Multi-thread TPS plot

Closes #2 (closed).

#30 (closed).17

sohstationviewer/view/plotting/time_power_squared_dialog.py

 # Display time-power-squared values for waveform data
 from math import sqrt
-from typing import Optional
+from typing import Optional, List
 
 import numpy as np
 
@@ -61,7 +61,13 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
         """
         self.tps_t = 0
 
-        self.tps_processor: Optional[TimePowerSquaredProcessor] = None
+        self.tps_processors: List[TimePowerSquaredProcessor] = []
+        self.channels = []
+        self.processed_channels = []
+        # The post-processing step does not take too much time so there is no
+        # need to limit the number of threads that can run at once.
+        self.thread_pool = QtCore.QThreadPool()
+        self.finished_lock = QtCore.QMutex()
 
         super().__init__(*args, **kwarg)
 
@@ -78,6 +84,11 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
         :param waveform_data: dict - read waveform data of selected data set,
             refer to DataTypeModel.__init__.waveform_data[key]['read_data']
         """
+        self.processed_channels = []
+        self.channels = []
+        self.tps_processors = []
+
+        display_tracking_info(self.tracking_box, 'Plotting TPS data...')
         self.processing_log = []  # [(message, type)]
         self.gap_bar = None
         self.min_x = max(data_time[0], start_tm)
@@ -111,8 +122,37 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
         self.each_day5_min_list = get_each_day_5_min_list(self.min_x,
                                                           self.max_x)
         for chan_id in self.plotting_data1:
-            ax = self.get_plot_data(self.plotting_data1[chan_id], chan_id)
-            self.axes.append(ax)
+            c_data = self.plotting_data1[chan_id]
+            if 'tps_data' not in c_data:
+                # get new minX, maxX according to exact start time  of days
+                self.channels.append(chan_id)
+                channel_processor = TimePowerSquaredProcessor(
+                    chan_id, c_data, self.min_x, self.max_x,
+                    self.each_day5_min_list
+                )
+                channel_processor.signals.finished.connect(self.channel_done)
+                self.tps_processors.append(channel_processor)
+
+        # Because the widget determine if processing is done by comparing the
+        # lists of scheduled and finished channels, if a channel runs fast
+        # enough that it finishes before any other channel can be scheduled,
+        # it will be the only channel executed. To prevent this, we tell the
+        # threadpool to only start running the processors once all channels
+        # have been scheduled.
+        for processor in self.tps_processors:
+            self.thread_pool.start(processor)
+
+    @QtCore.Slot()
+    def channel_done(self, chan_id):
+        self.finished_lock.lock()
+        ax = self.plot_channel(self.plotting_data1[chan_id], chan_id)
+        self.axes.append(ax)
+        self.processed_channels.append(chan_id)
+        if len(self.processed_channels) == len(self.channels):
+            self.done()
+        self.finished_lock.unlock()
+
+    def done(self):
         self.set_legend()
         # Set view size fit with the given data
         if self.main_widget.geometry().height() < self.plotting_bot_pixel:
@@ -120,7 +160,7 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
         self.set_lim_markers()
         self.draw()
 
-    def get_plot_data(self, c_data, chan_id):
+    def plot_channel(self, c_data, chan_id):
         """
         TPS is plotted in lines of small rectangular, so called bars.
         Each line is a day so - y value is the order of days
@@ -132,10 +172,8 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
             based on mapping between tps value of the five minutes against
             the selected color range.
 
-        This function trim data to minx, max_x and calculate time-power-square
-            for each 5 minute into c_data['tps_data'] then draw each 5 minute
-            with the color corresponding to value.
-        Create ruler, zoom_marker1, zoom_marker2 for the channel.
+        This function draws each 5 minute with the color corresponding to
+        value and create ruler, zoom_marker1, and zoom_marker2 for the channel.
 
         :param c_data: dict - data of the channel which includes down-sampled
             data in keys 'times' and 'data'. Refer to
@@ -143,12 +181,7 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
         :param chan_id: str - name of channel
         :return ax: matplotlib.axes.Axes - axes of the channel
         """
-        if 'tps_data' not in c_data:
-            # get new minX, maxX according to exact start time  of days
-            self.tps_processor = TimePowerSquaredProcessor(
-                c_data, self.min_x, self.max_x, self.each_day5_min_list
-            )
-            self.tps_processor.run()
+
         total_days = c_data['tps_data'].shape[0]
         plot_h = self.plotting_axes.get_height(
             1.5 * total_days, bw_plots_distance=0.003)
@@ -302,7 +335,7 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
                 xdata = 287
             ydata = round(event.mouseevent.ydata)       # y value on the plot
 
-            # refer to description in get_plot_data to understand x,y vs
+            # refer to description in plot_channel to understand x,y vs
             # day_index, five_min_index
             day_index = - ydata
             five_min_index = xdata