UI: run set_brightness in QtConcurrent (commaai#23326)

* use QFuture

* update at 10 hz

* don't change frequency

Author: deanlee

selfdrive/ui/ui.cc

@@ -3,6 +3,8 @@
 #include <cassert>
 #include <cmath>
 
+#include <QtConcurrent>
+
 #include "common/transformations/orientation.hpp"
 #include "selfdrive/common/params.h"
 #include "selfdrive/common/swaglog.h"
@@ -290,9 +292,11 @@ void Device::updateBrightness(const UIState &s) {
   }
 
   if (brightness != last_brightness) {
-    std::thread{Hardware::set_brightness, brightness}.detach();
+    if (!brightness_future.isRunning()) {
+      brightness_future = QtConcurrent::run(Hardware::set_brightness, brightness);
+      last_brightness = brightness;
+    }
   }
-  last_brightness = brightness;
 }
 
 bool Device::motionTriggered(const UIState &s) {

selfdrive/ui/ui.h

@@ -7,6 +7,7 @@
 #include <QObject>
 #include <QTimer>
 #include <QColor>
+#include <QFuture>
 #include <QTransform>
 
 #include "cereal/messaging/messaging.h"
@@ -162,6 +163,7 @@ class Device : public QObject {
   bool ignition_on = false;
   int last_brightness = 0;
   FirstOrderFilter brightness_filter;
+  QFuture<void> brightness_future;
 
   void updateBrightness(const UIState &s);
   void updateWakefulness(const UIState &s);