ui/util: add a helper class ParamWatcher (#28978)

* new class ParamWatcher

* Update selfdrive/ui/qt/util.cc

* Update selfdrive/ui/qt/util.h

* Update selfdrive/ui/qt/util.cc

* Update selfdrive/ui/qt/util.cc

---------

Co-authored-by: Adeeb Shihadeh <adeebshihadeh@gmail.com>
old-commit-hash: b4f7e76531

selfdrive/ui/qt/offroad/settings.h

@@ -1,7 +1,6 @@
 #pragma once
 
 #include <QButtonGroup>
-#include <QFileSystemWatcher>
 #include <QFrame>
 #include <QLabel>
 #include <QPushButton>
@@ -9,6 +8,7 @@
 #include <QWidget>
 
 
+#include "selfdrive/ui/qt/util.h"
 #include "selfdrive/ui/qt/widgets/controls.h"
 
 // ********** settings window + top-level panels **********
@@ -88,5 +88,5 @@ private:
   ButtonControl *targetBranchBtn;
 
   Params params;
-  QFileSystemWatcher *fs_watch;
+  ParamWatcher *fs_watch;
 };

selfdrive/ui/qt/offroad/software_settings.cc

@@ -83,8 +83,8 @@ SoftwarePanel::SoftwarePanel(QWidget* parent) : ListWidget(parent) {
   });
   addItem(uninstallBtn);
 
-  fs_watch = new QFileSystemWatcher(this);
-  QObject::connect(fs_watch, &QFileSystemWatcher::fileChanged, [=](const QString path) {
+  fs_watch = new ParamWatcher(this);
+  QObject::connect(fs_watch, &ParamWatcher::paramChanged, [=](const QString &param_name, const QString &param_value) {
     updateLabels();
   });
 
@@ -105,10 +105,10 @@ void SoftwarePanel::showEvent(QShowEvent *event) {
 
 void SoftwarePanel::updateLabels() {
   // add these back in case the files got removed
-  fs_watch->addPath(QString::fromStdString(params.getParamPath("LastUpdateTime")));
-  fs_watch->addPath(QString::fromStdString(params.getParamPath("UpdateFailedCount")));
-  fs_watch->addPath(QString::fromStdString(params.getParamPath("UpdaterState")));
-  fs_watch->addPath(QString::fromStdString(params.getParamPath("UpdateAvailable")));
+  fs_watch->addParam("LastUpdateTime");
+  fs_watch->addParam("UpdateFailedCount");
+  fs_watch->addParam("UpdaterState");
+  fs_watch->addParam("UpdateAvailable");
 
   if (!isVisible()) {
     return;

selfdrive/ui/qt/util.cc

@@ -2,6 +2,7 @@
 
 #include <QApplication>
 #include <QFile>
+#include <QFileInfo>
 #include <QHash>
 #include <QJsonDocument>
 #include <QJsonObject>
@@ -11,7 +12,6 @@
 #include <QTextStream>
 #include <QtXml/QDomDocument>
 
-#include "common/params.h"
 #include "common/swaglog.h"
 #include "system/hardware/hw.h"
 
@@ -252,3 +252,27 @@ bool hasLongitudinalControl(const cereal::CarParams::Reader &car_params) {
              ? Params().getBool("ExperimentalLongitudinalEnabled")
              : car_params.getOpenpilotLongitudinalControl();
 }
+
+// ParamWatcher
+
+ParamWatcher::ParamWatcher(QObject *parent) : QObject(parent) {
+  watcher = new QFileSystemWatcher(this);
+  QObject::connect(watcher, &QFileSystemWatcher::fileChanged, this, &ParamWatcher::fileChanged);
+}
+
+void ParamWatcher::fileChanged(const QString &path) {
+  auto param_name = QFileInfo(path).fileName();
+  auto param_value = QString::fromStdString(params.get(param_name.toStdString()));
+
+  auto it = params_hash.find(param_name);
+  bool content_changed = (it == params_hash.end()) || (it.value() != param_value);
+  params_hash[param_name] = param_value;
+  // emit signal when the content changes.
+  if (content_changed) {
+    emit paramChanged(param_name, param_value);
+  }
+}
+
+void ParamWatcher::addParam(const QString &param_name) {
+  watcher->addPath(QString::fromStdString(params.getParamPath(param_name.toStdString())));
+}

selfdrive/ui/qt/util.h

@@ -3,6 +3,7 @@
 #include <optional>
 
 #include <QDateTime>
+#include <QFileSystemWatcher>
 #include <QLayout>
 #include <QPainter>
 #include <QPixmap>
@@ -10,6 +11,7 @@
 #include <QWidget>
 
 #include "cereal/gen/cpp/car.capnp.h"
+#include "common/params.h"
 
 QString getVersion();
 QString getBrand();
@@ -36,3 +38,21 @@ struct InterFont : public QFont {
     setWeight(weight);
   }
 };
+
+class ParamWatcher : public QObject {
+  Q_OBJECT
+
+public:
+  ParamWatcher(QObject *parent);
+  void addParam(const QString &param_name);
+
+signals:
+  void paramChanged(const QString &param_name, const QString &param_value);
+
+private:
+  void fileChanged(const QString &path);
+
+  QFileSystemWatcher *watcher;
+  QHash<QString, QString> params_hash;
+  Params params;
+};