PERF: delay updating cell sizes on scroll

Author: gdementen

larray_editor/arraywidget.py

@@ -63,7 +63,8 @@
 import numpy as np
 
 from qtpy import QtCore
-from qtpy.QtCore import Qt, QPoint, QItemSelection, QItemSelectionModel, Signal, QSize, QModelIndex
+from qtpy.QtCore import (Qt, QPoint, QItemSelection, QItemSelectionModel,
+                         Signal, QSize, QModelIndex, QTimer)
 from qtpy.QtGui import (QDoubleValidator, QIntValidator, QKeySequence, QFontMetrics, QCursor, QPixmap, QPainter, QIcon,
                         QWheelEvent, QMouseEvent)
 from qtpy.QtWidgets import (QApplication, QTableView, QItemDelegate, QLineEdit, QCheckBox,
@@ -1290,6 +1291,8 @@ def get_numbers_width(self, int_digits, frac_digits=0, need_sign=False, scientif
 
 class ArrayEditorWidget(QWidget):
     dataChanged = Signal(list)
+    # milliseconds between a scroll event and updating cell sizes
+    UPDATE_SIZES_FROM_CONTENT_DELAY = 100
 
     def __init__(self, parent, data=None, readonly=False, attributes=None, bg_gradient='blue-red',
                  minvalue=None, maxvalue=None, digits=None):
@@ -1512,6 +1515,12 @@ def hidden_vscroll_range_changed(min_value: int, max_value: int):
         self._updating_vlabels_row_heights = False
         self._updating_axes_row_heights = False
 
+        update_timer = QTimer(self)
+        update_timer.setSingleShot(True)
+        update_timer.setInterval(self.UPDATE_SIZES_FROM_CONTENT_DELAY)
+        update_timer.timeout.connect(self.update_cell_sizes_from_content)
+        self.update_cell_sizes_timer = update_timer
+
     def visible_cols(self, include_partial=True):
         """number of visible columns *including* partially visible ones"""
 
@@ -1650,20 +1659,24 @@ def visible_vscroll_changed(self, value):
             model_data.set_v_offset(new_v_offset)
             self.model_vlabels.set_v_offset(new_v_offset)
             self._update_selection(model_data.h_offset, new_v_offset)
-            # TODO: scrolling feels *much* snappier (especially for in-memory
-            #       datasets) without these, but not having them at all is
-            #       annoying. Can we make that faster?
-            #       * Would computing the sizeHint ourselves help?
-            #       * For many in-memory (especially numerical) containers,
-            #         it would be cheaper to compute that once for the
-            #         whole array instead
-            self._update_hlabels_column_widths_from_content()
-            # we do not need to update axes cell size on scroll but vlabels
-            # width can change on scroll (and they are linked to axes widths)
-            self._update_axes_column_widths_from_content()
-            self._update_vlabels_row_heights_from_content()
+            self.update_cell_sizes_timer.start()
+
         hidden_vscroll.setValue(new_hidden_offset)
 
+    def update_cell_sizes_from_content(self):
+        logger.debug("ArrayEditorWidget.update_cell_sizes_from_content()")
+        # TODO: having this in a timer alleviates the scrolling speed issue
+        #       but we could also try to make this faster:
+        #       * Would computing the sizeHint ourselves help?
+        #       * For many in-memory (especially numerical) containers,
+        #         it would be cheaper to compute that once for the
+        #         whole array instead of after each scroll
+        self._update_hlabels_column_widths_from_content()
+        # we do not need to update axes cell size on scroll but vlabels
+        # width can change on scroll (and they are linked to axes widths)
+        self._update_axes_column_widths_from_content()
+        self._update_vlabels_row_heights_from_content()
+
     def visible_hscroll_changed(self, value):
         # 'value' will be the first visible column
         assert value >= 0, f"value must be >= 0 but is {value!r}"
@@ -1715,11 +1728,7 @@ def visible_hscroll_changed(self, value):
             model_data.set_h_offset(new_h_offset)
             self.model_hlabels.set_h_offset(new_h_offset)
             self._update_selection(new_h_offset, model_data.v_offset)
-            self._update_hlabels_column_widths_from_content()
-            # we do not need to update axes cell size on scroll but vlabels
-            # width can change on scroll (and they are linked to axes widths)
-            self._update_axes_column_widths_from_content()
-            self._update_vlabels_row_heights_from_content()
+            self.update_cell_sizes_timer.start()
         hidden_hscroll.setValue(new_hidden_offset)
 
     def on_axes_column_resized(self, logical_index, old_size, new_size):