98 lines
4.1 KiB
Markdown
98 lines
4.1 KiB
Markdown
# phantompy
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A simple replacement for phantomjs using PyQt.
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This code is based on a brilliant idea of
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[Michael Franzl](https://gist.github.com/michaelfranzl/91f0cc13c56120391b949f885643e974/raw/a0601515e7a575bc4c7d4d2a20973b29b6c6f2df/phantom.py)
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that he wrote up in his blog:
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* https://blog.michael.franzl.name/2017/10/16/phantomjs-alternative-write-short-pyqt-scripts-instead-phantom-py/
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* https://blog.michael.franzl.name/2017/10/16/phantom-py/
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## Features
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* Generate a PDF screenshot of the web page after it is completely loaded.
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* Optionally execute a local JavaScript file specified by the argument
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```javascript-file``` after the web page is completely loaded, and before the
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PDF is generated. (YMMV - it segfaults for me. )
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* Generate a HTML save file screenshot of the web page after it is
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completely loaded and the javascript has run.
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* console.log's will be printed to stdout.
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* Easily add new features by changing the source code of this script,
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without compiling C++ code. For more advanced applications, consider
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attaching PyQt objects/methods to WebKit's JavaScript space by using
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QWebFrame::addToJavaScriptWindowObject().
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If you execute an external ```javascript-file```, phantompy has no
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way of knowing when that script has finished doing its work. For this
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reason, the external script should execute at the end
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```console.log("__PHANTOM_PY_DONE__");``` when done. This will trigger
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the PDF generation or the file saving, after which phantompy will exit.
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If you do not want to run any javascipt file, this trigger is provided
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in the code by default.
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It is important to remember that since you're just running WebKit, you can
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use everything that WebKit supports, including the usual JS client
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libraries, CSS, CSS @media types, etc.
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Qt picks up proxies from the environment, so this will respect
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```https_proxy``` or ```http_proxy``` if set.
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## Dependencies
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* Python3
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* PyQt5 (this should work with PySide2 and PyQt6 - let us know.)
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* [qasnyc](https://github.com/CabbageDevelopment/qasync) for the
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standalone program ```qasync_phantompy.py```
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## Standalone
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A standalone program is a little tricky as PyQt PyQt5.QtWebEngineWidgets'
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QWebEnginePage uses callbacks at each step of the way:
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1) loading the page = ```Render.run```
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2) running javascript in and on the page = ```Render._loadFinished```
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3) saving the page = ```Render.toHtml and _html_callback```
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4) printing the page = ```Render._print```
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The steps get chained by printing special messages to the Python
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renderer of the JavaScript console: ```Render. _onConsoleMessage```
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So it makes it hard if you want the standalone program to work without
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a GUI, or in combination with another Qt program that is responsible
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for the PyQt ```app.exec``` and the exiting of the program.
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We've decided to use the best of the shims that merge the Python
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```asyncio``` and Qt event loops:
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[qasyc](https://github.com/CabbageDevelopment/qasync). This is seen as
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the successor to the sorta abandoned [quamash](https://github.com/harvimt/quamash).
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The code is based on a
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[comment](https://github.com/CabbageDevelopment/qasync/issues/35#issuecomment-1315060043)
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by [Alex March](https://github.com/hosaka) who's excellent code helped me.
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As this is my first use of ```asyncio``` and ```qasync``` I may have
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introduced some errors and it may be improved on, but it works, and
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it not a monolithic Qt program, so it can be used as a library.
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## Usage
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The standalone program is ```quash_phantompy.py```
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### Arguments
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```
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--js_input (optional) Path and name of a JavaScript file to execute on the HTML
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--html_output <html-file> (optional) Path a HTML output file to generate after JS is applied
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--pdf_output <pdf-file> (optional) Path and name of PDF file to generate after JS is applied
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--log_level 10=debug 20=info 30=warn 40=error
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html_or_url - required argument, a http(s) URL or a path to a local file.
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```
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Setting ```DEBUG=1``` in the environment will give debugging messages
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on ```stderr```.
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## Postscript
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When I think of all the trouble people went to compiling and
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maintaining the tonnes of C++ code that went into
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[phantomjs](https://github.com/ariya/phantomjs), I am amazed that it
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can be replaced with a couple of hundred lines of Python!
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