Bug fix: The spectrum graph is sometimes not displayed after change spectrums type (betaflight#837)

* Resolved random bug of lose dataBuffer data by change spectrum type

* Code style improvement

Co-authored-by: Mark Haslinghuis <[email protected]>

---------

Co-authored-by: Mark Haslinghuis <[email protected]>

Author: demvlad

src/graph_spectrum.js

@@ -17,15 +17,16 @@ export function FlightLogAnalyser(flightLog, canvas, analyserCanvas) {
   let that = this,
     analyserZoomX = 1.0 /* 100% */,
     analyserZoomY = 1.0 /* 100% */,
-    dataBuffer = {
-      fieldIndex: 0,
-      curve: 0,
-      fieldName: null,
-    },
     dataReload = false,
     fftData = null,
     prefs = new PrefStorage();
 
+  this.dataBuffer = {
+    fieldIndex: 0,
+    curve: 0,
+    fieldName: null,
+  };
+
   try {
     let isFullscreen = false;
 
@@ -100,9 +101,8 @@ export function FlightLogAnalyser(flightLog, canvas, analyserCanvas) {
       });
     };
 
-    let dataLoad = function () {
-      GraphSpectrumCalc.setDataBuffer(dataBuffer);
-
+    const dataLoad = function () {
+      GraphSpectrumCalc.setDataBuffer(that.dataBuffer);
       switch (userSettings.spectrumType) {
         case SPECTRUM_TYPE.FREQ_VS_THROTTLE:
           fftData = GraphSpectrumCalc.dataLoadFrequencyVsThrottle();
@@ -128,19 +128,16 @@ export function FlightLogAnalyser(flightLog, canvas, analyserCanvas) {
            analyser on screen*/
     this.plotSpectrum = function (fieldIndex, curve, fieldName) {
       // Store the data pointers
-      dataBuffer = {
-        fieldIndex: fieldIndex,
-        curve: curve,
-        fieldName: fieldName,
-      };
 
+      that.dataBuffer.fieldIndex = fieldIndex;
+      that.dataBuffer.curve = curve;
+      that.dataBuffer.fieldName = fieldName;
       // Detect change of selected field.... reload and redraw required.
       if (fftData == null || fieldIndex != fftData.fieldIndex || dataReload) {
         dataReload = false;
         dataLoad();
         GraphSpectrumPlot.setData(fftData, userSettings.spectrumType);
       }
-
       that.draw(); // draw the analyser on the canvas....
     };
 
@@ -211,9 +208,9 @@ export function FlightLogAnalyser(flightLog, canvas, analyserCanvas) {
           // Recalculate the data, for the same curve than now, and draw it
           dataReload = true;
           that.plotSpectrum(
-            dataBuffer.fieldIndex,
-            dataBuffer.curve,
-            dataBuffer.fieldName
+            that.dataBuffer.fieldIndex,
+            that.dataBuffer.curve,
+            that.dataBuffer.fieldName,
           );
         }