def generate(env):
    """Add Builders and construction variables for pdftex to an Environment."""
    global PDFTeXAction
    if PDFTeXAction is None:
        PDFTeXAction = SCons.Action.Action('$PDFTEXCOM', '$PDFTEXCOMSTR')

    global PDFLaTeXAction
    if PDFLaTeXAction is None:
        PDFLaTeXAction = SCons.Action.Action("$PDFLATEXCOM", "$PDFLATEXCOMSTR")

    global PDFTeXLaTeXAction
    if PDFTeXLaTeXAction is None:
        PDFTeXLaTeXAction = SCons.Action.Action(PDFTeXLaTeXFunction,
                              strfunction=SCons.Tool.tex.TeXLaTeXStrFunction)

    env.AppendUnique(LATEXSUFFIXES=SCons.Tool.LaTeXSuffixes)

    from . import pdf
    pdf.generate(env)

    bld = env['BUILDERS']['PDF']
    bld.add_action('.tex', PDFTeXLaTeXAction)
    bld.add_emitter('.tex', SCons.Tool.tex.tex_pdf_emitter)

    # Add the epstopdf builder after the pdftex builder 
    # so pdftex is the default for no source suffix
    pdf.generate2(env)

    SCons.Tool.tex.generate_common(env)
Add Builders and construction variables for pdftex to an Environment.