Override the inverse transform func from pg

piker/ui/_exec.py

@@ -42,6 +42,7 @@ import tractor
 from outcome import Error
 
 from ..log import get_logger
+from ._pg_overrides import _do_overrides
 
 log = get_logger(__name__)
 
@@ -50,6 +51,10 @@ log = get_logger(__name__)
 pg.useOpenGL = True
 pg.enableExperimental = True
 
+# engage core tweaks that give us better response
+# latency then the average pg user
+_do_overrides()
+
 
 # singleton app per actor
 _qt_app: QtGui.QApplication = None

piker/ui/_pg_overrides.py

@@ -0,0 +1,48 @@
+# piker: trading gear for hackers
+# Copyright (C) Tyler Goodlet (in stewardship for piker0)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+"""
+Customization of ``pyqtgraph`` core routines to speed up our use mostly
+based on not requiring "scentific precision" for pixel perfect view
+transforms.
+
+"""
+import pyqtgraph as pg
+
+
+def invertQTransform(tr):
+    """Return a QTransform that is the inverse of *tr*.
+    Raises an exception if tr is not invertible.
+
+    Note that this function is preferred over QTransform.inverted() due to
+    bugs in that method. (specifically, Qt has floating-point precision issues
+    when determining whether a matrix is invertible)
+
+    """
+    # see https://doc.qt.io/qt-5/qtransform.html#inverted
+
+    # NOTE: if ``invertable == False``, ``qt_t`` is an identity
+    qt_t, invertable = tr.inverted()
+
+    return qt_t
+
+
+def _do_overrides() -> None:
+    """Dooo eeet.
+
+    """
+    # we don't care about potential fp issues inside Qt
+    pg.functions.invertQTransform = invertQTransform