gui: Show a message when no tabs are loaded

Instead of just showing a blank screen (which can be interpreted as the GUI
hanging), when there are no data files loaded show buttons to load a data file
or run a new test.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

flent/gui.py

@@ -278,6 +278,10 @@ def __init__(self, settings):
         self.viewArea.tabCloseRequested.connect(self.close_tab)
         self.viewArea.currentChanged.connect(self.activate_tab)
 
+        self.openFileButton.clicked.connect(self.on_open)
+        self.runTestButton.clicked.connect(self.run_test)
+        self.update_empty_view()
+
         self.plotDock.visibilityChanged.connect(self.plot_visibility)
         self.metadataDock.visibilityChanged.connect(self.metadata_visibility)
         self.plotSettingsDock.visibilityChanged.connect(self.plot_settings_visibility)
@@ -409,6 +413,14 @@ def read_settings(self):
             self.openFilesView.horizontalHeader().restoreState(value)
             self.openFilesView.setSortingEnabled(True)
 
+    def update_empty_view(self):
+        if self.viewArea.count():
+            self.viewArea.show()
+            self.emptyWidget.hide()
+        else:
+            self.viewArea.hide()
+            self.emptyWidget.show()
+
     def closeEvent(self, event):
         # Cleaning up matplotlib figures can take a long time; disable it when
         # the application is exiting.
@@ -654,6 +666,7 @@ def close_tab(self, idx=None):
             widget.setParent(None)
             widget.deleteLater()
             self.shorten_tabs()
+        self.update_empty_view()
         self.busy_end()
 
     def close_all(self):
@@ -662,6 +675,7 @@ def close_all(self):
         for i in range(self.viewArea.count()):
             widgets.append(self.viewArea.widget(i))
         self.viewArea.clear()
+        self.update_empty_view()
         for w in widgets:
             w.setUpdatesEnabled(False)
             w.disconnect_all()
@@ -775,6 +789,7 @@ def add_tab(self, results=None, title=None, plot=None, focus=True):
         if title is None:
             title = widget.title
         idx = self.viewArea.addTab(widget, title)
+        self.update_empty_view()
         if hasattr(widget, "long_title"):
             self.viewArea.setTabToolTip(idx, widget.long_title)
         if focus or self.focus_new:

flent/ui/mainwindow.ui

@@ -18,6 +18,100 @@
   </property>
   <widget class="QWidget" name="centralwidget">
    <layout class="QHBoxLayout" name="horizontalLayout">
+    <item>
+     <widget class="QWidget" name="emptyWidget" native="true">
+      <layout class="QVBoxLayout" name="verticalLayout_2">
+       <item>
+        <spacer name="verticalSpacer">
+         <property name="orientation">
+          <enum>Qt::Vertical</enum>
+         </property>
+         <property name="sizeHint" stdset="0">
+          <size>
+           <width>20</width>
+           <height>40</height>
+          </size>
+         </property>
+        </spacer>
+       </item>
+       <item>
+        <widget class="QLabel" name="emptyLabel">
+         <property name="text">
+          <string>No data files loaded. To show data, open a data file or run a new test.</string>
+         </property>
+         <property name="alignment">
+          <set>Qt::AlignCenter</set>
+         </property>
+         <property name="wordWrap">
+          <bool>true</bool>
+         </property>
+         <property name="margin">
+          <number>10</number>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QWidget" name="widget" native="true">
+         <layout class="QHBoxLayout" name="horizontalLayout_2">
+          <item>
+           <spacer name="horizontalSpacer">
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+            <property name="sizeHint" stdset="0">
+             <size>
+              <width>40</width>
+              <height>20</height>
+             </size>
+            </property>
+           </spacer>
+          </item>
+          <item>
+           <widget class="QPushButton" name="openFileButton">
+            <property name="text">
+             <string>Open data file</string>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <widget class="QPushButton" name="runTestButton">
+            <property name="text">
+             <string>Run new test</string>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <spacer name="horizontalSpacer_2">
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+            <property name="sizeHint" stdset="0">
+             <size>
+              <width>40</width>
+              <height>20</height>
+             </size>
+            </property>
+           </spacer>
+          </item>
+         </layout>
+        </widget>
+       </item>
+       <item>
+        <spacer name="verticalSpacer_2">
+         <property name="orientation">
+          <enum>Qt::Vertical</enum>
+         </property>
+         <property name="sizeHint" stdset="0">
+          <size>
+           <width>20</width>
+           <height>40</height>
+          </size>
+         </property>
+        </spacer>
+       </item>
+      </layout>
+     </widget>
+    </item>
     <item>
      <widget class="QTabWidget" name="viewArea">
       <property name="sizePolicy">