replace phantomjs with Firefox/geckodriver

- phantomjs is deprecated and didn't work correctly
  when used inside a Docker container
  (RST tree would have no EDU texts when converted to .png images)

Dockerfile

@@ -1,18 +1,26 @@
 FROM nlpbox/nlpbox-base:16.04
 
 RUN apt-get update -y && apt-get upgrade -y && \
-    apt-get install -y python-pip phantomjs && \
+    apt-get install -y python-pip phantomjs firefox && \
     pip2 install selenium pudb
 
+# settings for interactive debugging
 ADD pudb.cfg /root/
 
+# install geckodriver for headless browsing with selenium
+WORKDIR /usr/local/bin
+RUN wget https://github.com/mozilla/geckodriver/releases/download/v0.19.1/geckodriver-v0.19.1-linux64.tar.gz && \
+    tar -xvzf geckodriver-v0.19.1-linux64.tar.gz && \
+    rm geckodriver-v0.19.1-linux64.tar.gz
+
+
 WORKDIR /opt
 RUN git clone https://github.com/arne-cl/rstviewer.git
 
 WORKDIR /opt/rstviewer
 RUN python2 setup.py install
 
 # workaround for PhantomJS error "QXcbConnection: Could not connect to display "
-ENV QT_QPA_PLATFORM offscreen
+# ENV QT_QPA_PLATFORM offscreen
 
 ENTRYPOINT ["rstviewer"]

src/rstviewer/main.py

@@ -305,12 +305,14 @@ def rs3topng(rs3_filepath, png_filepath=None):
     temp.close()
 
     try:
-        driver = webdriver.PhantomJS()
+        opts = webdriver.firefox.options.Options()
+        opts.add_argument('--headless')
+        driver = webdriver.Firefox(options=opts)
     except WebDriverException as err:
         raise WebDriverException(
-           'Please install phantomjs: http://phantomjs.org/\n' + err.msg)
+           'Please install Firefox and geckodriver: https://github.com/mozilla/geckodriver/releases\n' + err.msg)
 
-    driver.get(temp.name)
+    driver.get("file://{}".format(temp.name))
     os.unlink(temp.name)
 
     png_str = driver.get_screenshot_as_png()