[Impeller] switch Rect fields to LTRB implementation (flutter#49816)

Switches the Rect class implementation to an LTRB (Left, Top, Right, Bottom) set of fields for efficiency in performing rectangle operations. Additionally, the methods have been somewhat hardened to the following issues:

- NaN values should always act as if the rect is empty
  - Helps with flutter#132770
- Saturated math methods are added to avoid overflow for integer rects
- Normalized treatment of empty rectangles in rect/rect operations
  - empty.Union(anything) == anything
  - empty.Intersection(anything) == empty
  - empty.IntersectsWith(anything) == false
  - empty.Contains(anything) == false
  - non-empty.Contains(empty) == true
- MakeMaximum now returns finite rectangles which should produce non-nan values from all getters
- A lot more testing of all of these behaviors within the unit tests

In addition, the new rectangle is closer to what DisplayList and the Skia backend have been using all along so we might be able to switch to using Impeller geometry inside DisplayList to reduce overhead for both backends.

Author: flar

ci/licenses_golden/excluded_files

@@ -161,6 +161,7 @@
 ../../../flutter/impeller/geometry/matrix_unittests.cc
 ../../../flutter/impeller/geometry/path_unittests.cc
 ../../../flutter/impeller/geometry/rect_unittests.cc
+../../../flutter/impeller/geometry/saturated_math_unittests.cc
 ../../../flutter/impeller/geometry/size_unittests.cc
 ../../../flutter/impeller/geometry/trig_unittests.cc
 ../../../flutter/impeller/golden_tests/README.md

ci/licenses_golden/licenses_flutter

@@ -5292,6 +5292,7 @@ ORIGIN: ../../../flutter/impeller/geometry/quaternion.cc + ../../../flutter/LICE
 ORIGIN: ../../../flutter/impeller/geometry/quaternion.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/geometry/rect.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/geometry/rect.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/geometry/saturated_math.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/geometry/scalar.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/geometry/shear.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/geometry/shear.h + ../../../flutter/LICENSE
@@ -8129,6 +8130,7 @@ FILE: ../../../flutter/impeller/geometry/quaternion.cc
 FILE: ../../../flutter/impeller/geometry/quaternion.h
 FILE: ../../../flutter/impeller/geometry/rect.cc
 FILE: ../../../flutter/impeller/geometry/rect.h
+FILE: ../../../flutter/impeller/geometry/saturated_math.h
 FILE: ../../../flutter/impeller/geometry/scalar.h
 FILE: ../../../flutter/impeller/geometry/shear.cc
 FILE: ../../../flutter/impeller/geometry/shear.h

impeller/entity/geometry/stroke_path_geometry.cc

@@ -508,7 +508,6 @@ std::optional<Rect> StrokePathGeometry::GetCoverage(
   if (!path_bounds.has_value()) {
     return std::nullopt;
   }
-  auto path_coverage = path_bounds->TransformBounds(transform);
 
   Scalar max_radius = 0.5;
   if (stroke_cap_ == Cap::kSquare) {
@@ -522,12 +521,8 @@ std::optional<Rect> StrokePathGeometry::GetCoverage(
     return std::nullopt;
   }
   Scalar min_size = 1.0f / sqrt(std::abs(determinant));
-  Vector2 max_radius_xy =
-      transform
-          .TransformDirection(Vector2(max_radius, max_radius) *
-                              std::max(stroke_width_, min_size))
-          .Abs();
-  return path_coverage.Expand(max_radius_xy);
+  max_radius *= std::max(stroke_width_, min_size);
+  return path_bounds->Expand(max_radius).TransformBounds(transform);
 }
 
 }  // namespace impeller

impeller/geometry/BUILD.gn

@@ -29,6 +29,7 @@ impeller_component("geometry") {
     "quaternion.h",
     "rect.cc",
     "rect.h",
+    "saturated_math.h",
     "scalar.h",
     "shear.cc",
     "shear.h",
@@ -66,6 +67,7 @@ impeller_component("geometry_unittests") {
     "matrix_unittests.cc",
     "path_unittests.cc",
     "rect_unittests.cc",
+    "saturated_math_unittests.cc",
     "size_unittests.cc",
     "trig_unittests.cc",
   ]

impeller/geometry/geometry_asserts.h

@@ -54,10 +54,10 @@ inline ::testing::AssertionResult QuaternionNear(impeller::Quaternion a,
 }
 
 inline ::testing::AssertionResult RectNear(impeller::Rect a, impeller::Rect b) {
-  auto equal = NumberNear(a.GetX(), b.GetX()) &&
-               NumberNear(a.GetY(), b.GetY()) &&
-               NumberNear(a.GetWidth(), b.GetWidth()) &&
-               NumberNear(a.GetHeight(), b.GetHeight());
+  auto equal = NumberNear(a.GetLeft(), b.GetLeft()) &&
+               NumberNear(a.GetTop(), b.GetTop()) &&
+               NumberNear(a.GetRight(), b.GetRight()) &&
+               NumberNear(a.GetBottom(), b.GetBottom());
 
   return equal ? ::testing::AssertionSuccess()
                : ::testing::AssertionFailure()