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                         Using Scroll-Bar Controls
 
This section explains how to create and use scroll bars in an application.
Scroll bars are most often used in frame windows to let the user scroll data
in the corresponding client window.
 
Creating Scroll Bars
 
You can add scroll bars to a frame window by using the FCF_HORZSCROLL flag,
the FCF_VERTSCROLL flag, or both flags when creating the frame window with
the WinCreateStdWindow function. This adds a horizontal and/or a vertical
scroll bar to the frame window. Because the frame window owns the scroll
bars, it passes notification messages from these controls to the client
window.
 
The following code fragment adds scroll bars to a frame window:
 
/* Set flags for a main window with scroll bars. */
 
ULONG ulFrameControlFlags =
    FCF_STANDARD | FCF_HORZSCROLL | FCF_VERTSCROLL;
 
/* Create the window. */
 
hwndFrame = WinCreateStdWindow(HWND_DESKTOP, WS_VISIBLE,
    &ulFrameControlFlags, szClientClass, szFrameTitle,
    0L, NULL, 0L, &hwndClient);
 
Scroll bars created this way have the FID_HORZSCROLL or FID_VERTSCROLL
window identifier. The frame window determines the size and position of the
scroll bars. A frame window uses the standard size specified by the system
values SV_CXVSCROLL and SV_CYHSCROLL. The position is always the right and
bottom edges of the frame window.
 
Another way to create scroll bars is by using the WinCreateWindow function.
This is most common for stand-alone scroll bars. Creating scroll bars in
this way lets you set the size and position of the scroll bars. You can also
specify the window to receive notification messages.
 
The following code fragment creates a stand-alone scroll bar:
 
HWND hwndScroll;             /* scroll-bar handle              */
 
hwndScroll = WinCreateWindow(
    hwndClient               /* scroll-bar parent              */
    WC_SCROLLBAR,            /* preregistered scroll-bar class */
    NULL,                    /* no window title                */
    SBS_VERT | WS_VISIBLE,   /* vertical style and visible     */
    10, 10,                  /* position                       */
    20, 100,                 /* size                           */
    hwndClient,              /* owner                          */
    HWND_TOP,                /* Z order position               */
    1,                       /* scroll-bar ID                  */
    NULL,                    /* no class-specific data         */
    NULL);                   /* no presentation parameters     */
 
Retrieving a Scroll-Bar Handle
 
If you create a scroll bar as a child window of the frame window by using
the WinCreateStdWindow function, you need a way to retrieve the scroll-bar
handle. One way is to use the WinWindowFromID function, the frame-window
handle, and a predefined identifier (such as FID_HORZSCROLL or
FID_VERTSCROLL) to retrieve the scroll-bar handle.
 
hwndHorzScroll = WinWindowFromID(hwndFrame, FID_HORZSCROLL);
hwndVertScroll = WinWindowFromID(hwndFrame, FID_VERTSCROLL);
 
If the standard frame window includes a client window, you can use that
handle to access the scroll bars. The idea is to get the frame-window handle
first, then the scroll-bar handle.
 
/* Get a handle to the horizontal scroll bar. */
 
hwndScroll = WinWindowFromID(
    WinQueryWindow(hwndClient, QW_PARENT, FALSE),
    FID_HORZSCROLL);
 
Using the Scroll-Bar Range and Position
 
You can initialize a scroll bar's current value and range to nondefault
values by sending the SBCDATA structure with class-specific data for a call
to the WinCreateWindow function:
 
SBCDATA sbcd;
 
/* Set up scroll-bar control data. */
 
sbcd.posFirst = 200;
sbcd.posLast = 400;
sbcd.posThumb = 300;
 
/* Create the scroll bar. */
 
hwndScroll = WinCreateWindow(hwndClient, WC_SCROLLBAR, NULL,
    SBS_VERT | WS_VISIBLE,
    10, 10, 20, 100,
    hwndClient, HWND_TOP, 1,
    &sbcd,       /* class-specific data */
    NULL);
 
You can adjust a scroll-bar value and range by sending it an
SBM_SETSCROLLBAR message:
 
/* Set the scroll-bar value and range. */
 
WinSendMsg(hwndScroll, SBM_SETSCROLLBAR,
    MPFROM2SHORT(300, 0),
    MPFROM2SHORT(200, 400));
 
You can read a scroll-bar value by sending it an SBM_QUERYPOS message:
 
USHORT usSliderPos;
 
/* Read the scroll-bar value. */
 
usSliderPos = (USHORT) WinSendMsg(hwndScroll,
    SBM_QUERYPOS, NULL, NULL);
 
Similarly, you can set a scroll-bar value by sending an SBM_SETPOS message:
 
/* Set the vertical scroll-bar value. */
 
WinSendMsg(hwndScroll, SBM_QUERYPOS, MPFROM2SHORT(300, 0), NULL);
 
You can read a scroll-bar range by sending it an SBM_QUERYRANGE message:
 
MRESULT mr;
USHORT iMinimum, iMaximum;
 
/* Read the vertical scroll-bar range. */
 
mr = WinSendMsg(hwndScroll, SBM_QUERYRANGE, NULL, NULL);
 
iMinimum = SHORT1FROMMR(mr);  /* minimum in the low word  */
iMaximum = SHORT2FROMMR(mr);  /* maximum in the high word */
 
 
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