Add smooth tab widget with fade transitions

Introduce SmoothTabWidget and a FadingStackedWidget to provide cross-fade transitions between tabs. Added ytsage/gui/ytsage_smooth_tab_widget.py which implements a QTabBar + FadingStackedWidget (default 300ms fade) and overlay-based fade logic. Updated ytsage/gui/ytsage_gui_dialogs/ytsage_dialogs_custom.py to use SmoothTabWidget instead of QTabWidget and adjusted the stylesheet selector to target the new content frame (#tabContent) so existing styles continue to apply.

ytsage/gui/ytsage_gui_dialogs/ytsage_dialogs_custom.py

@@ -29,6 +29,7 @@ from PySide6.QtWidgets import (
     QWidget,
 )
 
+from ..ytsage_smooth_tab_widget import SmoothTabWidget
 from ...core.ytsage_yt_dlp import get_yt_dlp_path
 from ...core.ytsage_utils import update_auto_update_settings
 from ...utils.ytsage_constants import YTDLP_DOCS_URL
@@ -115,7 +116,7 @@ class CustomOptionsDialog(QDialog):
         layout = QVBoxLayout(self)
 
         # Create tab widget to organize content
-        self.tab_widget = QTabWidget()
+        self.tab_widget = SmoothTabWidget()
         layout.addWidget(self.tab_widget)
 
         # === Cookies Tab ===
@@ -542,7 +543,7 @@ class CustomOptionsDialog(QDialog):
             QDialog {
                 background-color: #15181b;
             }
-            QTabWidget::pane { 
+            QFrame#tabContent { 
                 border: 1px solid #3d3d3d;
                 background-color: #15181b;
             }

ytsage/gui/ytsage_smooth_tab_widget.py

@@ -0,0 +1,123 @@
+from PySide6.QtCore import QEasingCurve, QPropertyAnimation, Qt
+from PySide6.QtGui import QPixmap
+from PySide6.QtWidgets import (
+    QFrame,
+    QGraphicsOpacityEffect,
+    QLabel,
+    QStackedWidget,
+    QTabBar,
+    QVBoxLayout,
+    QWidget,
+)
+
+class FadingStackedWidget(QStackedWidget):
+    """
+    A QStackedWidget that cross-fades between widgets.
+    """
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self.fade_duration = 300 
+        self.fade_easing = QEasingCurve.Type.OutQuad
+
+    def setCurrentIndex(self, index):
+        curr_index = self.currentIndex()
+        if index == curr_index:
+            return
+
+        widget = self.widget(index)
+        curr_widget = self.widget(curr_index)
+        
+        # If widget isn't visible or valid, just swap
+        if not self.isVisible() or not curr_widget:
+            super().setCurrentIndex(index)
+            return
+
+        # 1. Capture the current view (the "old" tab)
+        # Use grab() for simplicity and reliability in PySide6
+        pixmap = self.grab()
+        
+        # 2. Create an overlay label to hold this "old" view
+        overlay = QLabel(self)
+        overlay.setPixmap(pixmap)
+        overlay.setGeometry(0, 0, self.width(), self.height())
+        overlay.setAttribute(Qt.WidgetAttribute.WA_TransparentForMouseEvents) # Don't block clicks
+        overlay.show()
+        
+        # 3. Switch the actual stack to the "new" view
+        super().setCurrentIndex(index)
+        
+        # CRITICAL: Ensure overlay stays on top of the new widget
+        overlay.raise_()
+        
+        # 4. Fade OUT the overlay, revealing the new view
+        effect = QGraphicsOpacityEffect(overlay)
+        overlay.setGraphicsEffect(effect)
+
+        
+        anim = QPropertyAnimation(effect, b"opacity", overlay)
+        anim.setDuration(self.fade_duration)
+        anim.setStartValue(1.0)
+        anim.setEndValue(0.0)
+        anim.setEasingCurve(self.fade_easing)
+        
+        # Cleanup when done
+        anim.finished.connect(lambda: self._cleanup(overlay))
+        
+        # Keep reference to prevent GC
+        self._active_anim = anim 
+        anim.start(QPropertyAnimation.DeletionPolicy.DeleteWhenStopped)
+
+    def _cleanup(self, overlay):
+        overlay.hide()
+        overlay.deleteLater()
+
+
+class SmoothTabWidget(QWidget):
+    """
+    A unified Widget that behaves like a QTabWidget but uses smooth fading transitions.
+    Includes a QTabBar and a FadingStackedWidget.
+    """
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        
+        # Main Layout
+        self.layout = QVBoxLayout(self)
+        self.layout.setContentsMargins(0, 0, 0, 0)
+        self.layout.setSpacing(0)
+        
+        # Tab Bar
+        self.tab_bar = QTabBar(self)
+        self.tab_bar.setDrawBase(False) # We draw border on content instead
+        self.tab_bar.currentChanged.connect(self.set_current_index)
+        self.layout.addWidget(self.tab_bar)
+        
+        # Content Area (Frame) - Mimics QTabWidget::pane
+        self.content_frame = QFrame(self)
+        self.content_frame.setObjectName("tabContent") 
+        
+        # Layout inside the content frame
+        self.content_layout = QVBoxLayout(self.content_frame)
+        self.content_layout.setContentsMargins(0, 0, 0, 0)
+        self.content_layout.setSpacing(0)
+        
+        # The Stack
+        self.stack = FadingStackedWidget(self.content_frame)
+        self.content_layout.addWidget(self.stack)
+        
+        self.layout.addWidget(self.content_frame)
+
+    def addTab(self, widget, label):
+        """Add a tab with the given widget and label."""
+        self.stack.addWidget(widget)
+        self.tab_bar.addTab(label)
+
+    def set_current_index(self, index):
+        """Slot to handle tab bar clicks."""
+        self.tab_bar.setCurrentIndex(index)
+        self.stack.setCurrentIndex(index)
+
+    def currentWidget(self):
+        return self.stack.currentWidget()
+
+    def currentIndex(self):
+        return self.stack.currentIndex()