Fixes #10928. Fix race in LoadInBackground() handling.

mythtv/libs/libmythbase/mythversion.h

@@ -12,7 +12,7 @@
 /// Update this whenever the plug-in API changes.
 /// Including changes in the libmythbase, libmyth, libmythtv, libmythav* and
 /// libmythui class methods used by plug-ins.
-#define MYTH_BINARY_VERSION "0.26.20120721-1"
+#define MYTH_BINARY_VERSION "0.26.20120724-1"
 
 /** \brief Increment this whenever the MythTV network protocol changes.
  *

mythtv/libs/libmythui/mythscreentype.cpp

@@ -22,16 +22,18 @@ QEvent::Type ScreenLoadCompletionEvent::kEventType =
 class ScreenLoadTask : public QRunnable
 {
   public:
-    ScreenLoadTask(MythScreenType *parent) : m_parent(parent) {}
+    ScreenLoadTask(MythScreenType &parent) : m_parent(parent) {}
 
   private:
-    void run()
+    void run(void)
     {
-        if (m_parent)
-            m_parent->LoadInForeground();
+        m_parent.Load();
+        m_parent.m_IsLoaded = true;
+        m_parent.m_IsLoading = false;
+        m_parent.m_LoadLock.unlock();
     }
 
-    MythScreenType *m_parent;
+    MythScreenType &m_parent;
 };
 
 MythScreenType::MythScreenType(MythScreenStack *parent, const QString &name,
@@ -80,6 +82,9 @@ MythScreenType::~MythScreenType()
 //    gCoreContext->SendSystemEvent(
 //        QString("SCREEN_TYPE DESTROYED %1").arg(objectName()));
 
+    // locking ensures background screen load can finish running
+    QMutexLocker locker(&m_LoadLock);
+
     m_CurrentFocusWidget = NULL;
     emit Exiting();
 }
@@ -294,18 +299,26 @@ void MythScreenType::Load(void)
 
 void MythScreenType::LoadInBackground(QString message)
 {
+    m_LoadLock.lock();
+
     m_IsLoading = true;
+    m_IsLoaded = false;
+
     m_ScreenStack->AllowReInit();
 
     OpenBusyPopup(message);
 
-    ScreenLoadTask *loadTask = new ScreenLoadTask(this);
+    ScreenLoadTask *loadTask = new ScreenLoadTask(*this);
     MThreadPool::globalInstance()->start(loadTask, "ScreenLoad");
 }
 
 void MythScreenType::LoadInForeground(void)
 {
+    QMutexLocker locker(&m_LoadLock);
+
     m_IsLoading = true;
+    m_IsLoaded = false;
+
     m_ScreenStack->AllowReInit();
     Load();
     m_IsLoaded = true;
@@ -365,6 +378,8 @@ bool MythScreenType::IsInitialized(void) const
 
 void MythScreenType::doInit(void)
 {
+    QMutexLocker locker(&m_LoadLock); // don't run while loading..
+
     CloseBusyPopup();
     Init();
     m_IsInitialized = true;

mythtv/libs/libmythui/mythscreentype.h

@@ -5,8 +5,11 @@
 #include "mythuitext.h"
 #include "mythuiutils.h"
 
+#include <QWaitCondition>
+#include <QMutex>
 #include <QHash>
 
+class ScreenLoadTask;
 class MythScreenStack;
 class MythUIBusyDialog;
 
@@ -40,6 +43,8 @@ class MUI_PUBLIC MythScreenType : public MythUIType
 {
     Q_OBJECT
 
+    friend class ScreenLoadTask;
+
   public:
     MythScreenType(MythScreenStack *parent, const QString &name,
                    bool fullscreen = true);
@@ -108,8 +113,10 @@ class MUI_PUBLIC MythScreenType : public MythUIType
 
     bool m_FullScreen;
     bool m_IsDeleting;
-    bool m_IsLoading;
-    bool m_IsLoaded;
+
+    QMutex m_LoadLock;
+    volatile bool m_IsLoading;
+    volatile bool m_IsLoaded;
     bool m_IsInitialized;
 
     MythUIType *m_CurrentFocusWidget;