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script: Eagerly update the Device in Layout when it changes #40432

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Merged
mrobinson merged 1 commit into from
Nov 5, 2025
Merged

script: Eagerly update the Device in Layout when it changes #40432

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36 changes: 18 additions & 18 deletions Cargo.lock
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114 changes: 45 additions & 69 deletions components/layout/layout_impl.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,10 @@ pub struct LayoutThread {
/// Whether or not user agent stylesheets have been added to the Stylist or not.
have_added_user_agent_stylesheets: bool,

/// Whether or not this [`LayoutImpl`]'s [`Device`] has changed since the last restyle.
/// If it has, a restyle is pending.
device_has_changed: bool,

/// Is this the first reflow in this LayoutThread?
have_ever_generated_display_list: Cell<bool>,

Expand Down Expand Up @@ -227,6 +231,33 @@ impl Layout for LayoutThread {
self.stylist.device()
}

fn set_theme(&mut self, theme: Theme) -> bool {
let theme: PrefersColorScheme = theme.into();
let device = self.stylist.device_mut();
if theme == device.color_scheme() {
return false;
}

device.set_color_scheme(theme);
self.device_has_changed = true;
true
}

fn set_viewport_details(&mut self, viewport_details: ViewportDetails) -> bool {
let device = self.stylist.device_mut();
let device_pixel_ratio = Scale::new(viewport_details.hidpi_scale_factor.get());
if device.viewport_size() == viewport_details.size &&
device.device_pixel_ratio() == device_pixel_ratio
{
return false;
}

device.set_viewport_size(viewport_details.size);
device.set_device_pixel_ratio(device_pixel_ratio);
self.device_has_changed = true;
true
}

fn load_web_fonts_from_stylesheet(&self, stylesheet: &ServoArc<Stylesheet>) {
let guard = stylesheet.shared_lock.read();
self.load_all_web_fonts_from_stylesheet_with_guard(
Expand Down Expand Up @@ -700,6 +731,7 @@ impl LayoutThread {
font_context: config.font_context,
have_added_user_agent_stylesheets: false,
have_ever_generated_display_list: Cell::new(false),
device_has_changed: false,
need_overflow_calculation: Cell::new(false),
need_new_display_list: Cell::new(false),
need_new_stacking_context_tree: Cell::new(false),
Expand Down Expand Up @@ -893,25 +925,6 @@ impl LayoutThread {
})
}

fn update_device_if_necessary(
&mut self,
reflow_request: &ReflowRequest,
viewport_changed: bool,
guards: &StylesheetGuards,
) -> bool {
let had_used_viewport_units = self.stylist.device().used_viewport_units();
let theme_changed = self.theme_did_change(reflow_request.theme);
if !viewport_changed && !theme_changed {
return false;
}
self.update_device(
reflow_request.viewport_details,
reflow_request.theme,
guards,
);
(viewport_changed && had_used_viewport_units) || theme_changed
}

#[servo_tracing::instrument(skip_all)]
fn prepare_stylist_for_reflow<'dom>(
&mut self,
Expand Down Expand Up @@ -972,16 +985,23 @@ impl LayoutThread {
let author_guard = document_shared_lock.read();
let ua_stylesheets = &*UA_STYLESHEETS;
let ua_or_user_guard = ua_stylesheets.shared_lock.read();
let rayon_pool = STYLE_THREAD_POOL.lock();
let rayon_pool = rayon_pool.pool();
let rayon_pool = rayon_pool.as_ref();
let guards = StylesheetGuards {
author: &author_guard,
ua_or_user: &ua_or_user_guard,
};

let viewport_changed = self.viewport_did_change(reflow_request.viewport_details);
if self.update_device_if_necessary(reflow_request, viewport_changed, &guards) {
let rayon_pool = STYLE_THREAD_POOL.lock();
let rayon_pool = rayon_pool.pool();
let rayon_pool = rayon_pool.as_ref();

let device_has_changed = std::mem::replace(&mut self.device_has_changed, false);
if device_has_changed {
let sheet_origins_affected_by_device_change = self
.stylist
.media_features_change_changed_style(&guards, self.device());
self.stylist
.force_stylesheet_origins_dirty(sheet_origins_affected_by_device_change);

if let Some(mut data) = root_element.mutate_data() {
data.hint.insert(RestyleHint::recascade_subtree());
}
Expand Down Expand Up @@ -1053,7 +1073,7 @@ impl LayoutThread {
}

let root_node = root_element.as_node();
let damage_from_environment = if viewport_changed {
let damage_from_environment = if device_has_changed {
RestyleDamage::RELAYOUT
} else {
Default::default()
Expand Down Expand Up @@ -1354,50 +1374,6 @@ impl LayoutThread {
},
})
}

fn viewport_did_change(&mut self, viewport_details: ViewportDetails) -> bool {
let new_pixel_ratio = viewport_details.hidpi_scale_factor.get();
let new_viewport_size = Size2D::new(
Au::from_f32_px(viewport_details.size.width),
Au::from_f32_px(viewport_details.size.height),
);

let device = self.stylist.device();
let size_did_change = device.au_viewport_size() != new_viewport_size;
let pixel_ratio_did_change = device.device_pixel_ratio().get() != new_pixel_ratio;

size_did_change || pixel_ratio_did_change
}

fn theme_did_change(&self, theme: Theme) -> bool {
let theme: PrefersColorScheme = theme.into();
theme != self.device().color_scheme()
}

/// Update layout given a new viewport. Returns true if the viewport changed or false if it didn't.
fn update_device(
&mut self,
viewport_details: ViewportDetails,
theme: Theme,
guards: &StylesheetGuards,
) {
let device = Device::new(
MediaType::screen(),
self.stylist.quirks_mode(),
viewport_details.size,
Scale::new(viewport_details.hidpi_scale_factor.get()),
Box::new(LayoutFontMetricsProvider(self.font_context.clone())),
self.stylist.device().default_computed_values().to_arc(),
theme.into(),
);

// Preserve any previously computed root font size.
device.set_root_font_size(self.stylist.device().root_font_size().px());

let sheet_origins_affected_by_device_change = self.stylist.set_device(device, guards);
self.stylist
.force_stylesheet_origins_dirty(sheet_origins_affected_by_device_change);
}
}

fn get_ua_stylesheets() -> Result<UserAgentStylesheets, &'static str> {
Expand Down
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