democompositor: Keep track of running apps and enforce singleton

Modify the ProcessLauncher to keep track of running apps in the
m_appStates vector. Answer if an AppEntry has a AppState associated
and use it to not launch a second instance of the application. In
the future this could be an attribute of the .apps file.

Change-Id: I19ed2840e0a64eb7f35fba0cb171e1c7fd722b06
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

3 files changed, 76 insertions, 11 deletions

diff --git a/wayland/democompositor/processlauncher.cpp b/wayland/democompositor/processlauncher.cpp
index 40b3b8b..c8fe15c 100644
--- a/wayland/democompositor/processlauncher.cpp
+++ b/wayland/democompositor/processlauncher.cpp
@@ -55,6 +55,16 @@
 
 Q_LOGGING_CATEGORY(procs, "launcher.procs")
 
+/*
+ * Two AppState's are equal if they are managing the same
+ * QProcess. It is assumed that no AppState survives beyond
+ * the QProcess.
+ */
+bool operator==(const AppState& lhs, const AppState& rhs)
+{
+    return lhs.process == rhs.process;
+}
+
 WaylandProcessLauncher::WaylandProcessLauncher(QObject *parent)
     : QObject(parent)
 {
@@ -64,26 +74,52 @@ WaylandProcessLauncher::~WaylandProcessLauncher()
 {
 }
 
+bool WaylandProcessLauncher::isRunning(const AppEntry& entry) const
+{
+    for (auto state : m_appStates) {
+        if (state.appEntry.sourceFileName == entry.sourceFileName) {
+            qCDebug(procs) << "AppEntry associated to a state" << entry.executableName;
+            return true;
+        }
+    }
+
+    qCDebug(procs) << "AppEntry not associated to a state " << entry.executableName;
+    return false;
+}
+
 void WaylandProcessLauncher::launch(const AppEntry &entry)
 {
     qCDebug(procs) << "Launching" << entry.executableName;
 
     QProcess *process = new QProcess(this);
 
+    AppState state{process, entry};
+    m_appStates.push_back(state);
+
     /* handle potential errors and life cycle */
     connect(process, static_cast<void(QProcess::*)(int, QProcess::ExitStatus)>(&QProcess::finished),
-            [process, entry](int exitCode, QProcess::ExitStatus status) {
-                qCDebug(procs) << "AppEntry finished" << entry.executableName << exitCode << status;
-                process->deleteLater();
+            [state, this](int exitCode, QProcess::ExitStatus status) {
+                qCDebug(procs) << "AppEntry finished" << state.appEntry.executableName << exitCode << status;
+                emit appFinished(state, exitCode, status);
+                m_appStates.removeOne(state);
+                state.process->deleteLater();
     });
     connect(process, &QProcess::errorOccurred,
-            [process, entry](QProcess::ProcessError err) {
-                qCDebug(procs) << "AppEntry error occurred" << entry.executableName << err;
-                process->deleteLater();
+            [state, this](QProcess::ProcessError err) {
+                qCDebug(procs) << "AppEntry error occurred" << state.appEntry.executableName << err;
+
+                /* Maybe finished was already emitted. Let's not emit an error after that */
+                if (!m_appStates.removeOne(state))
+                    return;
+
+                if (err == QProcess::FailedToStart || err == QProcess::UnknownError)
+                    emit appNotStarted(state);
+                state.process->deleteLater();
     });
     connect(process, &QProcess::started,
-            [process, entry]() {
-                qCDebug(procs) << "AppEntry started" << entry.executableName;
+            [state, this]() {
+                qCDebug(procs) << "AppEntry started" << state.appEntry.executableName;
+                emit appStarted(state);
     });
 
     if (!entry.executablePath.isNull()) {
diff --git a/wayland/democompositor/processlauncher.h b/wayland/democompositor/processlauncher.h
index 092c0a3..84f9cb8 100644
--- a/wayland/democompositor/processlauncher.h
+++ b/wayland/democompositor/processlauncher.h
@@ -51,13 +51,27 @@
 #ifndef PROCESSLAUNCHER_H
 #define PROCESSLAUNCHER_H
 
+#include "apps/appentry.h"
+
 #include <QObject>
+#include <QProcess>
 #include <QLoggingCategory>
 
-class AppEntry;
-
 Q_DECLARE_LOGGING_CATEGORY(procs)
 
+/**
+ * Transient class. Do not keep AppState beyond the
+ * finished signal.
+ */
+class AppState {
+    Q_GADGET
+    Q_PROPERTY(QProcess *process MEMBER process CONSTANT)
+    Q_PROPERTY(AppEntry appEntry MEMBER appEntry CONSTANT)
+public:
+    QProcess *process;
+    AppEntry appEntry;
+};
+
 class WaylandProcessLauncher : public QObject
 {
     Q_OBJECT
@@ -66,6 +80,18 @@ public:
     explicit WaylandProcessLauncher(QObject *parent = 0);
     ~WaylandProcessLauncher();
     Q_INVOKABLE void launch(const AppEntry &entry);
+
+    Q_INVOKABLE bool isRunning(const AppEntry& entry) const;
+
+Q_SIGNALS:
+    void appStarted(const AppState &appState);
+    void appFinished(const AppState &appState, int exitCode, QProcess::ExitStatus exitStatus);
+    void appNotStarted(const AppState& appState);
+
+private:
+    QVector<AppState> m_appStates;
 };
 
+Q_DECLARE_METATYPE(AppState)
+
 #endif // PROCESSLAUNCHER_H
diff --git a/wayland/democompositor/qml/LaunchButton.qml b/wayland/democompositor/qml/LaunchButton.qml
index 2d3801a..80a057a 100644
--- a/wayland/democompositor/qml/LaunchButton.qml
+++ b/wayland/democompositor/qml/LaunchButton.qml
@@ -57,5 +57,8 @@ MyButton {
     text.maximumLineCount: 1
     iconSize: 32
 
-    onTriggered: launcher.launch(appEntry)
+    onTriggered: {
+        if (!launcher.isRunning(appEntry))
+            launcher.launch(appEntry)
+    }
 }