"""Qt presentation port: wheel pans X; Ctrl+wheel pans Y, never zooms."""
from PySide6.QtCore import Qt, Signal
from PySide6.QtWidgets import QScrollArea


class PlotScrollArea(QScrollArea):
    user_scrolled = Signal(str)

    def __init__(self, parent=None):
        super().__init__(parent)
        self._remainder = {'x': 0., 'y': 0.}

    def wheelEvent(self, event):
        axis = 'y' if event.modifiers() & Qt.KeyboardModifier.ControlModifier else 'x'
        bar = self.verticalScrollBar() if axis == 'y' else self.horizontalScrollBar()
        pixels, angle = event.pixelDelta(), event.angleDelta()
        if not pixels.isNull():
            delta = pixels.y() if pixels.y() else pixels.x()
        else:
            delta = (angle.y() if angle.y() else angle.x()) / 120. * 60.
        self._remainder[axis] -= delta
        movement = int(self._remainder[axis])
        self._remainder[axis] -= movement
        if delta:
            self.user_scrolled.emit(axis)
            bar.setValue(bar.value()+movement)
        event.accept()