A UI class for long operation feedback

CLongOperation is a class designed to give visual feedback for
long-lasting operations. It has support for:

• Displaying a wait cursor
• Showing a text in the status bar
• Displaying a progress bar in a dynamically created status
  bar pane

In the simplest case, this class can be used as a replacement
for MFC’s CWaitCursor:

	CLongOperation wait;
	// some hard work going here...

To display some textual progress information in the status
bar:

	CLongOperation wait;
	wait.SetText("Pass 1");
	// ...
	wait.SetText("Pass 2");
	// ...

To display a progress bar in the status bar:

	CLongOperation wait;
	for (int i = 0; i < count; i++)
	{
		wait.Step((100*i)/cnt);
		// ...
	}
	wait.Stop();

/////////////////////////////////////////////////////////////////
// LongOperation.h
// (c) 1997, Klaus G|tter
class CLongOperation : public CObject
{
public:
	// IDS_PLEASE_WAIT is a string resource ID for the default text,
	// e.g. "Please wait..."
	CLongOperation(UINT nIDText = IDS_PLEASE_WAIT, bool bStart = true);
	CLongOperation(LPCTSTR lpszText, bool bStart = true);
	~CLongOperation();

	void Start();
	void Stop();
	void Step(int nPercentage = -1);
	void SetText(LPCTSTR lpszText);

protected:
	CString m_strText;
	bool m_bStarted;
	HWND m_hwndProgress;
	void CreateProgressControl();
};


/////////////////////////////////////////////////////////////////
// LongOperation.cpp
// (c) 1997, Klaus G|tter

#include "stdafx.h"
#include <afxpriv.h> // defines WM_SETMESSAGESTRING
#include "LongOperation.h"

#ifdef _DEBUG
#undef THIS_FILE
#define new DEBUG_NEW
static char BASED_CODE THIS_FILE[] = __FILE__;
#endif

CLongOperation::CLongOperation(UINT nIDText, bool bStart)
:	m_bStarted(false)
,	m_hwndProgress(NULL)
{
	VERIFY(m_strText.LoadString(nIDText));
	if (bStart)
		Start();
}

CLongOperation::CLongOperation(LPCTSTR lpszText, bool bStart)
:	m_strText(lpszText)
,	m_bStarted(false)
,	m_hwndProgress(NULL)
{
	if (bStart)
		Start();
}

CLongOperation::~CLongOperation()
{
	if (m_bStarted)
		Stop();
}

void CLongOperation::Start()
{
	if (m_bStarted)
		Stop();

	// display text in the status bar
	CWnd* pMainWnd = ::AfxGetMainWnd();
	if (pMainWnd)
		pMainWnd->SendMessage(WM_SETMESSAGESTRING, 0, (LPARAM)(LPCTSTR)m_strText);

	// switch on wait cursor
	::AfxGetApp()->BeginWaitCursor();

	m_bStarted = true;
}

void CLongOperation::Stop()
{
	if (!m_bStarted)
		return;

	if (m_hwndProgress)
	{
		// clean up and destroy progress bar
		CStatusBar* pStatusBar = DYNAMIC_DOWNCAST(CStatusBar, CWnd::FromHandle(::GetParent(m_hwndProgress)));
		ASSERT_VALID(pStatusBar);

		::DestroyWindow(m_hwndProgress);
		m_hwndProgress = NULL;

		// remove progress bar pane
		int anPart[32];
		int nParts = pStatusBar->GetStatusBarCtrl().GetParts(31, anPart);
		nParts--;
		pStatusBar->GetStatusBarCtrl().SetParts(nParts, anPart+1);
	}

	// switch back to standard text in the status bar
	CWnd* pMainWnd = ::AfxGetMainWnd();
	if (pMainWnd)
		pMainWnd->SendMessage(WM_SETMESSAGESTRING, AFX_IDS_IDLEMESSAGE, 0);

	// switch off wait cursor
	::AfxGetApp()->EndWaitCursor();

	m_bStarted = false;
}

void CLongOperation::Step(int nPercentage)
{
	if (!m_bStarted)
		Start();

	::AfxGetApp()->RestoreWaitCursor();

	if (nPercentage >= 0)
	{
		ASSERT(nPercentage <= 100);
		// create or update a progress control in the status bar
		if (m_hwndProgress == NULL)
			CreateProgressControl();

		if (m_hwndProgress)
			::SendMessage(m_hwndProgress, PBM_SETPOS, (WPARAM)nPercentage, 0);
	}
}

void CLongOperation::SetText(LPCTSTR lpszText)
{
	m_strText = lpszText;
	CWnd* pMainWnd = ::AfxGetMainWnd();
	if (pMainWnd)
		pMainWnd->SendMessage(WM_SETMESSAGESTRING, 0, (LPARAM)(LPCTSTR)m_strText);
}

void CLongOperation::CreateProgressControl()
{
	ASSERT(m_hwndProgress == NULL);

	// find status bar
	CWnd* pMainWnd = ::AfxGetMainWnd();
	if (pMainWnd == NULL)
		return;
	CStatusBar* pStatusBar = DYNAMIC_DOWNCAST(CStatusBar,
		pMainWnd->GetDescendantWindow(AFX_IDW_STATUS_BAR, TRUE));
	if (pStatusBar == NULL || pStatusBar->m_hWnd == NULL)
		return;

	CRect rc; // this will be the location for the progress bar pane
	pStatusBar->GetItemRect(0, rc);
	if (!m_strText.IsEmpty())
	{
		// adjust so that the text in the leftmost pane will not be covered
		CClientDC dc(pStatusBar);
		dc.SelectObject(pStatusBar->GetFont());
		CSize sz = dc.GetTextExtent(m_strText);
		TEXTMETRIC tm;
		dc.GetTextMetrics(&tm);
		rc.left += sz.cx + 2*tm.tmAveCharWidth;
	}
	int cx = rc.Width();
	if (cx < 20)
	{
		// no sense in displaying such a small progress bar
		TRACE0("ProgressDisplay would be too smalln");
		return;
	}
	else if (cx > 200)
	{
		// arbitrarily limiting progress bar width to 200 pixel
		cx = 200;
		rc.left = rc.right - cx;
	}

	// add a pane between the text and the currently leftmost pane
	int anPart[32];
	int nParts = pStatusBar->GetStatusBarCtrl().GetParts(31, anPart+1);
	anPart[0] = rc.left;
	nParts++;
	pStatusBar->GetStatusBarCtrl().SetParts(nParts, anPart);
	pStatusBar->GetStatusBarCtrl().GetRect(1, rc);

	// create progress bar control
	m_hwndProgress = ::CreateWindow(PROGRESS_CLASS, "",
		WS_CHILD | WS_VISIBLE, rc.left, rc.top, rc.Width(), rc.Height(),
		pStatusBar->m_hWnd, (HMENU)1, AfxGetInstanceHandle(), NULL);

		pStatusBar->UpdateWindow();
}