Merge bitcoin-core#366: Dark Mode fixes/portability

9d5bf6b GUI: Always call parent changeEvent handler (Luke Dashjr)
c901d4d GUI: Enable palette change adaptation on all platforms (Luke Dashjr)

Pull request description:

  The changes to support macOS "Dark Mode" are valid for any platform, and should work so long as Qt implements the PaletteChange event. (Worst case, we're no worse off with trying.)

  Additionally, we shouldn't block the parent classes from implementing event handlers. Who knows what side effects that could have.

ACKs for top commit:
  hebasto:
    ACK 9d5bf6b, tested on Linux Mint 20.1 (Qt 5.12.8) with the [`qt5ct`](https://packages.ubuntu.com/focal/qt5ct) package installed.
  kristapsk:
    ACK 9d5bf6b. Tested on Gentoo Linux with Xfce4 and Qt 5.15.2, does not break anything on my computer.

Tree-SHA512: dce2fff0ff129eda208132390a37424ff9607539287dbdbfdfd659ed9c4ea0472541e987489a04fd935e391dc006a35bfc9cfa9bcff33602b7dbd29b81c51626

Author: hebasto

src/qt/bitcoingui.cpp

@@ -1173,14 +1173,12 @@ void BitcoinGUI::message(const QString& title, QString message, unsigned int sty
 
 void BitcoinGUI::changeEvent(QEvent *e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         overviewAction->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/overview")));
         sendCoinsAction->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/send")));
         receiveCoinsAction->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/receiving_addresses")));
         historyAction->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/history")));
     }
-#endif
 
     QMainWindow::changeEvent(e);
 
@@ -1511,14 +1509,14 @@ void UnitDisplayStatusBarControl::mousePressEvent(QMouseEvent *event)
 
 void UnitDisplayStatusBarControl::changeEvent(QEvent* e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         QString style = QString("QLabel { color : %1 }").arg(m_platform_style->SingleColor().name());
         if (style != styleSheet()) {
             setStyleSheet(style);
         }
     }
-#endif
+
+    QLabel::changeEvent(e);
 }
 
 /** Creates context menu, its actions, and wires up all the relevant signals for mouse events. */

src/qt/coincontroldialog.cpp

@@ -564,11 +564,11 @@ void CoinControlDialog::updateLabels(CCoinControl& m_coin_control, WalletModel *
 
 void CoinControlDialog::changeEvent(QEvent* e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         updateView();
     }
-#endif
+
+    QDialog::changeEvent(e);
 }
 
 void CoinControlDialog::updateView()

src/qt/guiutil.cpp

@@ -809,11 +809,10 @@ void ThemedLabel::setThemedPixmap(const QString& image_filename, int width, int
 
 void ThemedLabel::changeEvent(QEvent* e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         updateThemedPixmap();
     }
-#endif
+
     QLabel::changeEvent(e);
 }
 

src/qt/overviewpage.cpp

@@ -297,13 +297,13 @@ void OverviewPage::setWalletModel(WalletModel *model)
 
 void OverviewPage::changeEvent(QEvent* e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         QIcon icon = m_platform_style->SingleColorIcon(QStringLiteral(":/icons/warning"));
         ui->labelTransactionsStatus->setIcon(icon);
         ui->labelWalletStatus->setIcon(icon);
     }
-#endif
+
+    QWidget::changeEvent(e);
 }
 
 void OverviewPage::updateDisplayUnit()

src/qt/rpcconsole.cpp

@@ -882,7 +882,6 @@ void RPCConsole::keyPressEvent(QKeyEvent *event)
 
 void RPCConsole::changeEvent(QEvent* e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         ui->clearButton->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/remove")));
         ui->fontBiggerButton->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/fontbigger")));
@@ -896,7 +895,8 @@ void RPCConsole::changeEvent(QEvent* e)
                 platformStyle->SingleColorImage(ICON_MAPPING[i].source).scaled(QSize(consoleFontSize * 2, consoleFontSize * 2), Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
         }
     }
-#endif
+
+    QWidget::changeEvent(e);
 }
 
 void RPCConsole::message(int category, const QString &message, bool html)

src/qt/sendcoinsentry.cpp

@@ -238,15 +238,15 @@ void SendCoinsEntry::updateDisplayUnit()
 
 void SendCoinsEntry::changeEvent(QEvent* e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         ui->addressBookButton->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/address-book")));
         ui->pasteButton->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/editpaste")));
         ui->deleteButton->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/remove")));
         ui->deleteButton_is->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/remove")));
         ui->deleteButton_s->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/remove")));
     }
-#endif
+
+    QStackedWidget::changeEvent(e);
 }
 
 bool SendCoinsEntry::updateLabel(const QString &address)

src/qt/signverifymessagedialog.cpp

@@ -286,7 +286,6 @@ bool SignVerifyMessageDialog::eventFilter(QObject *object, QEvent *event)
 
 void SignVerifyMessageDialog::changeEvent(QEvent* e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         ui->addressBookButton_SM->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/address-book")));
         ui->pasteButton_SM->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/editpaste")));
@@ -297,5 +296,6 @@ void SignVerifyMessageDialog::changeEvent(QEvent* e)
         ui->verifyMessageButton_VM->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/transaction_0")));
         ui->clearButton_VM->setIcon(platformStyle->SingleColorIcon(QStringLiteral(":/icons/remove")));
     }
-#endif
+
+    QDialog::changeEvent(e);
 }

src/qt/transactionview.cpp

@@ -245,7 +245,6 @@ void TransactionView::setModel(WalletModel *_model)
 
 void TransactionView::changeEvent(QEvent* e)
 {
-#ifdef Q_OS_MACOS
     if (e->type() == QEvent::PaletteChange) {
         watchOnlyWidget->setItemIcon(
             TransactionFilterProxy::WatchOnlyFilter_Yes,
@@ -254,7 +253,8 @@ void TransactionView::changeEvent(QEvent* e)
             TransactionFilterProxy::WatchOnlyFilter_No,
             m_platform_style->SingleColorIcon(QStringLiteral(":/icons/eye_minus")));
     }
-#endif
+
+    QWidget::changeEvent(e);
 }
 
 void TransactionView::chooseDate(int idx)