SF: Switch computeBounds to return FloatRect

Switches Layer::computeBounds to return a FloatRect instead of a Rect.

During the computation of the bounds, we apply the layer transformation
to its nominal dimensions, clip it against its bounds (which are either
its parents bounds or the screen bounds), and apply the inverse of the
layer transformation.

Previously, the intermediate position (after transformation/clip, but
before inverse transformation) was stored as Rect, which is to say that
it was truncated to integer coordinates. After applying the inverse
transformation, this loss of precision can cause glitches where a layer
that should be clipped against, e.g., the side of the screen no longer
creates a watertight seal against that side.

In order to fix this, we now store the intermediate value as a FloatRect
and propagate float precision back through computeBounds. The callers of
computeBounds tend to then immediately apply the transform again, at
which point it is safe to round back to integer.

Bug: 64070729
Bug: 66431327
Bug: 69935057
Test: Modified android.view.cts.SurfaceViewSyncTest#
      testSurfaceViewBigScale no longer produces bogus display frames
Change-Id: If5987ca4ad76657f9670a5f59258f896180352e2
(cherry picked from commit 80d611613ef1a9c05a31cd3f47badfd4de9b1418)
Merged-In: If5987ca4ad76657f9670a5f59258f896180352e2

2 files changed, 20 insertions, 0 deletions

diff --git a/libs/ui/include/ui/FloatRect.h b/libs/ui/include/ui/FloatRect.h
index 270675cba2..6a7479a68a 100644
--- a/libs/ui/include/ui/FloatRect.h
+++ b/libs/ui/include/ui/FloatRect.h
@@ -27,6 +27,17 @@ public:
     float getWidth() const { return right - left; }
     float getHeight() const { return bottom - top; }
 
+    FloatRect intersect(const FloatRect& other) const {
+        return {
+            // Inline to avoid tromping on other min/max defines or adding a
+            // dependency on STL
+            (left > other.left) ? left : other.left,
+            (top > other.top) ? top : other.top,
+            (right < other.right) ? right : other.right,
+            (bottom < other.bottom) ? bottom : other.bottom
+        };
+    }
+
     float left = 0.0f;
     float top = 0.0f;
     float right = 0.0f;
diff --git a/libs/ui/include/ui/Rect.h b/libs/ui/include/ui/Rect.h
index b50e4ec656..c099a026aa 100644
--- a/libs/ui/include/ui/Rect.h
+++ b/libs/ui/include/ui/Rect.h
@@ -69,6 +69,15 @@ public:
         bottom = rb.y;
     }
 
+    inline explicit Rect(const FloatRect& floatRect) {
+        // Ideally we would use std::round, but we don't want to add an STL
+        // dependency here, so we use an approximation
+        left = static_cast<int32_t>(floatRect.left + 0.5f);
+        top = static_cast<int32_t>(floatRect.top + 0.5f);
+        right = static_cast<int32_t>(floatRect.right + 0.5f);
+        bottom = static_cast<int32_t>(floatRect.bottom + 0.5f);
+    }
+
     void makeInvalid();
 
     inline void clear() {