PostScript 执行程序的用户交互

发布于 2024-12-03 05:15:17 字数 139 浏览 5 评论 0原文

我正在用 PostScript 构建一个应用程序，需要在提示时从用户那里获取输入（我将使用 GhostScript 执行程序，并且文件不会发送到打印机）。我在 PostScript 语言参考手册中看不到任何表明这是可能的内容，而且我不想回到执行人员，那么这可能吗？

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时光礼记 2024-12-10 05:15:17

并不是那么绝望！但这也并不容易。除了 %stdin 之外，还有两个特殊文件可供您读取。 (%lineedit)(r)file dup bytesavailable string readstring pop 将从标准输入读取一行到字符串中。还有 (%statementedit) 文件，该文件将一直读取，直到键入语法上有效的后记片段（加上换行符）。这将匹配括号和花括号，但不匹配方括号。在阅读之前，您应该发出类似 (> )printlush 的提示。

另一件事是，您可以通过将所有这些包装在 stopped 上下文中来捕获 ^D。

{ %stopped
    (> )print flush
    (%lineedit)(r)file
    dup bytesavailable string readstring pop
} stopped not {
    (successfully read: )print
    print
}{
    (received EOF indication)print
}ifelse

您可以使用它来廉价地检测空输入行，而不是在读取字符串后弹出该布尔值。另请注意，在 EOF 上触发的停止来自 file 中的错误（ghostscript 将其称为 /invalidfilename），但尽管定义了 file作为一个操作符，操作符应该在发出错误信号时将它们的参数推回到堆栈上，我注意到 Ghostscript 不一定会这样做（我忘记了它留下了什么，但它不是像你期望的那样 2 个字符串），所以你可能想把mark 在前面，cleartomark pop 在整个块后面。

特殊文件 (%lineedit) 和 (%statementedit)（如果可用）将成功处理退格键和 control-U 以及可能的其他控件。我相信真正的 Adobe 打印机会用某种状态消息响应 ^T。但我从来没有见过。

附言。：！

我的后记调试器。这是一个更好的版本的调试器，但它可能不太适合用作例子。

It's not that hopeless! But it ain't exactly easy, either. There are two other special files besides %stdin that you can read from. (%lineedit)(r)file dup bytesavailable string readstring pop will read a line from stdin into a string. There is also the (%statementedit) file which will read until a syntactically valid postscript fragment is typed (plus newline). This will match parentheses and curlies, but not square brackets. Before reading, you should issue a prompt like (> )print flush.

One more thing, you can catch ^D by wrapping all this in a stopped context.

{ %stopped
    (> )print flush
    (%lineedit)(r)file
    dup bytesavailable string readstring pop
} stopped not {
    (successfully read: )print
    print
}{
    (received EOF indication)print
}ifelse

Instead of popping that bool after readstring, you could use it to cheaply detect an empty input line. Note also, that the stop that triggers on EOF is from an error in file (ghostscript calls it /invalidfilename), but although file is defined as an operator, and operators are supposed to push their arguments back on the stack when signaling an error, I've noticed ghostscript doesn't necessarily do this (I forget what it leaves, but it's not 2 strings like you'd expect), so you might want to put mark in front and cleartomark pop after this whole block.

The special files (%lineedit) and (%statementedit), if available, will successfully process backspaces and control-U and possibly other control. I believe real Adobe printers will respond to ^T with some kind of status message. But I've never seen it.

PS. :!

I've got a more extensive example of interactive postscript in my postscript debugger. Here's a better version of the debugger, but it's probably less useable as an example.

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