experimental UI: update progress bar on progress events

In the experimental UI, use progress events as an occasion to
update the progress bar. However, to avoid unnecessary noise, only
do so, if the progress bar potentially changes with time.

--
Change-Id: I9bee093c29e0eb50e7fcce2fa6e941a02d615def
Reviewed-on: https://bazel-review.googlesource.com/#/c/3206
MOS_MIGRATED_REVID=118944208

2 files changed, 19 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalEventHandler.java b/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalEventHandler.java
index 0073c245ce..dc488bd6e0 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalEventHandler.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalEventHandler.java
@@ -115,6 +115,10 @@ public class ExperimentalEventHandler extends BlazeCommandEventHandler {
             }
             terminal.flush();
             break;
+          case PROGRESS:
+            if (stateTracker.progressBarTimeDependent()) {
+              refresh();
+            }
         }
       }
     } catch (IOException e) {
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalStateTracker.java b/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalStateTracker.java
index 889222228c..0764d53778 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalStateTracker.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalStateTracker.java
@@ -147,6 +147,21 @@ class ExperimentalStateTracker {
     }
   }
 
+  /***
+   * Predicate indicating whether the contents of the progress bar can change, if the
+   * only thing that happens is that time passes; this is the case, e.g., if the progress
+   * bar shows time information relative to the current time.
+   */
+  boolean progressBarTimeDependent() {
+    if (status != null) {
+      return false;
+    }
+    if (runningActions.size() >= 1) {
+      return true;
+    }
+    return false;
+  }
+
   synchronized void writeProgressBar(AnsiTerminalWriter terminalWriter) throws IOException {
     if (status != null) {
       if (ok) {