[IFC] Incorrect box height when scrollbar takes padding box space

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[cathiechen]

Created attachment 425979 [details]
selection-crash.html

This issue occurs on the Debug building with LAYOUT_FORMATTING_CONTEXT enabled.
The code is updated to commit 80e1bf3d759003a97b3e676d78fca630407fdd35.

The test case contains inline-block box and text.
The height of body is 35px, but others are 24px.

It crashes when select the text.

Debug a bit:
  - During layout, in RenderBlockFlow::layoutInlineChildren, it uses layoutModernLines() to layout lines. The logical height is 35.
  - During select, in RenderBlockFlow::ensureLineBoxes, it calls complexLineLayout.layoutLineBoxes. The logical height is 24.
  - Then it fails `ASSERT(didNeedLayout || ceilf(logicalHeight()) == ceilf(oldHeight));` in RenderBlockFlow::ensureLineBoxes.

[zalan]

Created attachment 425983 [details]
(another)test case

[zalan]

Actually this is about the reserved space for always-on scrollbars (15px here in MiniBrowser -which explains the 11px diff (15px scrollbar - 4px descent))

[Radar WebKit Bug Importer]

<rdar://problem/76666402>

[zalan]

ok, so this is broken when the padding box can't accommodate the scrollbar.
this fixes the vertical aspect of it:

-    auto verticalSpaceReservedForScrollbar = std::min(replacedOrInlineBlock.height() - replacedOrInlineBlock.paddingBoxHeight(), LayoutUnit(replacedOrInlineBlock.horizontalScrollbarHeight()));
+    auto paddingBoxHeight = replacedOrInlineBlock.paddingBoxHeight();
+    auto horizontalScrollbarHeight = LayoutUnit { replacedOrInlineBlock.horizontalScrollbarHeight() };
+    auto verticalSpaceReservedForScrollbar = horizontalScrollbarHeight > paddingBoxHeight ? paddingBoxHeight : std::min(replacedOrInlineBlock.height() - paddingBoxHeight, horizontalScrollbarHeight);


will upload the patch tomorrow morning.

[zalan]

Created attachment 426095 [details]
Patch

[zalan]

Created attachment 426110 [details]
Patch

[EWS]

Committed r276135 (236629@main): <https://commits.webkit.org/236629@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 426110 [details].