Fix icon color change in some situations (eg. Appimage)

BUG: 450556
(cherry picked from commit 4ca161d5)

src/main.cpp

@@ -181,16 +181,16 @@ int main(int argc, char *argv[])
     KConfigGroup grp(config, "unmanaged");
     if (!grp.exists()) {
         QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
-        if (env.contains(QStringLiteral("XDG_CURRENT_DESKTOP")) && env.value(QStringLiteral("XDG_CURRENT_DESKTOP")).toLower() == QLatin1String("kde")) {
-            qCDebug(KDENLIVE_LOG) << "KDE Desktop detected, using system icons";
+        if (env.value(QStringLiteral("XDG_CURRENT_DESKTOP")).toLower() == QLatin1String("kde") && packageType != QStringLiteral("appimage")) {
+            qCDebug(KDENLIVE_LOG) << "KDE Desktop detected and not Appimage, using system icons";
         } else {
-            // We are not on a KDE desktop, force breeze icon theme
+            // We are not on a KDE desktop or in an Appimage, force breeze icon theme
             // Check if breeze theme is available
             QStringList iconThemes = KIconTheme::list();
             if (iconThemes.contains(QStringLiteral("breeze"))) {
                 grp.writeEntry("force_breeze", true);
                 grp.writeEntry("use_dark_breeze", true);
-                qCDebug(KDENLIVE_LOG) << "Non KDE Desktop detected, forcing Breeze icon theme";
+                qCDebug(KDENLIVE_LOG) << "Non KDE Desktop or Appimage detected, forcing Breeze icon theme";
             }
         }
     }

src/mainwindow.cpp

@@ -893,8 +893,14 @@ void MainWindow::slotThemeChanged(const QString &name)
 
     KSharedConfigPtr kconfig = KSharedConfig::openConfig();
     KConfigGroup initialGroup(kconfig, "version");
-    if (initialGroup.exists() && KdenliveSettings::force_breeze() && useDarkIcons != KdenliveSettings::use_dark_breeze()) {
-        // We need to reload icon theme
+    QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
+    bool isAppimage = pCore->packageType() == QStringLiteral("appimage");
+    bool isKDE = env.value(QStringLiteral("XDG_CURRENT_DESKTOP")).toLower() == QLatin1String("kde");
+    bool forceBreeze = initialGroup.exists() && KdenliveSettings::force_breeze();
+    if ((!isKDE || isAppimage || forceBreeze) &&
+        ((useDarkIcons && QIcon::themeName() == QStringLiteral("breeze")) || (!useDarkIcons && QIcon::themeName() == QStringLiteral("breeze-dark")))) {
+        // We need to reload icon theme, on KDE desktops this is not necessary, however for the Appimage it is even on KDE Desktop
+        // See also https://kate-editor.org/post/2021/2021-03-07-cross-platform-light-dark-themes-and-icons/
         QIcon::setThemeName(useDarkIcons ? QStringLiteral("breeze-dark") : QStringLiteral("breeze"));
         KdenliveSettings::setUse_dark_breeze(useDarkIcons);
     }