Delegate loading/saving scenarios to the PyQt wrapper app.

vasl_templates/main_window.py

@@ -1,40 +1,24 @@
 """ Main application window. """
 
-import os
 import re
 
-from PyQt5.QtWidgets import QWidget, QVBoxLayout, QLabel, QFileDialog, QMessageBox
+from PyQt5.QtWidgets import QWidget, QVBoxLayout, QLabel, QMessageBox
 from PyQt5.QtWebEngineWidgets import QWebEngineView, QWebEngineProfile, QWebEnginePage
 from PyQt5.QtWebChannel import QWebChannel
 from PyQt5.QtGui import QDesktopServices
-from PyQt5.QtCore import QObject, QUrl, pyqtSlot
+from PyQt5.QtCore import QUrl, pyqtSlot
 
 from vasl_templates.webapp.config.constants import APP_NAME
 from vasl_templates.webapp import app as webapp
+from vasl_templates.web_channel import WebChannelHandler
+from vasl_templates.utils import log_exceptions
 
 _CONSOLE_SOURCE_REGEX = re.compile( r"^http://.+?/static/(.*)$" )
 
 # ---------------------------------------------------------------------
 
-class WebChannelHandler( QObject ):
-    """Handle web channel requests."""
-
-    def __init__( self, window ):
-        # initialize
-        super().__init__()
-        self.window = window
-
-    @pyqtSlot( str )
-    def on_scenario_name_change( self, val ):
-        """Update the main window title to show the scenario name."""
-        self.window.setWindowTitle(
-            "{} - {}".format( APP_NAME, val ) if val else APP_NAME
-        )
-
-# ---------------------------------------------------------------------
-
 class AppWebPage( QWebEnginePage ):
-    """Main webapp page."""
+    """Application web page."""
 
     def javaScriptConsoleMessage( self, level, msg, line_no, source_id ): #pylint: disable=unused-argument,no-self-use
         """Log a Javascript console message."""
@@ -47,19 +31,14 @@ class AppWebPage( QWebEnginePage ):
 class MainWindow( QWidget ):
     """Main application window."""
 
-    _main_window = None
-    _curr_scenario_fname = None
-
     def __init__( self, url ):
 
         # initialize
-        assert MainWindow._main_window is None
-        MainWindow._main_window = self
-        self.view = None
+        super().__init__()
+        self._view = None
         self._is_closing = False
 
         # initialize
-        super().__init__()
         self.setWindowTitle( APP_NAME )
 
         # initialize the layout
@@ -72,28 +51,27 @@ class MainWindow( QWidget ):
         if not webapp.config.get( "DISABLE_WEBENGINEVIEW" ):
 
             # initialize the web view
-            self.view = QWebEngineView()
-            layout.addWidget( self.view )
+            self._view = QWebEngineView()
+            layout.addWidget( self._view )
 
             # initialize the web page
             # nb: we create an off-the-record profile to stop the view from using cached JS files :-/
-            profile = QWebEngineProfile( None, self.view )
-            profile.downloadRequested.connect( self.onDownloadRequested )
-            page = AppWebPage( profile, self.view )
-            self.view.setPage( page )
+            profile = QWebEngineProfile( None, self._view )
+            page = AppWebPage( profile, self._view )
+            self._view.setPage( page )
 
             # create a web channel to communicate with the front-end
             web_channel = QWebChannel( page )
             # FUDGE! We would like to register a WebChannelHandler instance as the handler, but this crashes PyQt :-/
             # Instead, we register ourself as the handler, and delegate processing to a WebChannelHandler.
             # The downside is that PyQt emits lots of warnings about our member variables not being properties :-/
-            self.web_channel_handler = WebChannelHandler( self )
+            self._web_channel_handler = WebChannelHandler( self )
             web_channel.registerObject( "handler", self )
             page.setWebChannel( web_channel )
 
             # load the webapp
             url += "?pyqt=1"
-            self.view.load( QUrl(url) )
+            self._view.load( QUrl(url) )
 
         else:
 
@@ -109,7 +87,7 @@ class MainWindow( QWidget ):
         """Handle requests to close the window (i.e. exit the application)."""
 
         # check if we need to check for a dirty scenario
-        if self.view is None or self._is_closing:
+        if self._view is None or self._is_closing:
             return
 
         # check if the scenario is dirty
@@ -121,7 +99,7 @@ class MainWindow( QWidget ):
                 self.close()
                 return
             # yup - ask the user to confirm the close
-            rc = QMessageBox.question( self, "Close program",
+            rc = self.ask(
                 "This scenario has been changed\n\nDo you want to close the program, and lose your changes?",
                 QMessageBox.Yes | QMessageBox.No,
                 QMessageBox.No
@@ -130,36 +108,41 @@ class MainWindow( QWidget ):
                 # confirmed - close the window
                 self._is_closing = True
                 self.close()
-        self.view.page().runJavaScript( "is_scenario_dirty()", callback )
+        self._view.page().runJavaScript( "is_scenario_dirty()", callback )
         evt.ignore() # nb: we wait until the Javascript finishes to process the event
 
-    @staticmethod
-    def onDownloadRequested( item ):
-        """Handle download requests."""
-
-        # ask the user where to save the scenario
-        dlg = QFileDialog(
-            MainWindow._main_window, "Save scenario",
-            os.path.split(MainWindow._curr_scenario_fname)[0] if MainWindow._curr_scenario_fname else None,
-            "Scenario files (*.json);;All files(*)"
-        )
-        dlg.setDefaultSuffix( ".json" )
-        if MainWindow._curr_scenario_fname:
-            dlg.selectFile( os.path.split(MainWindow._curr_scenario_fname)[1] )
-        fname, _  = QFileDialog.getSaveFileName(
-            MainWindow._main_window, "Save scenario",
-            None,
-            "Scenario files (*.json);;All files(*)"
-        )
-        if not fname:
-            return
+    def showInfoMsg( self, msg ):
+        """Show an informational message."""
+        QMessageBox.information( self , APP_NAME , msg )
+
+    def showErrorMsg( self, msg ):
+        """Show an error message."""
+        QMessageBox.warning( self , APP_NAME , msg )
+
+    def ask( self, msg , buttons , default ) :
+        """Ask the user a question."""
+        return QMessageBox.question( self , APP_NAME , msg , buttons , default )
+
+    @pyqtSlot()
+    @log_exceptions( caption="SLOT EXCEPTION" )
+    def on_new_scenario( self):
+        """Called when the user wants to load a scenario."""
+        self._web_channel_handler.on_new_scenario()
+
+    @pyqtSlot( result=str )
+    @log_exceptions( caption="SLOT EXCEPTION" )
+    def load_scenario( self ):
+        """Called when the user wants to load a scenario."""
+        return self._web_channel_handler.load_scenario()
 
-        # accept the download request
-        item.setPath( fname )
-        item.accept()
-        MainWindow._curr_scenario_fname = fname
+    @pyqtSlot( str, result=bool )
+    @log_exceptions( caption="SLOT EXCEPTION" )
+    def save_scenario( self, data ):
+        """Called when the user wants to save a scenario."""
+        return self._web_channel_handler.save_scenario( data )
 
     @pyqtSlot( str )
+    @log_exceptions( caption="SLOT EXCEPTION" )
     def on_scenario_name_change( self, val ):
         """Update the main window title to show the scenario name."""
-        self.web_channel_handler.on_scenario_name_change( val )
+        self._web_channel_handler.on_scenario_name_change( val )

vasl_templates/utils.py

@@ -0,0 +1,23 @@
+""" Miscellaneous utilities. """
+
+import functools
+import logging
+import traceback
+
+# ---------------------------------------------------------------------
+
+def log_exceptions( caption="EXCEPTION" ):
+    """Decorator that logs exceptions thrown by the wrapped function."""
+    def decorator( func ):
+        """The real decorator function."""
+        @functools.wraps( func )
+        def wrapper( *args, **kwargs ):
+            """Wrapper around the function being decorated."""
+            try:
+                return func( *args, **kwargs )
+            except Exception as ex:
+                logging.critical( "%s: %s", caption, ex )
+                logging.critical( traceback.format_exc() )
+                raise
+        return wrapper
+    return decorator

vasl_templates/web_channel.py

@@ -0,0 +1,88 @@
+""" Web channel handler. """
+
+import os
+
+from PyQt5.QtWidgets import QFileDialog
+
+from vasl_templates.webapp.config.constants import APP_NAME
+
+# ---------------------------------------------------------------------
+
+class WebChannelHandler:
+    """Handle web channel requests."""
+
+    _FILE_FILTERS = "Scenario files (*.json);;All files (*)"
+
+    def __init__( self, window ):
+
+        # initialize
+        self._window = window
+
+        # NOTE: While loading/saving scenarios works fine when handled by the embedded browser,
+        # we can't get the full path of the file saved loaded (because of browser security).
+        # This means that we can't e.g. default saving a scenario to the same file it was loaded from.
+        # This is such a lousy UX, we handle load/save operations ourself, where we can manage this.
+        self._curr_scenario_fname = None
+
+    def on_new_scenario( self ):
+        """Called when the scenario is reset."""
+        self._curr_scenario_fname = None
+
+    def load_scenario( self ):
+        """Called when the user wants to load a scenario."""
+
+        # ask the user which file to load
+        fname, _  = QFileDialog.getOpenFileName(
+            self._window, "Load scenario",
+            os.path.split(self._curr_scenario_fname)[0] if self._curr_scenario_fname else None,
+            WebChannelHandler._FILE_FILTERS
+        )
+        if not fname:
+            return None
+
+        # load the scenario
+        try:
+            with open( fname, "r", encoding="utf-8" ) as fp:
+                data = fp.read()
+        except Exception as ex: #pylint: disable=broad-except
+            self._window.showErrorMsg( "Can't load the scenario:\n\n{}".format( ex ) )
+            return None
+        self._curr_scenario_fname = fname
+
+        return data
+
+    def save_scenario( self, data ):
+        """Called when the user wants to save a scenario."""
+
+        # ask the user where to save the scenario
+        fname, _  = QFileDialog.getSaveFileName(
+            self._window, "Save scenario",
+            self._curr_scenario_fname,
+            WebChannelHandler._FILE_FILTERS
+        )
+        if not fname:
+            return False
+
+        # check the file extension
+        extn = os.path.splitext( fname )[1]
+        if not extn:
+            fname += ".json"
+        elif fname.endswith( "." ):
+            fname = fname[:-1]
+
+        # save the file
+        try:
+            with open( fname, "w", encoding="utf-8" ) as fp:
+                fp.write( data )
+        except Exception as ex: #pylint: disable=broad-except
+            self._window.showErrorMsg( "Can't save the scenario:\n\n{}".format( ex ) )
+            return False
+        self._curr_scenario_fname = fname
+
+        return True
+
+    def on_scenario_name_change( self, val ):
+        """Update the main window title to show the scenario name."""
+        self._window.setWindowTitle(
+            "{} - {}".format( APP_NAME, val ) if val else APP_NAME
+        )

vasl_templates/webapp/static/snippets.js

@@ -456,11 +456,21 @@ function on_load_scenario()
         // the browser will use native controls), so we get the data from a <textarea>).
         if ( getUrlParam( "scenario_persistence" ) ) {
             var $elem = $( "#_scenario-persistence_" ) ;
-            do_load_scenario( JSON.parse( $elem.val() ) ) ;
+            do_load_scenario( $elem.val() ) ;
             showInfoMsg( "The scenario was loaded." ) ; // nb: the tests are looking for this
             return ;
         }
 
+        // if we are running inside the PyQt wrapper, let it handle everything
+        if ( gWebChannelHandler ) {
+            gWebChannelHandler.load_scenario( function( data ) {
+                if ( ! data )
+                    return ;
+                do_load_scenario( data ) ;
+            } ) ;
+            return ;
+        }
+
         // ask the user to upload the scenario file
         $("#load-scenario").trigger( "click" ) ;
     }
@@ -470,21 +480,24 @@ function on_load_scenario_file_selected()
 {
     // read the selected file
     var fileReader = new FileReader() ;
-    fileReader.onload = function() {
-        var data ;
-        try {
-            data = JSON.parse( fileReader.result ) ;
-        } catch( ex ) {
-            showErrorMsg( "Can't load the scenario file:<div class='pre'>" + escapeHTML(ex) + "</div>" ) ;
-            return ;
-        }
-        do_load_scenario( data ) ;
-        showInfoMsg( "The scenario was loaded." ) ;
-    } ;
+    fileReader.onload = function() { do_load_scenario( fileReader.result ) ; } ;
     fileReader.readAsText( $("#load-scenario").prop("files")[0] ) ;
 }
 
-function do_load_scenario( params )
+function do_load_scenario( data )
+{
+    // load the scenario
+    try {
+        data = JSON.parse( data ) ;
+    } catch( ex ) {
+        showErrorMsg( "Can't load the scenario file:<div class='pre'>" + escapeHTML(ex) + "</div>" ) ;
+        return ;
+    }
+    do_load_scenario_data( data ) ;
+    showInfoMsg( "The scenario was loaded." ) ;
+}
+
+function do_load_scenario_data( params )
 {
     // reset the scenario
     reset_scenario() ;
@@ -605,18 +618,34 @@ function on_save_scenario()
     var params = unload_params_for_save() ;
     var data = JSON.stringify( params ) ;
 
-    // remember this as the last saved scenario
-    gLastSavedScenario = params ;
-
     // FOR TESTING PORPOISES! We can't control a file download from Selenium (since
-    // the browser will use native controls), so we store the result in a <textarea>).
+    // the browser will use native controls), so we store the result in a <textarea>
+    // and the test suite will collect it from there).
     if ( getUrlParam( "scenario_persistence" ) ) {
         $("#_scenario-persistence_").val( data ) ;
+        gLastSavedScenario = params ;
+        return ;
+    }
+
+    // if we are running inside the PyQt wrapper, let it handle everything
+    if ( gWebChannelHandler ) {
+        gWebChannelHandler.save_scenario( data, function( result ) {
+            if ( ! result )
+                return ;
+            gLastSavedScenario = params ;
+            showInfoMsg( "The scenario was saved." ) ;
+        } ) ;
         return ;
     }
 
     // return the parameters to the user as a downloadable file
     download( data, "scenario.json", "application/json" ) ;
+    // NOTE: We get no indication if the download was successful, so we can't show feedback :-/
+    // Also, if the download didn't actually happen (e.g. because it was cancelled), then setting
+    // the last saved scenario here is not quite the right thing to do, since subsequent checks
+    // for a dirty scenario will return the wrong result, since they assume that the scenario
+    // was saved properly here :-/
+    gLastSavedScenario = params ;
 }
 
 function unload_params_for_save()
@@ -663,11 +692,11 @@ function on_new_scenario( verbose )
     function do_on_new_scenario() {
         // load the default scenario
         if ( gDefaultScenario )
-            do_load_scenario( gDefaultScenario ) ;
+            do_load_scenario_data( gDefaultScenario ) ;
         else {
             $.getJSON( gGetDefaultScenarioUrl, function(data) {
                 gDefaultScenario = data ;
-                do_load_scenario( data ) ;
+                do_load_scenario_data( data ) ;
                 update_page_load_status( "default-scenario" ) ;
             } ).fail( function( xhr, status, errorMsg ) {
                 showErrorMsg( "Can't get the default scenario:<div class='pre'>" + escapeHTML(errorMsg) + "</div>" ) ;
@@ -675,6 +704,10 @@ function on_new_scenario( verbose )
             } ) ;
         }
 
+        // notify the PyQt wrapper application
+        if ( gWebChannelHandler )
+            gWebChannelHandler.on_new_scenario() ;
+
         // provide some feedback to the user
         if ( verbose )
             showInfoMsg( "The scenario was reset." ) ;