Add flag to enable shared x-axis for local event log visualization.

Bug: None
Change-Id: I4aea047c905aa8acbe25fd325bc92bb65b8d0826
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132557
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27583}

rtc_tools/event_log_visualizer/main.cc

@@ -214,6 +214,12 @@ WEBRTC_DEFINE_bool(
     true,
     "Normalize the log timestamps so that the call starts at time 0.");
 
+WEBRTC_DEFINE_bool(shared_xaxis,
+                   false,
+                   "Share x-axis between all plots so that zooming in one plot "
+                   "updates all the others too. A downside is that certain "
+                   "operations like panning become much slower.");
+
 WEBRTC_DEFINE_bool(protobuf_output,
                    false,
                    "Output charts as protobuf instead of python code.");
@@ -294,7 +300,7 @@ int main(int argc, char* argv[]) {
   if (FLAG_protobuf_output) {
     collection.reset(new webrtc::ProtobufPlotCollection());
   } else {
-    collection.reset(new webrtc::PythonPlotCollection());
+    collection.reset(new webrtc::PythonPlotCollection(FLAG_shared_xaxis));
   }
 
   if (FLAG_plot_incoming_packet_sizes) {

rtc_tools/event_log_visualizer/plot_python.cc

@@ -158,7 +158,8 @@ void PythonPlot::Draw() {
   }
 }
 
-PythonPlotCollection::PythonPlotCollection() {}
+PythonPlotCollection::PythonPlotCollection(bool shared_xaxis)
+    : shared_xaxis_(shared_xaxis) {}
 
 PythonPlotCollection::~PythonPlotCollection() {}
 
@@ -170,11 +171,13 @@ void PythonPlotCollection::Draw() {
   printf("import colorsys\n");
   for (size_t i = 0; i < plots_.size(); i++) {
     printf("plt.figure(%zu)\n", i);
-    // Link x-axes across all figures for synchronized zooming.
-    if (i == 0) {
-      printf("axis0 = plt.subplot(111)\n");
-    } else {
-      printf("plt.subplot(111, sharex=axis0)\n");
+    if (shared_xaxis_) {
+      // Link x-axes across all figures for synchronized zooming.
+      if (i == 0) {
+        printf("axis0 = plt.subplot(111)\n");
+      } else {
+        printf("plt.subplot(111, sharex=axis0)\n");
+      }
     }
     plots_[i]->Draw();
   }

rtc_tools/event_log_visualizer/plot_python.h

@@ -23,10 +23,13 @@ class PythonPlot final : public Plot {
 
 class PythonPlotCollection final : public PlotCollection {
  public:
-  PythonPlotCollection();
+  explicit PythonPlotCollection(bool shared_xaxis = false);
   ~PythonPlotCollection() override;
   void Draw() override;
   Plot* AppendNewPlot() override;
+
+ private:
+  bool shared_xaxis_;
 };
 
 }  // namespace webrtc