ScrollBar 始终显示 QTextBrowser 流式文本的底部

Question

我正在将 "stdout" 和 "stderr" 传送到 pyqt5 GUI 中的嵌入式 QTextBrowser 小部件。一切正常，但如果我通过管道传输很长的输出（这种情况一直发生），则小部件的滚动条始终位于最后一个上部位置，因此我无法实时看到新输出。这真的很烦人！我尝试了我在互联网上可以找到的所有内容，但仍然没有成功。不能太难....请睁开眼睛！

我使用的代码在这里（我想是在 Whosebug 上找到的）：

import sys
from PyQt4 import QtCore, QtGui

import logging
logger = logging.getLogger(__name__)

class QtHandler(logging.Handler):

    def __init__(self):
        logging.Handler.__init__(self)

    def emit(self, record):
        record = self.format(record)
        XStream.stdout().write("{}\n".format(record))

handler = QtHandler()
handler.setFormatter(logging.Formatter("%(levelname)s: %(message)s"))
logger.addHandler(handler)
logger.setLevel(logging.DEBUG)



class XStream(QtCore.QObject):
    _stdout = None
    _stderr = None
    messageWritten = QtCore.pyqtSignal(str)
    def flush( self ):
        pass
    def fileno( self ):
        return -1
    def write( self, msg ):
        if ( not self.signalsBlocked() ):
            self.messageWritten.emit(msg)
    @staticmethod
    def stdout():
        if ( not XStream._stdout ):
            XStream._stdout = XStream()
            sys.stdout = XStream._stdout
        return XStream._stdout
    @staticmethod
    def stderr():
        if ( not XStream._stderr ):
            XStream._stderr = XStream()
            sys.stderr = XStream._stderr

        return XStream._stderr

class MyDialog(QtGui.QDialog):
    def __init__( self, parent = None ):
        super(MyDialog, self).__init__(parent)

        self._console = QtGui.QTextBrowser(self)      
        self._console.moveCursor(QtGui.QTextCursor.End)

        layout = QtGui.QVBoxLayout()
        layout.addWidget(self._console)
        self.setLayout(layout)

        XStream.stdout().messageWritten.connect(self._console.insertPlainText)
        XStream.stderr().messageWritten.connect(self._console.insertPlainText)

        self.pipe_output()


    def pipe_output( self ):
        logger.debug('debug message')
        logger.info('info message')
        logger.warning('warning message')
        logger.error('error message')
        #print('Old school hand made print message')

if ( __name__ == '__main__' ):
    #app = None
    # if ( not QtGui.QApplication.instance() ):
    app = QtGui.QApplication([])
    dlg = MyDialog()
    dlg.show()

    #if ( app ):
    app.exec_()

这是打印屏幕

Answer 1

我过去做过类似的东西，一个日志消息查看器，当添加新消息时会滚动到底部。它基于 QTextEdit，但由于 QTextBrowser 也有一个 verticalScrolBar 方法，我相信您可以轻松地将其用于 QTextBrower.

class LogMessageViewer(QtWidgets.QTextEdit):

    def __init__(self, parent=None):
        super().__init__(parent=parent)
        self.setReadOnly(True)
        self.setLineWrapMode(QtWidgets.QTextEdit.NoWrap)


    @pyqtSlot(str)
    def appendLogMessage(self, msg):
        horScrollBar = self.horizontalScrollBar()
        verScrollBar = self.verticalScrollBar()
        scrollIsAtEnd = verScrollBar.maximum() - verScrollBar.value() <= 10

        self.append(msg)

        if scrollIsAtEnd:
            verScrollBar.setValue(verScrollBar.maximum()) # Scrolls to the bottom
            horScrollBar.setValue(0) # scroll to the left

请注意，只有当当前滚动位置已经在距离底部 10 像素以内时，它才会自动滚动。这使您可以向上滚动并查看较早的文本，而不会被新输出打断。只需滚动回底部即可再次获取实时更新。

Answer 2

多亏了titusjan和eyllanesc，我才能如愿以偿！

有效的代码是：

import sys
from PyQt5 import QtCore, QtGui

import logging
logger = logging.getLogger(__name__)

class QtHandler(logging.Handler):

    def __init__(self):
        logging.Handler.__init__(self)

    def emit(self, record):
        record = self.format(record)
        XStream.stdout().write("{}\n".format(record))

handler = QtHandler()
handler.setFormatter(logging.Formatter("%(levelname)s: %(message)s"))
logger.addHandler(handler)
logger.setLevel(logging.DEBUG)

class XStream(QtCore.QObject):
    _stdout = None
    _stderr = None
    messageWritten = QtCore.pyqtSignal(str)
    def flush( self ):
        pass
    def fileno( self ):
        return -1
    def write( self, msg ):
        if ( not self.signalsBlocked() ):
            self.messageWritten.emit(msg)
    @staticmethod
    def stdout():
        if ( not XStream._stdout ):
            XStream._stdout = XStream()
            sys.stdout = XStream._stdout
        return XStream._stdout
    @staticmethod
    def stderr():
        if ( not XStream._stderr ):
            XStream._stderr = XStream()
            sys.stderr = XStream._stderr

        return XStream._stderr

class LogMessageViewer(QtGui.QTextBrowser):

    def __init__(self, parent=None):
        super(LogMessageViewer,self).__init__(parent)
        self.setReadOnly(True)
        #self.setLineWrapMode(QtGui.QTextEdit.NoWrap)


    @QtCore.pyqtSlot(str)
    def appendLogMessage(self, msg):
        horScrollBar = self.horizontalScrollBar()
        verScrollBar = self.verticalScrollBar()
        scrollIsAtEnd = verScrollBar.maximum() - verScrollBar.value() <= 10

        self.insertPlainText(msg)

        if scrollIsAtEnd:
            verScrollBar.setValue(verScrollBar.maximum()) # Scrolls to the bottom
            horScrollBar.setValue(0) # scroll to the left

class MyDialog(QtGui.QDialog):
    def __init__( self, parent = None ):
        super(MyDialog, self).__init__(parent)

        self._console = LogMessageViewer(self)

        layout = QtGui.QVBoxLayout()
        layout.addWidget(self._console)
        self.setLayout(layout)

        XStream.stdout().messageWritten.connect(self._console.appendLogMessage)
        XStream.stderr().messageWritten.connect(self._console.appendLogMessage)


if ( __name__ == '__main__' ):

    app = QtGui.QApplication([])
    dlg = MyDialog()
    dlg.show()

    app.exec_()

并且：

ScrollBar 始终显示 QTextBrowser 流式文本的底部

ScrollBar to always show the bottom of a QTextBrowser streamed text

python

pyqt

pyqt4