[LayoutNG] Pixel-snap column rules.

Bug: 829028 Change-Id: I252901109502256f14bc68e64d4303006db50a13 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1944350 Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org> Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org> Cr-Commit-Position: refs/heads/master@{#720302}

[LayoutNG] Pixel-snap column rules.
Bug: 829028 Change-Id: I252901109502256f14bc68e64d4303006db50a13 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1944350 Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org> Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org> Cr-Commit-Position: refs/heads/master@{#720302}
467dd283 · Morten Stenshorne · Commit Bot · 1320c3c6 · 467dd283 · 467dd283
Commit 467dd283 authored Nov 29, 2019 by Morten Stenshorne Committed by Commit Bot Nov 29, 2019
2 changed files
--- a/third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.cc
+++ b/third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.cc
@@ -904,9 +904,11 @@ void NGBoxFragmentPainter::PaintColumnRules(
    // specified and columns are balanced).

    rule.Move(paint_offset);
-    ObjectPainter::DrawLineForBoxSide(paint_info.context, rule.X(), rule.Y(),
-                                      rule.Right(), rule.Bottom(), box_side,
-                                      rule_color, rule_style, 0, 0, true);
+    IntRect snapped_rule = PixelSnappedIntRect(rule);
+    ObjectPainter::DrawLineForBoxSide(paint_info.context, snapped_rule.X(),
+                                      snapped_rule.Y(), snapped_rule.MaxX(),
+                                      snapped_rule.MaxY(), box_side, rule_color,
+                                      rule_style, 0, 0, true);

    previous_column = current_column;
  }

--- a/third_party/blink/web_tests/external/wpt/css/css-multicol/equal-gap-and-rule.html
+++ b/third_party/blink/web_tests/external/wpt/css/css-multicol/equal-gap-and-rule.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/#column-gaps-and-rules">
+<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:8; column-fill:auto; column-gap:5px; column-rule:5px solid green; width:100px; height:100px; background:red;">
+  <div style="height:800px; background:green;"></div>
+</div>