1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

use std::collections::{HashMap, HashSet};
use std::default::Default;
use std::hash::{BuildHasherDefault, Hash, Hasher};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;

use app_units::Au;
use crossbeam_channel::unbounded;
use fnv::FnvHasher;
use fonts_traits::WebFontLoadFinishedCallback;
use log::{debug, trace};
use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
use malloc_size_of_derive::MallocSizeOf;
use net_traits::request::{Destination, Referrer, RequestBuilder};
use net_traits::{fetch_async, CoreResourceThread, FetchResponseMsg, ResourceThreads};
use parking_lot::{Mutex, RwLock};
use servo_arc::Arc as ServoArc;
use servo_url::ServoUrl;
use style::computed_values::font_variant_caps::T as FontVariantCaps;
use style::font_face::{FontFaceSourceFormat, FontFaceSourceFormatKeyword, Source, UrlSource};
use style::media_queries::Device;
use style::properties::style_structs::Font as FontStyleStruct;
use style::shared_lock::SharedRwLockReadGuard;
use style::stylesheets::{CssRule, DocumentStyleSheet, FontFaceRule, StylesheetInDocument};
use style::values::computed::font::{FamilyName, FontFamilyNameSyntax, SingleFontFamily};
use style::Atom;
use url::Url;
use webrender_api::{FontInstanceFlags, FontInstanceKey, FontKey};
use webrender_traits::CrossProcessCompositorApi;

use crate::font::{
    Font, FontDescriptor, FontFamilyDescriptor, FontGroup, FontRef, FontSearchScope,
};
use crate::font_store::CrossThreadFontStore;
use crate::font_template::{FontTemplate, FontTemplateRef, FontTemplateRefMethods};
use crate::platform::font::PlatformFont;
use crate::system_font_service::{CSSFontFaceDescriptors, FontIdentifier};
use crate::{FontData, LowercaseFontFamilyName, PlatformFontMethods, SystemFontServiceProxy};

static SMALL_CAPS_SCALE_FACTOR: f32 = 0.8; // Matches FireFox (see gfxFont.h)

/// The FontContext represents the per-thread/thread state necessary for
/// working with fonts. It is the public API used by the layout and
/// paint code. It talks directly to the system font service where
/// required.
pub struct FontContext {
    system_font_service_proxy: Arc<SystemFontServiceProxy>,
    resource_threads: Mutex<CoreResourceThread>,

    /// A sender that can send messages and receive replies from the compositor.
    compositor_api: Mutex<CrossProcessCompositorApi>,

    /// The actual instances of fonts ie a [`FontTemplate`] combined with a size and
    /// other font properties, along with the font data and a platform font instance.
    fonts: RwLock<HashMap<FontCacheKey, Option<FontRef>>>,

    /// A caching map between the specification of a font in CSS style and
    /// resolved [`FontGroup`] which contains information about all fonts that
    /// can be selected with that style.
    resolved_font_groups:
        RwLock<HashMap<FontGroupCacheKey, Arc<RwLock<FontGroup>>, BuildHasherDefault<FnvHasher>>>,

    web_fonts: CrossThreadFontStore,

    /// A collection of WebRender [`FontKey`]s generated for the web fonts that this
    /// [`FontContext`] controls.
    webrender_font_keys: RwLock<HashMap<FontIdentifier, FontKey>>,

    /// A collection of WebRender [`FontInstanceKey`]s generated for the web fonts that
    /// this [`FontContext`] controls.
    webrender_font_instance_keys: RwLock<HashMap<(FontKey, Au), FontInstanceKey>>,

    /// The data for each web font [`FontIdentifier`]. This data might be used by more than one
    /// [`FontTemplate`] as each identifier refers to a URL.
    font_data: RwLock<HashMap<FontIdentifier, FontData>>,

    have_removed_web_fonts: AtomicBool,
}

impl MallocSizeOf for FontContext {
    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
        let font_cache_size = self
            .fonts
            .read()
            .iter()
            .map(|(key, font)| {
                key.size_of(ops) + font.as_ref().map_or(0, |font| (*font).size_of(ops))
            })
            .sum::<usize>();
        let font_group_cache_size = self
            .resolved_font_groups
            .read()
            .iter()
            .map(|(key, font_group)| key.size_of(ops) + (*font_group.read()).size_of(ops))
            .sum::<usize>();
        font_cache_size + font_group_cache_size
    }
}

impl FontContext {
    pub fn new(
        system_font_service_proxy: Arc<SystemFontServiceProxy>,
        compositor_api: CrossProcessCompositorApi,
        resource_threads: ResourceThreads,
    ) -> Self {
        #[allow(clippy::default_constructed_unit_structs)]
        Self {
            system_font_service_proxy,
            resource_threads: Mutex::new(resource_threads.core_thread),
            compositor_api: Mutex::new(compositor_api),
            fonts: Default::default(),
            resolved_font_groups: Default::default(),
            web_fonts: Arc::new(RwLock::default()),
            webrender_font_keys: RwLock::default(),
            webrender_font_instance_keys: RwLock::default(),
            have_removed_web_fonts: AtomicBool::new(false),
            font_data: RwLock::default(),
        }
    }

    pub fn web_fonts_still_loading(&self) -> usize {
        self.web_fonts.read().number_of_fonts_still_loading()
    }

    fn get_font_data(&self, identifier: &FontIdentifier) -> Option<FontData> {
        match identifier {
            FontIdentifier::Web(_) => self.font_data.read().get(identifier).cloned(),
            FontIdentifier::Local(_) => None,
        }
    }

    /// Handle the situation where a web font finishes loading, specifying if the load suceeded or failed.
    fn handle_web_font_load_finished(
        &self,
        finished_callback: &WebFontLoadFinishedCallback,
        succeeded: bool,
    ) {
        if succeeded {
            self.invalidate_font_groups_after_web_font_load();
        }
        finished_callback(succeeded);
    }

    /// Returns a `FontGroup` representing fonts which can be used for layout, given the `style`.
    /// Font groups are cached, so subsequent calls with the same `style` will return a reference
    /// to an existing `FontGroup`.
    pub fn font_group(&self, style: ServoArc<FontStyleStruct>) -> Arc<RwLock<FontGroup>> {
        let font_size = style.font_size.computed_size().into();
        self.font_group_with_size(style, font_size)
    }

    /// Like [`Self::font_group`], but overriding the size found in the [`FontStyleStruct`] with the given size
    /// in pixels.
    pub fn font_group_with_size(
        &self,
        style: ServoArc<FontStyleStruct>,
        size: Au,
    ) -> Arc<RwLock<FontGroup>> {
        let cache_key = FontGroupCacheKey { size, style };
        if let Some(font_group) = self.resolved_font_groups.read().get(&cache_key) {
            return font_group.clone();
        }

        let mut descriptor = FontDescriptor::from(&*cache_key.style);
        descriptor.pt_size = size;

        let font_group = Arc::new(RwLock::new(FontGroup::new(&cache_key.style, descriptor)));
        self.resolved_font_groups
            .write()
            .insert(cache_key, font_group.clone());
        font_group
    }

    /// Returns a font matching the parameters. Fonts are cached, so repeated calls will return a
    /// reference to the same underlying `Font`.
    pub fn font(
        &self,
        font_template: FontTemplateRef,
        font_descriptor: &FontDescriptor,
    ) -> Option<FontRef> {
        self.get_font_maybe_synthesizing_small_caps(
            font_template,
            font_descriptor,
            true, /* synthesize_small_caps */
        )
    }

    fn get_font_maybe_synthesizing_small_caps(
        &self,
        font_template: FontTemplateRef,
        font_descriptor: &FontDescriptor,
        synthesize_small_caps: bool,
    ) -> Option<FontRef> {
        // TODO: (Bug #3463): Currently we only support fake small-caps
        // painting. We should also support true small-caps (where the
        // font supports it) in the future.
        let synthesized_small_caps_font =
            if font_descriptor.variant == FontVariantCaps::SmallCaps && synthesize_small_caps {
                let mut small_caps_descriptor = font_descriptor.clone();
                small_caps_descriptor.pt_size =
                    font_descriptor.pt_size.scale_by(SMALL_CAPS_SCALE_FACTOR);
                self.get_font_maybe_synthesizing_small_caps(
                    font_template.clone(),
                    &small_caps_descriptor,
                    false, /* synthesize_small_caps */
                )
            } else {
                None
            };

        let cache_key = FontCacheKey {
            font_identifier: font_template.identifier(),
            font_descriptor: font_descriptor.clone(),
        };

        if let Some(font) = self.fonts.read().get(&cache_key).cloned() {
            return font;
        }

        debug!(
            "FontContext::font cache miss for font_template={:?} font_descriptor={:?}",
            font_template, font_descriptor
        );

        // TODO: Inserting `None` into the cache here is a bit bogus. Instead we should somehow
        // mark this template as invalid so it isn't tried again.
        let font = self
            .create_font(
                font_template,
                font_descriptor.to_owned(),
                synthesized_small_caps_font,
            )
            .ok();
        self.fonts.write().insert(cache_key, font.clone());
        font
    }

    fn matching_web_font_templates(
        &self,
        descriptor_to_match: &FontDescriptor,
        family_descriptor: &FontFamilyDescriptor,
    ) -> Option<Vec<FontTemplateRef>> {
        if family_descriptor.scope != FontSearchScope::Any {
            return None;
        }

        // Do not look for generic fonts in our list of web fonts.
        let SingleFontFamily::FamilyName(ref family_name) = family_descriptor.family else {
            return None;
        };

        self.web_fonts
            .read()
            .families
            .get(&family_name.name.clone().into())
            .map(|templates| templates.find_for_descriptor(Some(descriptor_to_match)))
    }

    /// Try to find matching templates in this [`FontContext`], first looking in the list of web fonts and
    /// falling back to asking the [`super::SystemFontService`] for a matching system font.
    pub fn matching_templates(
        &self,
        descriptor_to_match: &FontDescriptor,
        family_descriptor: &FontFamilyDescriptor,
    ) -> Vec<FontTemplateRef> {
        self.matching_web_font_templates(descriptor_to_match, family_descriptor)
            .unwrap_or_else(|| {
                self.system_font_service_proxy.find_matching_font_templates(
                    Some(descriptor_to_match),
                    &family_descriptor.family,
                )
            })
    }

    /// Create a `Font` for use in layout calculations, from a `FontTemplateData` returned by the
    /// cache thread and a `FontDescriptor` which contains the styling parameters.
    #[cfg_attr(
        feature = "tracing",
        tracing::instrument(skip_all, fields(servo_profiling = true))
    )]
    fn create_font(
        &self,
        font_template: FontTemplateRef,
        font_descriptor: FontDescriptor,
        synthesized_small_caps: Option<FontRef>,
    ) -> Result<FontRef, &'static str> {
        Ok(Arc::new(Font::new(
            font_template.clone(),
            font_descriptor.clone(),
            self.get_font_data(&font_template.identifier()),
            synthesized_small_caps,
        )?))
    }

    pub(crate) fn create_font_instance_key(&self, font: &Font) -> FontInstanceKey {
        match font.template.identifier() {
            FontIdentifier::Local(_) => self.system_font_service_proxy.get_system_font_instance(
                font.template.identifier(),
                font.descriptor.pt_size,
                font.webrender_font_instance_flags(),
            ),
            FontIdentifier::Web(_) => self.create_web_font_instance(
                font.template.clone(),
                font.descriptor.pt_size,
                font.webrender_font_instance_flags(),
            ),
        }
    }

    fn create_web_font_instance(
        &self,
        font_template: FontTemplateRef,
        pt_size: Au,
        flags: FontInstanceFlags,
    ) -> FontInstanceKey {
        let identifier = font_template.identifier().clone();
        let font_data = self
            .get_font_data(&identifier)
            .expect("Web font should have associated font data");
        let font_key = *self
            .webrender_font_keys
            .write()
            .entry(identifier.clone())
            .or_insert_with(|| {
                let font_key = self.system_font_service_proxy.generate_font_key();
                self.compositor_api.lock().add_font(
                    font_key,
                    font_data.as_ipc_shared_memory(),
                    identifier.index(),
                );
                font_key
            });

        let key = *self
            .webrender_font_instance_keys
            .write()
            .entry((font_key, pt_size))
            .or_insert_with(|| {
                let font_instance_key = self.system_font_service_proxy.generate_font_instance_key();
                self.compositor_api.lock().add_font_instance(
                    font_instance_key,
                    font_key,
                    pt_size.to_f32_px(),
                    flags,
                );
                font_instance_key
            });
        key
    }

    fn invalidate_font_groups_after_web_font_load(&self) {
        self.resolved_font_groups.write().clear();
    }
}

#[derive(Clone)]
pub(crate) struct WebFontDownloadState {
    pub(crate) css_font_face_descriptors: Arc<CSSFontFaceDescriptors>,
    remaining_sources: Vec<Source>,
    finished_callback: WebFontLoadFinishedCallback,
    core_resource_thread: CoreResourceThread,
    local_fonts: Arc<HashMap<Atom, Option<FontTemplateRef>>>,
    pub(crate) stylesheet: DocumentStyleSheet,
}

pub trait FontContextWebFontMethods {
    fn add_all_web_fonts_from_stylesheet(
        &self,
        stylesheet: &DocumentStyleSheet,
        guard: &SharedRwLockReadGuard,
        device: &Device,
        finished_callback: WebFontLoadFinishedCallback,
        synchronous: bool,
    ) -> usize;
    fn remove_all_web_fonts_from_stylesheet(&self, stylesheet: &DocumentStyleSheet);
    fn collect_unused_webrender_resources(&self, all: bool)
        -> (Vec<FontKey>, Vec<FontInstanceKey>);
}

impl FontContextWebFontMethods for Arc<FontContext> {
    fn add_all_web_fonts_from_stylesheet(
        &self,
        stylesheet: &DocumentStyleSheet,
        guard: &SharedRwLockReadGuard,
        device: &Device,
        finished_callback: WebFontLoadFinishedCallback,
        synchronous: bool,
    ) -> usize {
        let (finished_callback, synchronous_receiver) = if synchronous {
            let (sender, receiver) = unbounded();
            let finished_callback = move |_succeeded: bool| {
                let _ = sender.send(());
            };
            (
                Arc::new(finished_callback) as WebFontLoadFinishedCallback,
                Some(receiver),
            )
        } else {
            (finished_callback, None)
        };

        let mut number_loading = 0;
        for rule in stylesheet.effective_rules(device, guard) {
            let CssRule::FontFace(ref lock) = *rule else {
                continue;
            };

            let rule: &FontFaceRule = lock.read_with(guard);
            let Some(font_face) = rule.font_face() else {
                continue;
            };

            let sources: Vec<Source> = font_face
                .sources()
                .0
                .iter()
                .rev()
                .filter(is_supported_web_font_source)
                .cloned()
                .collect();
            if sources.is_empty() {
                continue;
            }

            // Fetch all local fonts first, beacause if we try to fetch them later on during the process of
            // loading the list of web font `src`s we may be running in the context of the router thread, which
            // means we won't be able to seend IPC messages to the FontCacheThread.
            //
            // TODO: This is completely wrong. The specification says that `local()` font-family should match
            // against full PostScript names, but this is matching against font family names. This works...
            // sometimes.
            let mut local_fonts = HashMap::new();
            for source in sources.iter() {
                if let Source::Local(family_name) = source {
                    local_fonts
                        .entry(family_name.name.clone())
                        .or_insert_with(|| {
                            let family = SingleFontFamily::FamilyName(FamilyName {
                                name: family_name.name.clone(),
                                syntax: FontFamilyNameSyntax::Quoted,
                            });
                            self.system_font_service_proxy
                                .find_matching_font_templates(None, &family)
                                .first()
                                .cloned()
                        });
                }
            }

            number_loading += 1;
            self.web_fonts
                .write()
                .handle_web_font_load_started_for_stylesheet(stylesheet);

            self.process_next_web_font_source(WebFontDownloadState {
                css_font_face_descriptors: Arc::new(rule.into()),
                remaining_sources: sources,
                finished_callback: finished_callback.clone(),
                core_resource_thread: self.resource_threads.lock().clone(),
                local_fonts: Arc::new(local_fonts),
                stylesheet: stylesheet.clone(),
            });

            // If the load is synchronous wait for it to be signalled.
            if let Some(ref synchronous_receiver) = synchronous_receiver {
                synchronous_receiver.recv().unwrap();
            }
        }

        number_loading
    }

    fn remove_all_web_fonts_from_stylesheet(&self, stylesheet: &DocumentStyleSheet) {
        let mut web_fonts = self.web_fonts.write();
        let mut fonts = self.fonts.write();
        let mut font_groups = self.resolved_font_groups.write();

        // Cancel any currently in-progress web font loads.
        web_fonts.handle_stylesheet_removed(stylesheet);

        let mut removed_any = false;
        for family in web_fonts.families.values_mut() {
            removed_any |= family.remove_templates_for_stylesheet(stylesheet);
        }
        if !removed_any {
            return;
        };

        fonts.retain(|_, font| match font {
            Some(font) => font.template.borrow().stylesheet.as_ref() != Some(stylesheet),
            _ => true,
        });

        // Removing this stylesheet modified the available fonts, so invalidate the cache
        // of resolved font groups.
        font_groups.clear();

        // Ensure that we clean up any WebRender resources on the next display list update.
        self.have_removed_web_fonts.store(true, Ordering::Relaxed);
    }

    fn collect_unused_webrender_resources(
        &self,
        all: bool,
    ) -> (Vec<FontKey>, Vec<FontInstanceKey>) {
        if all {
            let mut webrender_font_keys = self.webrender_font_keys.write();
            let mut webrender_font_instance_keys = self.webrender_font_instance_keys.write();
            self.have_removed_web_fonts.store(false, Ordering::Relaxed);
            return (
                webrender_font_keys.drain().map(|(_, key)| key).collect(),
                webrender_font_instance_keys
                    .drain()
                    .map(|(_, key)| key)
                    .collect(),
            );
        }

        if !self.have_removed_web_fonts.load(Ordering::Relaxed) {
            return (Vec::new(), Vec::new());
        }

        // Lock everything to prevent adding new fonts while we are cleaning up the old ones.
        let web_fonts = self.web_fonts.write();
        let mut font_data = self.font_data.write();
        let _fonts = self.fonts.write();
        let _font_groups = self.resolved_font_groups.write();
        let mut webrender_font_keys = self.webrender_font_keys.write();
        let mut webrender_font_instance_keys = self.webrender_font_instance_keys.write();

        let mut unused_identifiers: HashSet<FontIdentifier> =
            webrender_font_keys.keys().cloned().collect();
        for templates in web_fonts.families.values() {
            templates.for_all_identifiers(|identifier| {
                unused_identifiers.remove(identifier);
            });
        }

        font_data.retain(|font_identifier, _| unused_identifiers.contains(font_identifier));

        self.have_removed_web_fonts.store(false, Ordering::Relaxed);

        let mut removed_keys: HashSet<FontKey> = HashSet::new();
        webrender_font_keys.retain(|identifier, font_key| {
            if unused_identifiers.contains(identifier) {
                removed_keys.insert(*font_key);
                false
            } else {
                true
            }
        });

        let mut removed_instance_keys: HashSet<FontInstanceKey> = HashSet::new();
        webrender_font_instance_keys.retain(|(font_key, _), instance_key| {
            if removed_keys.contains(font_key) {
                removed_instance_keys.insert(*instance_key);
                false
            } else {
                true
            }
        });

        (
            removed_keys.into_iter().collect(),
            removed_instance_keys.into_iter().collect(),
        )
    }
}

impl FontContext {
    fn process_next_web_font_source(self: &Arc<FontContext>, mut state: WebFontDownloadState) {
        let Some(source) = state.remaining_sources.pop() else {
            self.web_fonts
                .write()
                .handle_web_font_failed_to_load(&state);
            self.handle_web_font_load_finished(&state.finished_callback, false);
            return;
        };

        let this = self.clone();
        let web_font_family_name = state.css_font_face_descriptors.family_name.clone();
        match source {
            Source::Url(url_source) => {
                RemoteWebFontDownloader::download(url_source, this, web_font_family_name, state)
            },
            Source::Local(ref local_family_name) => {
                if let Some(new_template) = state
                    .local_fonts
                    .get(&local_family_name.name)
                    .cloned()
                    .flatten()
                    .and_then(|local_template| {
                        let template = FontTemplate::new_for_local_web_font(
                            local_template.clone(),
                            &state.css_font_face_descriptors,
                            state.stylesheet.clone(),
                        )
                        .ok()?;
                        Some(template)
                    })
                {
                    let not_cancelled = self
                        .web_fonts
                        .write()
                        .handle_web_font_loaded(&state, new_template);
                    self.handle_web_font_load_finished(&state.finished_callback, not_cancelled);
                } else {
                    this.process_next_web_font_source(state);
                }
            },
        }
    }
}

struct RemoteWebFontDownloader {
    font_context: Arc<FontContext>,
    url: ServoArc<Url>,
    web_font_family_name: LowercaseFontFamilyName,
    response_valid: Mutex<bool>,
    response_data: Mutex<Vec<u8>>,
}

enum DownloaderResponseResult {
    InProcess,
    Finished,
    Failure,
}

impl RemoteWebFontDownloader {
    fn download(
        url_source: UrlSource,
        font_context: Arc<FontContext>,
        web_font_family_name: LowercaseFontFamilyName,
        state: WebFontDownloadState,
    ) {
        // https://drafts.csswg.org/css-fonts/#font-fetching-requirements
        let url = match url_source.url.url() {
            Some(url) => url.clone(),
            None => return,
        };

        // FIXME: This shouldn't use NoReferrer, but the current documents url
        let request = RequestBuilder::new(url.clone().into(), Referrer::NoReferrer)
            .destination(Destination::Font);

        debug!("Loading @font-face {} from {}", web_font_family_name, url);
        let downloader = Self {
            font_context,
            url,
            web_font_family_name,
            response_valid: Mutex::new(false),
            response_data: Mutex::default(),
        };

        let core_resource_thread_clone = state.core_resource_thread.clone();
        fetch_async(
            &core_resource_thread_clone,
            request,
            None,
            Box::new(move |response_message| {
                match downloader.handle_web_font_fetch_message(response_message) {
                    DownloaderResponseResult::InProcess => {},
                    DownloaderResponseResult::Finished => {
                        if !downloader.process_downloaded_font_and_signal_completion(&state) {
                            downloader
                                .font_context
                                .process_next_web_font_source(state.clone())
                        }
                    },
                    DownloaderResponseResult::Failure => downloader
                        .font_context
                        .process_next_web_font_source(state.clone()),
                }
            }),
        )
    }

    /// After a download finishes, try to process the downloaded data, returning true if
    /// the font is added successfully to the [`FontContext`] or false if it isn't.
    fn process_downloaded_font_and_signal_completion(&self, state: &WebFontDownloadState) -> bool {
        if self
            .font_context
            .web_fonts
            .read()
            .font_load_cancelled_for_stylesheet(&state.stylesheet)
        {
            self.font_context
                .handle_web_font_load_finished(&state.finished_callback, false);
            // Returning true here prevents trying to load the next font on the source list.
            return true;
        }

        let font_data = std::mem::take(&mut *self.response_data.lock());
        trace!(
            "@font-face {} data={:?}",
            self.web_font_family_name,
            font_data
        );

        let font_data = match fontsan::process(&font_data) {
            Ok(bytes) => FontData::from_bytes(&bytes),
            Err(error) => {
                debug!(
                    "Sanitiser rejected web font: family={} url={:?} with {error:?}",
                    self.web_font_family_name, self.url,
                );
                return false;
            },
        };

        let url: ServoUrl = self.url.clone().into();
        let identifier = FontIdentifier::Web(url.clone());
        let Ok(handle) = PlatformFont::new_from_data(identifier, &font_data, None) else {
            return false;
        };
        let mut descriptor = handle.descriptor();
        descriptor
            .override_values_with_css_font_template_descriptors(&state.css_font_face_descriptors);

        let new_template = FontTemplate::new(
            FontIdentifier::Web(url),
            descriptor,
            Some(state.stylesheet.clone()),
        );
        self.font_context
            .font_data
            .write()
            .insert(new_template.identifier.clone(), font_data);

        let not_cancelled = self
            .font_context
            .web_fonts
            .write()
            .handle_web_font_loaded(state, new_template);
        self.font_context
            .handle_web_font_load_finished(&state.finished_callback, not_cancelled);

        // If the load was canceled above, then we still want to return true from this function in
        // order to halt any attempt to load sources that come later on the source list.
        true
    }

    fn handle_web_font_fetch_message(
        &self,
        response_message: FetchResponseMsg,
    ) -> DownloaderResponseResult {
        match response_message {
            FetchResponseMsg::ProcessRequestBody(..) | FetchResponseMsg::ProcessRequestEOF(..) => {
                DownloaderResponseResult::InProcess
            },
            FetchResponseMsg::ProcessResponse(_, meta_result) => {
                trace!(
                    "@font-face {} metadata ok={:?}",
                    self.web_font_family_name,
                    meta_result.is_ok()
                );
                *self.response_valid.lock() = meta_result.is_ok();
                DownloaderResponseResult::InProcess
            },
            FetchResponseMsg::ProcessResponseChunk(_, new_bytes) => {
                trace!(
                    "@font-face {} chunk={:?}",
                    self.web_font_family_name,
                    new_bytes
                );
                if *self.response_valid.lock() {
                    self.response_data.lock().extend(new_bytes)
                }
                DownloaderResponseResult::InProcess
            },
            FetchResponseMsg::ProcessResponseEOF(_, response) => {
                trace!(
                    "@font-face {} EOF={:?}",
                    self.web_font_family_name,
                    response
                );
                if response.is_err() || !*self.response_valid.lock() {
                    return DownloaderResponseResult::Failure;
                }
                DownloaderResponseResult::Finished
            },
        }
    }
}

#[derive(Debug, Eq, Hash, MallocSizeOf, PartialEq)]
struct FontCacheKey {
    font_identifier: FontIdentifier,
    font_descriptor: FontDescriptor,
}

#[derive(Debug, MallocSizeOf)]
struct FontGroupCacheKey {
    #[ignore_malloc_size_of = "This is also stored as part of styling."]
    style: ServoArc<FontStyleStruct>,
    size: Au,
}

impl PartialEq for FontGroupCacheKey {
    fn eq(&self, other: &FontGroupCacheKey) -> bool {
        self.style == other.style && self.size == other.size
    }
}

impl Eq for FontGroupCacheKey {}

impl Hash for FontGroupCacheKey {
    fn hash<H>(&self, hasher: &mut H)
    where
        H: Hasher,
    {
        self.style.hash.hash(hasher)
    }
}

fn is_supported_web_font_source(source: &&Source) -> bool {
    let url_source = match source {
        Source::Url(ref url_source) => url_source,
        Source::Local(_) => return true,
    };
    let format_hint = match url_source.format_hint {
        Some(ref format_hint) => format_hint,
        None => return true,
    };

    if matches!(
        format_hint,
        FontFaceSourceFormat::Keyword(
            FontFaceSourceFormatKeyword::Truetype |
                FontFaceSourceFormatKeyword::Opentype |
                FontFaceSourceFormatKeyword::Woff |
                FontFaceSourceFormatKeyword::Woff2
        )
    ) {
        return true;
    }

    if let FontFaceSourceFormat::String(string) = format_hint {
        return string == "truetype" ||
            string == "opentype" ||
            string == "woff" ||
            string == "woff2";
    }

    false
}