Bug 75508 – Analyze stylesheet scope to minimize style recalcs

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

[Antti Koivisto]

It is a relatively common pattern to use inline stylesheets in document body where all rules are scoped using descendant selector

<style>
#foo {...}
#foo div {...}
#foo .bar {...}
</style>

When this pattern is used it is also common that the rules only apply to elements that come after the style element. 

When the set of active stylesheets changes we invalidate and recompute the entire document style. This is very expensive.  We can detect the case above and avoid the style recalc.

[Antti Koivisto]

Created attachment 121038 [details]
patch

On engadget.com, this patch cuts the time spent in style recalcs to roughly half. There are further savings from reduced relayouts. In total the engine CPU time used over the page load is reduced by ~10%.

[WebKit Review Bot]

Comment on attachment 121038 [details]
patch

Attachment 121038 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/11082256

[Antti Koivisto]

Created attachment 121113 [details]
Chromium build fix plus some cleanups

[Antti Koivisto]

Created attachment 121115 [details]
update to tot

[Dave Hyatt]

Comment on attachment 121115 [details]
update to tot

I think RecalcStyleOnlyifNeeded would be better than PendingStylesheetCompleted.

r=me

[Antti Koivisto]

<rdar://problem/10643107>

[Antti Koivisto]

http://trac.webkit.org/changeset/104060

[Philippe Normand]

(In reply to comment #7)
> http://trac.webkit.org/changeset/104060

It seems this patch broke a test in GTK: http://build.webkit.org/results/GTK%20Linux%2064-bit%20Release/r104153%20(15719)/fast/forms/textarea-metrics-diff.txt

--- /home/slave/webkitgtk/gtk-linux-64-release/build/layout-test-results/fast/forms/textarea-metrics-expected.txt 
+++ /home/slave/webkitgtk/gtk-linux-64-release/build/layout-test-results/fast/forms/textarea-metrics-actual.txt 
@@ -88,84 +88,84 @@
 
 Testing CSS1Compat document.
 Properties = none
-PASS CSS1Compatdoc.getElementById('no-styles').clientWidth is 54
-PASS CSS1Compatdoc.getElementById('no-styles').clientHeight is 54
-PASS CSS1Compatdoc.getElementById('no-styles').offsetWidth is 56
-PASS CSS1Compatdoc.getElementById('no-styles').offsetHeight is 56
-PASS CSS1Compatdoc.getElementById('no-styles').scrollWidth is 54
-PASS CSS1Compatdoc.getElementById('no-styles').scrollHeight is 54
+FAIL CSS1Compatdoc.getElementById('no-styles').clientWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('no-styles').clientHeight should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('no-styles').offsetWidth should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('no-styles').offsetHeight should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('no-styles').scrollWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('no-styles').scrollHeight should be 54. Was 48.
 
 Properties = disabled: "true",
-PASS CSS1Compatdoc.getElementById('-disabled-true-').clientWidth is 54
-PASS CSS1Compatdoc.getElementById('-disabled-true-').clientHeight is 54
-PASS CSS1Compatdoc.getElementById('-disabled-true-').offsetWidth is 56
-PASS CSS1Compatdoc.getElementById('-disabled-true-').offsetHeight is 56
-PASS CSS1Compatdoc.getElementById('-disabled-true-').scrollWidth is 54
-PASS CSS1Compatdoc.getElementById('-disabled-true-').scrollHeight is 54
+FAIL CSS1Compatdoc.getElementById('-disabled-true-').clientWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-disabled-true-').clientHeight should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-disabled-true-').offsetWidth should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-disabled-true-').offsetHeight should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-disabled-true-').scrollWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-disabled-true-').scrollHeight should be 54. Was 48.
 
 Properties = innerHTML: "A",
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-').clientWidth is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-').clientHeight is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-').offsetWidth is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-').offsetHeight is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-').scrollWidth is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-').scrollHeight is 54
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-').clientWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-').clientHeight should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-').offsetWidth should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-').offsetHeight should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-').scrollWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-').scrollHeight should be 54. Was 48.
 
 Properties = innerHTML: "AAAAAAAAA",
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').clientWidth is 37
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').clientHeight is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').offsetWidth is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').offsetHeight is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').scrollWidth is 37
-FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').scrollHeight should be 64. Was 104.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').clientWidth should be 37. Was 31.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').clientHeight should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').offsetWidth should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').offsetHeight should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').scrollWidth should be 37. Was 31.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-').scrollHeight should be 64. Was 184.
 
 Properties = innerHTML: "A", disabled: "true",
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').clientWidth is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').clientHeight is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').offsetWidth is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').offsetHeight is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').scrollWidth is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').scrollHeight is 54
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').clientWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').clientHeight should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').offsetWidth should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').offsetHeight should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').scrollWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-disabled-true-').scrollHeight should be 54. Was 48.
 
 Properties = innerHTML: "AAAAAAAAA", disabled: "true",
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').clientWidth is 37
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').clientHeight is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').offsetWidth is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').offsetHeight is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').scrollWidth is 37
-FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').scrollHeight should be 64. Was 104.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').clientWidth should be 37. Was 31.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').clientHeight should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').offsetWidth should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').offsetHeight should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').scrollWidth should be 37. Was 31.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-disabled-true-').scrollHeight should be 64. Was 184.
 
 Properties = innerHTML: "A", style: "padding:8px",
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').clientWidth is 66
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').clientHeight is 66
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').offsetWidth is 68
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').offsetHeight is 68
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').scrollWidth is 66
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').scrollHeight is 66
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').clientWidth should be 66. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').clientHeight should be 66. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').offsetWidth should be 68. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').offsetHeight should be 68. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').scrollWidth should be 66. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-style-padding-8px-').scrollHeight should be 66. Was 48.
 
 Properties = innerHTML: "AAAAAAAAA", style: "padding:8px",
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').clientWidth is 49
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').clientHeight is 66
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').offsetWidth is 68
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').offsetHeight is 68
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').scrollWidth is 49
-FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').scrollHeight should be 76. Was 116.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').clientWidth should be 49. Was 31.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').clientHeight should be 66. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').offsetWidth should be 68. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').offsetHeight should be 68. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').scrollWidth should be 49. Was 31.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-style-padding-8px-').scrollHeight should be 76. Was 196.
 
 Properties = innerHTML: "A", rows: "10",
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').clientWidth is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').clientHeight is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').offsetWidth is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').offsetHeight is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').scrollWidth is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').scrollHeight is 54
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').clientWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').clientHeight should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').offsetWidth should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').offsetHeight should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').scrollWidth should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-A-rows-10-').scrollHeight should be 54. Was 48.
 
 Properties = innerHTML: "AAAAAAAAA", rows: "10",
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').clientWidth is 37
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').clientHeight is 54
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').offsetWidth is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').offsetHeight is 56
-PASS CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').scrollWidth is 37
-FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').scrollHeight should be 64. Was 104.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').clientWidth should be 37. Was 31.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').clientHeight should be 54. Was 48.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').offsetWidth should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').offsetHeight should be 56. Was 50.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').scrollWidth should be 37. Was 31.
+FAIL CSS1Compatdoc.getElementById('-innerHTML-AAAAAAAAA-rows-10-').scrollHeight should be 64. Was 184.
 
 PASS successfullyParsed is true

[Antti Koivisto]

Filed bug 75644: REGRESSION (r104060): fast/forms/textarea-metrics.html.

Philippe, next time please file a new bug instead of pasting stuff to the bug you think is causing the regression.

[Philippe Wittenbergh]

Did this cause bug 75772 ?

[Mihai Parparita]

FWIW, this causes http://crbug.com/109888. I'll see if I can create a reduced test case, and file a separate bug.

[Mihai Parparita]

(In reply to comment #11)
> FWIW, this causes http://crbug.com/109888. I'll see if I can create a reduced test case, and file a separate bug.

I filed https://bugs.webkit.org/show_bug.cgi?id=76590