"""Queued redraws and cached static layers for Qt plots (Qt 5/6)."""
try:
    from PySide6.QtCore import QTimer, Qt
    from PySide6.QtGui import QPixmap, QPainter
except ImportError:
    from PySide2.QtCore import QTimer, Qt
    from PySide2.QtGui import QPixmap, QPainter

class PlotLayers:
    def init_plot_layers(self):
        self._static_revision = 0
        self._static_plot_layer = None
        self._redraw_timer = QTimer(self)
        self._redraw_timer.setSingleShot(True)
        self._redraw_timer.timeout.connect(self._flush_plot_update)

    def update(self, *args):
        if not hasattr(self, '_redraw_timer'):
            return super().update(*args)
        self._static_revision += 1
        self.update_overlay()

    def update_overlay(self):
        if not hasattr(self, '_redraw_timer'):
            return super().update()
        if not self._redraw_timer.isActive():
            self._redraw_timer.start(0)

    def _flush_plot_update(self):
        super().update()

    def paint_static_layer(self, painter, draw):
        ratio = self.devicePixelRatioF()
        key = (self._static_revision, self.width(), self.height(), ratio,
               tuple(self.plot_rect().getRect()))
        if self._static_plot_layer is None or self._static_plot_layer[0] != key:
            image = QPixmap(round(self.width()*ratio), round(self.height()*ratio))
            image.setDevicePixelRatio(ratio)
            image.fill(Qt.GlobalColor.transparent)
            layer = QPainter(image)
            try:
                draw(layer)
            finally:
                layer.end()
            self._static_plot_layer = key, image
        painter.drawPixmap(0, 0, self._static_plot_layer[1])