From 38cfe4255d05924eeec1f3d4392ffa12b8a3e313 Mon Sep 17 00:00:00 2001
From: Philipp Wolfer <ph.wolfer@gmail.com>
Date: Wed, 7 Oct 2020 15:21:47 +0200
Subject: [PATCH] Time based approach for process_events_iter

---
 picard/tagger.py        | 11 +++++++++--
 picard/util/__init__.py | 27 +++++++++++++++++++--------
 2 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/picard/tagger.py b/picard/tagger.py
index d625a1524..aca08eb95 100644
--- a/picard/tagger.py
+++ b/picard/tagger.py
@@ -523,8 +523,15 @@ class Tagger(QtWidgets.QApplication):
             new_files.sort(key=lambda x: x.filename)
             self.window.set_sorting(False)
             self._pending_files_count += len(new_files)
-            for file in process_events_iter(new_files):
+            for i, file in enumerate(new_files):
                 file.load(partial(self._file_loaded, target=target))
+                # Calling processEvents helps processing the _file_loaded
+                # callbacks in between, which keeps the UI more responsive.
+                # Avoid calling it to often to not slow down the loading to much
+                # Using an uneven number to have the unclustered file counter
+                # not look stuck in certain digits.
+                if i % 17 == 0:
+                    QtCore.QCoreApplication.processEvents()
 
     @staticmethod
     def _scan_paths_recursive(paths, recursive, ignore_hidden):
@@ -820,7 +827,7 @@ class Tagger(QtWidgets.QApplication):
         for name, artist, files in Cluster.cluster(files, 1.0, self):
             cluster = self.load_cluster(name, artist)
             cluster_files[cluster].extend(files)
-        for cluster, files in process_events_iter(cluster_files.items(), steps=2):
+        for cluster, files in process_events_iter(cluster_files.items()):
             cluster.add_files(files)
         self.window.set_sorting(True)
 
diff --git a/picard/util/__init__.py b/picard/util/__init__.py
index 64f7620c0..250960e47 100644
--- a/picard/util/__init__.py
+++ b/picard/util/__init__.py
@@ -47,7 +47,7 @@ from operator import attrgetter
 import os
 import re
 import sys
-from time import time
+from time import monotonic
 import unicodedata
 
 from dateutil.parser import parse
@@ -88,17 +88,28 @@ class LockableObject(QtCore.QObject):
         self.__lock.unlock()
 
 
-def process_events_iter(iterable, steps=10):
+def process_events_iter(iterable, interval=0.1):
     """
     Creates an iterator over iterable that calls QCoreApplication.processEvents()
-    in certain iteration steps.
+    after certain time intervals.
 
     This must only be used in the main thread.
+
+    Args:
+        iterable: iterable object to iterate over
+        interval: interval in seconds to call QCoreApplication.processEvents()
     """
-    for i, item in enumerate(iterable):
-        if (i + 1) % steps == 0:
-            QtCore.QCoreApplication.processEvents()
+    if interval:
+        start = monotonic()
+    for item in iterable:
+        if interval:
+            now = monotonic()
+            delta = now - start
+            if delta > interval:
+                start = now
+                QtCore.QCoreApplication.processEvents()
         yield item
+    QtCore.QCoreApplication.processEvents()
 
 
 _io_encoding = sys.getfilesystemencoding()
@@ -291,7 +302,7 @@ def throttle(interval):
         def later():
             mutex.lock()
             func(*decorator.args, **decorator.kwargs)
-            decorator.prev = time()
+            decorator.prev = monotonic()
             decorator.is_ticking = False
             mutex.unlock()
 
@@ -303,7 +314,7 @@ def throttle(interval):
                 mutex.unlock()
                 return
             mutex.lock()
-            now = time()
+            now = monotonic()
             r = interval - (now-decorator.prev)*1000.0
             if r <= 0:
                 func(*args, **kwargs)