[IFC][Ruby] Line spacing is not even for contents that has ruby

https://bugs.webkit.org/show_bug.cgi?id=271295
<rdar://122436686>

Reviewed by Antti Koivisto.

Let annotation spill into previous/next line's half-leading to keep vertical (horizontal) rhythm (i.e. do not stretch lines with ruby too much even if it means overlapping adjacent line boxes).

* LayoutTests/fast/ruby/tight-line-spacing-with-line-height-expected.html: Added.
* LayoutTests/fast/ruby/tight-line-spacing-with-line-height.html: Added.
* Source/WebCore/layout/formattingContexts/inline/ruby/RubyFormattingContext.cpp:
(WebCore::Layout::RubyFormattingContext::adjustLayoutBoundsAndStretchAncestorRubyBase):

Canonical link: https://commits.webkit.org/276402@main

LayoutTests/fast/ruby/tight-line-spacing-with-line-height-expected.html

@@ -0,0 +1,17 @@
+<style>
+div {
+  padding-top: 5px;
+  padding-bottom: 5px;
+  line-height: 16px;
+  font-size: 16px;
+  font-family: Ahem;
+  width: 150px;
+  outline: 1px solid blue;
+}
+rt {
+  font-size: 16px;
+}
+</style>
+<div>X<br>X<br>X<br></div>
+
+<pre>PASS if annotation tightly fits.</pre>

LayoutTests/fast/ruby/tight-line-spacing-with-line-height.html

@@ -0,0 +1,15 @@
+<style>
+div {
+  line-height: 26px;
+  font-size: 16px;
+  font-family: Ahem;
+  width: 150px;
+  outline: 1px solid blue;
+}
+rt {
+  font-size: 16px;
+}
+</style>
+<div>X<br><ruby>X<rt>x</rt></ruby></div>
+
+<pre>PASS if annotation tightly fits.</pre>

LayoutTests/platform/ios/TestExpectations

@@ -4676,6 +4676,7 @@ imported/w3c/web-platform-tests/css/css-ruby/ruby-text-combine-upright-002a.html
 imported/w3c/web-platform-tests/css/css-ruby/ruby-text-combine-upright-002b.html [ ImageOnlyFailure ]
 imported/w3c/web-platform-tests/css/css-ruby/line-break-around-ruby-001.html [ Failure ]
 fast/ruby/annotation-with-line-gap.html [ ImageOnlyFailure ]
+fast/ruby/tight-line-spacing-with-line-height.html [ ImageOnlyFailure ]
 
 webkit.org/b/264001 [ Debug ] imported/w3c/web-platform-tests/requestidlecallback/callback-multiple-calls.html [ Pass Failure ]
 

Source/WebCore/layout/formattingContexts/inline/ruby/RubyFormattingContext.cpp

@@ -416,7 +416,8 @@ void RubyFormattingContext::adjustLayoutBoundsAndStretchAncestorRubyBase(LineBox
     auto over = InlineLayoutUnit { };
     auto under = InlineLayoutUnit { };
     auto annotationBoxLogicalHeight = InlineLayoutUnit { inlineFormattingContext.geometryForBox(*annotationBox).marginBoxHeight() };
-    if (rubyPosition(rubyBaseLayoutBox) == RubyPosition::Before)
+    auto isAnnotationBefore = rubyPosition(rubyBaseLayoutBox) == RubyPosition::Before;
+    if (isAnnotationBefore)
         over = annotationBoxLogicalHeight;
     else
         under = annotationBoxLogicalHeight;
@@ -453,8 +454,13 @@ void RubyFormattingContext::adjustLayoutBoundsAndStretchAncestorRubyBase(LineBox
             layoutBounds.descent = std::max(descentWithAnnotation, layoutBounds.descent);
         } else if (layoutBounds.height() < ascentWithAnnotation + descentWithAnnotation) {
             // In case line-height does not produce enough space for annotation.
-            layoutBounds.ascent = std::max(ascentWithAnnotation, layoutBounds.ascent);
-            layoutBounds.descent = std::max(descentWithAnnotation, layoutBounds.descent);
+            auto extraSpaceNeededForAnnotation = (ascentWithAnnotation + descentWithAnnotation) - layoutBounds.height();
+            // Note that this makes annotation leak into previous/next line's (bottom/top) half leading. It ensures though that we don't
+            // overly stretch lines and break (logical) vertical rhythm too much.
+            if (isAnnotationBefore)
+                layoutBounds.ascent += extraSpaceNeededForAnnotation;
+            else
+                layoutBounds.descent += extraSpaceNeededForAnnotation;
         }
     }