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Merged
merged 3 commits into from
Oct 23, 2017
Merged

Doc draw event details #9505

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6789aed
DOC: add docs warning about triggering recursions in draw_event
tacaswell Oct 21, 2017
9b8a944
MNT: project Qt backends from recursive draws
tacaswell Oct 21, 2017
9a99efb
DOC: put docstring back in sensible order
tacaswell Oct 23, 2017
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8 changes: 4 additions & 4 deletions doc/users/event_handling.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -57,12 +57,12 @@ Here are the events that you can connect to, the class instances that
are sent back to you when the event occurs, and the event descriptions


======================= ======================================================================================
======================= =============================================================================================
Event name Class and description
======================= ======================================================================================
======================= =============================================================================================
'button_press_event' :class:`~matplotlib.backend_bases.MouseEvent` - mouse button is pressed
'button_release_event' :class:`~matplotlib.backend_bases.MouseEvent` - mouse button is released
'draw_event' :class:`~matplotlib.backend_bases.DrawEvent` - canvas draw
'draw_event' :class:`~matplotlib.backend_bases.DrawEvent` - canvas draw (but before screen update)
'key_press_event' :class:`~matplotlib.backend_bases.KeyEvent` - key is pressed
'key_release_event' :class:`~matplotlib.backend_bases.KeyEvent` - key is released
'motion_notify_event' :class:`~matplotlib.backend_bases.MouseEvent` - mouse motion
Expand All @@ -73,7 +73,7 @@ Event name Class and description
'figure_leave_event' :class:`~matplotlib.backend_bases.LocationEvent` - mouse leaves a figure
'axes_enter_event' :class:`~matplotlib.backend_bases.LocationEvent` - mouse enters a new axes
'axes_leave_event' :class:`~matplotlib.backend_bases.LocationEvent` - mouse leaves an axes
======================= ======================================================================================
======================= =============================================================================================

.. _event-attributes:

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10 changes: 10 additions & 0 deletions lib/matplotlib/backend_bases.py
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Expand Up @@ -1425,6 +1425,16 @@ class DrawEvent(Event):
"""
An event triggered by a draw operation on the canvas

In most backends callbacks subscribed to this callback will be
fired after the rendering is complete but before the screen is
updated. Any extra artists drawn to the canvas's renderer will
be reflected without an explicit call to ``blit``.

.. warning ::

Calling ``canvas.draw`` and ``canvas.blit`` in these callbacks may
not be safe with all backends and may cause infinite recursion.
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nice :)

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It is nice to at least warn the user they have acquired a foot-cannon.....


In addition to the :class:`Event` attributes, the following event
attributes are defined:

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10 changes: 7 additions & 3 deletions lib/matplotlib/backends/backend_qt5agg.py
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Expand Up @@ -140,18 +140,22 @@ def draw_idle(self):
QtCore.QTimer.singleShot(0, self.__draw_idle_agg)

def __draw_idle_agg(self, *args):
# if nothing to do, bail
if not self._agg_draw_pending:
return
# we have now tried this function at least once, do not run
# again until re-armed. Doing this here rather than after
# protects against recursive calls triggered through self.draw
self._agg_draw_pending = False
# if negative size, bail
if self.height() < 0 or self.width() < 0:
self._agg_draw_pending = False
return
try:
# actually do the drawing
self.draw()
except Exception:
# Uncaught exceptions are fatal for PyQt5, so catch them instead.
traceback.print_exc()
finally:
self._agg_draw_pending = False

def blit(self, bbox=None):
"""Blit the region in bbox.
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