From 1501f45c335f0a82843e3133ec2ef54d93546cf9 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Mon, 5 Dec 2022 14:44:49 +0100
Subject: [PATCH] QFont: replace a QVLA with a C array

QVarLengthArray doesn't allocate, but is nevertheless dynamically
initialized, incl. thread-safe static overhead.

Turn the QVLA<QPair<int,int>> into a std::array<int,2>[] instead. This
container has constant initialization and the use of array<int>
instead of pair<int, int> means we can use the bool inverted argument
as an index into the array instead of having to switch over .first and
.second.

Saves ~600B in text size and ~100B in BSS on optimized Clang 15 AMD64
Linux builds, and the copying, under mutex protection, of the data at
runtime.

Amends 3558704ed5c3d2c6dc6d024dfa454997469ca75f.

Pick-to: 6.4
Change-Id: Iad48eca4eef77011d4094125670ea302e8beae46
Reviewed-by: Jonas Karlsson <jonas.karlsson@qt.io>
---
 src/gui/text/qfont.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/gui/text/qfont.cpp b/src/gui/text/qfont.cpp
index 2b649a7dd8..0db9bbac3f 100644
--- a/src/gui/text/qfont.cpp
+++ b/src/gui/text/qfont.cpp
@@ -31,6 +31,8 @@
 #include <QtCore/QMutexLocker>
 #include <QtCore/QMutex>
 
+#include <array>
+
 // #define QFONTCACHE_DEBUG
 #ifdef QFONTCACHE_DEBUG
 #  define FC_DEBUG qDebug
@@ -140,7 +142,7 @@ Q_GUI_EXPORT int qt_defaultDpi()
 /* Helper function to convert between legacy Qt and OpenType font weights. */
 static int convertWeights(int weight, bool inverted)
 {
-    static const QVarLengthArray<QPair<int, int>, 9> legacyToOpenTypeMap = {
+    static constexpr std::array<int, 2> legacyToOpenTypeMap[] = {
         { 0, QFont::Thin },    { 12, QFont::ExtraLight }, { 25, QFont::Light },
         { 50, QFont::Normal }, { 57, QFont::Medium },     { 63, QFont::DemiBold },
         { 75, QFont::Bold },   { 81, QFont::ExtraBold },  { 87, QFont::Black },
@@ -151,8 +153,8 @@ static int convertWeights(int weight, bool inverted)
 
     // Go through and find the closest mapped value
     for (auto mapping : legacyToOpenTypeMap) {
-        const int weightOld = inverted ? mapping.second : mapping.first;
-        const int weightNew = inverted ? mapping.first : mapping.second;
+        const int weightOld = mapping[ inverted];
+        const int weightNew = mapping[!inverted];
         const int dist = qAbs(weightOld - weight);
         if (dist < closestDist) {
             result = weightNew;