SageTube/ytsage/gui/ytsage_smooth_tab_widget.py

from PySide6.QtCore import QEasingCurve, QPropertyAnimation, Qt, Signal
from PySide6.QtGui import QPixmap
from PySide6.QtOpenGLWidgets import QOpenGLWidget
from PySide6.QtWidgets import (
    QFrame,
    QGraphicsOpacityEffect,
    QHBoxLayout,
    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

    @staticmethod
    def _contains_gl(widget):
        """Whether an OpenGL surface lives anywhere under this page."""
        if widget is None:
            return False
        return isinstance(widget, QOpenGLWidget) or widget.findChild(QOpenGLWidget) is not None

    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

        # Never fade a page containing an OpenGL surface. grab() on one
        # returns a black rectangle -- so the "fade" was a black slab sliding
        # over the new tab -- and forcing a framebuffer readback plus a
        # QGraphicsEffect over that subtree is a way to lose the GL context,
        # which for the embedded mpv player means a crash.
        if self._contains_gl(widget) or self._contains_gl(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.
    """
    #: Emitted after the visible page has actually changed. The QTabBar's own
    #: currentChanged is not usable for this: it fires before the stack has
    #: switched, and it re-enters through set_current_index.
    currentChanged = Signal(int)

    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, plus a right-aligned slot for a corner widget. Wrapped in a
        # row so something (the account button) can sit opposite the tabs the
        # way QTabWidget::setCornerWidget would allow.
        self.tab_row = QWidget(self)
        tab_row_layout = QHBoxLayout(self.tab_row)
        tab_row_layout.setContentsMargins(0, 0, 0, 0)
        tab_row_layout.setSpacing(0)

        self.tab_bar = QTabBar(self.tab_row)
        self.tab_bar.setDrawBase(False)  # We draw border on content instead
        self.tab_bar.currentChanged.connect(self.set_current_index)
        tab_row_layout.addWidget(self.tab_bar)
        tab_row_layout.addStretch(1)

        self.corner_widget = None
        self._switching = False
        self._tab_row_layout = tab_row_layout
        self.layout.addWidget(self.tab_row)

        # 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, icon=None):
        """Add a tab with the given widget, label and optional icon."""
        self.stack.addWidget(widget)
        if icon is not None:
            self.tab_bar.addTab(icon, label)
        else:
            self.tab_bar.addTab(label)

    def setCornerWidget(self, widget):
        """Place a widget at the right-hand end of the tab row."""
        if self.corner_widget is not None:
            self.corner_widget.setParent(None)
        self.corner_widget = widget
        if widget is not None:
            widget.setParent(self.tab_row)
            self._tab_row_layout.addWidget(widget)

    def set_current_index(self, index):
        """Slot to handle tab bar clicks."""
        if index == self.stack.currentIndex() and self.tab_bar.currentIndex() == index:
            return
        # setCurrentIndex on the bar emits its own currentChanged, which is
        # connected straight back here -- and at that moment the stack has not
        # moved yet, so a plain index comparison does not catch the re-entry.
        # Without this flag every switch emitted currentChanged twice and each
        # page's activation hook ran twice.
        if self._switching:
            return
        self._switching = True
        try:
            self.tab_bar.setCurrentIndex(index)
            self.stack.setCurrentIndex(index)
        finally:
            self._switching = False
        self.currentChanged.emit(index)

    def currentWidget(self):
        return self.stack.currentWidget()

    def currentIndex(self):
        return self.stack.currentIndex()