[PATCH] GuiManager TickObjects performance fix

[Jorma Rebane]

As reported in the Performance ticket: #1995

GuiManager::TickObjects made a full copy of PageStackType m_PageStack in every tick:

	PageStackType pageStack = m_PageStack;

PageStackType itself is an std::vector<SGUIPage> (yes, a by-value vector):

	typedef std::vector<SGUIPage> PageStackType;

SGUIPage is defined as:

	struct SGUIPage
	{
		CStrW name;
		boost::unordered_set<VfsPath> inputs;
		JSContext* cx;
		CScriptValRooted initData;
		shared_ptr<CGUI> gui;
	};

Due to these non-trivial types like unordered_set and CStrW, making a full copy of the pagestack vector resulted in some pretty serious memory allocation overhead. The data itself is in the #1995 performance ticket.

This patch provides a simple fix by using a const reference instead

[historic_bruno]

Needs a solution that allows tick handlers to modify the page stack (was introduced in r7649)

[Jorma Rebane]

Change the tickobjects loop to use indices instead of iterators.

[historic_bruno]

The solution depends on the intended behavior of changing pages: should it wait until after the tick handlers are called for all pages before the stack is modified (as the current implementation does) or take affect immediately in the middle of a handler, as it would with the patch? Before r7649 it was broken either way, but I don't know whether the fix is deliberately or accidentally making the logic choice. I guess it will take testing and deeper investigation into it, which is annoying :(

[Jorma Rebane]

Replying to historic_bruno: The 'immediate' switch is intended behaviour. No reason to process gui pages that have been actually thrown away. In some aspect this feels like a more correct solution.

[historic_bruno]

Closing these tickets as no further active development is expected. See Philip's megapatch-split git branch for an attempt at splitting megapatch into it's separate parts: ​http://git.wildfiregames.com/gitweb/?p=0ad.git;a=shortlog;h=refs/heads/projects/philip/megapatch-split