// Copyright 2026 The Chromium Authors // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "third_party/blink/renderer/core/skeleton/skeleton_loader.h" #include "testing/gtest/include/gtest/gtest.h" #include "third_party/blink/renderer/core/css/style_engine.h" #include "third_party/blink/renderer/core/dom/document.h" #include "third_party/blink/renderer/core/dom/element.h" #include "third_party/blink/renderer/core/dom/pseudo_element.h" #include "third_party/blink/renderer/core/dom/shadow_root.h" #include "third_party/blink/renderer/core/html/html_document.h" #include "third_party/blink/renderer/core/html/html_html_element.h" #include "third_party/blink/renderer/core/layout/layout_object.h" #include "third_party/blink/renderer/core/testing/null_execution_context.h" #include "third_party/blink/renderer/core/testing/page_test_base.h" #include "third_party/blink/renderer/core/testing/sim/sim_request.h" #include "third_party/blink/renderer/core/testing/sim/sim_test.h" #include "third_party/blink/renderer/platform/testing/runtime_enabled_features_test_helpers.h" namespace blink { class SkeletonLoaderSimTest : public SimTest, public ScopedDeclarativeSkeletonsForTest { public: SkeletonLoaderSimTest() : ScopedDeclarativeSkeletonsForTest(true) {} protected: void SetUp() override { SimTest::SetUp(); // Start with a basic page load so we have a valid document structure. SimRequest main("https://example.com/", "text/html"); LoadURL("https://example.com/"); main.Complete(""); Compositor().BeginFrame(); } }; class SkeletonLoaderTest : public PageTestBase, public ScopedDeclarativeSkeletonsForTest { public: SkeletonLoaderTest() : ScopedDeclarativeSkeletonsForTest(true) {} protected: void InsertSkeletonTree(const String& source) { ScopedNullExecutionContext execution_context; HTMLDocument* skeleton_document = HTMLDocument::CreateForTest(execution_context.GetExecutionContext()); skeleton_document->SetContent(source); SkeletonLoader::Ensure(GetDocument()) .InsertSkeletonTree(*skeleton_document); } void RemoveSkeletonTree() { SkeletonLoader::Ensure(GetDocument()).RemoveSkeletonTree(); } }; TEST_F(SkeletonLoaderSimTest, Basic) { KURL next_page_url("https://example.com/page.html"); KURL skeleton_url("https://example.com/skeleton.html"); SimRequest::Params head_params; head_params.response_http_headers = { {http_names::kLink, "; rel=skeleton"}}; SimRequest next_page_head_request(next_page_url, "text/html", head_params); SimRequest skeleton_request(skeleton_url, "text/html"); Document& document = GetDocument(); SkeletonLoader& loader = SkeletonLoader::Ensure(document); loader.AddSkeletonPrefetchLink(next_page_url); // Check that the Document does not initially have a ::skeleton pseudo-element Element* root = document.documentElement(); ASSERT_NE(root, nullptr); EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); next_page_head_request.Complete(""); skeleton_request.Complete("

Skeleton

"); EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); loader.NavigateTo(next_page_url); Compositor().BeginFrame(); // Check that the Document now renders the skeleton PseudoElement* skeleton_pseudo = root->GetPseudoElement(kPseudoIdSkeleton); ASSERT_TRUE(skeleton_pseudo); ShadowRoot* shadow_root = skeleton_pseudo->GetShadowRoot(); ASSERT_TRUE(shadow_root); EXPECT_EQ(shadow_root->innerHTML(), "

Skeleton

"); // Call CancelNavigation() to remove the skeleton loader.CancelNavigation(); Compositor().BeginFrame(); // The Document should no longer have a ::skeleton pseudo-element EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); } TEST_F(SkeletonLoaderSimTest, SkeletonLoadsAfterNavigation) { KURL next_page_url("https://example.com/page.html"); KURL skeleton_url("https://example.com/skeleton.html"); SimRequest::Params head_params; head_params.response_http_headers = { {http_names::kLink, "; rel=skeleton"}}; SimRequest next_page_head_request(next_page_url, "text/html", head_params); SimRequest skeleton_request(skeleton_url, "text/html"); Document& document = GetDocument(); SkeletonLoader& loader = SkeletonLoader::Ensure(document); loader.AddSkeletonPrefetchLink(next_page_url); // Check that the Document does not initially have a ::skeleton pseudo-element Element* root = document.documentElement(); ASSERT_NE(root, nullptr); EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); loader.NavigateTo(next_page_url); // Navigation triggered, but skeleton still loading EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); next_page_head_request.Complete(""); skeleton_request.Complete("

Skeleton

"); Compositor().BeginFrame(); // Check that the Document now renders the skeleton PseudoElement* skeleton_pseudo = root->GetPseudoElement(kPseudoIdSkeleton); ASSERT_TRUE(skeleton_pseudo); ShadowRoot* shadow_root = skeleton_pseudo->GetShadowRoot(); ASSERT_TRUE(shadow_root); EXPECT_EQ(shadow_root->innerHTML(), "

Skeleton

"); } TEST_F(SkeletonLoaderSimTest, NoSkeletonLink) { KURL next_page_url("https://example.com/page.html"); SimRequest next_page_head_request(next_page_url, "text/html"); Document& document = GetDocument(); SkeletonLoader& loader = SkeletonLoader::Ensure(document); loader.AddSkeletonPrefetchLink(next_page_url); // Check that the Document does not initially have a ::skeleton pseudo-element Element* root = document.documentElement(); ASSERT_NE(root, nullptr); EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); next_page_head_request.Complete(""); loader.NavigateTo(next_page_url); // Navigation triggered, no Link header EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); } TEST_F(SkeletonLoaderSimTest, SkeletonLinkNotFound) { KURL next_page_url("https://example.com/page.html"); KURL skeleton_url("https://example.com/skeleton.html"); SimRequest::Params head_params; head_params.response_http_headers = { {http_names::kLink, "; rel=skeleton"}}; SimRequest next_page_head_request(next_page_url, "text/html", head_params); SimRequest::Params skeleton_params; skeleton_params.response_http_status = 404; SimRequest skeleton_request(skeleton_url, "text/html", skeleton_params); Document& document = GetDocument(); SkeletonLoader& loader = SkeletonLoader::Ensure(document); loader.AddSkeletonPrefetchLink(next_page_url); // Check that the Document does not initially have a ::skeleton pseudo-element Element* root = document.documentElement(); ASSERT_NE(root, nullptr); EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); next_page_head_request.Complete(""); skeleton_request.Complete(""); loader.NavigateTo(next_page_url); // Skeleton request failed, no skeleton should be rendered. EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); } TEST_F(SkeletonLoaderTest, PseudoElementRecalcRoot) { Element* root = GetDocument().documentElement(); UpdateAllLifecyclePhasesForTest(); EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); InsertSkeletonTree(R"HTML(

Skeleton

)HTML"); PseudoElement* skeleton_pseudo = root->GetPseudoElement(kPseudoIdSkeleton); ASSERT_TRUE(skeleton_pseudo); EXPECT_EQ(GetDocument().GetStyleEngine().style_recalc_root_.GetRootNode(), skeleton_pseudo); RemoveSkeletonTree(); EXPECT_EQ(root->GetPseudoElement(kPseudoIdSkeleton), nullptr); EXPECT_EQ(GetDocument().GetStyleEngine().style_recalc_root_.GetRootNode(), nullptr); } TEST_F(SkeletonLoaderTest, PropagateColorScheme) { UpdateAllLifecyclePhasesForTest(); InsertSkeletonTree( R"HTML(Skeleton)HTML"); UpdateAllLifecyclePhasesForTest(); const Element* root = GetDocument().documentElement(); const PseudoElement* pseudo = root->GetPseudoElement(kPseudoIdSkeleton); ASSERT_TRUE(pseudo); ASSERT_TRUE(pseudo->GetLayoutObject()); EXPECT_EQ(pseudo->GetLayoutObject()->StyleRef().UsedColorScheme(), blink::mojom::ColorScheme::kDark); } TEST_F(SkeletonLoaderTest, PropagateColorSchemeDynamic) { UpdateAllLifecyclePhasesForTest(); InsertSkeletonTree(R"HTML(Skeleton)HTML"); UpdateAllLifecyclePhasesForTest(); const Element* root = GetDocument().documentElement(); const PseudoElement* pseudo = root->GetPseudoElement(kPseudoIdSkeleton); ASSERT_TRUE(pseudo); ASSERT_TRUE(pseudo->GetLayoutObject()); EXPECT_EQ(pseudo->GetLayoutObject()->StyleRef().UsedColorScheme(), blink::mojom::ColorScheme::kLight); const ShadowRoot* shadow_root = pseudo->GetShadowRoot(); ASSERT_TRUE(shadow_root); Element* skeleton_root = To(shadow_root->firstChild()); skeleton_root->SetInlineStyleProperty(CSSPropertyID::kColorScheme, "dark"); UpdateAllLifecyclePhasesForTest(); EXPECT_EQ(pseudo->GetLayoutObject()->StyleRef().UsedColorScheme(), blink::mojom::ColorScheme::kDark); } TEST_F(SkeletonLoaderTest, InheritInitialPosition) { UpdateAllLifecyclePhasesForTest(); InsertSkeletonTree( R"HTML(Skeleton)HTML"); UpdateAllLifecyclePhasesForTest(); const Element* root = GetDocument().documentElement(); const PseudoElement* pseudo = root->GetPseudoElement(kPseudoIdSkeleton); ASSERT_TRUE(pseudo); const ShadowRoot* shadow_root = pseudo->GetShadowRoot(); ASSERT_TRUE(shadow_root); HTMLHtmlElement* skeleton_root = To(shadow_root->firstChild()); EXPECT_EQ(skeleton_root->ComputedStyleRef().GetPosition(), EPosition::kStatic); } } // namespace blink