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at 2024-12-09T16:40:36+00:00

Bug 1909625 - Ignore CSS zoom and text zoom for canvas. r=gfx-reviewers,lsalzman

The spec doesn't mention anything about applying them, and other
browsers don't, so let's just be consistent...

Differential Revision: https://phabricator.services.mozilla.com/D221709

@@ -6,6 +6,7 @@
  #include "CanvasRenderingContext2D.h"
  #include "mozilla/gfx/Helpers.h"
 +#include "nsCSSValue.h"
  #include "nsXULElement.h"
  #include "nsMathUtils.h"
@@ -2585,14 +2586,8 @@ static already_AddRefed<StyleLockedDeclarationBlock> CreateDeclarationForServo(
      return nullptr;
+   }
 -  // From canvas spec, force to set line-height property to 'normal' font
 -  // property.
    if (aProperty == eCSSProperty_font) {
 -    const nsCString normalString = "normal"_ns;
 -    Servo_DeclarationBlock_SetPropertyById(
 -        servoDeclarations, eCSSProperty_line_height, &normalString, false,
 -        env.mUrlExtraData, StyleParsingMode::DEFAULT, env.mCompatMode,
 -        env.mLoader, env.mRuleType, {});
 +    Servo_DeclarationBlock_SanitizeForCanvas(servoDeclarations);
+   }
    return servoDeclarations.forget();
@@ -2657,12 +2652,9 @@ static already_AddRefed<const ComputedStyle> GetFontStyleForServo(
    // The font-size component must be converted to CSS px for reserialization,
    // so we update the declarations with the value from the computed style.
    if (!sc->StyleFont()->mFont.family.is_system_font) {
 -    nsAutoCString computedFontSize;
 -    sc->GetComputedPropertyValue(eCSSProperty_font_size, computedFontSize);
 -    Servo_DeclarationBlock_SetPropertyById(
 -        declarations, eCSSProperty_font_size, &computedFontSize, false, nullptr,
 -        StyleParsingMode::DEFAULT, eCompatibility_FullStandards, nullptr,
 -        StyleCssRuleType::Style, {});
 +    float px = sc->StyleFont()->mFont.size.ToCSSPixels();
 +    Servo_DeclarationBlock_SetLengthValue(declarations, eCSSProperty_font_size,
 +                                          px, eCSSUnit_Pixel);
+   }
    // The font getter is required to be reserialized based on what we

@@ -1247,7 +1247,7 @@ impl<'b> Cascade<'b> {
          );
          debug_assert!(
              !text_scale.text_zoom_enabled(),
 -            "We only ever disable text zoom (in svg:text), never enable it"
 +            "We only ever disable text zoom never enable it"
          );
          let device = builder.device;
          builder.mutate_font().unzoom_fonts(device);
@@ -1257,9 +1257,8 @@ impl<'b> Cascade<'b> {
          debug_assert!(self.seen.contains(LonghandId::Zoom));
          // NOTE(emilio): Intentionally not using the effective zoom here, since all the inherited
          // zooms are already applied.
 -        let zoom = builder.get_box().clone_zoom();
          let old_size = builder.get_font().clone_font_size();
 -        let new_size = old_size.zoom(zoom);
 +        let new_size = old_size.zoom(builder.resolved_specified_zoom());
          if old_size == new_size {
              return;
+         }

@@ -2711,6 +2711,19 @@ impl<'a> StyleBuilder<'a> {
          self.get_box().clone_zoom()
+     }
 +    /// The zoom we need to apply for this element, without including ancestor effective zooms.
 +    pub fn resolved_specified_zoom(&self) -> computed::Zoom {
 +        let zoom = self.specified_zoom();
 +        if zoom.is_document() {
 +            // If our inherited effective zoom has derived to zero, there's not much we can do.
 +            // This value is not exposed to content anyways (it's used for scrollbars and to avoid
 +            // zoom affecting canvas).
 +            self.inherited_effective_zoom().inverted().unwrap_or(computed::Zoom::ONE)
 +        } else {
 +            zoom
 +        }
 +    }
++
      /// Inherited zoom.
      pub fn inherited_effective_zoom(&self) -> computed::Zoom {
          self.inherited_style.effective_zoom
@@ -2747,7 +2760,7 @@ impl<'a> StyleBuilder<'a> {
          let lh = device.calc_line_height(&font, writing_mode, None);
          if line_height_base == LineHeightBase::InheritedStyle {
              // Apply our own zoom if our style source is the parent style.
 -            computed::NonNegativeLength::new(self.get_box().clone_zoom().zoom(lh.px()))
 +            computed::NonNegativeLength::new(self.resolved_specified_zoom().zoom(lh.px()))
          } else {
              lh
+         }

@@ -357,6 +357,21 @@ impl Zoom {
          self == Self::ONE
+     }
 +    /// Returns whether we're the `document` keyword.
 +    #[inline]
 +    pub fn is_document(self) -> bool {
 +        self == Self::DOCUMENT
 +    }
++
 +    /// Returns the inverse of our value.
 +    #[inline]
 +    pub fn inverted(&self) -> Option<Self> {
 +        if self.0.value == 0 {
 +            return None;
 +        }
 +        Some(Self(Self::ONE.0 / self.0))
 +    }
++
      /// Returns the value as a float.
      #[inline]
      pub fn value(&self) -> f32 {

@@ -103,7 +103,7 @@ impl FontBaseSize {
              Self::InheritedStyle => {
                  // If we're using the size from our inherited style, we still need to apply our
                  // own zoom.
 -                let zoom = style.get_box().clone_zoom();
 +                let zoom = style.resolved_specified_zoom();
                  style.get_parent_font().clone_font_size().zoom(zoom)
              },
+         }

morgan pushed to branch tor-browser-128.5.0esr-14.5-1 at The Tor Project / Applications / Tor Browser

Commits:

9 changed files:

Changes:

@@ -4972,6 +4972,21 @@ fn set_property(
+     )
+ }
 +#[no_mangle]
 +pub unsafe extern "C" fn Servo_DeclarationBlock_SanitizeForCanvas(
 +    declarations: &LockedDeclarationBlock,
 +) {
 +    use style::properties::PropertyDeclaration;
 +    use style::values::specified::{LineHeight, XTextScale, Zoom};
 +    // From canvas spec, force to set line-height property to 'normal' font property.
 +    // Also, for compat, disable text scaling and CSS zoom.
 +    write_locked_arc(declarations, |decls: &mut PropertyDeclarationBlock| {
 +        decls.push(PropertyDeclaration::LineHeight(LineHeight::Normal), Importance::Normal);
 +        decls.push(PropertyDeclaration::Zoom(Zoom::Document), Importance::Normal);
 +        decls.push(PropertyDeclaration::XTextScale(XTextScale::None), Importance::Normal);
 +    });
 +}
++
  #[no_mangle]
  pub unsafe extern "C" fn Servo_DeclarationBlock_SetProperty(
      declarations: &LockedDeclarationBlock,

 +<!DOCTYPE html>
 +<style>
 +canvas {
 +  width: 600px;
 +  height: 200px;
 +}
 +</style>
 +<script>
 +document.addEventListener("DOMContentLoaded", () => {
 +  const ctx = document.getElementById("canvas").getContext("2d");
 +  ctx.font = "48px serif";
 +  ctx.fillText(ctx.font, 10, 50);
 +});
 +</script>
 +<canvas id="canvas" width="300" height="100"></canvas>

 +<style>
 +*:nth-of-type(1) {
 +  zoom: 5%;
 +}
 +</style>
 +<textarea>