v.0;
-    }
-
-    #[allow(non_snake_case)]
-    pub fn copy__x_text_zoom_from(&mut self, other: &Self) {
-        self.gecko.mAllowZoomAndMinSize = other.gecko.mAllowZoomAndMinSize;
-    }
-
-    #[allow(non_snake_case)]
-    pub fn reset__x_text_zoom(&mut self, other: &Self) {
-        self.copy__x_text_zoom_from(other)
-    }
-
-    #[allow(non_snake_case)]
-    pub fn clone__x_text_zoom(&self) -> longhands::_x_text_zoom::computed_value::T {
-        longhands::_x_text_zoom::computed_value::T(self.gecko.mAllowZoomAndMinSize)
-    }
 
-    <% impl_simple_type_with_conversion("font_language_override", "mFont.languageOverride") %>
+    ${impl_simple_type_with_conversion("font_language_override", "mFont.languageOverride")}
     ${impl_simple_type_with_conversion("font_variant_ligatures", "mFont.variantLigatures")}
     ${impl_simple_type_with_conversion("font_variant_east_asian", "mFont.variantEastAsian")}
     ${impl_simple_type_with_conversion("font_variant_numeric", "mFont.variantNumeric")}
diff --git a/components/style/properties/longhands/font.mako.rs b/components/style/properties/longhands/font.mako.rs
index c3833a25420..e116f305e28 100644
--- a/components/style/properties/longhands/font.mako.rs
+++ b/components/style/properties/longhands/font.mako.rs
@@ -331,9 +331,9 @@ ${helpers.predefined_type(
 )}
 
 ${helpers.predefined_type(
-    "-x-text-zoom",
-    "XTextZoom",
-    "computed::XTextZoom(true)",
+    "-x-text-scale",
+    "XTextScale",
+    "computed::XTextScale::All",
     engines="gecko",
     animation_value_type="none",
     enabled_in="",
diff --git a/components/style/properties/properties.mako.rs b/components/style/properties/properties.mako.rs
index 17e74cf0cc2..c42e9de6e31 100644
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@@ -915,9 +915,7 @@ CASCADE_GROUPS = {
     # Cascade::fixup_font_stuff.
     "fonts_and_color": [
         # Needed to properly compute the zoomed font-size.
-        # FIXME(emilio): This could probably just be a cascade flag
-        # like IN_SVG_SUBTREE or such, and we could nuke this property.
-        "-x-text-zoom",
+        "-x-text-scale",
         # Needed to do font-size computation in a language-dependent way.
         "-x-lang",
         # Needed for ruby to respect language-dependent min-font-size
diff --git a/components/style/values/computed/font.rs b/components/style/values/computed/font.rs
index 900a0a0dc5d..4f51f8a99ff 100644
--- a/components/style/values/computed/font.rs
+++ b/components/style/values/computed/font.rs
@@ -30,7 +30,7 @@ pub use crate::values::specified::font::{FontPalette, FontSynthesis};
 pub use crate::values::specified::font::MozScriptSizeMultiplier;
 pub use crate::values::specified::font::{
     FontVariantAlternates, FontVariantEastAsian, FontVariantLigatures, FontVariantNumeric, XLang,
-    XTextZoom,
+    XTextScale,
 };
 pub use crate::values::specified::Integer as SpecifiedInteger;
 pub use crate::values::specified::Number as SpecifiedNumber;
diff --git a/components/style/values/computed/mod.rs b/components/style/values/computed/mod.rs
index ff1e0696bc9..54b33253955 100644
--- a/components/style/values/computed/mod.rs
+++ b/components/style/values/computed/mod.rs
@@ -71,7 +71,7 @@ pub use self::font::{FontFeatureSettings, FontVariantLigatures, FontVariantNumer
 pub use self::font::{FontSize, FontSizeAdjust, FontStretch, FontSynthesis};
 pub use self::font::{FontVariantAlternates, FontWeight};
 pub use self::font::{FontVariantEastAsian, FontVariationSettings};
-pub use self::font::{MathDepth, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextZoom};
+pub use self::font::{MathDepth, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextScale};
 pub use self::image::{Gradient, Image, ImageRendering, LineDirection, MozImageRect};
 pub use self::length::{CSSPixelLength, NonNegativeLength};
 pub use self::length::{Length, LengthOrNumber, LengthPercentage, NonNegativeLengthOrNumber};
@@ -390,10 +390,7 @@ impl<'a> Context<'a> {
     /// Apply text-zoom if enabled.
     #[cfg(feature = "gecko")]
     pub fn maybe_zoom_text(&self, size: CSSPixelLength) -> CSSPixelLength {
-        // We disable zoom for <svg:text> by unsetting the
-        // -x-text-zoom property, which leads to a false value
-        // in mAllowZoomAndMinSize
-        if self.style().get_font().gecko.mAllowZoomAndMinSize {
+        if self.style().get_font().clone__x_text_scale().text_zoom_enabled() {
             self.device().zoom_text(size)
         } else {
             size
diff --git a/components/style/values/specified/font.rs b/components/style/values/specified/font.rs
index a73e658a2fc..4e0a730e9c5 100644
--- a/components/style/values/specified/font.rs
+++ b/components/style/values/specified/font.rs
@@ -1936,6 +1936,7 @@ impl MetricsOverride {
     Copy,
     Debug,
     MallocSizeOf,
+    Parse,
     PartialEq,
     SpecifiedValueInfo,
     ToComputedValue,
@@ -1943,19 +1944,22 @@ impl MetricsOverride {
     ToResolvedValue,
     ToShmem,
 )]
-/// text-zoom. Enable if true, disable if false
-pub struct XTextZoom(#[css(skip)] pub bool);
+#[repr(u8)]
+/// How to do font-size scaling.
+pub enum XTextScale {
+    /// Both min-font-size and text zoom are enabled.
+    All,
+    /// Text-only zoom is enabled, but min-font-size is not honored.
+    ZoomOnly,
+    /// Neither of them is enabled.
+    None,
+}
 
-impl Parse for XTextZoom {
-    fn parse<'i, 't>(
-        _: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<XTextZoom, ParseError<'i>> {
-        debug_assert!(
-            false,
-            "Should be set directly by presentation attributes only."
-        );
-        Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+impl XTextScale {
+    /// Returns whether text zoom is enabled.
+    #[inline]
+    pub fn text_zoom_enabled(self) -> bool {
+        self != Self::None
     }
 }
 
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index b0c155a81ab..f9c7d159119 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -58,7 +58,7 @@ pub use self::font::{FontFeatureSettings, FontVariantLigatures, FontVariantNumer
 pub use self::font::{FontSize, FontSizeAdjust, FontSizeKeyword, FontStretch, FontSynthesis};
 pub use self::font::{FontVariantAlternates, FontWeight};
 pub use self::font::{FontVariantEastAsian, FontVariationSettings};
-pub use self::font::{MathDepth, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextZoom};
+pub use self::font::{MathDepth, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextScale};
 pub use self::image::{EndingShape as GradientEndingShape, Gradient};
 pub use self::image::{Image, ImageRendering, MozImageRect};
 pub use self::length::{AbsoluteLength, CalcLengthPercentage, CharacterWidth};