Mouse-tracking speedIn the past, users have had to use separate applications to set the extended fea-tures of the mouse. In Windows 3.1, separate applications are no longer necessary.
Instead, users can now view and set the extended features using Control Panel,
and the mouse driver's custom mouse-settings dialog box.
The following sections explain how to create an custom mouse-settings dialog box for a mouse driver.
The custom mouse-settings dialog box serves as a replacement for Control Panel's standard mouse dialog box. When a mouse driver has a custom mouse-settings dialog box, Control Panel displays it instead of the standard dialog box when the user chooses the mouse icon in Control Panel.
To display the custom dialog box, Control Panel checks for the CplApplet function in the mouse driver. If the function is present, Control Panel calls CplApplet with the NEWINQUIRE function value. If this call fails, Control Panel calls the CplApplet function with the INQUIRE function value. This gives the driver two chances to display its custom dialog box. If CplApplet does not contain the NEWINQUIRE or INQUIRE values, Control Panel displays the standard dialog box.
Because Windows loads the mouse driver before USER.EXE, the driver must not contain implicit links to USER functions such as DialogBox. This means that if the mouse driver calls the DialogBox function, it must use the GetProcAddress function to retrieve the address of the function. The mouse driver cannot rely on Windows to automatically create the dynamic link when Windows loads it.
One recommendation is to place all code required to display the custom dialog box in a separate dynamic-link library. In this case, the CplApplet function in the mouse driver loads the library and calls the function in the library that displays the dialog box. One benefit of this approach is that the dynamic-link library can also be used with Windows 3.0.
Mouse vendors will be able to create their own pointing-device icon and corresponding text title for display in the Control Panel window. This will allow the mouse driver to display a graphic more appropriate to the pointing device than the default icon.
When Control Panel runs, it calls the CplApplet function in the mouse driver as follows:
#define INQUIRE 3
#define NEWINQUIRE 8
if (CplApplet(hwndControlPanel, NEWINQUIRE, NULL, &newcplinfo)!=TRUE)
if (CplApplet(hwndControlPanel, INQUIRE, NULL, &cplinfo)!=TRUE)
/* Display standard dialog box */
Control Panel first calls CplApplet with a NEWINQUIRE function value, giving a pointer to a NEWCPLINFO structure. This call allows the driver to specify the help file or icon to use. In this case, the icon does not have to reside as a resource in the driver as it does with the INQUIRE function value. This call fails if the size member within the NEWCPLINFO structure has an incorrect value.
If the CplApplet function with the NEWINQUIRE value fails, Control Panel calls CplApplet with an INQUIRE function value, giving a pointer to a CPLINFO structure that has the following form:
typedef struct tag CPLINFO {
int idIcon;
int idName;
int idInfo; // not used
LONG lData; // not used
} CPLINFO;
The driver fills in the CPLINFO structure with the resource identifiers of its icon and description, and returns to Control Panel. Control Panel loads the resource data specified by the icon and description identifiers, and uses these in the Control Panel window instead of the icon. Note that the idInfo and lData members are not used.
The custom dialog box lets users set extended mouse features, but it also must let users view and set the following standard mouse features:
Mouse-tracking speed
Double-click speed
Button swapping
During initialization, the dialog procedure for the custom dialog box uses the SystemParametersInfo function to retrieve the current values for these settings. If the user changes the settings, the dialog procedure uses the SystemParametersInfo function to change the settings for the current Windows session and update the corresponding settings in the WIN.INI file.
Note:
The SystemParametersInfo function is not available with Windows 3.0. If the custom dialog box is also intended for Windows 3.0, the mouse driver must use functions such as ControlPanelInfo, SetDoubleClickSpeed, and SwapMouseButton to change the standard mouse settings. Since these func-tions do not modify the mouse setting in the WIN.INI file, the mouse driver must use the WriteProfileString function to preserve these changes for subsequent Windows sessions.
Mouse-Tracking Speed
The mouse-tracking speed defines how quickly the cursor moves relative to the speed of the mouse. Windows uses three values to control mouse tracking: MouseSpeed, MouseThreshold1, and MouseThreshold2. These values, described in detail in the WININI.WRI file, define how and when to accelerate the cursor motion. The cursor speed can remain constant, or it can double or quadruple depending on the current mouse thresholds and speed.
Control Panel uses a 7-position scroll bar to set the mouse-tracking value. The 7 settings are as follows:
| Scroll position | MouseSpeed | MouseThreshold1 | MouseThreshold2 |
| 0 | 0 | 0 | 0 |
| 1 | 1 | 10 | 0 |
| 2 | 1 | 7 | 0 |
| 3 | 1 | 4 | 0 |
| 4 | 2 | 4 | 12 |
| 5 | 2 | 4 | 9 |
| 6 | 2 | 4 | 6 |
Control Panel calculates these settings using to the following algorithm:
switch (scrollPos) {
case 0:
MouseSpeed = 0;
MouseThreshold1 = 0;
MouseThreshold2 = 0;
break;
case 1: case 2: case 3:
MouseSpeed = 1;
MouseThreshold1 = 13 - 3 * scrollPos;
MouseThreshold2 = 0;
break;
case 4: case 5: case 6:
MouseSpeed = 2;
MouseThreshold1 = 4;
MouseThreshold2 = 24 - 3 * scrollPos;
break;
}
When Control Panel displays the mouse dialog box, it calculates the initial scroll bar position from the system values as follows:
switch (MouseSpeed) {
case 0:
scrollPos = 0;
break;
case 1:
scrollPos = (13 - MouseThreshold1) / 3;
break;
case 2:
scrollPos = (24 - MouseThreshold2) / 3;
break;
}
If the user changes the mouse-tracking settings directly in the WIN.INI file instead of through the dialog box, Control Panel checks for out-of-bounds values and adjusts the values accordingly.
Double-Click Speed
The double-click time is the maximum number of milliseconds that may occur between the first and second clicks of a double-click of the mouse button. Control Panel uses a scroll bar to set double-click speed. The range is from 100 to 900 milliseconds, with line-up and line-down increments 1/50 of this range, and page-up and page-down increments 1/5 of this range. Windows records the double- click speed using the DoubleClickSpeed setting in the [Windows] section of the WIN.INI file.
A mouse driver can use the GetDoubleClickTime function to determine the current double-click speed, and use the SystemParametersInfo function and SPI_SETDOUBLECLICKSPEED option to change double-click time.
Swapping Left and Right Mouse Buttons
Button swapping lets Windows generate right-button mouse messages when the left button is pressed, and left-button messages when the right button is pressed. Control Panel uses a check box to switch mouse buttons. Windows records the state of the buttons using the SwapMouseButtons setting in the [Windows] section of the WIN.INI file.
A mouse driver can use the GetSystemMetrics function with the SM_SWAPBUTTON option to determine whether the mouse buttons are currently reversed, and use the SystemParametersInfo function and the SPI_SETMOUSEBUTTONSWAP option to swap the mouse buttons.
Control Panel displays Help information when the user presses the F1 key, or chooses the Help button while viewing the Mouse dialog box. If the user presses F1 or chooses Help while the driver's dialog box is displayed, the mouse driver is responsible for displaying its own online Help.
To display Help, the dialog procedure for the mouse driver must register a private message called “ShellHelp” during initialization. When the dialog procedure receives this message, it can call the WinHelp function specifying the appropriate Help file.
The following sample code illustrates how to incorporate Help support in the dialog procedure:
LONG FAR PASCAL AddOnDlgProc(HWND hDlg, WORD msg, WORD wParam,
LONG lParam)
{
static WORD wHelpMessage;
switch (msg) {
case WM_INITDIALOG:
.
.
.
wHelpMessage = RegisterWindowMessage("ShellHelp");
break;
case WM_COMMAND:
switch (wParam) {
case IDD_HELP: // from "Help..." button
goto DoHelp;
.
.
.
case IDOK:
case IDCANCEL:
.
.
.
WinHelp(hDlg, szHelpFile, HELP_QUIT, 0L);
EndDialog(hDlg, wParam);
break;
.
.
.
}
.
.
.
default:
if (msg == wHelpMessage) {
DoHelp:
WinHelp(hDlg, szHelpFile, HELP_CONTEXT, context_value);
return TRUE;
} else
return FALSE;
}
return FALSE;
}
The dialog procedure calls the WinHelp function with the HELP_QUIT option just before calling the EndDialog function. This is required to ensure that Help is shut down before the dialog box closes.