REGRESSION(265135@main): CSS filter is not applied on SVG element

https://bugs.webkit.org/show_bug.cgi?id=260152
rdar://114204485

Reviewed by Said Abou-Hallawa.

Before 265135@main, an SVG root with a filter specified as presentation attribute
(e.g: <svg filter="...">) was filtered twice instead of once: once by SVGRenderingContext,
and another by RenderLayer. 265135@main attempted to fix this by instructing RenderLayer
not to apply filters when rendering an SVG root. This caused a regression where an SVG root
with a filter specified using CSS filter property is not filtered, because SVGRenderingContext
is not responsible for apply CSS filters, and RenderLayer refuses to filter because it's an
SVG root. Fix the previous attempt by fixing SVGRenderingContext to not filter when rendering
an SVG root, so RenderLayer is now solely responsible for filtering SVG roots.

Test: LayoutTests/svg/filters/css-filter-specified-on-svg-root.html

* LayoutTests/svg/filters/css-filter-specified-on-svg-root-expected.html: Added.
* LayoutTests/svg/filters/css-filter-specified-on-svg-root.html: Added.
* Source/WebCore/rendering/RenderLayer.cpp:
(WebCore::RenderLayer::paintsWithFilters const):
(WebCore::RenderLayer::calculateClipRects const):
* Source/WebCore/rendering/svg/SVGRenderingContext.cpp:
(WebCore::SVGRenderingContext::prepareToRenderSVGContent):

Canonical link: https://commits.webkit.org/267236@main

LayoutTests/svg/filters/css-filter-specified-on-svg-root-expected.html

@@ -0,0 +1,10 @@
+<style>
+  #rect {
+    width: 100px;
+    height: 100px;
+    background-color: red;
+    filter: drop-shadow(10px 10px 0px green);
+  }
+</style>
+
+<div id="rect"></div>

LayoutTests/svg/filters/css-filter-specified-on-svg-root.html

@@ -0,0 +1,11 @@
+<style>
+  svg {
+    width: 100px;
+    height: 100px;
+    filter: drop-shadow(10px 10px 0px green);
+  }
+</style>
+
+<svg width="100" height="100">
+  <rect width="100" height="100" fill="red"/>
+</svg>

Source/WebCore/rendering/RenderLayer.cpp

@@ -886,11 +886,6 @@ bool RenderLayer::paintsWithFilters() const
     if (!hasFilter())
         return false;
 
-    // The SVG rendering codepath should've already applied the filter to the SVG root,
-    // so do not apply the filter again.
-    if (renderer().isSVGRootOrLegacySVGRoot())
-        return false;
-
     if (RenderLayerFilters::isIdentity(renderer()))
         return false;
 
@@ -5584,8 +5579,9 @@ void RenderLayer::updateFiltersAfterStyleChange(StyleDifference diff, const Rend
         return;
     }
 
-    // Add the filter as a client to this renderer.
-    if (renderer().style().filter().hasReferenceFilter()) {
+    // Add the filter as a client to this renderer, unless we are a RenderLayer accommodating
+    // an SVG. In that case it takes care of its own resource management for filters.
+    if (renderer().style().filter().hasReferenceFilter() && !renderer().isSVGRootOrLegacySVGRoot()) {
         ensureLayerFilters();
         m_filters->updateReferenceFilterClients(renderer().style().filter());
     } else if (m_filters)

Source/WebCore/rendering/svg/SVGRenderingContext.cpp

@@ -159,7 +159,9 @@ void SVGRenderingContext::prepareToRenderSVGContent(RenderElement& renderer, Pai
             return;
     }
 
-    if (!isRenderingMask) {
+    // SVG roots with filters specified (using CSS or SVG presentation attributes) are applied
+    // as CSSFilter by RenderLayer, so don't reapply the filter here.
+    if (!isRenderingMask && !renderer.isSVGRootOrLegacySVGRoot()) {
         m_filter = resources->filter();
         if (m_filter && !m_filter->isIdentity()) {
             m_savedContext = &m_paintInfo->context();