
A progress bar is a window that an application can use to indicate the progress of a lengthy operation. It consists of a rectangle that is gradually filled with the system highlight color as an operation progresses. The following illustration shows a progress bar positioned along the bottom of a window.
Progress Bar Control Updates in Internet Explorer
Progress Bar Control Reference
You create a progress bar by using the CreateWindowEx function, specifying the PROGRESS_CLASS window class. This window class is registered when the common control dynamic-link library (DLL) is loaded. To ensure that this DLL is loaded, use the InitCommonControls function first.
A progress bar's range represents the entire duration of the operation, and the current position represents the progress that the application has made toward completing the operation. The window procedure uses the range and the current position to determine the percentage of the progress bar to fill with the highlight color as well as to determine the text, if any, to display within the progress bar. Because the range and current position values are expressed as unsigned integers, the highest possible range or current position value is 65,535.
The minimum value in the range can be from 0 to 65,535. Likewise, the maximum value can be from 0 to 65,535. If you do not set the range values, the system sets the minimum value to 0 and the maximum value to 100. You can adjust the range to convenient integers by using the PBM_SETRANGE message.
A progress bar provides several messages that you can use to set the current position. The PBM_SETPOS message sets the position to a given value. The PBM_DELTAPOS message advances the position by adding a specified value to the current position.
The PBM_SETSTEP message allows you to specify a step increment for a progress bar. Subsequently, whenever you send the PBM_STEPIT message to the progress bar, the current position advances by the specified increment. By default, the step increment is set to 10.
This section describes the messages handled by the window procedure for the PROGRESS_CLASS class.
| Message | Processing performed |
| WM_CREATE | Allocates and initializes an initial structure. |
| WM_DESTROY | Frees all resources associated with the progress bar. |
| WM_ERASEBKGND | Draws the background and borders of the progress bar. |
| WM_GETFONT | Returns the handle to the font that the progress bar is currently using to draw text. |
| WM_PAINT | Draws the progress bar. If the wParam parameter is non-NULL, the control assumes that the value is an HDC and paints using that device context. |
| WM_SETFONT | Saves the handle to the new font and returns the handle to the previous font. |
The following example shows how to use a progress bar to indicate the progress of a lengthy file-parsing operation. The example creates a progress bar and positions it along the bottom of the parent window's client area. The height of the progress bar is based on the height of the arrow bitmap used in a scroll bar. The range is based on the size of the file divided by 2048, which is the size of each "chunk" of data read from the file. The example also sets an increment and advances the current position of the progress bar by the increment after parsing each chunk.
// ParseALargeFile - parses a large file and uses a progress bar to
// indicate the progress of the parsing operation.
// Returns TRUE if successful, or FALSE otherwise.
// hwndParent - parent window of the progress bar.
// lpszFileName - name of the file to parse.
//
// Global variable
// g_hinst - instance handle
extern HINSTANCE g_hinst;
BOOL ParseALargeFile(HWND hwndParent, LPSTR lpszFileName)
{
RECT rcClient; // client area of parent window
int cyVScroll; // height of scroll bar arrow
HWND hwndPB; // handle of progress bar
HANDLE hFile; // handle of file
DWORD cb; // size of file and count of bytes read
LPCH pch; // address of data read from file
LPCH pchTmp; // temporary pointer
// Ensure that the common control DLL is loaded and create a
// progress bar along the bottom of the client area of the
// parent window. Base the height of the progress bar on
// the height of a scroll bar arrow.
InitCommonControls();
GetClientRect(hwndParent, &rcClient);
cyVScroll = GetSystemMetrics(SM_CYVSCROLL);
hwndPB = CreateWindowEx(0, PROGRESS_CLASS, (LPSTR) NULL,
WS_CHILD | WS_VISIBLE, rcClient.left,
rcClient.bottom - cyVScroll,
rcClient.right, cyVScroll,
hwndParent, (HMENU) 0, g_hinst, NULL);
// Open the file for reading, and retrieve the size of the file.
hFile = CreateFile(lpszFileName, GENERIC_READ, FILE_SHARE_READ,
(LPSECURITY_ATTRIBUTES) NULL, OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL, (HANDLE) NULL);
if (hFile == (HANDLE) INVALID_HANDLE_VALUE)
return FALSE;
cb = GetFileSize(hFile, (LPDWORD) NULL);
// Set the range and increment of the progress bar.
SendMessage(hwndPB, PBM_SETRANGE, 0, MAKELPARAM(0, cb / 2048));
SendMessage(hwndPB, PBM_SETSTEP, (WPARAM) 1, 0);
// Parse the file.
pch = (LPCH) LocalAlloc(LPTR, sizeof(char) * 2048);
pchTmp = pch;
do {
ReadFile(hFile, pchTmp, sizeof(char) * 2048, &cb,
(LPOVERLAPPED) NULL);
.
. // Include here any code that parses the file.
.
// Advance the current position of the progress bar
// by the increment.
SendMessage(hwndPB, PBM_STEPIT, 0, 0);
} while (cb);
CloseHandle((HANDLE) hFile);
DestroyWindow(hwndPB);
return TRUE;
}
Progress bar controls in Microsoft® Internet Explorer support the following new features.
This section contains information about the following programming elements used with progress bar controls.
| Messages |
| PBM_DELTAPOS |
| PBM_GETPOS |
| PBM_GETRANGE |
| PBM_SETBARCOLOR |
| PBM_SETBKCOLOR |
| PBM_SETPOS |
| PBM_SETRANGE |
| PBM_SETRANGE32 |
| PBM_SETSTEP |
| PBM_STEPIT |
| Structures |
| PBRANGE |
Progress bar controls now support control styles. You can set progress bar styles in the same way as other common controls (CreateWindowEx, GetWindowLong, SetWindowLong). The following are the supported styles:
| PBS_SMOOTH | Version 4.70. The progress bar displays progress status in a smooth scrolling bar instead of the default segmented bar. |
| PBS_VERTICAL | Version 4.70. The progress bar displays progress status vertically, from bottom to top. |
This section includes information about the messages used with progress bar controls.
PBM_DELTAPOS
wParam = (WPARAM) nIncrement
lParam = 0;
Advances the current position of a progress bar by a specified increment and redraws the bar to reflect the new position.
PBM_GETPOS
wParam = 0;
lParam = 0;
Retrieves the current position of the progress bar.
Version 4.70
PBM_GETRANGE
wParam = (WPARAM)(BOOL) fWhichLimit;
lParam = (LPARAM)(PPBRANGE) ppBRange;
Retrieves information about the current high and low limits of a given progress bar control.
| TRUE | Return the low limit. |
| FALSE | Return the high limit. |
Version 4.70
PBM_SETBARCOLOR
wParam = 0;
lParam = (LPARAM)(COLORREF)clrBar;
Sets the color of the progress indicator bar in the progress bar control.
Version 4.71
PBM_SETBKCOLOR
wParam = 0;
lParam = (LPARAM)(COLORREF)clrBk;
Sets the background color in the progress bar.
Version 4.71
PBM_SETPOS
wParam = (WPARAM) nNewPos;
lParam = 0;
Sets the current position for a progress bar and redraws the bar to reflect the new position.
PBM_SETRANGE
wParam = 0;
lParam = MAKELPARAM(nMinRange, nMaxRange);
Sets the minimum and maximum values for a progress bar and redraws the bar to reflect the new range.
PBM_SETRANGE32
wParam = (WPARAM)(int) iLowLim;
lParam = (LPARAM)(int) iHighLim;
Sets the range of a progress bar control to a 32-bit value.
To retrieve the entire high and low 32-bit values, use the PBM_GETRANGE message.
Version 4.70
PBM_SETSTEP
wParam = (WPARAM) nStepInc;
lParam = 0;
Specifies the step increment for a progress bar. The step increment is the amount by which the progress bar increases its current position whenever it receives a PBM_STEPIT message. By default, the step increment is set to 10.
PBM_STEPIT
wParam = 0;
lParam = 0;
Advances the current position for a progress bar by the step increment and redraws the bar to reflect the new position. An application sets the step increment by sending the PBM_SETSTEP message.
When the position exceeds the maximum range value, this message resets the current position so that the progress indicator starts over again from the beginning.
This section contains information about the structure used with progress bar controls.
typedef struct {
int iLow;
int iHigh;
} PBRANGE, *PPBRANGE;
Contains information about the high and low limits of a progress bar control. This structure is used with the PBM_GETRANGE message.
Version 4.70
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