Unify system palette initialization during style change

We let initSystemPalette() do all the work, instead of leaving the first
time initialization of the system palette to the caller, which makes the
logic harder to follow.

This also means first time initialization of the system palette will
pick up a platform theme if available and resolve the palette using
that, which was missing from the original logic.

Change-Id: I84da557caf8ecedf6d96d87ebee93168ea9d73ba
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

1 files changed, 16 insertions, 15 deletions

diff --git a/src/widgets/kernel/qapplication.cpp b/src/widgets/kernel/qapplication.cpp
index b3938df78a..37948ecd8c 100644
--- a/src/widgets/kernel/qapplication.cpp
+++ b/src/widgets/kernel/qapplication.cpp
@@ -142,16 +142,19 @@ QApplicationPrivate *QApplicationPrivate::self = 0;
 
 static void initSystemPalette()
 {
-    if (!QApplicationPrivate::sys_pal) {
-        QPalette defaultPlatte;
-        if (QApplicationPrivate::app_style)
-            defaultPlatte = QApplicationPrivate::app_style->standardPalette();
-        if (const QPalette *themePalette = QGuiApplicationPrivate::platformTheme()->palette()) {
-            QApplicationPrivate::setSystemPalette(themePalette->resolve(defaultPlatte));
-            QApplicationPrivate::initializeWidgetPaletteHash();
-        } else {
-            QApplicationPrivate::setSystemPalette(defaultPlatte);
-        }
+    if (QApplicationPrivate::sys_pal)
+        return; // Already initialized
+
+    QPalette defaultPalette;
+    if (QApplicationPrivate::app_style)
+        defaultPalette = QApplicationPrivate::app_style->standardPalette();
+
+    auto *platformTheme = QGuiApplicationPrivate::platformTheme();
+    if (const QPalette *themePalette = platformTheme ? platformTheme->palette() : nullptr) {
+        QApplicationPrivate::setSystemPalette(themePalette->resolve(defaultPalette));
+        QApplicationPrivate::initializeWidgetPaletteHash();
+    } else {
+        QApplicationPrivate::setSystemPalette(defaultPalette);
     }
 }
 
@@ -1130,12 +1133,10 @@ void QApplication::setStyle(QStyle *style)
     // might call QApplication::setPalette() itself
     if (QApplicationPrivate::set_pal) {
         QApplication::setPalette(*QApplicationPrivate::set_pal);
-    } else if (QApplicationPrivate::sys_pal) {
-        clearSystemPalette();
+    } else {
+        if (QApplicationPrivate::sys_pal)
+            clearSystemPalette();
         initSystemPalette();
-    } else if (!QApplicationPrivate::sys_pal) {
-        // Initialize the sys_pal if it hasn't happened yet...
-        QApplicationPrivate::setSystemPalette(QApplicationPrivate::app_style->standardPalette());
     }
 
     // The default widget font hash is based on the platform theme,