From 6bb49105c62a27eced91b2fba7b546be5b94d9b0 Mon Sep 17 00:00:00 2001
From: Ting-Yu Lin <tlin@mozilla.com>
Date: Mon, 18 Dec 2023 18:18:28 +0000
Subject: [PATCH] Bug 1870572 - Use constexpr variables instead of macro to
 define layout constants. r=layout-reviewers,emilio

Here are some benefits to define those constants in constexpr variables:

1. Better assertion messages. For example, without this patch, the assertion in
   bug 1870103 looks like:

```
Assertion failure: cbSize.BSize(wm) == nscoord((1 << 30) - 1)
```

With this patch, it looks like:

```
Assertion failure: cbSize.BSize(wm) == NS_UNCONSTRAINEDSIZE
```

2. We can use those constants in a debugger.

This patch doesn't change behavior.

Differential Revision: https://phabricator.services.mozilla.com/D196708
---
 gfx/src/nsCoord.h             | 6 +++---
 gfx/src/nsSize.h              | 2 +-
 layout/base/LayoutConstants.h | 9 ++++-----
 3 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/gfx/src/nsCoord.h b/gfx/src/nsCoord.h
index 9d2241f15a98..6c2cd62be16a 100644
--- a/gfx/src/nsCoord.h
+++ b/gfx/src/nsCoord.h
@@ -25,9 +25,9 @@
  * 96dpi as possible.
  */
 
-typedef int32_t nscoord;
-#define nscoord_MAX nscoord((1 << 30) - 1)
-#define nscoord_MIN (-nscoord_MAX)
+using nscoord = int32_t;
+inline constexpr nscoord nscoord_MAX = (1 << 30) - 1;
+inline constexpr nscoord nscoord_MIN = -nscoord_MAX;
 
 namespace mozilla {
 struct AppUnit {};
diff --git a/gfx/src/nsSize.h b/gfx/src/nsSize.h
index b80d1bde74a1..df1fa5570e46 100644
--- a/gfx/src/nsSize.h
+++ b/gfx/src/nsSize.h
@@ -12,7 +12,7 @@
 #include "mozilla/gfx/Point.h"
 
 // Maximum allowable size
-#define NS_MAXSIZE nscoord_MAX
+inline constexpr nscoord NS_MAXSIZE = nscoord_MAX;
 
 typedef mozilla::gfx::IntSize nsIntSize;
 
diff --git a/layout/base/LayoutConstants.h b/layout/base/LayoutConstants.h
index d976afe99b4d..e8c7bb4221b9 100644
--- a/layout/base/LayoutConstants.h
+++ b/layout/base/LayoutConstants.h
@@ -10,7 +10,6 @@
 #define LayoutConstants_h___
 
 #include "mozilla/EnumSet.h"
-#include "nsSize.h"  // for NS_MAXSIZE
 #include "Units.h"
 
 /**
@@ -20,15 +19,15 @@
  *       values, so user should not depend on the underlying numeric values. If
  *       new specific use cases arise, define a new constant here.
  */
-#define NS_UNCONSTRAINEDSIZE NS_MAXSIZE
+inline constexpr nscoord NS_UNCONSTRAINEDSIZE = nscoord_MAX;
 
 // NS_AUTOOFFSET is assumed to have the same value as NS_UNCONSTRAINEDSIZE.
-#define NS_AUTOOFFSET NS_UNCONSTRAINEDSIZE
+inline constexpr nscoord NS_AUTOOFFSET = NS_UNCONSTRAINEDSIZE;
 
 // +1 is to avoid clamped huge margin values being processed as auto margins
-#define NS_AUTOMARGIN (NS_UNCONSTRAINEDSIZE + 1)
+inline constexpr nscoord NS_AUTOMARGIN = NS_UNCONSTRAINEDSIZE + 1;
 
-#define NS_INTRINSIC_ISIZE_UNKNOWN nscoord_MIN
+inline constexpr nscoord NS_INTRINSIC_ISIZE_UNKNOWN = nscoord_MIN;
 
 namespace mozilla {