[glass] Fix plots (#2943)

glass/src/app/native/cpp/main.cpp

@@ -93,7 +93,7 @@ int main() {
 
   gui::ConfigurePlatformSaveFile("glass.ini");
   gPlotProvider->GlobalInit();
-  gui::AddInit([] { gPlotProvider->ResetTime(); });
+  gui::AddInit([] { glass::ResetTime(); });
   gNtProvider->GlobalInit();
   gui::AddInit(NtInitialize);
 
@@ -102,6 +102,10 @@ int main() {
   gui::AddLateExecute([] {
     ImGui::BeginMainMenuBar();
     gui::EmitViewMenu();
+    if (ImGui::BeginMenu("View")) {
+      if (ImGui::MenuItem("Reset Time")) glass::ResetTime();
+      ImGui::EndMenu();
+    }
     if (ImGui::BeginMenu("NetworkTables")) {
       if (gNetworkTablesSettingsWindow)
         gNetworkTablesSettingsWindow->DisplayMenuItem("NetworkTables Settings");
@@ -116,7 +120,6 @@ int main() {
       if (ImGui::MenuItem("Pause All Plots", nullptr, &paused)) {
         gPlotProvider->SetPaused(paused);
       }
-      if (ImGui::MenuItem("Reset Plot Time")) gPlotProvider->ResetTime();
       ImGui::Separator();
       gPlotProvider->DisplayMenu();
       ImGui::EndMenu();

glass/src/lib/native/cpp/Context.cpp

@@ -15,6 +15,7 @@
 #include <imgui_internal.h>
 #include <imgui_stdlib.h>
 #include <wpi/StringRef.h>
+#include <wpi/timestamp.h>
 #include <wpigui.h>
 
 #include "glass/ContextInternal.h"
@@ -211,6 +212,10 @@ Context* glass::GetCurrentContext() { return gContext; }
 
 void glass::SetCurrentContext(Context* ctx) { gContext = ctx; }
 
+void glass::ResetTime() { gContext->zeroTime = wpi::Now(); }
+
+uint64_t glass::GetZeroTime() { return gContext->zeroTime; }
+
 Storage::Value& Storage::GetValue(wpi::StringRef key) {
   auto it = std::find(m_keys.begin(), m_keys.end(), key);
   if (it == m_keys.end()) {

glass/src/lib/native/cpp/other/Plot.cpp

@@ -55,8 +55,6 @@ class PlotSeries {
   void SetSource(DataSource* source);
   DataSource* GetSource() const { return m_source; }
 
-  void Clear() { m_size = 0; }
-
   bool ReadIni(wpi::StringRef name, wpi::StringRef value);
   void WriteIni(ImGuiTextBuffer* out);
 
@@ -110,8 +108,6 @@ class Plot {
   bool ReadIni(wpi::StringRef name, wpi::StringRef value);
   void WriteIni(ImGuiTextBuffer* out);
 
-  void Clear();
-
   void DragDropTarget(PlotView& view, size_t i, bool inPlot);
   void EmitPlot(PlotView& view, double now, bool paused, size_t i);
   void EmitSettings(size_t i);
@@ -146,8 +142,6 @@ class PlotView : public View {
  public:
   explicit PlotView(PlotProvider* provider) : m_provider{provider} {}
 
-  void Clear();
-
   void Display() override;
 
   void MovePlot(PlotView* fromView, size_t fromIndex, size_t toIndex);
@@ -312,20 +306,24 @@ PlotSeries::Action PlotSeries::EmitPlot(PlotView& view, double now, size_t i,
   // we handle the offset logic ourselves to avoid wrap issues with size + 1
   struct GetterData {
     double now;
+    double zeroTime;
     ImPlotPoint* data;
     int size;
     int offset;
   };
-  GetterData getterData = {now, m_data, size, offset};
+  GetterData getterData = {now, GetZeroTime() * 1.0e-6, m_data, size, offset};
   auto getter = [](void* data, int idx) {
     auto d = static_cast<GetterData*>(data);
     if (idx == d->size)
       return ImPlotPoint{
-          d->now, d->data[d->offset == 0 ? d->size - 1 : d->offset - 1].y};
+          d->now - d->zeroTime,
+          d->data[d->offset == 0 ? d->size - 1 : d->offset - 1].y};
+    ImPlotPoint* point;
     if (d->offset + idx < d->size)
-      return d->data[d->offset + idx];
+      point = &d->data[d->offset + idx];
     else
-      return d->data[d->offset + idx - d->size];
+      point = &d->data[d->offset + idx - d->size];
+    return ImPlotPoint{point->x - d->zeroTime, point->y};
   };
 
   if (m_color.w == IMPLOT_AUTO_COL.w) m_color = ImPlot::GetColormapColor(i);
@@ -543,10 +541,6 @@ void Plot::WriteIni(ImGuiTextBuffer* out) {
   }
 }
 
-void Plot::Clear() {
-  for (auto&& series : m_series) series->Clear();
-}
-
 void Plot::DragDropTarget(PlotView& view, size_t i, bool inPlot) {
   if (!ImGui::BeginDragDropTarget()) return;
   // handle dragging onto a specific Y axis
@@ -601,8 +595,9 @@ void Plot::EmitPlot(PlotView& view, double now, bool paused, size_t i) {
                                ImGuiCond_Always);
   } else {
     // also force-pause plots if overall timing is paused
+    double zeroTime = GetZeroTime() * 1.0e-6;
     ImPlot::SetNextPlotLimitsX(
-        now - m_viewTime, now,
+        now - zeroTime - m_viewTime, now - zeroTime,
         (paused || m_paused) ? ImGuiCond_Once : ImGuiCond_Always);
   }
 
@@ -688,10 +683,6 @@ void Plot::EmitSettings(size_t i) {
   }
 }
 
-void PlotView::Clear() {
-  for (auto&& plot : m_plots) plot->Clear();
-}
-
 void PlotView::Display() {
   if (ImGui::BeginPopupContextItem()) {
     if (ImGui::Button("Add plot"))
@@ -760,7 +751,7 @@ void PlotView::Display() {
     }
   }
 
-  double now = (wpi::Now() - m_provider->GetStartTime()) * 1.0e-6;
+  double now = wpi::Now() * 1.0e-6;
   for (size_t i = 0; i < m_plots.size(); ++i) {
     ImGui::PushID(i);
     m_plots[i]->EmitPlot(*this, now, m_provider->IsPaused(), i);
@@ -821,15 +812,6 @@ void PlotProvider::GlobalInit() {
   });
 }
 
-void PlotProvider::ResetTime() {
-  m_startTime = wpi::Now();
-  for (auto&& window : m_windows) {
-    if (auto view = static_cast<PlotView*>(window->GetView())) {
-      view->Clear();
-    }
-  }
-}
-
 void PlotProvider::DisplayMenu() {
   for (size_t i = 0; i < m_windows.size(); ++i) {
     m_windows[i]->DisplayMenuItem();

glass/src/lib/native/include/glass/Context.h

@@ -25,6 +25,16 @@ void DestroyContext(Context* ctx = nullptr);
 Context* GetCurrentContext();
 void SetCurrentContext(Context* ctx);
 
+/**
+ * Resets zero time to current time.
+ */
+void ResetTime();
+
+/**
+ * Gets the zero time.
+ */
+uint64_t GetZeroTime();
+
 /**
  * Storage provides both persistent and non-persistent key/value storage for
  * widgets.

glass/src/lib/native/include/glass/ContextInternal.h

@@ -7,6 +7,8 @@
 
 #pragma once
 
+#include <stdint.h>
+
 #include <memory>
 
 #include <imgui.h>
@@ -42,6 +44,7 @@ struct Context {
   wpi::StringMap<std::unique_ptr<Storage>> storage;
   wpi::StringMap<bool> deviceHidden;
   IniSaverString<DataSourceName> sources{"Data Sources"};
+  uint64_t zeroTime = 0;
 };
 
 extern Context* gContext;

glass/src/lib/native/include/glass/other/Plot.h

@@ -31,14 +31,6 @@ class PlotProvider : private WindowManager {
    */
   bool IsPaused() { return m_paused; }
 
-  /**
-   * Resets time on all plots such that 0 = time when this function is called.
-   * Also clears the plot data.
-   */
-  void ResetTime();
-
-  uint64_t GetStartTime() const { return m_startTime; }
-
   void DisplayMenu() override;
 
  private:
@@ -60,7 +52,6 @@ class PlotProvider : private WindowManager {
 
   IniSaver m_plotSaver;
   IniSaver m_seriesSaver;
-  uint64_t m_startTime = 0;
   bool m_paused = false;
 };