Honor min-block-size when calculating balanced column block-size.

We paid attention to block-size and max-block-size, but not min-block-size. Bug: 829028 Change-Id: Iad8920b7d46e3cd6b73645343d85ff9f1ee532dd Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2566750Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org> Commit-Queue: Morten Stenshorne <mstensho@chromium.org> Cr-Commit-Position: refs/heads/master@{#832225}

Honor min-block-size when calculating balanced column block-size.
We paid attention to block-size and max-block-size, but not min-block-size. Bug: 829028 Change-Id: Iad8920b7d46e3cd6b73645343d85ff9f1ee532dd Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2566750Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org> Commit-Queue: Morten Stenshorne <mstensho@chromium.org> Cr-Commit-Position: refs/heads/master@{#832225}
09c506b2 · Morten Stenshorne · Chromium LUCI CQ · 2f1a893e · 09c506b2 · 09c506b2
Commit 09c506b2 authored Dec 01, 2020 by Morten Stenshorne Committed by Chromium LUCI CQ Dec 01, 2020
2 changed files
--- a/third_party/blink/renderer/core/layout/ng/ng_column_layout_algorithm.cc
+++ b/third_party/blink/renderer/core/layout/ng/ng_column_layout_algorithm.cc
@@ -1004,11 +1004,16 @@ LayoutUnit NGColumnLayoutAlgorithm::ConstrainColumnBlockSize(
    extent = ResolveMainBlockLength(ConstraintSpace(), style, BorderPadding(),
                                    style.LogicalHeight(), kIndefiniteSize,
                                    LengthResolvePhase::kLayout);
+    // A specified block-size will just constrain the maximum length.
+    if (extent != kIndefiniteSize)
+      max = std::min(max, extent);
  }
-  if (extent != kIndefiniteSize) {
-    // A specified height/width will just constrain the maximum length.
-    max = std::min(max, extent);
-  }
+
+  // A specified min-block-size may increase the maximum length.
+  LayoutUnit min = ResolveMinBlockLength(
+      ConstraintSpace(), style, BorderPadding(), style.LogicalMinHeight(),
+      LengthResolvePhase::kLayout);
+  max = std::max(max, min);

  // If this multicol container is nested inside another fragmentation
  // context, we need to subtract the space consumed in previous fragments.

--- a/third_party/blink/web_tests/external/wpt/css/css-multicol/multicol-fill-balance-005.html
+++ b/third_party/blink/web_tests/external/wpt/css/css-multicol/multicol-fill-balance-005.html
+<!DOCTYPE html>
+<link rel="author" title="Morten Stenshorne" href="mailto:mstensho@chromium.org">
+<link rel="help" href="https://www.w3.org/TR/css-multicol-1/#filling-columns">
+<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
+<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+<div style="columns:2; column-gap:0; width:100px; height:20px; max-height:40px; min-height:100px; background:red;">
+  <div style="height:200px; background:green;"></div>
+</div>