Removed existing docking nodes when closing and resetting a session. Fixes #934.

Author: azonenberg

release-notes/CHANGELOG.md

@@ -27,6 +27,7 @@ We try to maintain compatibility with older versions of ngscopeclient but occasi
 * Filters: FFT waveforms were shifted one bin to the right of the correct position
 * Filters: Frequency and period measurement had a rounding error during integer-to-floating-point conversion causing half a cycle of the waveform to be dropped under some circumstances leading to an incorrect result, with worse error at low frequencies and short memory depths. This only affected the "summary" output not the trend plot.
 * GUI: Pressing middle mouse on the Y axis to autoscale would fail, setting the full scale range to zero volts, if the waveform was resident in GPU memory and the CPU-side copy of the buffer was stale
+* GUI: Crash when closing a session (https://github.com/ngscopeclient/scopehal-apps/issues/934)
 
 ## Other changes since v0.1.1
 

src/ngscopeclient/MainWindow.cpp

@@ -1315,6 +1315,9 @@ void MainWindow::DockingArea()
 		{
 			LogTrace("Docking initial workspace\n");
 
+			//Undock anything that might already be there
+			ImGui::DockBuilderRemoveNodeChildNodes(topNode->ID);
+
 			//Split the top into two sub nodes (unless imgui already did it for us during a session reset)
 			ImGuiID leftPanelID;
 			ImGuiID rightPanelID;
@@ -1329,10 +1332,10 @@ void MainWindow::DockingArea()
 			ImGui::DockBuilderDockWindow(m_streamBrowser->GetTitleAndID().c_str(), leftPanelID);
 			ImGui::DockBuilderDockWindow(m_initialWorkspaceDockRequest->GetTitleAndID().c_str(), rightPanelID);
 
-			m_initialWorkspaceDockRequest = nullptr;
-
 			//Finish up
 			ImGui::DockBuilderFinish(dockspace_id);
+
+			m_initialWorkspaceDockRequest = nullptr;
 		}
 	}
 	else