Creating a Keyboard Interface for a Standard Scroll Bar

Although a scroll bar control provides a built-in keyboard interface, a standard scroll bar does not. To implement a keyboard interface for a standard scroll bar, a window procedure must process the WM_KEYDOWN message and examine the virtual-key code specified by the wParam parameter. If the virtual-key code corresponds to an arrow key, the window procedure sends itself a WM_HSCROLL or WM_VSCROLL message with the low-order word of the wParam parameter set to the appropriate scroll bar notification message. For example, when the user presses the UP arrow key, the window procedure receives a WM_KEYDOWN message with wParam equal to VK_UP. In response, the window procedure sends itself a WM_VSCROLL message with the low-order word of wParam set to the SB_LINEUP notification message.

The following example shows how to include a keyboard interface for a standard scroll bar.

WORD wScrollNotify = 0xFFFF;

.

.

.

case WM_KEYDOWN:

switch (wParam) {

case VK_UP:

wScrollNotify = SB_LINEUP;

break;

case VK_PRIOR:

wScrollNotify = SB_PAGEUP;

break;

case VK_NEXT:

wScrollNotify = SB_PAGEDOWN;

break;

case VK_DOWN:

wScrollNotify = SB_LINEDOWN;

break;

case VK_HOME:

wScrollNotify = SB_TOP;

break;

case VK_END:

wScrollNotify = SB_BOTTOM;

break;

}

if (wScrollNotify != -1)

SendMessage(hwnd, WM_VSCROLL,

MAKELONG(wScrollNotify, 0), 0L);

break;

.

.

.

Software for developers

Delphi Components
.Net Components
Software for Android Developers

More information resources

MegaDetailed.Net
Unix Manual Pages
Delphi Examples

Databases for Amazon shops developers

Amazon Categories Database
Browse Nodes Database