Better handling border color style decoration

Source/core/paint/ObjectPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/ObjectPainter.h"
 
 #include "core/paint/DrawingRecorder.h"
 #include "core/rendering/PaintInfo.h"
 #include "core/rendering/RenderObject.h"
@@ skipping 116 matching lines @@
     case DOUBLE:
         drawDoubleBoxSide(graphicsContext, x1, y1, x2, y2, length, side, color,
             thickness, adjacentWidth1, adjacentWidth2, antialias);
         break;
     case RIDGE:
     case GROOVE:
         drawRidgeOrGrooveBoxSide(graphicsContext, x1, y1, x2, y2, side, color,
             style, adjacentWidth1, adjacentWidth2, antialias);
         break;
     case INSET:
-        // FIXME: Maybe we should lighten the colors on one side like Firefox.
-        // https://bugs.webkit.org/show_bug.cgi?id=58608
-        if (side == BSTop || side == BSLeft)
-            color = color.dark();
-        // fall through
     case OUTSET:
-        if (style == OUTSET && (side == BSBottom || side == BSRight))
-            color = color.dark();
+        calculateBorderStyleColor(style, side, color);
         // fall through
     case SOLID:
         drawSolidBoxSide(graphicsContext, x1, y1, x2, y2, side, color, adjacentWidth1, adjacentWidth2, antialias);
         break;
     }
 }
 
 void ObjectPainter::drawDashedOrDottedBoxSide(GraphicsContext* graphicsContext, int x1, int y1, int x2, int y2,
     BoxSide side, Color color, int thickness, EBorderStyle style, bool antialias)
 {
@@ skipping 183 matching lines @@
         quad[0] = FloatPoint(x1, y1 + std::max(adjacentWidth1, 0));
         quad[1] = FloatPoint(x1, y2 - std::max(adjacentWidth2, 0));
         quad[2] = FloatPoint(x2, y2 - std::max(-adjacentWidth2, 0));
         quad[3] = FloatPoint(x2, y1 + std::max(-adjacentWidth1, 0));
         break;
     }
 
     graphicsContext->fillPolygon(4, quad, color, antialias);
 }
 
+void ObjectPainter::calculateBorderStyleColor(const EBorderStyle& style, const BoxSide& side, Color& color)

[mstensho (USE GERRIT), 2014/11/27 09:33:29]

Should probably be called modifyBorderColorForStyleIfNeeded() or something like
that.

+{
+    const RGBA32 baseDarkColor = 0xFF202020;
+    const RGBA32 baseLightColor = 0xFFEBEBEB;
+
+    if ((side == BSTop || side == BSLeft)) {

[mstensho (USE GERRIT), 2014/11/27 09:33:29]

Extraneous pair of parentheses.

+        if (style == INSET) {
+            if (differenceSquared(color, Color::black) > differenceSquared(baseDarkColor, Color::black))
+                color = color.dark();
+        } else if (style == OUTSET) {
+            if (differenceSquared(color, Color::white) > differenceSquared(baseLightColor, Color::white))
+                color = color.light();
+        }
+    }
+
+    if ((side == BSBottom || side == BSRight)) {

[mstensho (USE GERRIT), 2014/11/27 09:33:29]

Should be "else if", or actually just "else" (I mean, are there more than those
four sides?) Also extraneous pair of parentheses.

But it strikes me that this block is very similar to the block above.

How about simplifying everything to:

enum Operation { Darken, Lighten };
Operation operation = (side == BSTop || side == BSLeft) == (style == INSET) ?
Darken : Lighten;
if (operation == Darken) {
    if (differenceSquared(color, Color::black) >
differenceSquared(baseDarkColor, Color::black))
        color = color.dark();
} else {
    if (differenceSquared(color, Color::white) >
differenceSquared(baseLightColor, Color::white))
        color = color.light();
}

+        if (style == INSET) {
+            if (differenceSquared(color, Color::white) > differenceSquared(baseLightColor, Color::white))
+                color = color.light();
+        } else if (style == OUTSET) {
+            if (differenceSquared(color, Color::black) > differenceSquared(baseDarkColor, Color::black))
+                color = color.dark();
+        }
+    }
+}
+
 } // namespace blink