better component error messages

fatal errors cancel the export instead of crashing

src/component.py

@@ -5,13 +5,12 @@
 from PyQt5 import uic, QtCore, QtWidgets
 import os
 
-from presetmanager import getPresetDir
-
 
 def commandWrapper(func):
     '''Intercepts each component's command() method to check for global args'''
     def decorator(self, arg):
         if arg.startswith('preset='):
+            from presetmanager import getPresetDir
             _, preset = arg.split('=', 1)
             path = os.path.join(getPresetDir(self), preset)
             if not os.path.exists(path):
@@ -29,6 +28,26 @@ def commandWrapper(func):
     return decorator
 
 
+def propertiesWrapper(func):
+    '''Intercepts the usual properties if the properties are locked.'''
+    def decorator(self):
+        if self._lockedProperties is not None:
+            return self._lockedProperties
+        else:
+            return func(self)
+    return decorator
+
+
+def errorWrapper(func):
+    '''Intercepts the usual error message if it is locked.'''
+    def decorator(self):
+        if self._lockedError is not None:
+            return self._lockedError
+        else:
+            return func(self)
+    return decorator
+
+
 class ComponentMetaclass(type(QtCore.QObject)):
     '''
         Checks the validity of each Component class imported, and
@@ -37,25 +56,33 @@ class ComponentMetaclass(type(QtCore.QObject)):
     '''
     def __new__(cls, name, parents, attrs):
         if 'ui' not in attrs:
-            # use module name as ui filename by default
+            # Use module name as ui filename by default
             attrs['ui'] = '%s.ui' % os.path.splitext(
                     attrs['__module__'].split('.')[-1]
                 )[0]
 
-        # Turn certain class methods into properties and classmethods
+        # if parents[0] == QtCore.QObject: else:
-        for key in ('error', 'properties', 'audio'):
+        decorate = ('names', 'error', 'audio', 'command', 'properties')
+
+        # Auto-decorate methods
+        for key in decorate:
             if key not in attrs:
                 continue
-            attrs[key] = property(attrs[key])
 
-        for key in ('names'):
+            if key in ('names'):
-            if key not in attrs:
+                attrs[key] = classmethod(attrs[key])
-                continue
-            attrs[key] = classmethod(key)
 
-        # Do not apply these mutations to the base class
+            if key in ('audio'):
-        if parents[0] != QtCore.QObject:
+                attrs[key] = property(attrs[key])
-            attrs['command'] = commandWrapper(attrs['command'])
+
+            if key == 'command':
+                attrs[key] = commandWrapper(attrs[key])
+
+            if key == 'properties':
+                attrs[key] = propertiesWrapper(attrs[key])
+
+            if key == 'error':
+                attrs[key] = errorWrapper(attrs[key])
 
         # Turn version string into a number
         try:
@@ -83,13 +110,13 @@ class Component(QtCore.QObject, metaclass=ComponentMetaclass):
 
     name = 'Component'
     # ui = 'nameOfNonDefaultUiFile'
+
     version = '1.0.0'
     # The major version (before the first dot) is used to determine
     # preset compatibility; the rest is ignored so it can be non-numeric.
 
     modified = QtCore.pyqtSignal(int, dict)
-    # ^ Signal used to tell core program that the component state changed,
+    _error = QtCore.pyqtSignal(str, str)
-    # you shouldn't need to use this directly, it is used by self.update()
 
     def __init__(self, moduleIndex, compPos, core):
         super().__init__()
@@ -100,6 +127,9 @@ class Component(QtCore.QObject, metaclass=ComponentMetaclass):
 
         self._trackedWidgets = {}
         self._presetNames = {}
+        self._commandArgs = {}
+        self._lockedProperties = None
+        self._lockedError = None
 
         # Stop lengthy processes in response to this variable
         self.canceled = False
@@ -127,6 +157,7 @@ class Component(QtCore.QObject, metaclass=ComponentMetaclass):
     def error(self):
         '''
             Return a string containing an error message, or None for a default.
+            Or tuple of two strings for a message with details.
         '''
         return
 
@@ -141,12 +172,6 @@ class Component(QtCore.QObject, metaclass=ComponentMetaclass):
             https://ffmpeg.org/ffmpeg-filters.html
         '''
 
-    def names():
-        '''
-            Alternative names for renaming a component between project files.
-        '''
-        return []
-
     # =~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~==~=~=~=~=~=~=~=~=~=~=~=~=~=~
     # Methods
     # =~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~==~=~=~=~=~=~=~=~=~=~=~=~=~=~
@@ -181,15 +206,29 @@ class Component(QtCore.QObject, metaclass=ComponentMetaclass):
         for widget in widgets['comboBox']:
             widget.currentIndexChanged.connect(self.update)
 
-    def trackWidgets(self, trackDict, presetNames=None):
+    def trackWidgets(self, trackDict, **kwargs):
         '''
-            Name widgets to track in update(), savePreset(), and loadPreset()
+            Name widgets to track in update(), savePreset(), loadPreset(), and
-            Accepts a dict with attribute names as keys and widgets as values.
+            command(). Requires a dict of attr names as keys, widgets as values
-            Optional: a dict of attribute names to map to preset variable names
+
+            Optional args:
+                'presetNames': preset variable names to replace attr names
+                'commandArgs': arg keywords that differ from attr names
+
+            NOTE: Any kwarg key set to None will selectively disable tracking.
         '''
         self._trackedWidgets = trackDict
-        if type(presetNames) is dict:
+        for kwarg in kwargs:
-            self._presetNames = presetNames
+            try:
+                if kwarg in ('presetNames', 'commandArgs'):
+                    setattr(self, '_%s' % kwarg, kwargs[kwarg])
+                else:
+                    raise BadComponentInit(
+                        self,
+                        'Nonsensical keywords to trackWidgets.',
+                        immediate=True)
+            except BadComponentInit:
+                continue
 
     def update(self):
         '''
@@ -277,6 +316,22 @@ class Component(QtCore.QObject, metaclass=ComponentMetaclass):
         self.commandHelp()
         quit(0)
 
+    # =~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~==~=~=~=~=~=~=~=~=~=~=~=~=~=~
+    # "Private" Methods
+    # =~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~==~=~=~=~=~=~=~=~=~=~=~=~=~=~
+
+    def lockProperties(self, propList):
+        self._lockedProperties = propList
+
+    def lockError(self, msg):
+        self._lockedError = msg
+
+    def unlockProperties(self):
+        self._lockedProperties = None
+
+    def unlockError(self):
+        self._lockedError = None
+
     def loadUi(self, filename):
         '''Load a Qt Designer ui file to use for this component's widget'''
         return uic.loadUi(os.path.join(self.core.componentsPath, filename))
@@ -287,6 +342,8 @@ class Component(QtCore.QObject, metaclass=ComponentMetaclass):
 
     def reset(self):
         self.canceled = False
+        self.unlockProperties()
+        self.unlockError()
 
     '''
     ### Reference methods for creating a new component
@@ -309,16 +366,40 @@ class Component(QtCore.QObject, metaclass=ComponentMetaclass):
     '''
 
 
-class BadComponentInit(Exception):
+class BadComponentInit(AttributeError):
     '''
-        General purpose exception that components can raise to indicate
+        Indicates a Python error in constructing a component.
-        a Python issue with e.g., dynamic creation of instances or something.
+        Raising this locks the component into an error state,
-        Decorative for now, may have future use for logging.
+        and gives the MainWindow a traceback to display.
     '''
-    def __init__(self, arg, name):
+    def __init__(self, caller, name, immediate=False):
-        string = '''################################
+        from toolkit import formatTraceback
-Mandatory argument "%s" not specified
+        import sys
-  in %s instance initialization
+        if sys.exc_info()[0] is not None:
-###################################'''
+            string = (
-        print(string % (arg, name))
+                "%s component's %s encountered %s %s." % (
-        quit()
+                    caller.__class__.name,
+                    name,
+                    'an' if any([
+                        sys.exc_info()[0].__name__.startswith(vowel)
+                        for vowel in ('A', 'I')
+                    ]) else 'a',
+                    sys.exc_info()[0].__name__,
+                )
+            )
+            detail = formatTraceback(sys.exc_info()[2])
+        else:
+            string = name
+            detail = "Methods:\n%s" % (
+                "\n".join(
+                    [m for m in dir(caller) if not m.startswith('_')]
+                )
+            )
+
+        if immediate:
+            caller.parent.showMessage(
+                msg=string, detail=detail, icon='Warning'
+            )
+        else:
+            caller.lockProperties(['error'])
+            caller.lockError((string, detail))

src/components/original.py

@@ -15,7 +15,7 @@ class Component(Component):
     name = 'Classic Visualizer'
     version = '1.0.0'
 
-    def names():
+    def names(*args):
         return ['Original Audio Visualization']
 
     def widget(self, *args):

src/components/sound.py

@@ -18,6 +18,8 @@ class Component(Component):
             'chorus': self.page.checkBox_chorus,
             'delay': self.page.spinBox_delay,
             'volume': self.page.spinBox_volume,
+        }, commandArgs={
+            'sound': None,
         })
 
     def previewRender(self, previewWorker):

src/components/video.py

@@ -14,7 +14,7 @@ from toolkit import openPipe, checkOutput
 
 
 class Video:
-    '''Video Component Frame-Fetcher'''
+    '''Opens a pipe to ffmpeg and stores a buffer of raw video frames.'''
     def __init__(self, **kwargs):
         mandatoryArgs = [
             'ffmpeg',     # path to ffmpeg, usually self.core.FFMPEG_BIN
@@ -28,10 +28,7 @@ class Video:
             'component',  # component object
         ]
         for arg in mandatoryArgs:
-            try:
+            setattr(self, arg, kwargs[arg])
-                setattr(self, arg, kwargs[arg])
-            except KeyError:
-                raise BadComponentInit(arg, self.__doc__)
 
         self.frameNo = -1
         self.currentFrame = 'None'
@@ -196,13 +193,16 @@ class Component(Component):
         height = int(self.settings.value('outputHeight'))
         self.blankFrame_ = BlankFrame(width, height)
         self.updateChunksize(width, height)
-        self.video = Video(
+        try:
-            ffmpeg=self.core.FFMPEG_BIN, videoPath=self.videoPath,
+            self.video = Video(
-            width=width, height=height, chunkSize=self.chunkSize,
+                ffmpeg=self.core.FFMPEG_BIN, #videoPath=self.videoPath,
-            frameRate=int(self.settings.value("outputFrameRate")),
+                width=width, height=height, chunkSize=self.chunkSize,
-            parent=self.parent, loopVideo=self.loopVideo,
+                frameRate=int(self.settings.value("outputFrameRate")),
-            component=self, scale=self.scale
+                parent=self.parent, loopVideo=self.loopVideo,
-        ) if os.path.exists(self.videoPath) else None
+                component=self, scale=self.scale
+            ) if os.path.exists(self.videoPath) else None
+        except KeyError:
+            raise BadComponentInit(self, 'Frame Fetcher initialization')
 
     def frameRender(self, layerNo, frameNo):
         if self.video:

src/core.py

@@ -22,13 +22,12 @@ class Core:
     '''
 
     def __init__(self):
-        self.findComponents()
+        self.importComponents()
         self.selectedComponents = []
         self.savedPresets = {}  # copies of presets to detect modification
         self.openingProject = False
 
-    def findComponents(self):
+    def importComponents(self):
-        '''Imports all the component modules'''
         def findComponents():
             for f in os.listdir(Core.componentsPath):
                 name, ext = os.path.splitext(f)
@@ -225,9 +224,8 @@ class Core:
                 return
             if hasattr(loader, 'createNewProject'):
                 loader.createNewProject(prompt=False)
-            import traceback
+            msg = '%s: %s\n\n' % (typ.__name__, value)
-            msg = '%s: %s\n\nTraceback:\n' % (typ.__name__, value)
+            msg += toolkit.formatTraceback(tb)
-            msg += "\n".join(traceback.format_tb(tb))
             loader.showMessage(
                 msg="Project file '%s' is corrupted." % filepath,
                 showCancel=False,

src/mainwindow.py

@@ -571,6 +571,15 @@ class MainWindow(QtWidgets.QMainWindow):
         self.videoWorker.encoding.connect(self.changeEncodingStatus)
         self.createVideo.emit()
 
+    @QtCore.pyqtSlot(str, str)
+    def videoThreadError(self, msg, detail):
+        self.showMessage(
+            msg=msg,
+            detail=detail,
+            icon='Warning',
+        )
+        self.stopVideo()
+
     def changeEncodingStatus(self, status):
         self.encoding = status
         if status:
@@ -675,6 +684,8 @@ class MainWindow(QtWidgets.QMainWindow):
         # connect to signal that adds an asterisk when modified
         self.core.selectedComponents[index].modified.connect(
             self.updateComponentTitle)
+        self.core.selectedComponents[index]._error.connect(
+            self.videoThreadError)
 
         self.pages.insert(index, self.core.selectedComponents[index].page)
         stackedWidget.insertWidget(index, self.pages[index])
@@ -751,7 +762,7 @@ class MainWindow(QtWidgets.QMainWindow):
         if mousePos > -1:
             change = (componentList.currentRow() - mousePos) * -1
         else:
-            change = (componentList.count() - componentList.currentRow() -1)
+            change = (componentList.count() - componentList.currentRow() - 1)
         self.moveComponent(change)
 
     def changeComponentWidget(self):
@@ -936,7 +947,7 @@ class MainWindow(QtWidgets.QMainWindow):
         if event.type() == QtCore.QEvent.WindowActivate \
                 or event.type() == QtCore.QEvent.FocusIn:
             Core.windowHasFocus = True
-        elif event.type()== QtCore.QEvent.WindowDeactivate \
+        elif event.type() == QtCore.QEvent.WindowDeactivate \
                 or event.type() == QtCore.QEvent.FocusOut:
                     Core.windowHasFocus = False
         return False

src/toolkit/common.py

@@ -107,3 +107,11 @@ def rgbFromString(string):
         return tup
     except:
         return (255, 255, 255)
+
+
+def formatTraceback(tb=None):
+    import traceback
+    if tb is None:
+        import sys
+        tb = sys.exc_info()[2]
+    return 'Traceback:\n%s' % "\n".join(traceback.format_tb(tb))

src/toolkit/ffmpeg.py

@@ -103,7 +103,7 @@ def createFfmpegCommand(inputFile, outputFile, components, duration=-1):
     globalFilters = 0  # increase to add global filters
     extraAudio = [
         comp.audio for comp in components
-        if 'audio' in comp.properties
+        if 'audio' in comp.properties()
     ]
     if extraAudio or globalFilters > 0:
         # Add -i options for extra input files

src/video_thread.py

@@ -18,7 +18,7 @@ from threading import Thread, Event
 import time
 import signal
 
-import core
+from component import BadComponentInit
 from toolkit import openPipe
 from toolkit.ffmpeg import readAudioFile, createFfmpegCommand
 from toolkit.frame import Checkerboard
@@ -105,8 +105,7 @@ class Worker(QtCore.QObject):
 
         while not self.stopped:
             audioI, frame = self.previewQueue.get()
-            if core.Core.windowHasFocus \
+            if time.time() - self.lastPreview >= 0.06 or audioI == 0:
-                    and time.time() - self.lastPreview >= 0.06 or audioI == 0:
                 image = Image.alpha_composite(background.copy(), frame)
                 self.imageCreated.emit(QtGui.QImage(ImageQt(image)))
                 self.lastPreview = time.time()
@@ -153,39 +152,48 @@ class Worker(QtCore.QObject):
         ]))
         self.staticComponents = {}
         for compNo, comp in enumerate(reversed(self.components)):
-            comp.preFrameRender(
+            try:
-                worker=self,
+                comp.preFrameRender(
-                completeAudioArray=self.completeAudioArray,
+                    worker=self,
-                sampleSize=self.sampleSize,
+                    completeAudioArray=self.completeAudioArray,
-                progressBarUpdate=self.progressBarUpdate,
+                    sampleSize=self.sampleSize,
-                progressBarSetText=self.progressBarSetText
+                    progressBarUpdate=self.progressBarUpdate,
-            )
+                    progressBarSetText=self.progressBarSetText
+                )
+            except BadComponentInit:
+                pass
 
-            if 'error' in comp.properties:
+            if 'error' in comp.properties():
                 self.cancel()
                 self.canceled = True
                 canceledByComponent = True
-                errMsg = "Component #%s encountered an error!" % compNo \
+                compError = comp.error() \
-                    if comp.error is None else 'Component #%s (%s): %s' % (
+                    if type(comp.error()) is tuple else (comp.error(), '')
+                errMsg = (
+                    "Component #%s encountered an error!" % compNo
+                    if comp.error() is None else
+                    'Export cancelled by component #%s (%s): %s' % (
                         str(compNo),
                         str(comp),
-                        comp.error
+                        compError[0]
-                    )
-                self.parent.showMessage(
-                        msg=errMsg,
-                        icon='Warning',
-                        parent=None  # MainWindow is in a different thread
                     )
+                )
+                comp._error.emit(errMsg, compError[1])
                 break
-            if 'static' in comp.properties:
+            if 'static' in comp.properties():
                 self.staticComponents[compNo] = \
                     comp.frameRender(compNo, 0).copy()
 
         if self.canceled:
             if canceledByComponent:
                 print('Export cancelled by component #%s (%s): %s' % (
-                    compNo, str(comp), comp.error
+                    compNo,
-                ))
+                    comp.name,
+                    'No message.' if comp.error() is None else (
+                        comp.error() if type(comp.error()) is str
+                        else comp.error()[0])
+                    )
+                )
             self.cancelExport()
             return