layout/base/ShapeUtils.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_ShapeUtils_h
   8 #define mozilla_ShapeUtils_h
   9
  10 #include "nsCoord.h"
  11 #include "nsSize.h"
  12 #include "nsStyleConsts.h"
  13 #include "nsTArray.h"
  14
  15 struct nsPoint;
  16 struct nsRect;
  17
  18 namespace mozilla {
  19 // ShapeUtils is a namespace class containing utility functions related to
  20 // processing basic shapes in the CSS Shapes Module.
  21 // https://drafts.csswg.org/css-shapes/#basic-shape-functions
  22 //
  23 struct ShapeUtils final {
  24   // Compute the length of a keyword <shape-radius>, i.e. closest-side or
  25   // farthest-side, for a circle or an ellipse on a single dimension. The
  26   // caller needs to call for both dimensions and combine the result.
  27   // https://drafts.csswg.org/css-shapes/#typedef-shape-radius.
  28   // @return The length of the radius in app units.
  29   static nscoord ComputeShapeRadius(const StyleShapeRadius& aType,
  30                                     const nscoord aCenter,
  31                                     const nscoord aPosMin,
  32                                     const nscoord aPosMax);
  33
  34   // Compute the center of a circle or an ellipse.
  35   // @param aRefBox The reference box of the basic shape.
  36   // @return The point of the center.
  37   static nsPoint ComputeCircleOrEllipseCenter(const StyleBasicShape&,
  38                                               const nsRect& aRefBox);
  39
  40   // Compute the radius for a circle.
  41   // @param aCenter the center of the circle.
  42   // @param aRefBox the reference box of the circle.
  43   // @return The length of the radius in app units.
  44   static nscoord ComputeCircleRadius(const StyleBasicShape&,
  45                                      const nsPoint& aCenter,
  46                                      const nsRect& aRefBox);
  47
  48   // Compute the radii for an ellipse.
  49   // @param aCenter the center of the ellipse.
  50   // @param aRefBox the reference box of the ellipse.
  51   // @return The radii of the ellipse in app units. The width and height
  52   // represent the x-axis and y-axis radii of the ellipse.
  53   static nsSize ComputeEllipseRadii(const StyleBasicShape&,
  54                                     const nsPoint& aCenter,
  55                                     const nsRect& aRefBox);
  56
  57   // Compute the rect for an inset. If the inset amount is larger than
  58   // aRefBox itself, this will return a rect the same shape as the inverse
  59   // rect that would be created by insetting aRefBox by the inset amount.
  60   // This process is *not* what is called for by the current spec at
  61   // https://drafts.csswg.org/css-shapes-1/#supported-basic-shapes.
  62   // The spec currently treats empty shapes, including overly-inset rects, as
  63   // defining 'empty float areas' that don't affect layout. However, it is
  64   // practically useful to treat empty shapes as having edges for purposes of
  65   // affecting layout, and there is growing momentum for the approach we
  66   // are taking here.
  67   // @param aRefBox the reference box of the inset.
  68   // @return The inset rect in app units.
  69   static nsRect ComputeInsetRect(const StyleBasicShape&, const nsRect& aRefBox);
  70
  71   // Compute the radii for an inset.
  72   // @param aRefBox the reference box of the inset.
  73   // @param aRadii the returned radii in app units.
  74   // @return true if any of the radii is nonzero; false otherwise.
  75   static bool ComputeInsetRadii(const StyleBasicShape&, const nsRect& aRefBox,
  76                                 nscoord aRadii[8]);
  77
  78   // Compute the vertices for a polygon.
  79   // @param aRefBox the reference box of the polygon.
  80   // @return The vertices in app units; the coordinate space is the same
  81   //         as aRefBox.
  82   static nsTArray<nsPoint> ComputePolygonVertices(const StyleBasicShape&,
  83                                                   const nsRect& aRefBox);
  84 };
  85
  86 }  // namespace mozilla
  87
  88 #endif  // mozilla_ShapeUtils_h