Select the default selected thread by the thread activity

Previously we were only getting the first tab process main thread
as the selected thread, which wasn't the track we want most of the time.

Author: canova

src/actions/receive-profile.js

@@ -319,7 +319,8 @@ export function finalizeFullProfileView(
     const selectedThreadIndexes = initializeSelectedThreadIndex(
       maybeSelectedThreadIndexes,
       getVisibleThreads(tracksWithOrder, hiddenTracks),
-      profile
+      profile,
+      threadActivityScores
     );
 
     let timelineType = null;
@@ -1549,7 +1550,8 @@ export function changeTabFilter(tabID: TabID | null): ThunkAction<void> {
     const selectedThreadIndexes = initializeSelectedThreadIndex(
       null, // maybeSelectedThreadIndexes
       getVisibleThreads(tracksWithOrder, hiddenTracks),
-      profile
+      profile,
+      threadActivityScores
     );
 
     // If the currently selected tab is only visible when the selected track

src/profile-logic/profile-data.js

@@ -95,6 +95,7 @@ import type {
   TabID,
 } from 'firefox-profiler/types';
 import type { CallNodeInfo, SuffixOrderIndex } from './call-node-info';
+import type { ThreadActivityScore } from './tracks';
 
 /**
  * Various helpers for dealing with the profile as a data structure.
@@ -1286,8 +1287,12 @@ export function getTimeRangeIncludingAllThreads(
   return completeRange;
 }
 
-export function defaultThreadOrder(threads: RawThread[]): ThreadIndex[] {
-  const threadOrder = threads.map((thread, i) => i);
+export function defaultThreadOrder(
+  visibleThreadIndexes: ThreadIndex[],
+  threads: RawThread[],
+  threadActivityScores: Array<ThreadActivityScore>
+): ThreadIndex[] {
+  const threadOrder = [...visibleThreadIndexes];
 
   // Note: to have a consistent behavior independant of the sorting algorithm,
   // we need to be careful that the comparator function is consistent:
@@ -1299,7 +1304,10 @@ export function defaultThreadOrder(threads: RawThread[]): ThreadIndex[] {
     const nameB = threads[b].name;
 
     if (nameA === nameB) {
-      return a - b;
+      return (
+        threadActivityScores[b].boostedSampleScore -
+        threadActivityScores[a].boostedSampleScore
+      );
     }
 
     // Put the compositor/renderer thread last.

src/profile-logic/tracks.js

@@ -745,10 +745,15 @@ export function initializeGlobalTrackOrder(
 export function initializeSelectedThreadIndex(
   selectedThreadIndexes: Set<ThreadIndex> | null,
   visibleThreadIndexes: ThreadIndex[],
-  profile: Profile
+  profile: Profile,
+  threadActivityScores: Array<ThreadActivityScore>
 ): Set<ThreadIndex> {
   if (selectedThreadIndexes === null) {
-    return getDefaultSelectedThreadIndexes(visibleThreadIndexes, profile);
+    return getDefaultSelectedThreadIndexes(
+      visibleThreadIndexes,
+      profile,
+      threadActivityScores
+    );
   }
 
   // Filter out hidden threads from the set of selected threads.
@@ -758,7 +763,11 @@ export function initializeSelectedThreadIndex(
   );
   if (visibleSelectedThreadIndexes.size === 0) {
     // No selected threads were visible. Fall back to default selection.
-    return getDefaultSelectedThreadIndexes(visibleThreadIndexes, profile);
+    return getDefaultSelectedThreadIndexes(
+      visibleThreadIndexes,
+      profile,
+      threadActivityScores
+    );
   }
   return visibleSelectedThreadIndexes;
 }
@@ -767,7 +776,8 @@ export function initializeSelectedThreadIndex(
 // order.
 function getDefaultSelectedThreadIndexes(
   visibleThreadIndexes: ThreadIndex[],
-  profile: Profile
+  profile: Profile,
+  threadActivityScores: Array<ThreadActivityScore>
 ): Set<ThreadIndex> {
   if (profile.meta.initialSelectedThreads !== undefined) {
     return new Set(
@@ -785,10 +795,11 @@ function getDefaultSelectedThreadIndexes(
       })
     );
   }
-  const visibleThreads = visibleThreadIndexes.map(
-    (threadIndex) => profile.threads[threadIndex]
+  const defaultThread = _findDefaultThread(
+    visibleThreadIndexes,
+    profile.threads,
+    threadActivityScores
   );
-  const defaultThread = _findDefaultThread(visibleThreads);
   const defaultThreadIndex = profile.threads.indexOf(defaultThread);
   if (defaultThreadIndex === -1) {
     throw new Error('Expected to find a thread index to select.');
@@ -1309,16 +1320,30 @@ function _computeThreadSampleScore(
   return nonIdleSampleCount * referenceCPUDeltaPerInterval;
 }
 
-function _findDefaultThread(threads: RawThread[]): RawThread | null {
+function _findDefaultThread(
+  visibleThreadIndexes: ThreadIndex[],
+  threads: RawThread[],
+  threadActivityScores: Array<ThreadActivityScore>
+): RawThread | null {
   if (threads.length === 0) {
     // Tests may have no threads.
     return null;
   }
-  const contentThreadId = threads.findIndex(
-    (thread) => thread.name === 'GeckoMain' && thread.processType === 'tab'
+
+  const threadOrder = defaultThreadOrder(
+    visibleThreadIndexes,
+    threads,
+    threadActivityScores
   );
+
+  // Try to find a tab process with the highest activity score. If it can't
+  // find one, select the first thread with the highest one.
   const defaultThreadIndex =
-    contentThreadId !== -1 ? contentThreadId : defaultThreadOrder(threads)[0];
+    threadOrder.find(
+      (threadIndex) =>
+        threads[threadIndex].name === 'GeckoMain' &&
+        threads[threadIndex].processType === 'tab'
+    ) ?? threadOrder[0];
 
   return threads[defaultThreadIndex];
 }

src/test/store/receive-profile.test.js

@@ -265,9 +265,9 @@ describe('actions/receive-profile', function () {
 
       store.dispatch(viewProfile(profile));
       expect(getHumanReadableTracks(store.getState())).toEqual([
-        'hide [thread GeckoMain tab]',
         'show [thread GeckoMain tab] SELECTED',
         'hide [thread GeckoMain tab]',
+        'hide [thread GeckoMain tab]',
       ]);
     });
 
@@ -396,8 +396,8 @@ describe('actions/receive-profile', function () {
 
       store.dispatch(viewProfile(profile));
       expect(getHumanReadableTracks(store.getState())).toEqual([
-        'hide [thread GeckoMain tab]',
         'show [thread GeckoMain tab] SELECTED',
+        'hide [thread GeckoMain tab]',
       ]);
     });