From d4643a627b631a74cfaaa049dfd516cc734f367e Mon Sep 17 00:00:00 2001
From: Alessandro Portale <alessandro.portale@qt.io>
Date: Wed, 20 Jul 2022 12:21:52 +0200
Subject: [PATCH] App: Set QPixmapCache limit according to devicePixelRatio

Higher resolution also means more data to be cached. The default 10MB
cache limit don't cut it in HighDpi, especially in cache-intensive parts
like the welcome screen.

Change-Id: I653a939c3a37f80647d73e8de8df616d5386e39c
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
---
 src/app/main.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/app/main.cpp b/src/app/main.cpp
index 0ba1ea6a05a..8b7b8d62944 100644
--- a/src/app/main.cpp
+++ b/src/app/main.cpp
@@ -63,6 +63,7 @@
 
 #include <QApplication>
 #include <QMessageBox>
+#include <QPixmapCache>
 #include <QProcess>
 #include <QStandardPaths>
 #include <QTemporaryDir>
@@ -294,6 +295,14 @@ static void setHighDpiEnvironmentVariable()
     }
 }
 
+void setPixmapCacheLimit()
+{
+    const int originalLimit = QPixmapCache::cacheLimit();
+    const qreal dpr = qApp->devicePixelRatio();
+    const qreal multiplier = std::clamp(dpr * dpr, 1.0, 4.0);
+    QPixmapCache::setCacheLimit(originalLimit * multiplier);
+}
+
 void loadFonts()
 {
     const QDir dir(resourcePath() + "/fonts/");
@@ -562,6 +571,7 @@ int main(int argc, char **argv)
                                  QLatin1String(Core::Constants::IDE_SETTINGSVARIANT_STR),
                                  QLatin1String(Core::Constants::IDE_CASED_ID));
     Utils::TerminalCommand::setSettings(settings);
+    setPixmapCacheLimit();
     loadFonts();
 
     if (Utils::HostOsInfo::isWindowsHost()