Incorrect inline box decoration position when content box is vertical…

…ly shifted (text-underline-position/vertical edition)

https://bugs.webkit.org/show_bug.cgi?id=245316
<rdar://problem/100071411>

Reviewed by Simon Fraser.

This is a follow-up on 254554@main (https://commits.webkit.org/254554@main) where an inline box with vertical border/padding produces incorrect underline position.
This patch addresses both the vertical (ideographic baseline) and the "text-underline-position: under" cases where we use the inline box's logical height to compute the underline offset.

* LayoutTests/fast/inline/text-decoration-underline-inline-box-offset-expected.html: Added.
* LayoutTests/fast/inline/text-decoration-underline-inline-box-offset.html: Added.
* Source/WebCore/style/InlineTextBoxStyle.cpp: use the inline box's content box to compute the underline offset.
(WebCore::underlineOffsetForTextBoxPainting):

Canonical link: https://commits.webkit.org/254593@main

LayoutTests/fast/inline/text-decoration-underline-inline-box-offset-expected.html

@@ -0,0 +1,19 @@
+<style>
+div {
+  font-family: Monospace;
+  font-size: 40px;
+  margin: 50px;
+}
+span {
+  text-decoration: underline;
+  border: 20px solid transparent;
+  padding: 30px;
+}
+.vertical {
+  writing-mode: vertical-lr;
+  text-underline-position: under;
+  text-underline-offset: -10px;
+}
+</style>
+<div><span>XXX</span></div>
+<div class=vertical><span>XXX</span></div>

LayoutTests/fast/inline/text-decoration-underline-inline-box-offset.html

@@ -0,0 +1,16 @@
+<style>
+div {
+  font-family: Monospace;
+  font-size: 40px;
+  margin: 50px;
+}
+span {
+  text-decoration: underline;
+  text-underline-position: under;
+  text-underline-offset: -10px;
+  border: 20px solid transparent;
+  padding: 30px;
+}
+</style>
+<div><span>XXX</span></div>
+<div style="writing-mode: vertical-lr"><span>XXX</span></div>

Source/WebCore/style/InlineTextBoxStyle.cpp

@@ -307,7 +307,10 @@ float underlineOffsetForTextBoxPainting(const InlineIterator::InlineBox& inlineB
 
     if (underlinePositionValue == TextUnderlinePosition::Under) {
         auto textRunOffset = boxOffsetFromBottomMost(inlineBox.lineBox(), inlineBox.renderer(), inlineBox.logicalTop(), inlineBox.logicalBottom());
-        textUnderlinePositionUnder = TextUnderlinePositionUnder { inlineBox.logicalHeight(), textRunOffset };
+        auto inlineBoxContentBoxHeight = inlineBox.logicalHeight();
+        if (!inlineBox.isRootInlineBox())
+            inlineBoxContentBoxHeight -= (inlineBox.renderer().borderAndPaddingBefore() + inlineBox.renderer().borderAndPaddingAfter());
+        textUnderlinePositionUnder = TextUnderlinePositionUnder { inlineBoxContentBoxHeight, textRunOffset };
     }
 
     return computedUnderlineOffset({ style, underlinePositionValue, defaultGap(style), textUnderlinePositionUnder });