Updated the reverted fix for critical bug EXT-1655 ([BSI] Always flying after pressing "Stand" to stand up from an object), also integrated the fix for EXT-6786 ('Stand' button is corrupted if movement control floater is opened). Added some clarifying comments.

Reviewed by Tofu Linden at https://codereview.productengine.com/secondlife/r/253/.

--HG--
branch : product-engine

indra/newview/llagent.cpp

@@ -2296,6 +2296,13 @@ void LLAgent::stopAutoPilot(BOOL user_cancel)
 		{
 			resetAxes(mAutoPilotTargetFacing);
 		}
+		// Restore previous flying state before invoking mAutoPilotFinishedCallback to allow
+		// callback function to change the flying state (like in near_sit_down_point()).
+		// If the user cancelled, don't change the fly state
+		if (!user_cancel)
+		{
+			setFlying(mAutoPilotFlyOnStop);
+		}
 		//NB: auto pilot can terminate for a reason other than reaching the destination
 		if (mAutoPilotFinishedCallback)
 		{
@@ -2303,11 +2310,6 @@ void LLAgent::stopAutoPilot(BOOL user_cancel)
 		}
 		mLeaderID = LLUUID::null;
 
-		// If the user cancelled, don't change the fly state
-		if (!user_cancel)
-		{
-			setFlying(mAutoPilotFlyOnStop);
-		}
 		setControlFlags(AGENT_CONTROL_STOP);
 
 		if (user_cancel && !mAutoPilotBehaviorName.empty())

indra/newview/llmoveview.cpp

@@ -199,7 +199,12 @@ void LLFloaterMove::setFlyingMode(BOOL fly)
 	if (instance)
 	{
 		instance->setFlyingModeImpl(fly);
-		instance->showModeButtons(!fly);
+		LLVOAvatarSelf* avatar_object = gAgent.getAvatarObject();
+		BOOL is_sitting = avatar_object
+			&& (avatar_object->getRegion() != NULL)
+			&& (!avatar_object->isDead())
+			&& avatar_object->isSitting();
+		instance->showModeButtons(!fly && !is_sitting);
 	}
 	if (fly)
 	{
@@ -695,6 +700,7 @@ void LLPanelStandStopFlying::onStandButtonClick()
 	gAgent.setControlFlags(AGENT_CONTROL_STAND_UP);
 
 	setFocus(FALSE); // EXT-482
+	mStandButton->setVisible(FALSE); // force visibility changing to avoid seeing Stand & Move buttons at once.
 }
 
 void LLPanelStandStopFlying::onStopFlyingButtonClick()

indra/newview/llviewermessage.cpp

@@ -4169,6 +4169,9 @@ void process_avatar_sit_response(LLMessageSystem *mesgsys, void **user_data)
 	}
 	
 	gAgent.setForceMouselook(force_mouselook);
+	// Forcing turning off flying here to prevent flying after pressing "Stand"
+	// to stand up from an object. See EXT-1655.
+	gAgent.setFlying(FALSE);
 
 	LLViewerObject* object = gObjectList.findObject(sitObjectID);
 	if (object)

indra/newview/llvoavatar.cpp

@@ -5653,6 +5653,8 @@ void LLVOAvatar::sitOnObject(LLViewerObject *sit_object)
 	mDrawable->mXform.setRotation(mDrawable->getWorldRotation() * inv_obj_rot);
 
 	gPipeline.markMoved(mDrawable, TRUE);
+	// Notice that removing sitDown() from here causes avatars sitting on
+	// objects to be not rendered for new arrivals. See EXT-6835 and EXT-1655.
 	sitDown(TRUE);
 	mRoot.getXform()->setParent(&sit_object->mDrawable->mXform); // LLVOAvatar::sitOnObject
 	mRoot.setPosition(getPosition());