[Style] Confirm broken Windows styles with a dialog offering Fusion (#7507)

* [Style] Confirm broken Windows styles with a dialog offering Fusion

* [Style] Address review nits on broken style dialog

Extract Fusion index lookup into findFusionIndex helper and add all
message box buttons before choosing the default button.

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/interface/widgets/settings_page/appearance_settings_page.cpp

@@ -23,6 +23,7 @@
 #include <QGroupBox>
 #include <QMessageBox>
 #include <QObject>
+#include <QPushButton>
 #include <QSharedPointer>
 #include <QString>
 #include <QStringList>
@@ -84,10 +85,9 @@ AppearanceSettingsPage::AppearanceSettingsPage()
     const QString currentStyle = cfg.styleName;
     const int styleSeedIdx = currentStyle.isEmpty() ? 0 : styleCombo.findData(currentStyle);
     styleCombo.setCurrentIndex(styleSeedIdx >= 0 ? styleSeedIdx : 0);
+    previousStyle = styleCombo.currentData().toString();
 
-    connect(&styleCombo, &QComboBox::currentIndexChanged, this,
-            [this] { themeManager->setStyleName(styleCombo.currentData().toString()); });
-    connect(&styleCombo, &QComboBox::currentIndexChanged, this, &AppearanceSettingsPage::updateStyleWarning);
+    connect(&styleCombo, &QComboBox::currentIndexChanged, this, &AppearanceSettingsPage::styleComboChanged);
 
     connect(themeManager, &ThemeManager::themeChanged, this, [this, dirPath] {
         const QString newDir = themeManager->getAvailableThemes().value(SettingsCache::instance().getThemeName());
@@ -104,6 +104,7 @@ AppearanceSettingsPage::AppearanceSettingsPage()
         const int styleIdx = currentStyle.isEmpty() ? 0 : styleCombo.findData(currentStyle);
         styleCombo.setCurrentIndex(styleIdx >= 0 ? styleIdx : 0);
         styleCombo.blockSignals(false);
+        previousStyle = styleCombo.currentData().toString();
 
         updateStyleWarning();
     });
@@ -467,12 +468,88 @@ void AppearanceSettingsPage::updateHomeTabSettingsVisibility()
     homeTabDisplayCardNameCheckBox.setVisible(visible);
 }
 
+static bool isBrokenStyle(const QString &style)
+{
+    return style.compare("windows11", Qt::CaseInsensitive) == 0 ||
+           style.compare("windowsvista", Qt::CaseInsensitive) == 0;
+}
+
+static int findFusionIndex(const QComboBox &combo)
+{
+    int fusionIdx = combo.findData(QStringLiteral("Fusion"));
+    if (fusionIdx >= 0) {
+        return fusionIdx;
+    }
+    for (int i = 0; i < combo.count(); ++i) {
+        if (combo.itemData(i).toString().compare(QStringLiteral("Fusion"), Qt::CaseInsensitive) == 0) {
+            return i;
+        }
+    }
+    return -1;
+}
+
 void AppearanceSettingsPage::updateStyleWarning()
 {
-    const QString style = styleCombo.currentData().toString();
-    const bool broken =
-        style.compare("windows11", Qt::CaseInsensitive) == 0 || style.compare("windowsvista", Qt::CaseInsensitive) == 0;
-    styleWarningLabel.setVisible(broken);
+    styleWarningLabel.setVisible(isBrokenStyle(styleCombo.currentData().toString()));
+}
+
+void AppearanceSettingsPage::styleComboChanged(int index)
+{
+    if (index < 0) {
+        return;
+    }
+
+    const QString newStyle = styleCombo.itemData(index).toString();
+    if (!isBrokenStyle(newStyle)) {
+        themeManager->setStyleName(newStyle);
+        previousStyle = newStyle;
+        updateStyleWarning();
+        return;
+    }
+
+    QMessageBox msgBox(this);
+    msgBox.setWindowTitle(tr("Broken style"));
+    msgBox.setIcon(QMessageBox::Warning);
+    msgBox.setText(tr("The \"%1\" style is broken and can break the game view: dragging cards across zones can "
+                      "shrink the board to a tiny grey window that can only be fixed by rejoining the game.")
+                       .arg(newStyle));
+    msgBox.setInformativeText(
+        tr("It can also render controls such as combo boxes unreadable, especially in dark mode.\n\n"
+           "Fusion is the recommended style on every platform. Switch to Fusion instead?"));
+
+    int fusionIdx = findFusionIndex(styleCombo);
+    QPushButton *fusionButton = nullptr;
+    if (fusionIdx >= 0) {
+        fusionButton = msgBox.addButton(tr("Use Fusion instead"), QMessageBox::AcceptRole);
+    }
+    QPushButton *keepButton = msgBox.addButton(tr("Use %1 anyway").arg(newStyle), QMessageBox::DestructiveRole);
+    msgBox.addButton(QMessageBox::Cancel);
+    if (fusionButton != nullptr) {
+        msgBox.setDefaultButton(fusionButton);
+    } else {
+        msgBox.setDefaultButton(keepButton);
+    }
+
+    msgBox.exec();
+
+    const QAbstractButton *clicked = msgBox.clickedButton();
+    if (fusionButton != nullptr && clicked == fusionButton) {
+        styleCombo.setCurrentIndex(fusionIdx);
+        return;
+    }
+    if (clicked == keepButton) {
+        themeManager->setStyleName(newStyle);
+        previousStyle = newStyle;
+        updateStyleWarning();
+        return;
+    }
+
+    // Cancel: revert to the previously applied style without re-prompting
+    styleCombo.blockSignals(true);
+    const int previousIdx = styleCombo.findData(previousStyle);
+    styleCombo.setCurrentIndex(previousIdx >= 0 ? previousIdx : 0);
+    styleCombo.blockSignals(false);
+    updateStyleWarning();
 }
 
 void AppearanceSettingsPage::showShortcutsChanged(QT_STATE_CHANGED_T value)
@@ -538,9 +615,10 @@ void AppearanceSettingsPage::retranslateUi()
     styleComboLabel.setText(tr("Active theme style:"));
     styleCombo.setToolTip(tr("Qt widget style saved to this theme (\"System\" lets the application decide)"));
     styleWarningLabel.setText(
-        tr("Warning: the Windows 11 and Windows Vista styles are buggy and can render controls such as combo boxes "
-           "unreadable, especially in dark mode. Fusion is the recommended style on every platform: it is Qt's "
-           "cross-platform style and the one Cockatrice is developed against."));
+        tr("Warning: the Windows 11 and Windows Vista styles are broken and can break the game view (dragging "
+           "cards can shrink the board to a tiny grey window that requires rejoining to fix), and can render "
+           "controls such as combo boxes unreadable, especially in dark mode. Fusion is the recommended style on "
+           "every platform: it is Qt's cross-platform style and the one Cockatrice is developed against."));
     updateStyleWarning();
     editPaletteButton.setText(tr("Edit theme palette"));
 

cockatrice/src/interface/widgets/settings_page/appearance_settings_page.h

@@ -23,6 +23,7 @@ private slots:
     void editPalette();
     void updateHomeTabSettingsVisibility();
     void updateStyleWarning();
+    void styleComboChanged(int index);
     void showShortcutsChanged(QT_STATE_CHANGED_T enabled);
     void overrideAllCardArtWithPersonalPreferenceToggled(QT_STATE_CHANGED_T enabled);
 
@@ -40,6 +41,7 @@ private:
     QComboBox styleCombo;
     QLabel styleWarningLabel;
     QPushButton editPaletteButton;
+    QString previousStyle;
 
     QLabel homeTabBackgroundSourceLabel;
     QComboBox homeTabBackgroundSourceBox;