prevextent.cpp

在vc环境下

#include "StdAfx.h"
#include ".\prevextent.h"

/////////////////////////////////////////////////////////////////////////////
// CPrevExtent

STDMETHODIMP CPrevExtent::OnClick()
{

	IActiveViewPtr cpActiveView;
	GetFocusMapActiveView(&cpActiveView);
	if (cpActiveView==0) return S_OK;

	IExtentStackPtr cpExtentStack;
	HRESULT hr = cpActiveView->get_ExtentStack(&cpExtentStack);
	if (FAILED(hr)) return hr;
	if (cpExtentStack ==0) return S_OK;

	VARIANT_BOOL bCanUndo;
	hr = cpExtentStack->CanUndo(&bCanUndo);
	if (FAILED(hr)) return hr;

	if (bCanUndo == VARIANT_TRUE)
	{
		hr = cpExtentStack->Undo();
		if (FAILED(hr)) return hr;
	}

	return S_OK;
}

STDMETHODIMP CPrevExtent::get_Enabled(VARIANT_BOOL * Enabled)
{
	// Call base class,enabled - this checks for a focus map
	HRESULT hr = CMapCommandBase::get_Enabled(Enabled);

	if (SUCCEEDED(hr) && (*Enabled))
	{
		IActiveViewPtr cpActiveView;
		GetFocusMapActiveView(&cpActiveView);
		IExtentStackPtr cpExtentStack;
		HRESULT hr = cpActiveView->get_ExtentStack(&cpExtentStack);
		if (FAILED(hr)) return hr;

		hr = cpExtentStack->CanUndo(Enabled);
	}

	return hr;
}