如何正确设置打印机的painter？

Question

我正在打印一组 table，每个 table 应该有自己的页面并且可能很长。基础工作正常，但我没有绘制页脚。问题是页脚将在额外的文档中绘制。

根据文档，我必须为设备设置画家。设备是 painter，这是正确的，但是我如何将 painter 设置到正确的 Block？还是这样做不对？

目标是使用此文档两次。第一次尝试是打印，第二次是 QTextDocument，我可以在其中获取 QTextTable 并使用另一个文档元素对其进行编译。

工作示例

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtPrintSupport import *

content = [['section 1', [1,2,3,4]],['section2', [5,6,7,8]]]

app = QApplication(sys.argv)

document = QTextDocument ()
printer = QPrinter()
painter = QPainter(printer)
pageRect = printer.pageRect ()

tableFormat = QTextTableFormat ()
cellBlockFormat = QTextBlockFormat ()
cellCharFormat = QTextCharFormat ()
cellCharFormat.setFont (QFont ("Arial", 10))

for rownr, line in enumerate(content):
    cursor = QTextCursor (document)
    mainFrame = cursor.currentFrame ()
    # header
    cursor.setPosition (mainFrame.firstPosition ())
    cursor.insertHtml ("This is the table for  %s"%line[0])

    # table
    table = cursor.insertTable (3, 4, tableFormat)
    for colnr, col in enumerate(line[1]):
        print("col:", col)
        cellCursor = table.cellAt (rownr + 1, colnr).firstCursorPosition ()
        cellCursor.setBlockFormat (cellBlockFormat)
        cellCursor.insertText (str (col))

    #footer
    painter.begin(printer)
    painter.drawText (0, pageRect.bottom(), "I may be the footer")
    painter.end()
    # section finished
    cursor.setPosition (mainFrame.lastPosition ())
    tableFormat.setPageBreakPolicy (QTextFormat.PageBreak_AlwaysAfter)
    cursor.insertBlock (cellBlockFormat, cellCharFormat)
document.print_(printer)

Answer 1

前提：这与其说是一种解决方案，不如说是一种黑客攻击，因为它是一种肮脏的解决方法。

想法是子类化 QPrinter，覆盖 newPage 方法并相应地绘制页脚。这需要使用页脚手动更新 printer 实例。

不幸的是，还有一个重要问题：只要只有一页，我就无法打印页脚。

过几天我再研究一下，看看有没有解决办法。

import sys
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtPrintSupport import *


class FooterPrinter(QPrinter):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.footers = {}

    def paintEngine(self, *args):
        engine = super().paintEngine(*args)
        self.currentPage = 0
        return engine

    def drawFooter(self):
        text = self.footers.get(self.currentPage)
        if not text:
            return
        painter = super().paintEngine().painter()
        dpiy = painter.device().logicalDpiY()
        margin = dpiy * (2/2.54)
        rect = QRectF(margin, margin, self.width() - margin * 2, self.height() - margin * 2)
        fm = QFontMetrics(painter.font(), painter.device())
        size = fm.size(0, text)
        painter.drawText(rect.left(), rect.bottom() - size.height(), 
            size.width(), size.height(), Qt.AlignLeft|Qt.AlignTop, text)

    def newPage(self):
        self.drawFooter()
        newPage = super().newPage()
        if newPage:
            self.currentPage += 1
            self.drawFooter()
        return newPage

content = [['section 1', [1,2,3,4]],['section2', [5,6,7,8]]]

app = QApplication(sys.argv)

document = QTextDocument()
printer = FooterPrinter()
printer.setOutputFileName('/tmp/test.pdf')
pageRect = printer.pageRect ()

tableFormat = QTextTableFormat ()
cellBlockFormat = QTextBlockFormat ()
cellCharFormat = QTextCharFormat ()
cellCharFormat.setFont (QFont ("Arial", 10))

for rownr, line in enumerate(content):
    cursor = QTextCursor (document)
    mainFrame = cursor.currentFrame ()
    # header
    cursor.setPosition (mainFrame.firstPosition ())
    cursor.insertHtml ("This is the table for  %s"%line[0])

    # table
    table = cursor.insertTable (3, 4, tableFormat)
    for colnr, col in enumerate(line[1]):
        cellCursor = table.cellAt (rownr + 1, colnr).firstCursorPosition ()
        cellCursor.setBlockFormat (cellBlockFormat)
        cellCursor.insertText (str (col))
    cursor.setPosition (mainFrame.lastPosition ())
    tableFormat.setPageBreakPolicy (QTextFormat.PageBreak_AlwaysAfter)
    cursor.insertBlock (cellBlockFormat, cellCharFormat)

    printer.footers[rownr] = 'Note for page {}: some text.\nNew line\nAnother new line'.format(rownr + 1)

document.print_(printer)

如何正确设置打印机的painter？

How to set painter of printer correctly?

qpainter

qtextdocument

python-3.x

qprinter

pyqt5