Rollup merge of #92764 - GuillaumeGomez:fix-rust-logo-style, r=jsha

Fix rust logo style

The style on the rust logo is currently broken:

![Screenshot from 2022-01-11 13-36-30](https://user-images.githubusercontent.com/3050060/148946754-a1a57253-bed0-44cf-a41c-83e0eecbd6b5.png)

With this fix, we're back to normal:

![Screenshot from 2022-01-11 13-42-07](https://user-images.githubusercontent.com/3050060/148946778-99f44678-aac1-419f-bb8c-ffa837e0c1ee.png)

I also used a GUI test to prevent future silent regressions.

r? ```@jsha```

src/librustdoc/html/static/css/themes/ayu.css

@@ -61,7 +61,7 @@ pre, .rustdoc.source .example-wrap {
 	background-color: #14191f;
 }
 
-.rust-logo > img {
+.rust-logo {
 	filter: drop-shadow(1px 0 0px #fff)
 		drop-shadow(0 1px 0 #fff)
 		drop-shadow(-1px 0 0 #fff)

src/librustdoc/html/static/css/themes/dark.css

@@ -32,7 +32,7 @@ pre, .rustdoc.source .example-wrap {
 	background-color: #505050;
 }
 
-.rust-logo > img {
+.rust-logo {
 	filter: drop-shadow(1px 0 0px #fff)
 		drop-shadow(0 1px 0 #fff)
 		drop-shadow(-1px 0 0 #fff)

src/librustdoc/html/static/css/themes/light.css

@@ -43,7 +43,7 @@ pre, .rustdoc.source .example-wrap {
 	scrollbar-color: rgba(36, 37, 39, 0.6) #d9d9d9;
 }
 
-.rust-logo > img {
+.rust-logo {
 	/* No need for a border in here! */
 }
 

src/test/rustdoc-gui/rust-logo.goml

@@ -0,0 +1,78 @@
+// This test ensures that the correct style is applied to the rust logo in the sidebar.
+goto: file://|DOC_PATH|/test_docs/index.html
+
+// First we start with the dark theme.
+local-storage: {
+    "rustdoc-theme": "dark",
+    "rustdoc-preferred-dark-theme": "dark",
+    "rustdoc-use-system-theme": "false",
+}
+reload:
+
+assert-css: (
+    ".rust-logo",
+    {"filter": "drop-shadow(rgb(255, 255, 255) 1px 0px 0px) drop-shadow(rgb(255, 255, 255) 0px 1px 0px) drop-shadow(rgb(255, 255, 255) -1px 0px 0px) drop-shadow(rgb(255, 255, 255) 0px -1px 0px)"},
+)
+
+// In the source view page now.
+goto: file://|DOC_PATH|/src/test_docs/lib.rs.html
+
+local-storage: {
+    "rustdoc-theme": "dark",
+    "rustdoc-preferred-dark-theme": "dark",
+    "rustdoc-use-system-theme": "false",
+}
+reload:
+
+assert-css: (
+    ".rust-logo",
+    {"filter": "drop-shadow(rgb(255, 255, 255) 1px 0px 0px) drop-shadow(rgb(255, 255, 255) 0px 1px 0px) drop-shadow(rgb(255, 255, 255) -1px 0px 0px) drop-shadow(rgb(255, 255, 255) 0px -1px 0px)"},
+)
+
+// Then with the ayu theme.
+local-storage: {
+    "rustdoc-theme": "ayu",
+    "rustdoc-preferred-dark-theme": "ayu",
+    "rustdoc-use-system-theme": "false",
+}
+reload:
+
+assert-css: (
+    ".rust-logo",
+    {"filter": "drop-shadow(rgb(255, 255, 255) 1px 0px 0px) drop-shadow(rgb(255, 255, 255) 0px 1px 0px) drop-shadow(rgb(255, 255, 255) -1px 0px 0px) drop-shadow(rgb(255, 255, 255) 0px -1px 0px)"},
+)
+
+// In the source view page now.
+goto: file://|DOC_PATH|/src/test_docs/lib.rs.html
+
+local-storage: {
+    "rustdoc-theme": "ayu",
+    "rustdoc-preferred-dark-theme": "ayu",
+    "rustdoc-use-system-theme": "false",
+}
+reload:
+
+assert-css: (
+    ".rust-logo",
+    {"filter": "drop-shadow(rgb(255, 255, 255) 1px 0px 0px) drop-shadow(rgb(255, 255, 255) 0px 1px 0px) drop-shadow(rgb(255, 255, 255) -1px 0px 0px) drop-shadow(rgb(255, 255, 255) 0px -1px 0px)"},
+)
+
+// And finally with the light theme.
+local-storage: {"rustdoc-theme": "light", "rustdoc-use-system-theme": "false"}
+reload:
+
+assert-css: (
+    ".rust-logo",
+    {"filter": "none"},
+)
+
+// In the source view page now.
+goto: file://|DOC_PATH|/src/test_docs/lib.rs.html
+
+local-storage: {"rustdoc-theme": "light", "rustdoc-use-system-theme": "false"}
+reload:
+
+assert-css: (
+    ".rust-logo",
+    {"filter": "none"},
+)