Paint dotted borders using circular dots

third_party/WebKit/Source/platform/graphics/GraphicsContext.cpp

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 486 matching lines @@
   bool isVerticalLine = (p1.x() == p2.x());
   int width = roundf(strokeThickness());
 
   // We know these are vertical or horizontal lines, so the length will just
   // be the sum of the displacement component vectors give or take 1 -
   // probably worth the speed up of no square root, which also won't be exact.
   FloatSize disp = p2 - p1;
   int length = SkScalarRoundToInt(disp.width() + disp.height());
   PaintFlags flags(immutableState()->strokeFlags(length));
 
-  if (getStrokeStyle() == DottedStroke || getStrokeStyle() == DashedStroke) {
+  if (getStrokeStyle() == DashedStroke ||
+      (getStrokeStyle() == DottedStroke && width <= 3)) {

[f(malita), 2017/03/03 15:34:08]

Same question about 3.

     // Do a rect fill of our endpoints.  This ensures we always have the
-    // appearance of being a border.  We then draw the actual dotted/dashed
+    // appearance of being a border. We then draw the actual dotted/dashed
     // line.
     SkRect r1, r2;
     r1.set(p1.x(), p1.y(), p1.x() + width, p1.y() + width);
     r2.set(p2.x(), p2.y(), p2.x() + width, p2.y() + width);
 
     if (isVerticalLine) {
       r1.offset(-width / 2, 0);
       r2.offset(-width / 2, -width);
     } else {
       r1.offset(0, -width / 2);
       r2.offset(-width, -width / 2);
     }
     PaintFlags fillFlags;
     fillFlags.setColor(flags.getColor());
     drawRect(r1, fillFlags);
     drawRect(r2, fillFlags);
+  } else if (getStrokeStyle() == DottedStroke) {
+    // We draw thick dotted lines with 0 length dash strokes and round endcaps,
+    // producing circles. The endcaps extend beyond the line's endpoints,
+    // so move the start and end in.
+    if (isVerticalLine) {
+      p1.setY(p1.y() + width / 2.f);
+      p2.setY(p2.y() - width / 2.f);
+    } else {
+      p1.setX(p1.x() + width / 2.f);
+      p2.setX(p2.x() - width / 2.f);
+    }
   }
 
   adjustLineToPixelBoundaries(p1, p2, width, penStyle);
   m_canvas->drawLine(p1.x(), p1.y(), p2.x(), p2.y(), flags);
 }
 
 namespace {
 
 #if !OS(MACOSX)
 
@@ skipping 758 matching lines @@
 
 void GraphicsContext::adjustLineToPixelBoundaries(FloatPoint& p1,
                                                   FloatPoint& p2,
                                                   float strokeWidth,
                                                   StrokeStyle penStyle) {
   // For odd widths, we add in 0.5 to the appropriate x/y so that the float
   // arithmetic works out.  For example, with a border width of 3, WebKit will
   // pass us (y1+y2)/2, e.g., (50+53)/2 = 103/2 = 51 when we want 51.5.  It is
   // always true that an even width gave us a perfect position, but an odd width
   // gave us a position that is off by exactly 0.5.
-  if (penStyle == DottedStroke || penStyle == DashedStroke) {
+  if (penStyle == DashedStroke ||
+      (penStyle == DottedStroke && strokeWidth <= 3)) {

[f(malita), 2017/03/03 15:34:08]

Same.  Let's at least add a helper to encapsulate this logic
(shouldBeDashed()?).

[Stephen Chennney, 2017/03/03 22:19:23]

Helper done.

     if (p1.x() == p2.x()) {
       p1.setY(p1.y() + strokeWidth);
       p2.setY(p2.y() - strokeWidth);
     } else {
       p1.setX(p1.x() + strokeWidth);
       p2.setX(p2.x() - strokeWidth);
     }
   }
 
   if (static_cast<int>(strokeWidth) % 2) {  // odd
@@ skipping 24 matching lines @@
       break;
     default:
       NOTREACHED();
       break;
   }
 
   return nullptr;
 }
 
 }  // namespace blink