Merge pull request #40 from neutrons/fix_error_message_crash

Fix crash with error dialog

src/shiver/views/histogram.py

@@ -4,6 +4,7 @@
     QHBoxLayout,
     QErrorMessage,
 )
+from qtpy.QtCore import Signal
 
 from .loading_buttons import LoadingButtons
 from .histogram_parameters import HistogramParameter
@@ -13,6 +14,8 @@
 class Histogram(QWidget):
     """Histogram widget"""
 
+    error_message_signal = Signal(str)
+
     def __init__(self, parent=None):
         super().__init__(parent)
 
@@ -28,9 +31,17 @@ def __init__(self, parent=None):
         layout.addWidget(self.histogram_workspaces)
         self.setLayout(layout)
 
+        self.error_message_signal.connect(self._show_error_message)
+
     def show_error_message(self, msg):
-        """Will show a error dialog with the given message"""
-        error = QErrorMessage()
+        """Will show a error dialog with the given message
+
+        This will emit a signal so that other threads can call this but have the GUI thread execute"""
+        self.error_message_signal.emit(msg)
+
+    def _show_error_message(self, msg):
+        """Will show a error dialog with the given message from qt signal"""
+        error = QErrorMessage(self)
         error.showMessage(msg)
         error.exec_()
 

tests/views/test_histogram.py

@@ -1,11 +1,14 @@
 """UI test for the histogram tab"""
 import os
+from qtpy.QtCore import QTimer
+from qtpy.QtWidgets import QErrorMessage, QTextEdit
 from mantid.simpleapi import (  # pylint: disable=no-name-in-module
     LoadMD,
     MakeSlice,
     CreateSampleWorkspace,
 )
 from shiver import Shiver
+from shiver.views.histogram import Histogram
 
 
 def test_histogram(qtbot):
@@ -57,3 +60,21 @@ def test_histogram(qtbot):
     histogram_list = shiver.main_window.histogram.histogram_workspaces.histogram_workspaces
     assert histogram_list.count() == 1
     assert histogram_list.item(0).text() == "line"
+
+
+def test_msg_dialog(qtbot):
+    """Test the error message dialog in the histogram widget"""
+    histo = Histogram()
+    qtbot.addWidget(histo)
+    histo.show()
+
+    def test_dialog():
+        dialog = histo.findChild(QErrorMessage)
+        text_edit = dialog.findChild(QTextEdit)
+        dialog.close()
+        text = text_edit.toPlainText()
+        assert text == "This is only a test!"
+
+    QTimer.singleShot(100, test_dialog)
+
+    histo.show_error_message("This is only a test!")