Debugger: Fix switching to previous mode on exit

This behavior was broken with refactoring done in commit
3b5ecac238b87615b44b27375cef0b4f1d4637e4. This has two main components:
1. Perspective::select() needs to call EngineManager::activateDebugMode()
   in order to save the previous mode.
2. The contents of the previous function
   DebuggerPluginPrivate::activatePreviousMode() was placed in
   EngineManager::deactivateDebugMode() and is called in
   doFinishDebugger().

Task-number: QTCREATORBUG-21415
Change-Id: Ibca188ba740027769c497e25ea695af8e218ea4e
Reviewed-by: hjk <hjk@qt.io>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/plugins/debugger/enginemanager.cpp b/src/plugins/debugger/enginemanager.cpp
index 68f800c5b1e..8bb62ede9db 100644
--- a/src/plugins/debugger/enginemanager.cpp
+++ b/src/plugins/debugger/enginemanager.cpp
@@ -421,6 +421,18 @@ void EngineManager::activateDebugMode()
     }
 }
 
+void EngineManager::deactivateDebugMode()
+{
+    if (ModeManager::currentModeId() == Constants::MODE_DEBUG && d->m_previousMode.isValid()) {
+        // If stopping the application also makes Qt Creator active (as the
+        // "previously active application"), doing the switch synchronously
+        // leads to funny effects with floating dock widgets
+        const Core::Id mode = d->m_previousMode;
+        QTimer::singleShot(0, d, [mode]() { ModeManager::activateMode(mode); });
+        d->m_previousMode = Id();
+    }
+}
+
 bool EngineManager::isLastOf(const QString &type)
 {
     int count = 0;