调整reportlab.platypus.Paragraph流动对象的大小？

Question

我有一段代码，试图调整一个reportlab Platypus流动对象的字体大小，直到它适应我给定的高度。但是我发现，段落流动对象在每次递归循环中并没有保存它的style.fontSize属性，这导致Python出现了无限递归的问题。

def fits_space(w,h,aW,aH,p):
    """
    Determines if inputted text fits in the space given for a paragraph
    and if it doesn't, reduces the font-size until it does.

    """
    if w<=aW and h<=aH:
        # return font size to apply it to the para again
        print "final font_size: %d" % p.style.fontSize
        return p # now render the paragraph in the doctemplate
    else: 
        p.style.fontSize -= 1
        w,h = p.wrap(aW, aH)
        fits_space(w,h,aW,aH,p)

def renderPage(name, text):
    doc = SimpleDocTemplate("%s.pdf" % name)
    parts = []
    style = ParagraphStyle(name='fancy')
    style.fontSize = 150
    p = Paragraph(text, style)
    aW = PAGE_WIDTH-4*inch  # available width and height 
    aH = PAGE_HEIGHT-4*inch 
    w,h = p.wrap(aW, aH) # find required space
    p = fits_space(w,h,aW,aH,p) # recursively fit the font size to the text
    parts.append(p)
    doc.build(parts)

有没有人能告诉我，为什么在fits_space()函数的else部分，当我调用p.wrap(aW, aH)时，输出的值和我把段落的字体大小减1之前是一样的？如果我减小字体大小，包裹后的高度不应该变小吗？

有没有人能帮我找出我哪里出错了？

更新
Nitzie的代码几乎能用，只是我还需要在style.leading上添加一个调整器：

def shrink_font_size(aW, aH, text, style):
    """Shrinks font size by using pdfmetrics to calculate the height
    of a paragraph, given the font name, size, and available width."""
    def break_lines(text, aW):
        # simpleSplit calculates how reportlab will break up the lines for
        # display in a paragraph, by using width/fontsize.
        return simpleSplit(text, style.fontName, style.fontSize, aW)

    def line_wrap(lines, style):
        # Get overall width of text by getting stringWidth of longest line
        width = stringWidth(max(lines), style.fontName, style.fontSize)
        # Paragraph height can be calculated via line spacing and number of lines.
        height = style.leading * len(lines)
        return width, height

    lines = break_lines(text, aW)
    width, height = line_wrap(lines, style)

    while height > aH or width > aW:
        style.fontSize -= 1
        style.leading -= 1 # do this if you're leading is based on the fontSize
        lines = break_lines(text, aW)
        width, height = line_wrap(lines, style)

谢谢大家！

Answer 1

不知道为什么，p.wrap 在你第一次调用后，如果你改变了字体大小，它似乎不会真正重新计算高度和宽度。

我找到了一种可行的方法，通过使用 ReportLab 的 stringWidth 和 splitLines 方法来计算字体大小。虽然这样做意味着它不再是递归的：

from reportlab.platypus import SimpleDocTemplate
from reportlab.lib.styles import ParagraphStyle
from reportlab.lib.units import inch
from reportlab.lib.pagesizes import A4
from reportlab.platypus import Paragraph
from reportlab.lib.utils import simpleSplit
from reportlab.pdfbase.pdfmetrics import stringWidth

def shrink_font_size(aW, aH, text, style):
    """Shrinks font size by using pdfmetrics to calculate the height
    of a paragraph, given the font name, size, and available width."""
    def break_lines(text, aW):
        # simpleSplit calculates how reportlab will break up the lines for
        # display in a paragraph, by using width/fontsize.
        return simpleSplit(text, style.fontName, style.fontSize, aW)

    def line_wrap(lines, style):
        # Get overall width of text by getting stringWidth of longest line
        width = stringWidth(max(lines), style.fontName, style.fontSize)
        # Paragraph height can be calculated via line spacing and number of lines.
        height = style.leading * len(lines)
        return width, height

    lines = break_lines(text, aW)
    width, height = line_wrap(lines, style)

    while height > aH or width > aW:
        style.fontSize -= 1
        lines = break_lines(text, aW)
        width, height = line_wrap(lines, style)


def renderPage(name, text):
    doc = SimpleDocTemplate("%s.pdf" % name)
    parts = []
    # Wasn't sure where PAGE_WIDTH and PAGE_HEIGHT came from for OP,
    # so I just used a standard A4 page measurement.
    PAGE_WIDTH, PAGE_HEIGHT = A4
    aW = PAGE_WIDTH - 4*inch  # available width and height 
    aH = PAGE_HEIGHT - 4*inch

    style = ParagraphStyle(name='fancy')
    style.fontSize = 200
    style.leading = 20
    shrink_font_size(aW, aH, text, style)

    p = Paragraph(text, style)
    parts.append(p)
    doc.build(parts)

if __name__ == "__main__":
    renderPage('test', '12345689019283382848248284 842828428529392381472754 842828428529392381472754 842828428529392381472754\n' * 10)