From c096b46278449f2d0126a5c9327a8b0218dd5beb Mon Sep 17 00:00:00 2001
From: Moonchild <moonchild@palemoon.org>
Date: Fri, 2 Aug 2024 11:15:28 +0200
Subject: [PATCH] Issue #1925 - Convert NS_SIDE_TO_HALF_CORNER to a constexpr
 function.

---
 gfx/2d/Types.h                | 20 ++++++++++++++++++++
 layout/generic/nsFrame.cpp    | 12 ++++++------
 layout/style/nsStyleConsts.h  |  7 -------
 layout/style/nsStyleCoord.cpp |  5 +++--
 4 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/gfx/2d/Types.h b/gfx/2d/Types.h
index ad83a79889..43e8c14963 100644
--- a/gfx/2d/Types.h
+++ b/gfx/2d/Types.h
@@ -459,6 +459,9 @@ static inline mozilla::HalfCorner operator++(mozilla::HalfCorner& aHalfCorner) {
   return aHalfCorner;
 }
 
+// The result of the conversion functions below are exhaustively checked in
+// nsStyleCoord.cpp, which also serves as usage examples.
+
 constexpr bool HalfCornerIsX(HalfCorner aHalfCorner)
 {
   return !(aHalfCorner % 2);
@@ -489,6 +492,23 @@ constexpr Corner SideToFullCorner(Side aSide, bool aIsSecond)
   return Corner((aSide + aIsSecond) % 4);
 }
 
+/* @param aIsSecond: when true, return the clockwise second of the two
+ * corners associated with aSide. For example, with aSide = eSideBottom the
+ * result is eCornerBottomRight when aIsSecond is false, and
+ * eCornerBottomLeft when aIsSecond is true.
+ * @param aIsParallel: return the half-corner that is parallel with aSide
+ * when aIsParallel is true. For example with aSide=eSideTop, aIsSecond=true
+ * the result is eCornerTopRightX when aIsParallel is true, and
+ * eCornerTopRightY when aIsParallel is false (because "X" is parallel with
+ * eSideTop/eSideBottom, similarly "Y" is parallel with eSideLeft/eSideRight)
+ */
+constexpr HalfCorner SideToHalfCorner(Side aSide,
+                                      bool aIsSecond,
+                                      bool aIsParallel)
+{
+  return HalfCorner(((aSide + aIsSecond) * 2 + (aSide + !aIsParallel) % 2) % 8);
+}
+
 } // namespace mozilla
 
 #endif /* MOZILLA_GFX_TYPES_H_ */
diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index 451a1ff7cd..c7f2471bca 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -1284,8 +1284,8 @@ nsIFrame::ComputeBorderRadii(const nsStyleCorners& aBorderRadius,
   bool haveRadius = false;
   double ratio = 1.0f;
   NS_FOR_CSS_SIDES(side) {
-    uint32_t hc1 = NS_SIDE_TO_HALF_CORNER(side, false, true);
-    uint32_t hc2 = NS_SIDE_TO_HALF_CORNER(side, true, true);
+    uint32_t hc1 = SideToHalfCorner(side, false, true);
+    uint32_t hc2 = SideToHalfCorner(side, true, true);
     nscoord length =
       SideIsVertical(side) ? aBorderArea.height : aBorderArea.width;
     nscoord sum = aRadii[hc1] + aRadii[hc2];
@@ -1310,8 +1310,8 @@ nsIFrame::InsetBorderRadii(nscoord aRadii[8], const nsMargin &aOffsets)
 {
   NS_FOR_CSS_SIDES(side) {
     nscoord offset = aOffsets.Side(side);
-    uint32_t hc1 = NS_SIDE_TO_HALF_CORNER(side, false, false);
-    uint32_t hc2 = NS_SIDE_TO_HALF_CORNER(side, true, false);
+    uint32_t hc1 = SideToHalfCorner(side, false, false);
+    uint32_t hc2 = SideToHalfCorner(side, true, false);
     aRadii[hc1] = std::max(0, aRadii[hc1] - offset);
     aRadii[hc2] = std::max(0, aRadii[hc2] - offset);
   }
@@ -1322,8 +1322,8 @@ nsIFrame::OutsetBorderRadii(nscoord aRadii[8], const nsMargin &aOffsets)
 {
   NS_FOR_CSS_SIDES(side) {
     nscoord offset = aOffsets.Side(side);
-    uint32_t hc1 = NS_SIDE_TO_HALF_CORNER(side, false, false);
-    uint32_t hc2 = NS_SIDE_TO_HALF_CORNER(side, true, false);
+    uint32_t hc1 = SideToHalfCorner(side, false, false);
+    uint32_t hc2 = SideToHalfCorner(side, true, false);
     if (aRadii[hc1] > 0)
       aRadii[hc1] += offset;
     if (aRadii[hc2] > 0)
diff --git a/layout/style/nsStyleConsts.h b/layout/style/nsStyleConsts.h
index 96690ae2d8..9507ea6fab 100644
--- a/layout/style/nsStyleConsts.h
+++ b/layout/style/nsStyleConsts.h
@@ -16,13 +16,6 @@
 
 namespace mozilla {
 
-// The results of these conversion macros are exhaustively checked in
-// nsStyleCoord.cpp.
-// Arguments must not have side effects.
-
-#define NS_SIDE_TO_HALF_CORNER(side_, second_, parallel_) \
-  ((((side_) + !!(second_))*2 + ((side_) + !(parallel_))%2) % 8)
-
 // Basic shapes
 enum class StyleBasicShapeType : uint8_t {
   Polygon,
diff --git a/layout/style/nsStyleCoord.cpp b/layout/style/nsStyleCoord.cpp
index 263b0844b2..f93bb53f63 100644
--- a/layout/style/nsStyleCoord.cpp
+++ b/layout/style/nsStyleCoord.cpp
@@ -397,9 +397,10 @@ CASE(eSideLeft,   false, eCornerBottomLeft);
 CASE(eSideLeft,   true,  eCornerTopLeft);
 #undef CASE
 
+//Validation of SideToHalfCorner.
 #define CASE(side, second, parallel, result)                                  \
-  static_assert(NS_SIDE_TO_HALF_CORNER(side, second, parallel) == result,     \
-                "NS_SIDE_TO_HALF_CORNER is wrong")
+  static_assert(SideToHalfCorner(side, second, parallel) == result,     \
+                "SideToHalfCorner is wrong")
 CASE(eSideTop,    false, true,  eCornerTopLeftX);
 CASE(eSideTop,    false, false, eCornerTopLeftY);
 CASE(eSideTop,    true,  true,  eCornerTopRightX);