有没有办法在 PyQt5 中设置 QTextEdit.placeholderText() 的 alignment？

Question

I know you can set the alignment of the text using setAlignment() , but that has no effect on the placeholder text .我知道您可以使用setAlignment()设置文本的 alignment ，但这对占位符文本没有影响。 Maybe you would need to edit the styleSheet of the underlying document in order to do it?也许您需要编辑基础document的styleSheet表才能做到这一点？ Or is the document only relevant for the actual text but not the placeholder?还是文档仅与实际文本相关而不与占位符相关？

Here's an MWE to play around with:这是一个可以玩的MWE：

import sys

from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QDialog, QApplication, QGridLayout, QTextEdit


class Test(QDialog):
    def __init__(self):
        super().__init__()
        self.edit = QTextEdit()
        self.edit.setPlaceholderText(
            # '<html><body><p align="center">'
            'this is a placeholder'
            # '</p></body></html>'
        )
        self.edit.setAlignment(Qt.AlignHCenter)
        self.lay = QGridLayout(self)
        self.lay.addWidget(self.edit)
        self.setLayout(self.lay)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    GUI = Test()
    GUI.show()
    sys.exit(app.exec_())

Answer 1

The placeholder cannot be directly customized, as it is directly painted by the QTextEdit using the default top alignment, so the only solution is to subclass, overwrite the paintEvent and paint the placeholder using your own alignment.占位符不能直接自定义，因为它是由 QTextEdit 直接使用默认顶部 alignment 绘制的，因此唯一的解决方案是子类化，覆盖paintEvent并使用您自己的 alignment 绘制占位符。

You might also add much more control by using a QTextDocument, which will allow you to use html and custom colors/alignment/etc.您还可以通过使用 QTextDocument 添加更多控制，这将允许您使用 html 和自定义颜色/对齐/等。

class HtmlPlaceholderTextEdit(QTextEdit):
    _placeholderText = ''
    def setPlaceholderText(self, text):
        if Qt.mightBeRichText(text):
            self._placeholderText = QTextDocument()
            try:
                color = self.palette().placeholderText().color()
            except:
                # for Qt < 5.12
                color = self.palette().windowText().color()
                color.setAlpha(128)
            # IMPORTANT: the default stylesheet _MUST_ be set *before*
            # adding any text, otherwise it won't be used.
            self._placeholderText.setDefaultStyleSheet(
                '''body {{color: rgba({}, {}, {}, {});}}
                '''.format(*color.getRgb()))
            self._placeholderText.setHtml(text)
        else:
            self._placeholderText = text
        self.update()

    def placeholderText(self):
        return self._placeholderText

    def paintEvent(self, event):
        super().paintEvent(event)
        if self.document().isEmpty() and self.placeholderText():
            qp = QPainter(self.viewport())
            margin = self.document().documentMargin()
            r = QRectF(self.viewport().rect()).adjusted(margin, margin, -margin, -margin)
            text = self.placeholderText()
            if isinstance(text, str):
                try:
                    color = self.palette().placeholderText().color()
                except:
                    # for Qt < 5.12
                    color = self.palette().windowText().color()
                    color.setAlpha(128)
                qp.setPen(color)
                qp.drawText(r, self.alignment() | Qt.TextWordWrap, text)
            else:
                text.setPageSize(self.document().pageSize())
                text.drawContents(qp, r)


class Test(QDialog):
    def __init__(self):
        super().__init__()
        self.edit = HtmlPlaceholderTextEdit()
        self.edit.setPlaceholderText(
            '<html><body><p align="center">'
            'this is a <font color="blue">placeholder</font>'
            '</p></body></html>'
        )
        # ...

有没有办法在 PyQt5 中设置 QTextEdit.placeholderText() 的 alignment？

问题描述

1 个解决方案

解决方案1
1 已采纳 2020-04-06 10:55:01

有没有办法在 PyQt5 中设置 QTextEdit.placeholderText() 的 alignment？

问题描述

1 个解决方案

解决方案1 1 已采纳 2020-04-06 10:55:01

解决方案1
1 已采纳 2020-04-06 10:55:01