Allow the computation of inflated bounds for non matrix transform operations.

cc/animation/transform_operation.cc

 // Copyright 2013 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.
 
 // Needed on Windows to get |M_PI| from <cmath>
 #ifdef _WIN32
 #define _USE_MATH_DEFINES
 #endif
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 
 #include "base/logging.h"
 #include "cc/animation/transform_operation.h"
+#include "cc/animation/transform_operations.h"
 #include "ui/gfx/box_f.h"
+#include "ui/gfx/transform_util.h"
 #include "ui/gfx/vector3d_f.h"
 
 namespace {
 const SkMScalar kAngleEpsilon = 1e-4f;
 }
 
 namespace cc {
 
 bool TransformOperation::IsIdentity() const {
   return matrix.IsIdentity();
@@ skipping 216 matching lines @@
 }
 
 static float RadiansToDegrees(float radians) {
   return (180.f * radians) / M_PI;
 }
 
 static float DegreesToRadians(float degrees) {
   return (M_PI * degrees) / 180.f;
 }
 
-// Div by zero doesn't always result in Inf as you might hope, so we'll do this
-// explicitly here.
-static float SafeDivide(float numerator, float denominator) {
-  if (numerator == 0.f)
-    return 0.f;
-
-  if (denominator == 0.f) {
-    return numerator > 0.f ? std::numeric_limits<float>::infinity()
-                           : -std::numeric_limits<float>::infinity();
-  }
-
-  return numerator / denominator;
-}
-
 static void BoundingBoxForArc(const gfx::Point3F& point,
                               const TransformOperation* from,
                               const TransformOperation* to,
                               SkMScalar min_progress,
                               SkMScalar max_progress,
                               gfx::BoxF* box) {
   const TransformOperation* exemplar = from ? from : to;
   gfx::Vector3dF axis(exemplar->rotate.axis.x,
                       exemplar->rotate.axis.y,
                       exemplar->rotate.axis.z);
 
   const bool x_is_zero = axis.x() == 0.f;
   const bool y_is_zero = axis.y() == 0.f;
   const bool z_is_zero = axis.z() == 0.f;
 
   // We will have at most 6 angles to test (excluding from->angle and
   // to->angle).
   static const int kMaxNumCandidates = 6;
   double candidates[kMaxNumCandidates];
   int num_candidates = kMaxNumCandidates;
 
   if (x_is_zero && y_is_zero && z_is_zero)
     return;
 
   SkMScalar from_angle = from ? from->rotate.angle : 0.f;
   SkMScalar to_angle = to ? to->rotate.angle : 0.f;
 
+  // If the axes of rotation are pointing in opposite directions, we need to
+  // flip one of the angles. Note, if both |from| and |to| exist, then axis will
+  // correspond to |from|.
+  if (from && to) {
+    gfx::Vector3dF other_axis(
+        to->rotate.axis.x, to->rotate.axis.y, to->rotate.axis.z);
+    if (gfx::DotProduct(axis, other_axis) < 0.f)
+      to_angle *= -1.f;
+  }

[ajuma, 2013/11/01 21:02:08]

One thing I find confusing is that we don't need to use |to|'s axis at all after
this point. What am I missing? :)

[Ian Vollick, 2013/11/03 19:05:19]

Whoops, nothing! I thought that we'd enforced that the rotation operations
shared an axis before we got to this point, but we hadn't. I've added that check
and a unit test to ensure that it works. So in future, it'll be ok to stop
referring to |to|'s axis because it'll be the same as |from|'s.

+
   float min_degrees =
       SkMScalarToFloat(BlendSkMScalars(from_angle, to_angle, min_progress));
   float max_degrees =
       SkMScalarToFloat(BlendSkMScalars(from_angle, to_angle, max_progress));
   if (max_degrees < min_degrees)
     std::swap(min_degrees, max_degrees);
 
   gfx::Transform from_transform;
   from_transform.RotateAbout(axis, min_degrees);
   gfx::Transform to_transform;
@@ skipping 49 matching lines @@
 
     gfx::Point3F pz(0.f, 0.f, 1.f);
     gfx::Vector3dF to_pz = pz - center;
     gfx::Point3F pz_projected =
         pz - ScaleVector3d(normal, gfx::DotProduct(to_pz, normal));
     gfx::Vector3dF vz = pz_projected - origin;
 
     double phi_x = atan2(gfx::DotProduct(v2, vx), gfx::DotProduct(v1, vx));
     double phi_z = atan2(gfx::DotProduct(v2, vz), gfx::DotProduct(v1, vz));
 
-    // NB: it is fine if the denominators here are zero and these values go to
-    // infinity; atan can handle it.
-    double tan_theta1 = SafeDivide(normal.y(), (normal.x() * normal.z()));
-    double tan_theta2 = SafeDivide(-normal.z(), (normal.x() * normal.y()));
-
-    candidates[0] = atan(tan_theta1) + phi_x;
+    candidates[0] = atan2(normal.y(), normal.x() * normal.z()) + phi_x;
     candidates[1] = candidates[0] + M_PI;
-    candidates[2] = atan(tan_theta2) + phi_x;
+    candidates[2] = atan2(-normal.z(), normal.x() * normal.y()) + phi_x;
     candidates[3] = candidates[2] + M_PI;
-    candidates[4] = atan(-tan_theta1) + phi_z;
+    candidates[4] = atan2(normal.y(), -normal.x() * normal.z()) + phi_z;
     candidates[5] = candidates[4] + M_PI;
   }
 
   double min_radians = DegreesToRadians(min_degrees);
   double max_radians = DegreesToRadians(max_degrees);
 
   for (int i = 0; i < num_candidates; ++i) {
     double radians = candidates[i];
     while (radians < min_radians)
       radians += 2.0 * M_PI;
@@ skipping 25 matching lines @@
   }
 
   TransformOperation::Type interpolation_type =
       TransformOperation::TransformOperationIdentity;
   if (is_identity_to)
     interpolation_type = from->type;
   else
     interpolation_type = to->type;
 
   switch (interpolation_type) {
-    case TransformOperation::TransformOperationTranslate: {
-      SkMScalar from_x, from_y, from_z;
-      if (is_identity_from) {
-        from_x = from_y = from_z = 0.0;
-      } else {
-        from_x = from->translate.x;
-        from_y = from->translate.y;
-        from_z = from->translate.z;
-      }
-      SkMScalar to_x, to_y, to_z;
-      if (is_identity_to) {
-        to_x = to_y = to_z = 0.0;
-      } else {
-        to_x = to->translate.x;
-        to_y = to->translate.y;
-        to_z = to->translate.z;
-      }
+    case TransformOperation::TransformOperationIdentity:
       *bounds = box;
-      *bounds += gfx::Vector3dF(BlendSkMScalars(from_x, to_x, min_progress),
-                                BlendSkMScalars(from_y, to_y, min_progress),
-                                BlendSkMScalars(from_z, to_z, min_progress));
-      gfx::BoxF bounds_max = box;
-      bounds_max += gfx::Vector3dF(BlendSkMScalars(from_x, to_x, max_progress),
-                                   BlendSkMScalars(from_y, to_y, max_progress),
-                                   BlendSkMScalars(from_z, to_z, max_progress));
-      bounds->Union(bounds_max);
       return true;
-    }
+    case TransformOperation::TransformOperationTranslate:
+    case TransformOperation::TransformOperationSkew:
+    case TransformOperation::TransformOperationPerspective:
     case TransformOperation::TransformOperationScale: {
-      SkMScalar from_x, from_y, from_z;
-      if (is_identity_from) {
-        from_x = from_y = from_z = 1.0;
-      } else {
-        from_x = from->scale.x;
-        from_y = from->scale.y;
-        from_z = from->scale.z;
-      }
-      SkMScalar to_x, to_y, to_z;
-      if (is_identity_to) {
-        to_x = to_y = to_z = 1.0;
-      } else {
-        to_x = to->scale.x;
-        to_y = to->scale.y;
-        to_z = to->scale.z;
-      }
+      gfx::Transform from_transform;
+      gfx::Transform to_transform;
+      if (!BlendTransformOperations(from, to, min_progress, &from_transform) ||
+          !BlendTransformOperations(from, to, max_progress, &to_transform))
+        return false;
+
       *bounds = box;
-      ApplyScaleToBox(
-          SkMScalarToFloat(BlendSkMScalars(from_x, to_x, min_progress)),
-          SkMScalarToFloat(BlendSkMScalars(from_y, to_y, min_progress)),
-          SkMScalarToFloat(BlendSkMScalars(from_z, to_z, min_progress)),
-          bounds);
-      gfx::BoxF bounds_max = box;
-      ApplyScaleToBox(
-          SkMScalarToFloat(BlendSkMScalars(from_x, to_x, max_progress)),
-          SkMScalarToFloat(BlendSkMScalars(from_y, to_y, max_progress)),
-          SkMScalarToFloat(BlendSkMScalars(from_z, to_z, max_progress)),
-          &bounds_max);
-      if (!bounds->IsEmpty() && !bounds_max.IsEmpty()) {
-        bounds->Union(bounds_max);
-      } else if (!bounds->IsEmpty()) {
-        UnionBoxWithZeroScale(bounds);
-      } else if (!bounds_max.IsEmpty()) {
-        UnionBoxWithZeroScale(&bounds_max);
-        *bounds = bounds_max;
-      }
+      from_transform.TransformBox(bounds);
+
+      gfx::BoxF to_box = box;
+      to_transform.TransformBox(&to_box);
+      bounds->ExpandTo(to_box);
 
       return true;
     }
-    case TransformOperation::TransformOperationIdentity:
-      *bounds = box;
-      return true;
     case TransformOperation::TransformOperationRotate: {
       bool first_point = true;
       for (int i = 0; i < 8; ++i) {
         gfx::Point3F corner = box.origin();
         corner += gfx::Vector3dF(i & 1 ? box.width() : 0.f,
                                  i & 2 ? box.height() : 0.f,
                                  i & 4 ? box.depth() : 0.f);
         gfx::BoxF box_for_arc;
         BoundingBoxForArc(
             corner, from, to, min_progress, max_progress, &box_for_arc);
         if (first_point)
           *bounds = box_for_arc;
         else
           bounds->Union(box_for_arc);
         first_point = false;
       }
       return true;
     }
-    case TransformOperation::TransformOperationSkew:
-    case TransformOperation::TransformOperationPerspective:
     case TransformOperation::TransformOperationMatrix:
       return false;
   }
   NOTREACHED();
   return false;
 }
 
 }  // namespace cc