A simple program on the scroll bar has some practical significance.

# Include <windows. h> <br/> int idfocus; <br/> wndproc oldscroll [3]; <br/> lresult callback wndproc (hwnd, uint, wparam, lparam ); <br/> lresult callback scrollproc (hwnd, uint, wparam, lparam); </P> <p> int winapi winmain (hinstance, hinstance hprevinstance, lpstr szcmdline, int icmdshow) <br/>{< br/> static tchar szappname [] = text ("control"); <br/> hwnd; <br/> MSG; <br/> wndclass; <br/> Wndclass. style = cs_hredraw | cs_vredraw; <br/> wndclass. lpfnwndproc = wndproc; <br/> wndclass. cbclsextra = 0; <br/> wndclass. cbwndextra = 0; <br/> wndclass. hinstance = hinstance; <br/> wndclass. hicon = loadicon (null, idi_application); <br/> wndclass. hcursor = loadcursor (null, idc_arrow); <br/> wndclass. hbrbackground = createsolidbrush (0); <br/> wndclass. lpszmenuname = NULL; <br/> wndclass. lpszclassname = szappname; </P> <P> If (! Registerclass (& wndclass) <br/>{< br/> MessageBox (null, text ("this programe requires Windows NT"), szappname, mb_iconerror ); <br/> return 0; <br/>}</P> <p> hwnd = createwindow (szappname, <br/> text ("control scroll "), <br/> ws_overlappedwindow, <br/> cw_usedefault, <br/> null, <br/> null, <br/> hinstance, <br/> null <br/>); <br/> showwind Ow (hwnd, icmdshow); <br/> updatewindow (hwnd); </P> <p> while (getmessage (& MSG, null, 0, 0 )) <br/>{< br/> translatemessage (& MSG); <br/> dispatchmessage (& MSG); <br/>}</P> <p> return MSG. wparam; <br/>}</P> <p> lresult callback wndproc (hwnd, uint message, wparam, lparam) <br/>{< br/> HDC; <br/> paintstruct pS; <br/> static rect; <br/> hinstance; <br/> static int I, cxclient, Cyclient, cychar, color [3]; <br/> static tchar * szcolorlabel [] = {text ("red"), text ("green "), text ("blue") }; <br/> static colorref RGB [3] = {RGB (0,255, 0), RGB (, 0), RGB (, 0, 255) }; <br/> static hbrush [3], hbrushstatic; <br/> static hwnd hwndscroll [3], hwndlabel [3], hwndvalue [3], hwndrect; <br/> tchar szbuffer [10]; </P> <p> switch (Message) <br/> {<br/> case wm_create: <br/> hinstance = (hinstance) getwind Owlong (hwnd, gwl_hinstance); <br/> // obtain the hinstance of the program window handle <br/> // getwindowlong (hwnd, INT) used to obtain information about Windows related to hwnd </P> <p> hwndrect = createwindow (text ("static"), null, ws_visible | ws_child | ss_whiterect, 0, 0, 0, 0, hwnd, (hmenu) 9, hinstance, null); <br/> // create a static style window of the ss_whiterect type, as background </P> <p> for (I = 0; I <3; I ++) <br/> {<br/> hwndscroll [I] = createwindow (text ("scrollbar"), null, ws_child | ws_visible | ws_tabstop | sbs_vert, HW Nd, (hmenu) I, hinstance, null); <br/> // create three windows of the scrollbar type </P> <p> setscrollrange (hwndscroll [I], sb_ctl, 0,255, false); <br/> // scrollbar range: 0 to 255 </P> <p> setscrollpos (hwndscroll [I], sb_ctl, 0, false); <br/> // set its initial position to 0 </P> <p> hwndlabel [I] = createwindow (text ("static "), szcolorlabel [I], ws_child | ws_visible | ss_center, hwnd, (hmenu) (I + 3), hinstance, null ); // ss_center indicates text center <br/> // create three subwindows of tag type as the recording color tag </P> <P> hwndvalue [I] = createwindow (text ("static"), text ("0"), ws_child | ws_visible | ss_center, 0, 0, 0, 0, hwnd, (hmenu) (I + 6), hinstance, null); <br/> // create three subwindows of label type, tag used to record the actual RGB values </P> <p> oldscroll [I] = (wndproc) setwindowlong (hwndscroll [I], gwl_wndproc, (long) scrollproc ); <br/> // Add the wndproc function for the three scrollbar windows, obtain the wndproc function in the previous scrollbar window </P> <p> hbrush [I] = createsolidbrush (RGB [I]); <br/> // create three basic color paint brushes </P> <p >}</P> <p> hbrus Hstatic = createsolidbrush (getsyscolor (color_btnhighlight); </P> <p> cychar = hiword (getdialogbaseunits (); </P> <p> return 0; </P> <p> case wm_size: <br/> cxclient = loword (lparam); <br/> cyclient = hiword (lparam ); <br/> setrect (& rect, cxclient/, cxclient, cyclient); </P> <p> movewindow (hwndrect, cxclient/2, cyclient, true ); </P> <p> for (I = 0; I <3; I ++) <br/> {<br/> movewindow (hwndscroll [I], (2 * I + 1) * cxclient/14,2 * Cychar, cxclient/14, cyClient-4 * cychar, true); <br/> movewindow (hwndlabel [I], (4 * I + 1) * cxclient/28, cychar/2, cxclient/7, cychar, true); <br/> movewindow (hwndvalue [I], (4 * I + 1) * cxclient/28, cyClient-3 * cychar/2, cxclient/7, cychar, true); <br/>}< br/> // specifies the scrollbar initialization position </P> <p> setfocus (hwnd ); <br/> // focus on the main window <br/> return 0; </P> <p> case wm_setfocus: <br/> setfocus (hwndscroll [idfocus]); <br/> return 0; </P> <p> case Wm_vscroll: // scrollbar Control <br/> I = getwindowlong (hwnd) lparam, gwl_id); <br/> switch (loword (wparam )) <br/>{< br/> case sb_pagedown: <br/> color [I] + = 15; </P> <p> case sb_linedown: <br/> color [I] = min (255, color [I] + 1); <br/> break; </P> <p> case sb_pageup: <br/> color [I]-= 15; </P> <p> case sb_lineup: <br/> color [I] = max (0, color [I]-1); <br/> break; </P> <p> case sb_top: <br/> color [I] = 0; <br/> break; </P> <p> Ca Se sb_bottom: <br/> color [I] = 255; <br/> break; </P> <p> case sb_thumbposition: <br/> case sb_thumbtrack: <br/> color [I] = hiword (wparam); <br/> break; </P> <p> default: <br/> break; </P> <p >}< br/> setscrollpos (hwndscroll [I], sb_ctl, color [I], true); <br/> wsprintf (szbuffer, text ("% I"), color [I]); <br/> setwindowtext (hwndvalue [I], szbuffer); </P> <p> deleteobject (hbrush) setclasslong (hwnd, gcl_hbrbackground, (long) Createsolidbrush (RGB (color [0], color [1], color [2]); </P> <p> invalidaterect (hwnd, & rect, true); </P> <p> return 0; </P> <p> case wm_ctlcolorscrollbar: <br/> I = getwindowlong (hwnd) (lparam ), gwl_id); <br/> return (lresult) hbrush [I]; </P> <p> case wm_ctlcolorstatic: <br/> I = getwindowlong (hwnd) lparam, gwl_id); </P> <p> if (I> = 3 & I <= 8) <br/>{< br/> settextcolor (HDC (wparam ), RGB [I % 3]); <br/> setbkcolor (HDC (wparam), Getsyscolor (color_btnhighlight); <br/> // subclass of the window, and set "Hook" for the existing Window Process </P> <p> return (lresult) hbrushstatic; </P> <p >}< br/> break; </P> <p> case wm_syscolorchange: <br/> deleteobject (hbrushstatic ); <br/> hbrushstatic = createsolidbrush (getsyscolor (color_btnhighlight); <br/> return 0; </P> <p> case wm_destroy: <br/> deleteobject (hbrush) <br/> setclasslong (hwnd, gcl_hbrbackground, (long) getstockobject (white_brush ); <Br/> for (I = 0; I <3; I ++) <br/> deleteobject (hbrush [I]); </P> <p> deleteobject (hbrushstatic); </P> <p> postquitmessage (0); <br/> return 0; </P> <p >}< br/> return defwindowproc (hwnd, message, wparam, lparam ); <br/>}</P> <p> lresult callback scrollproc (hwnd, uint message, wparam, lparam) <br/>{< br/> int id = getwindowlong (hwnd, gwl_id); <br/> switch (Message) <br/>{< br/> case wm_keydown: <br /> If (wparam = vk_tab) <br/> setfocus (getdlgitem (getparent (hwnd), (ID + (getkeystate (vk_shift) <0? 2:1) % 3); <br/> break; </P> <p> case wm_setfocus: <br/> idfocus = ID; <br/> break; <br/>}</P> <p> return callwindowproc (oldscroll [ID], hwnd, message, wparam, lparam ); <br/> // use the old window callback function for other messages <br/>}< br/>