From 66b9023deadcb587d03c18f188e6900a75e00ffe Mon Sep 17 00:00:00 2001
From: Timothy Nikkel <tnikkel@gmail.com>
Date: Sun, 6 Sep 2026 09:14:24 +0000
Subject: [PATCH] Bug 2069594. Give nsRect the default copy constructor so the
 compiler knows it is trivially copyable. r=layout-reviewers,emilio

On some ABIs this means that it can be passed and returned in a register instead of in memory.

Differential Revision: https://phabricator.services.mozilla.com/D323836
---
 gfx/src/nsRect.h     | 28 +++++++++++++---------------
 widget/WidgetUtils.h |  1 +
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/gfx/src/nsRect.h b/gfx/src/nsRect.h
index 76ec0107b388..d0dd68edf09f 100644
--- a/gfx/src/nsRect.h
+++ b/gfx/src/nsRect.h
@@ -7,15 +7,15 @@
 
 #include <stdint.h>  // for int32_t, int64_t
 
-#include <algorithm>  // for min/max
+#include <algorithm>    // for min/max
+#include <type_traits>  // for is_trivially_copyable_v
 
 #include "mozilla/Likely.h"  // for MOZ_UNLIKELY
 #include "mozilla/gfx/BaseRect.h"
 #include "mozilla/gfx/Rect.h"
-#include "nsCoord.h"      // for nscoord, etc
-#include "nsISupports.h"  // for MOZ_COUNT_CTOR, etc
-#include "nsPoint.h"      // for nsIntPoint, nsPoint
-#include "nsSize.h"       // for IntSize, nsSize
+#include "nsCoord.h"  // for nscoord, etc
+#include "nsPoint.h"  // for nsIntPoint, nsPoint
+#include "nsSize.h"   // for IntSize, nsSize
 
 #if !defined(ANDROID) && (defined(__SSE2__) || defined(_M_X64) || \
                           (defined(_M_IX86_FP) && _M_IX86_FP >= 2))
@@ -38,19 +38,13 @@ struct nsRect : public mozilla::gfx::BaseRect<nscoord, nsRect, nsPoint, nsSize,
       Super;
 
   // Constructors
-  nsRect() { MOZ_COUNT_CTOR(nsRect); }
-  nsRect(const nsRect& aRect) : Super(aRect) { MOZ_COUNT_CTOR(nsRect); }
-  nsRect(const nsPoint& aOrigin, const nsSize& aSize) : Super(aOrigin, aSize) {
-    MOZ_COUNT_CTOR(nsRect);
-  }
+  nsRect() = default;
+  nsRect(const nsRect& aRect) = default;
+  nsRect(const nsPoint& aOrigin, const nsSize& aSize) : Super(aOrigin, aSize) {}
   nsRect(nscoord aX, nscoord aY, nscoord aWidth, nscoord aHeight)
-      : Super(aX, aY, aWidth, aHeight) {
-    MOZ_COUNT_CTOR(nsRect);
-  }
+      : Super(aX, aY, aWidth, aHeight) {}
   nsRect& operator=(const nsRect&) = default;
 
-  MOZ_COUNTED_DTOR(nsRect)
-
   // We have saturating versions of all the Union methods. These avoid
   // overflowing nscoord values in the 'width' and 'height' fields by
   // clamping the width and height values to nscoord_MAX if necessary.
@@ -172,6 +166,10 @@ struct nsRect : public mozilla::gfx::BaseRect<nscoord, nsRect, nsPoint, nsSize,
   }
 };
 
+static_assert(std::is_trivially_copyable_v<nsRect>,
+              "nsRect must stay trivially copyable so that it is passed and "
+              "returned in registers");
+
 /*
  * App Unit/Pixel conversions
  */
diff --git a/widget/WidgetUtils.h b/widget/WidgetUtils.h
index a7e1e8b38cd7..915697f30c10 100644
--- a/widget/WidgetUtils.h
+++ b/widget/WidgetUtils.h
@@ -8,6 +8,7 @@
 #include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/gfx/Matrix.h"
 #include "nsRect.h"
+#include "nsStringFwd.h"
 
 class nsIWidget;
 class nsPIDOMWindowOuter;