Changeset 173868 in webkit for trunk/Source/WebCore/rendering/RenderGrid.cpp

Timestamp:

Sep 23, 2014, 1:37:10 AM (11 years ago)

Author:

svillar@igalia.com

Message:

[CSS Grid Layout] Do not grow tracks when the growth factor is 0
​https://bugs.webkit.org/show_bug.cgi?id=136575

Reviewed by Darin Adler.

A couple of performance optimizations for the track sizing
algorithm. On the one hand we avoid the computation of the
available logical space share if the track has no growth potential
(the current breadth is the maximum breadth) and on the other
hand, we avoid calling RenderGrid::distributeSpaceToTracks() if
the available logical space is not greater than 0.

The combined effect of these two changes is an impressive +16%
improvement in auto-grid-lots-of-data.html performance test.

No new tests as there is no change in the functionality.

• rendering/RenderGrid.cpp:

(WebCore::RenderGrid::resolveContentBasedTrackSizingFunctionsForItems):
(WebCore::RenderGrid::distributeSpaceToTracks):

File:

• trunk/Source/WebCore/rendering/RenderGrid.cpp (modified) (3 diffs)

trunk/Source/WebCore/rendering/RenderGrid.cpp

@@ -610 +610 @@
 
     // FIXME: We should pass different values for |tracksForGrowthAboveMaxBreadth|.
-    distributeSpaceToTracks(sizingData.filteredTracks, &sizingData.filteredTracks, trackGetter, trackGrowthFunction, sizingData, additionalBreadthSpace);
+    // Specs mandate to floor additionalBreadthSpace (extra-space in specs) to 0. Instead we directly avoid the function
+    // call in those cases as it will be a noop in terms of track sizing.
+    if (additionalBreadthSpace > 0)
+        distributeSpaceToTracks(sizingData.filteredTracks, &sizingData.filteredTracks, trackGetter, trackGrowthFunction, sizingData, additionalBreadthSpace);
 }
 
@@ -620 +623 @@
 void RenderGrid::distributeSpaceToTracks(Vector<GridTrack*>& tracks, Vector<GridTrack*>* tracksForGrowthAboveMaxBreadth, AccumulatorGetter trackGetter, AccumulatorGrowFunction trackGrowthFunction, GridSizingData& sizingData, LayoutUnit& availableLogicalSpace)
 {
+    ASSERT(availableLogicalSpace > 0);
     std::sort(tracks.begin(), tracks.end(), sortByGridTrackGrowthPotential);
 
@@ -627 +631 @@
     for (size_t i = 0; i < tracksSize; ++i) {
         GridTrack& track = *tracks[i];
-        LayoutUnit availableLogicalSpaceShare = availableLogicalSpace / (tracksSize - i);
         LayoutUnit trackBreadth = (tracks[i]->*trackGetter)();
-        LayoutUnit growthShare = std::max(LayoutUnit(), std::min(availableLogicalSpaceShare, track.m_maxBreadth - trackBreadth));
-        // We should never shrink any grid track or else we can't guarantee we abide by our min-sizing function.
-        sizingData.distributeTrackVector[i] = trackBreadth + growthShare;
-        availableLogicalSpace -= growthShare;
+        LayoutUnit trackGrowthPotential = track.m_maxBreadth - trackBreadth;
+        sizingData.distributeTrackVector[i] = trackBreadth;
+        if (trackGrowthPotential > 0) {
+            LayoutUnit availableLogicalSpaceShare = availableLogicalSpace / (tracksSize - i);
+            LayoutUnit growthShare = std::min(availableLogicalSpaceShare, trackGrowthPotential);
+            // We should never shrink any grid track or else we can't guarantee we abide by our min-sizing function.
+            sizingData.distributeTrackVector[i] += growthShare;
+            availableLogicalSpace -= growthShare;
+        }
     }