Remove QT+GNOME+Wayland 'xcb' hack on fixed Qt versions (flameshot-org#3683)

* Bypass the Qt GNOME/Wayland workaround on fixed Qt versions

We implement code on GNOME desktops to force the
QT_QPA_PLATFORM to be 'xcb'; this works around a
clipboard-related bug on GNOME+Wayland+Qt.

This bug was fixed (or worked around) in Qt 5.15.2,
so we implement a version check; if the runtime Qt
version is < 5.15.2, still force the workaround;
otherwise, we don't need the workaround so we skip
it.

* Reformat with clang-format

Author: danudey

src/main.cpp

@@ -37,10 +37,28 @@
 // source: https://github.com/ksnip/ksnip/issues/416
 void wayland_hacks()
 {
-    // Workaround to https://github.com/ksnip/ksnip/issues/416
+    int suffixIndex;
     DesktopInfo info;
-    if (info.windowManager() == DesktopInfo::GNOME) {
-        qputenv("QT_QPA_PLATFORM", "xcb");
+
+    const char* qt_version = qVersion();
+
+    QVersionNumber targetVersion(5, 15, 2);
+    QString string(qt_version);
+    QVersionNumber currentVersion =
+      QVersionNumber::fromString(string, &suffixIndex);
+
+    if (currentVersion < targetVersion) {
+        if (info.windowManager() == DesktopInfo::GNOME) {
+            qWarning()
+              << "Qt versions lower than" << targetVersion.toString()
+              << "on GNOME using Wayland have a bug when accessing the "
+                 "clipboard."
+              << "Your version is" << currentVersion.toString()
+              << "so we're forcing QT_QPA_PLATFORM to 'xcb'."
+              << "To use native Wayland, please upgrade your Qt version to"
+              << targetVersion.toString() << "or higher";
+            qputenv("QT_QPA_PLATFORM", "xcb");
+        }
     }
 }
 #endif