Qt: Handle ApplicationPaletteChange events in the welcome page.

Update our various welcome page style sheets when we receive an
ApplicationPaletteChange event.

It looks like ApplicationPaletteChange is the proper way to detect a
system-wide theme change, since we can infinitely recurse if we hold
things wrong inside a regular PaletteChange event (I'm guessing setting
CSS background and foreground colors were the culprits in this case).
Switch from PaletteChange to ApplicationPaletteChange everywhere.

Ping-Bug: 15511
Change-Id: I6e7aa627d9ca1d1d3872ab31620ea5c579061191
Reviewed-on: https://code.wireshark.org/review/33703
Reviewed-by: Gerald Combs <gerald@wireshark.org>
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>

6 files changed, 121 insertions, 92 deletions

diff --git a/ui/qt/main_window.cpp b/ui/qt/main_window.cpp
index fabde28ecf..6f5593b20d 100644
--- a/ui/qt/main_window.cpp
+++ b/ui/qt/main_window.cpp
@@ -880,7 +880,7 @@ bool MainWindow::eventFilter(QObject *obj, QEvent *event) {
 bool MainWindow::event(QEvent *event)
 {
     switch (event->type()) {
-    case QEvent::PaletteChange:
+    case QEvent::ApplicationPaletteChange:
         initMainToolbarIcons();
         break;
     default:
diff --git a/ui/qt/utils/stock_icon.cpp b/ui/qt/utils/stock_icon.cpp
index b54b36dac8..6e3437937d 100644
--- a/ui/qt/utils/stock_icon.cpp
+++ b/ui/qt/utils/stock_icon.cpp
@@ -29,7 +29,6 @@
 // http://msdn.microsoft.com/en-us/library/ms246582.aspx
 
 // To do:
-// - Respond to dark mode changes via QEvent::PaletteChange.
 // - 32x32, 48x48, 64x64, and unscaled (.svg) icons.
 // - Indent find & go actions when those panes are open.
 // - Replace or remove:
diff --git a/ui/qt/welcome_page.cpp b/ui/qt/welcome_page.cpp
index 4826f82ef7..5c76f2832f 100644
--- a/ui/qt/welcome_page.cpp
+++ b/ui/qt/welcome_page.cpp
@@ -59,101 +59,14 @@ WelcomePage::WelcomePage(QWidget *parent) :
 
     welcome_ui_->captureFilterComboBox->setEnabled(false);
 
-    QColor hover_color = ColorUtils::alphaBlend(palette().window(), palette().highlight(), 0.5);
-
-    QString welcome_ss = QString(
-                "WelcomePage {"
-                "  padding: 1em;"
-                " }"
-                "WelcomePage, QAbstractItemView {"
-                "  background-color: palette(base);"
-                "  color: palette(text);"
-                " }"
-                "QAbstractItemView {"
-                "  border: 0;"
-                "}"
-                );
-#if !defined(Q_OS_WIN)
-    welcome_ss += QString(
-                "QAbstractItemView:item:hover {"
-                "  background-color: %1;"
-                "  color: palette(text);"
-                "}"
-                )
-            .arg(hover_color.name());
-#endif
-    setStyleSheet(welcome_ss);
-
-    QString banner_ss = QString(
-                "QLabel {"
-                "  border-radius: 0.33em;"
-                "  color: %1;"
-                "  background-color: %2;"
-                "  padding: 0.33em;"
-                "}"
-                )
-            .arg(QColor(tango_aluminium_6).name())   // Text color
-            .arg(QColor(tango_sky_blue_2).name());   // Background color
-    welcome_ui_->mainWelcomeBanner->setStyleSheet(banner_ss);
-
-    QString title_button_ss = QString(
-            "QLabel {"
-            "  color: %1;"
-            "}"
-            "QLabel::hover {"
-            "  color: %2;"
-            "}"
-            )
-            .arg(QColor(tango_aluminium_4).name())   // Text color
-            .arg(QColor(tango_sky_blue_4).name());   // Hover color
+    updateStyleSheets();
 
-    // XXX Is there a better term than "flavor"? Provider? Admonition (a la DocBook)?
-    // Release_source?
-    // Typical use cases are automated builds from wireshark.org and private,
-    // not-for-redistribution packages.
-    if (flavor_.isEmpty()) {
-        welcome_ui_->flavorBanner->hide();
-    } else {
-        // If needed there are a couple of ways we can make this customizable.
-        // - Add one or more classes, e.g. "note" or "warning" similar to
-        //   SyntaxLineEdit, which we can then expose vi #defines.
-        // - Just expose direct color values via #defines.
-        QString flavor_ss = QString(
-                    "QLabel {"
-                    "  border-radius: 0.25em;"
-                    "  color: %1;"
-                    "  background-color: %2;"
-                    "  padding: 0.25em;"
-                    "}"
-                    )
-                .arg("white") //   Text color
-                .arg("#2c4bc4"); // Background color. Matches capture start button.
-        //            .arg(QColor(tango_butter_5).name());      // "Warning" background
-
-        welcome_ui_->flavorBanner->setText(flavor_);
-        welcome_ui_->flavorBanner->setStyleSheet(flavor_ss);
-    }
-    welcome_ui_->captureLabel->setStyleSheet(title_button_ss);
-    welcome_ui_->recentLabel->setStyleSheet(title_button_ss);
-    welcome_ui_->helpLabel->setStyleSheet(title_button_ss);
 
 #ifdef Q_OS_MAC
     recent_files_->setAttribute(Qt::WA_MacShowFocusRect, false);
 #endif
 
     welcome_ui_->openFrame->hide();
-    recent_files_->setStyleSheet(
-            "QListWidget::item {"
-            "  padding-top: 0.2em;"
-            "  padding-bottom: 0.2em;"
-            "}"
-            "QListWidget::item::first {"
-            "  padding-top: 0;"
-            "}"
-            "QListWidget::item::last {"
-            "  padding-bottom: 0;"
-            "}"
-            );
     recent_files_->setTextElideMode(Qt::ElideLeft);
 
     recent_ctx_menu_ = new QMenu(this);
@@ -317,6 +230,19 @@ void WelcomePage::interfaceSelected()
     emit interfacesChanged();
 }
 
+bool WelcomePage::event(QEvent *event)
+{
+    switch (event->type()) {
+    case QEvent::ApplicationPaletteChange:
+        updateStyleSheets();
+        break;
+    default:
+        break;
+
+    }
+    return QFrame::event(event);
+}
+
 void WelcomePage::on_interfaceFrame_showExtcapOptions(QString device_name)
 {
     emit showExtcapOptions(device_name);
@@ -498,6 +424,107 @@ void WelcomePage::on_helpLabel_clicked()
     QDesktopServices::openUrl(QUrl(topic_online_url(ONLINEPAGE_DOCS)));
 }
 
+void WelcomePage::updateStyleSheets()
+{
+    QColor hover_color = ColorUtils::alphaBlend(palette().window(), palette().highlight(), 0.5);
+
+    QString welcome_ss = QString(
+                "WelcomePage {"
+                "  padding: 1em;"
+                " }"
+                "WelcomePage, QAbstractItemView {"
+                "  background-color: palette(base);"
+                "  color: palette(text);"
+                " }"
+                "QAbstractItemView {"
+                "  border: 0;"
+                "}"
+                );
+#if !defined(Q_OS_WIN)
+    welcome_ss += QString(
+                "QAbstractItemView:item:hover {"
+                "  background-color: %1;"
+                "  color: palette(text);"
+                "}"
+                )
+            .arg(hover_color.name());
+#endif
+    setStyleSheet(welcome_ss);
+
+    QString banner_ss = QString(
+                "QLabel {"
+                "  border-radius: 0.33em;"
+                "  color: %1;"
+                "  background-color: %2;"
+                "  padding: 0.33em;"
+                "}"
+                )
+            .arg(QColor(tango_aluminium_6).name())   // Text color
+            .arg(QColor(tango_sky_blue_2).name());   // Background color
+    welcome_ui_->mainWelcomeBanner->setStyleSheet(banner_ss);
+
+    QString title_button_ss = QString(
+            "QLabel {"
+            "  color: %1;"
+            "}"
+            "QLabel::hover {"
+            "  color: %2;"
+            "}"
+            )
+            .arg(QColor(tango_aluminium_4).name())   // Text color
+            .arg(QColor(tango_sky_blue_4).name());   // Hover color
+
+    // XXX Is there a better term than "flavor"? Provider? Admonition (a la DocBook)?
+    // Release_source?
+    // Typical use cases are automated builds from wireshark.org and private,
+    // not-for-redistribution packages.
+    if (flavor_.isEmpty()) {
+        welcome_ui_->flavorBanner->hide();
+    } else {
+        // If needed there are a couple of ways we can make this customizable.
+        // - Add one or more classes, e.g. "note" or "warning" similar to
+        //   SyntaxLineEdit, which we can then expose vi #defines.
+        // - Just expose direct color values via #defines.
+        QString flavor_ss = QString(
+                    "QLabel {"
+                    "  border-radius: 0.25em;"
+                    "  color: %1;"
+                    "  background-color: %2;"
+                    "  padding: 0.25em;"
+                    "}"
+                    )
+                .arg("white") //   Text color
+                .arg("#2c4bc4"); // Background color. Matches capture start button.
+        //            .arg(QColor(tango_butter_5).name());      // "Warning" background
+
+        welcome_ui_->flavorBanner->setText(flavor_);
+        welcome_ui_->flavorBanner->setStyleSheet(flavor_ss);
+    }
+    welcome_ui_->captureLabel->setStyleSheet(title_button_ss);
+    welcome_ui_->recentLabel->setStyleSheet(title_button_ss);
+    welcome_ui_->helpLabel->setStyleSheet(title_button_ss);
+
+    recent_files_->setStyleSheet(
+            "QListWidget::item {"
+            "  padding-top: 0.2em;"
+            "  padding-bottom: 0.2em;"
+            "}"
+            "QListWidget::item::first {"
+            "  padding-top: 0;"
+            "}"
+            "QListWidget::item::last {"
+            "  padding-bottom: 0;"
+            "}"
+            );
+
+    // The helpLinks markup includes its own <style>...</style> section.
+    // Replacing it with a stylesheet and reapplying it like we do above
+    // doesn't work, but this does.
+    QString hl_text = welcome_ui_->helpLinks->text();
+    welcome_ui_->helpLinks->clear();
+    welcome_ui_->helpLinks->setText(hl_text);
+}
+
 void WelcomePage::on_recentLabel_clicked()
 {
     wsApp->doTriggerMenuItem(WiresharkApplication::FileOpenDialog);
diff --git a/ui/qt/welcome_page.h b/ui/qt/welcome_page.h
index dce4a64e7e..73aa7f2218 100644
--- a/ui/qt/welcome_page.h
+++ b/ui/qt/welcome_page.h
@@ -37,6 +37,7 @@ public slots:
     void interfaceSelected();
 
 protected:
+    virtual bool event(QEvent *event);
     virtual void resizeEvent(QResizeEvent *event);
     virtual void changeEvent(QEvent* event);
 
@@ -46,6 +47,8 @@ protected slots:
     void on_helpLabel_clicked();
 
 private:
+    void updateStyleSheets();
+
     Ui::WelcomePage *welcome_ui_;
     QString flavor_;
     QString show_in_str_;
diff --git a/ui/qt/widgets/filter_expression_toolbar.cpp b/ui/qt/widgets/filter_expression_toolbar.cpp
index cc56e46c87..89cf3b648f 100644
--- a/ui/qt/widgets/filter_expression_toolbar.cpp
+++ b/ui/qt/widgets/filter_expression_toolbar.cpp
@@ -52,7 +52,7 @@ FilterExpressionToolBar::FilterExpressionToolBar(QWidget * parent) :
 bool FilterExpressionToolBar::event(QEvent *event)
 {
     switch (event->type()) {
-    case QEvent::PaletteChange:
+    case QEvent::ApplicationPaletteChange:
         updateStyleSheet();
         break;
     default:
diff --git a/ui/qt/widgets/stock_icon_tool_button.cpp b/ui/qt/widgets/stock_icon_tool_button.cpp
index 3db550ce78..548f851a6c 100644
--- a/ui/qt/widgets/stock_icon_tool_button.cpp
+++ b/ui/qt/widgets/stock_icon_tool_button.cpp
@@ -95,7 +95,7 @@ bool StockIconToolButton::event(QEvent *event)
         }
         break;
     }
-    case QEvent::PaletteChange:
+    case QEvent::ApplicationPaletteChange:
         setStockIcon();
         break;
     default: