Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 290 insertions, 0 deletions

diff --git a/gfx/2d/PathHelpers.cpp b/gfx/2d/PathHelpers.cpp
new file mode 100644
index 0000000000..66fce104b3
--- /dev/null
+++ b/gfx/2d/PathHelpers.cpp
@@ -0,0 +1,290 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "PathHelpers.h"
+
+namespace mozilla {
+namespace gfx {
+
+UserDataKey sDisablePixelSnapping;
+
+void AppendRectToPath(PathBuilder* aPathBuilder, const Rect& aRect,
+                      bool aDrawClockwise) {
+  if (aDrawClockwise) {
+    aPathBuilder->MoveTo(aRect.TopLeft());
+    aPathBuilder->LineTo(aRect.TopRight());
+    aPathBuilder->LineTo(aRect.BottomRight());
+    aPathBuilder->LineTo(aRect.BottomLeft());
+  } else {
+    aPathBuilder->MoveTo(aRect.TopRight());
+    aPathBuilder->LineTo(aRect.TopLeft());
+    aPathBuilder->LineTo(aRect.BottomLeft());
+    aPathBuilder->LineTo(aRect.BottomRight());
+  }
+  aPathBuilder->Close();
+}
+
+void AppendRoundedRectToPath(PathBuilder* aPathBuilder, const Rect& aRect,
+                             const RectCornerRadii& aRadii, bool aDrawClockwise,
+                             const Maybe<Matrix>& aTransform) {
+  // For CW drawing, this looks like:
+  //
+  //  ...******0**      1    C
+  //              ****
+  //                  ***    2
+  //                     **
+  //                       *
+  //                        *
+  //                         3
+  //                         *
+  //                         *
+  //
+  // Where 0, 1, 2, 3 are the control points of the Bezier curve for
+  // the corner, and C is the actual corner point.
+  //
+  // At the start of the loop, the current point is assumed to be
+  // the point adjacent to the top left corner on the top
+  // horizontal.  Note that corner indices start at the top left and
+  // continue clockwise, whereas in our loop i = 0 refers to the top
+  // right corner.
+  //
+  // When going CCW, the control points are swapped, and the first
+  // corner that's drawn is the top left (along with the top segment).
+  //
+  // There is considerable latitude in how one chooses the four
+  // control points for a Bezier curve approximation to an ellipse.
+  // For the overall path to be continuous and show no corner at the
+  // endpoints of the arc, points 0 and 3 must be at the ends of the
+  // straight segments of the rectangle; points 0, 1, and C must be
+  // collinear; and points 3, 2, and C must also be collinear.  This
+  // leaves only two free parameters: the ratio of the line segments
+  // 01 and 0C, and the ratio of the line segments 32 and 3C.  See
+  // the following papers for extensive discussion of how to choose
+  // these ratios:
+  //
+  //   Dokken, Tor, et al. "Good approximation of circles by
+  //      curvature-continuous Bezier curves."  Computer-Aided
+  //      Geometric Design 7(1990) 33--41.
+  //   Goldapp, Michael. "Approximation of circular arcs by cubic
+  //      polynomials." Computer-Aided Geometric Design 8(1991) 227--238.
+  //   Maisonobe, Luc. "Drawing an elliptical arc using polylines,
+  //      quadratic, or cubic Bezier curves."
+  //      http://www.spaceroots.org/documents/ellipse/elliptical-arc.pdf
+  //
+  // We follow the approach in section 2 of Goldapp (least-error,
+  // Hermite-type approximation) and make both ratios equal to
+  //
+  //          2   2 + n - sqrt(2n + 28)
+  //  alpha = - * ---------------------
+  //          3           n - 4
+  //
+  // where n = 3( cbrt(sqrt(2)+1) - cbrt(sqrt(2)-1) ).
+  //
+  // This is the result of Goldapp's equation (10b) when the angle
+  // swept out by the arc is pi/2, and the parameter "a-bar" is the
+  // expression given immediately below equation (21).
+  //
+  // Using this value, the maximum radial error for a circle, as a
+  // fraction of the radius, is on the order of 0.2 x 10^-3.
+  // Neither Dokken nor Goldapp discusses error for a general
+  // ellipse; Maisonobe does, but his choice of control points
+  // follows different constraints, and Goldapp's expression for
+  // 'alpha' gives much smaller radial error, even for very flat
+  // ellipses, than Maisonobe's equivalent.
+  //
+  // For the various corners and for each axis, the sign of this
+  // constant changes, or it might be 0 -- it's multiplied by the
+  // appropriate multiplier from the list before using.
+
+  const Float alpha = Float(0.55191497064665766025);
+
+  typedef struct {
+    Float a, b;
+  } twoFloats;
+
+  twoFloats cwCornerMults[4] = {{-1, 0},  // cc == clockwise
+                                {0, -1},
+                                {+1, 0},
+                                {0, +1}};
+  twoFloats ccwCornerMults[4] = {{+1, 0},  // ccw == counter-clockwise
+                                 {0, -1},
+                                 {-1, 0},
+                                 {0, +1}};
+
+  twoFloats* cornerMults = aDrawClockwise ? cwCornerMults : ccwCornerMults;
+
+  Point cornerCoords[] = {aRect.TopLeft(), aRect.TopRight(),
+                          aRect.BottomRight(), aRect.BottomLeft()};
+
+  Point pc, p0, p1, p2, p3;
+
+  if (aDrawClockwise) {
+    Point pt(aRect.X() + aRadii[eCornerTopLeft].width, aRect.Y());
+    if (aTransform) {
+      pt = aTransform->TransformPoint(pt);
+    }
+    aPathBuilder->MoveTo(pt);
+  } else {
+    Point pt(aRect.X() + aRect.Width() - aRadii[eCornerTopRight].width,
+             aRect.Y());
+    if (aTransform) {
+      pt = aTransform->TransformPoint(pt);
+    }
+    aPathBuilder->MoveTo(pt);
+  }
+
+  for (int i = 0; i < 4; ++i) {
+    // the corner index -- either 1 2 3 0 (cw) or 0 3 2 1 (ccw)
+    int c = aDrawClockwise ? ((i + 1) % 4) : ((4 - i) % 4);
+
+    // i+2 and i+3 respectively.  These are used to index into the corner
+    // multiplier table, and were deduced by calculating out the long form
+    // of each corner and finding a pattern in the signs and values.
+    int i2 = (i + 2) % 4;
+    int i3 = (i + 3) % 4;
+
+    pc = cornerCoords[c];
+
+    if (aRadii[c].width > 0.0 && aRadii[c].height > 0.0) {
+      p0.x = pc.x + cornerMults[i].a * aRadii[c].width;
+      p0.y = pc.y + cornerMults[i].b * aRadii[c].height;
+
+      p3.x = pc.x + cornerMults[i3].a * aRadii[c].width;
+      p3.y = pc.y + cornerMults[i3].b * aRadii[c].height;
+
+      p1.x = p0.x + alpha * cornerMults[i2].a * aRadii[c].width;
+      p1.y = p0.y + alpha * cornerMults[i2].b * aRadii[c].height;
+
+      p2.x = p3.x - alpha * cornerMults[i3].a * aRadii[c].width;
+      p2.y = p3.y - alpha * cornerMults[i3].b * aRadii[c].height;
+
+      if (aTransform.isNothing()) {
+        aPathBuilder->LineTo(p0);
+        aPathBuilder->BezierTo(p1, p2, p3);
+      } else {
+        const Matrix& transform = *aTransform;
+        aPathBuilder->LineTo(transform.TransformPoint(p0));
+        aPathBuilder->BezierTo(transform.TransformPoint(p1),
+                               transform.TransformPoint(p2),
+                               transform.TransformPoint(p3));
+      }
+    } else {
+      if (aTransform.isNothing()) {
+        aPathBuilder->LineTo(pc);
+      } else {
+        aPathBuilder->LineTo(aTransform->TransformPoint(pc));
+      }
+    }
+  }
+
+  aPathBuilder->Close();
+}
+
+void AppendEllipseToPath(PathBuilder* aPathBuilder, const Point& aCenter,
+                         const Size& aDimensions) {
+  Size halfDim = aDimensions / 2.f;
+  Rect rect(aCenter - Point(halfDim.width, halfDim.height), aDimensions);
+  RectCornerRadii radii(halfDim.width, halfDim.height);
+
+  AppendRoundedRectToPath(aPathBuilder, rect, radii);
+}
+
+bool SnapLineToDevicePixelsForStroking(Point& aP1, Point& aP2,
+                                       const DrawTarget& aDrawTarget,
+                                       Float aLineWidth) {
+  Matrix mat = aDrawTarget.GetTransform();
+  if (mat.HasNonTranslation()) {
+    return false;
+  }
+  if (aP1.x != aP2.x && aP1.y != aP2.y) {
+    return false;  // not a horizontal or vertical line
+  }
+  Point p1 = aP1 + mat.GetTranslation();  // into device space
+  Point p2 = aP2 + mat.GetTranslation();
+  p1.Round();
+  p2.Round();
+  p1 -= mat.GetTranslation();  // back into user space
+  p2 -= mat.GetTranslation();
+
+  aP1 = p1;
+  aP2 = p2;
+
+  bool lineWidthIsOdd = (int(aLineWidth) % 2) == 1;
+  if (lineWidthIsOdd) {
+    if (aP1.x == aP2.x) {
+      // snap vertical line, adding 0.5 to align it to be mid-pixel:
+      aP1 += Point(0.5, 0);
+      aP2 += Point(0.5, 0);
+    } else {
+      // snap horizontal line, adding 0.5 to align it to be mid-pixel:
+      aP1 += Point(0, 0.5);
+      aP2 += Point(0, 0.5);
+    }
+  }
+  return true;
+}
+
+void StrokeSnappedEdgesOfRect(const Rect& aRect, DrawTarget& aDrawTarget,
+                              const ColorPattern& aColor,
+                              const StrokeOptions& aStrokeOptions) {
+  if (aRect.IsEmpty()) {
+    return;
+  }
+
+  Point p1 = aRect.TopLeft();
+  Point p2 = aRect.BottomLeft();
+  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget,
+                                    aStrokeOptions.mLineWidth);
+  aDrawTarget.StrokeLine(p1, p2, aColor, aStrokeOptions);
+
+  p1 = aRect.BottomLeft();
+  p2 = aRect.BottomRight();
+  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget,
+                                    aStrokeOptions.mLineWidth);
+  aDrawTarget.StrokeLine(p1, p2, aColor, aStrokeOptions);
+
+  p1 = aRect.TopLeft();
+  p2 = aRect.TopRight();
+  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget,
+                                    aStrokeOptions.mLineWidth);
+  aDrawTarget.StrokeLine(p1, p2, aColor, aStrokeOptions);
+
+  p1 = aRect.TopRight();
+  p2 = aRect.BottomRight();
+  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget,
+                                    aStrokeOptions.mLineWidth);
+  aDrawTarget.StrokeLine(p1, p2, aColor, aStrokeOptions);
+}
+
+// The logic for this comes from _cairo_stroke_style_max_distance_from_path
+Margin MaxStrokeExtents(const StrokeOptions& aStrokeOptions,
+                        const Matrix& aTransform) {
+  double styleExpansionFactor = 0.5f;
+
+  if (aStrokeOptions.mLineCap == CapStyle::SQUARE) {
+    styleExpansionFactor = M_SQRT1_2;
+  }
+
+  if (aStrokeOptions.mLineJoin == JoinStyle::MITER &&
+      styleExpansionFactor < M_SQRT2 * aStrokeOptions.mMiterLimit) {
+    styleExpansionFactor = M_SQRT2 * aStrokeOptions.mMiterLimit;
+  }
+
+  styleExpansionFactor *= aStrokeOptions.mLineWidth;
+
+  double dx = styleExpansionFactor * hypot(aTransform._11, aTransform._21);
+  double dy = styleExpansionFactor * hypot(aTransform._22, aTransform._12);
+
+  // Even if the stroke only partially covers a pixel, it must still render to
+  // full pixels. Round up to compensate for this.
+  dx = ceil(dx);
+  dy = ceil(dy);
+
+  return Margin(dy, dx, dy, dx);
+}
+
+}  // namespace gfx
+}  // namespace mozilla