nixpkgs/pkgs/desktops/plasma-5/kwin/0001-NixOS-Unwrap-executable-name-for-.desktop-search.patch

From 29ec6fada935ef966e5859082435ed57daa9522d Mon Sep 17 00:00:00 2001
From: Samuel Dionne-Riel <samuel@dionne-riel.com>
Date: Tue, 16 Mar 2021 15:03:59 -0400
Subject: [PATCH] [NixOS] Unwrap executable name for .desktop search

Why is this necessary even though -a "$0" is used in the wrapper?
Because it's completely bypassing argv0! This looks at the executable
file in-use according to the kernel!

Wrappers cannot affect the `/proc/.../exe` symlink!
---
 service_utils.h | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/service_utils.h b/service_utils.h
index 8a70c1fad..6674f553b 100644
--- a/service_utils.h
+++ b/service_utils.h
@@ -26,8 +26,34 @@ namespace KWin
 const static QString s_waylandInterfaceName = QStringLiteral("X-KDE-Wayland-Interfaces");
 const static QString s_dbusRestrictedInterfaceName = QStringLiteral("X-KDE-DBUS-Restricted-Interfaces");
 
-static QStringList fetchProcessServiceField(const QString &executablePath, const QString &fieldName)
+static QStringList fetchProcessServiceField(const QString &in_executablePath, const QString &fieldName)
 {
+    // !! Start NixOS fix
+    // NixOS fixes many packaging issues through "wrapper" scripts that manipulates the environment or does
+    // miscellaneous trickeries and mischievous things to make the programs work.
+    // In turn, programs often employs different mischievous schemes and trickeries to do *other things.
+    // It often happens that they conflict.
+    // Here, `kwin` tries to detect the .desktop file for a given process.
+    // `kwin` followed the process `/proc/.../exe` up to the actual binary running.
+    // It normally would be fine, e.g. /usr/bin/foobar is what's in the desktop file.
+    // But it's not the truth here! It's extremely likely the resolved path is /nix/store/.../bin/.foobar-wrapped
+    // rather than what the desktop file points to, something like /nix/store/.../bin/foobar !!
+    // Since the wrappers for Nixpkgs *always* prepend a dot and append -wrapped, we assume here that we can keep
+    // `/^(.*)\/\.([^/]*)-wrapped/` until the (equivalent) regex does not match.
+    // This should canonicalize the wrapper name to the expected name to look for in the desktop file.
+
+    // Use a copy of the const string
+    QString executablePath(in_executablePath);
+
+    // While the parts needed are present, "unwrap" one layer of wrapper names.
+    while (executablePath.endsWith("-wrapped") && executablePath[executablePath.lastIndexOf("/")+1] == QChar('.')) {
+        // Approximately equivalent to s/-wrapped$//
+        executablePath.remove(executablePath.length() - 8, 8);
+        // Approximately equivalent to s;/\.;/;
+        executablePath.remove(executablePath.lastIndexOf("/")+1, 1);
+    }
+    // !! End NixOS fix
+
     // needed to be able to use the logging category in a header static function
     static QLoggingCategory KWIN_UTILS ("KWIN_UTILS", QtWarningMsg);
     const auto servicesFound = KApplicationTrader::query([&executablePath] (const KService::Ptr &service) {
-- 
2.28.0