Fixed bug where WaveformArea would fail to autoscale the Y axis if the waveform was only in GPU memory and there was no up to date copy on the CPU

Author: azonenberg

lib

@@ -22,6 +22,7 @@ We try to maintain compatibility with older versions of ngscopeclient but occasi
 
 ## Bugs fixed since v0.1.1
 
-* PcapNG export did not handle named pipes correctly (no github ticket)
+* Filters: PcapNG export did not handle named pipes correctly (no github ticket)
+* 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
 
 ## Other changes since v0.1.1

release-notes/CHANGELOG.md

@@ -2745,6 +2745,7 @@ void WaveformArea::RenderYAxis(ImVec2 size, map<float, float>& gridmap, float vb
 			for(auto& c : m_displayedChannels)
 			{
 				auto data = c->GetStream().GetData();
+				data->PrepareForCpuAccess();
 				auto sdata = dynamic_cast<SparseAnalogWaveform*>(data);
 				auto udata = dynamic_cast<UniformAnalogWaveform*>(data);
 				if(!sdata && !udata)