第四章 输出文字part2

 4.4建立更好的滚动:

Win32 API介绍的两个滚动条函数称作SetScrollInfo和GetScrollInfo。这些函数可以完成以前函数的全部功能，并增加了两个新特性。

SetScrollInfo (hwnd, iBar, &si, bRedraw) ;
GetScrollInfo (hwnd, iBar, &si) ;

Bar参数是SB_VERT或SB_HORZ,它还可以是用于滚动条控制的SB_CTL。SB是通知码的前缀。SetScrollInfo的最后一个参数可以是TRUE或FALSE，指出了是否要Windows重新绘制计算了新信息后的滚动条。

两个函数的第三个参数是SCROLLINFO结构，定义为：
typedef struct tagSCROLLINFO
{
UINT cbSize ;// set to sizeof (SCROLLINFO)
UINT fMask ; // values to set or get
int nMin ; // minimum range value
int nMax ; // maximum range value
UINT nPage ; // page size
int nPos ; // current position
int nTrackPos ;// current tracking position
}
SCROLLINFO, * PSCROLLINFO ;
WM_VSCROLL程序拦截SB_THUMBTRACK消息并忽略SB_THUMBPOSITION。
WM_HSCROLL处理拦截SB_THUMBPOSITION通知码并忽略SB_THUMBTRACK。

#include <windows.h> #include "sysmets.h" LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { static TCHAR szAppName[] = TEXT("SysMets3"); HWND hwnd; MSG msg; WNDCLASS wndclass; wndclass.style = CS_HREDRAW | CS_VREDRAW ; wndclass.lpfnWndProc = WndProc ; wndclass.cbClsExtra = 0 ; wndclass.cbWndExtra = 0 ; wndclass.hInstance = hInstance ; wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION); wndclass.hCursor = LoadCursor(NULL, IDC_ARROW); wndclass.hbrBackground= (HBRUSH)GetStockObject(WHITE_BRUSH); wndclass.lpszMenuName = NULL; wndclass.lpszClassName= szAppName; if (!RegisterClass (&wndclass)) { MessageBox(NULL, TEXT ("Program requires Windows NT!"), szAppName, MB_ICONERROR); return 0; } hwnd = CreateWindow (szAppName, TEXT ("Get System Metrics No. 3"), WS_OVERLAPPEDWINDOW | WS_VSCROLL | WS_HSCROLL, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL); ShowWindow(hwnd, iCmdShow); UpdateWindow(hwnd); while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg) ; DispatchMessage(&msg) ; } return msg.wParam; } LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static int cxChar, cxCaps, cyChar, cxClient, cyClient, iMaxWidth; HDC hdc; int i, x, y, iVertPos, iHorzPos, iPaintBeg, iPaintEnd; PAINTSTRUCT ps; SCROLLINFO si; TCHAR szBuffer[10]; TEXTMETRIC tm; switch (message) { case WM_CREATE: hdc = GetDC(hwnd); GetTextMetrics(hdc, &tm); cxChar = tm.tmAveCharWidth; cxCaps = (tm.tmPitchAndFamily & 1 ? 3 : 2) * cxChar / 2 ; cyChar = tm.tmHeight + tm.tmExternalLeading ; ReleaseDC(hwnd, hdc); // Save the width of the three columns iMaxWidth = 40 * cxChar + 22 * cxCaps; return 0; case WM_SIZE: cxClient = LOWORD(lParam); cyClient = HIWORD(lParam); // Set vertical scroll bar range and page size si.cbSize = sizeof (si);//结构的大小 //SIF_RANGE复制滚动范围到由lpsi指向的SCROLLINFO结构的nMin和nMax成员中。 //SIF_PAGE旗标能够取得页面大小 si.fMask = SIF_RANGE | SIF_PAGE; si.nMin = 0 ; si.nMax = NUMLINES - 1; si.nPage = cyClient / cyChar; SetScrollInfo(hwnd, SB_VERT, &si, TRUE); // Set horizontal scroll bar range and page size si.cbSize = sizeof (si); si.fMask = SIF_RANGE | SIF_PAGE; si.nMin = 0; si.nMax = 2 + iMaxWidth / cxChar; si.nPage = cxClient / cxChar; SetScrollInfo(hwnd, SB_HORZ, &si, TRUE); return 0; case WM_VSCROLL: //取得所有的垂直滚动条信息 si.cbSize = sizeof (si); si.fMask = SIF_ALL; GetScrollInfo(hwnd, SB_VERT, &si); // Save the position for comparison later on iVertPos = si.nPos; switch (LOWORD (wParam)) { case SB_TOP: si.nPos = si.nMin; break; case SB_BOTTOM: si.nPos = si.nMax; break; case SB_LINEUP: si.nPos -= 1; break; case SB_LINEDOWN: si.nPos += 1; break; case SB_PAGEUP: si.nPos -= si.nPage; break; case SB_PAGEDOWN: si.nPos += si.nPage; break; case SB_THUMBTRACK: //SCROLLINFO结构的nTrackPos字段将指出目前的32位的卷动方块位置 si.nPos = si.nTrackPos; break; default: break; } // Set the position and then retrieve it. Due to adjustments // by Windows it may not be the same as the value set. si.fMask = SIF_POS;//是SIF_RANGE、SIF_POS、SIF_PAGE和SIF_TRACKPOS的组合。 SetScrollInfo(hwnd, SB_VERT, &si, TRUE); GetScrollInfo(hwnd, SB_VERT, &si); // If the position has changed, scroll the window and update it if (si.nPos != iVertPos) { //在窗口的显示区域中卷动信息而不是重画它 //函数的第二个参数给出了水平卷动显示区域的数值，第三个参 //数是垂直卷动显示区域的数值，单位都是图素。 //最后两个参数设定为NULL，这指出了要卷动整个显示区域 ScrollWindow(hwnd, 0, cyChar * (iVertPos - si.nPos), NULL, NULL); //ScrollWindow不是GDI函数，因为它不需设备内容句柄。 UpdateWindow(hwnd); } return 0; case WM_HSCROLL: // Get all the vertical scroll bar information si.cbSize = sizeof(si); si.fMask = SIF_ALL;//是SIF_RANGE、SIF_POS、SIF_PAGE和SIF_TRACKPOS的组合。 // Save the position for comparison later on GetScrollInfo(hwnd, SB_HORZ, &si); iHorzPos = si.nPos; switch (LOWORD (wParam)) { case SB_LINELEFT: si.nPos -= 1; break; case SB_LINERIGHT: si.nPos += 1; break; case SB_PAGELEFT: si.nPos -= si.nPage; break; case SB_PAGERIGHT: si.nPos += si.nPage; break; case SB_THUMBPOSITION: si.nPos = si.nTrackPos; break; default: break; } // Set the position and then retrieve it. Due to adjustments // by Windows it may not be the same as the value set. si.fMask = SIF_POS; SetScrollInfo(hwnd, SB_HORZ, &si, TRUE); GetScrollInfo(hwnd, SB_HORZ, &si); // If the position has changed, scroll the window if (si.nPos != iHorzPos) { ScrollWindow(hwnd, cxChar * (iHorzPos - si.nPos), 0, NULL, NULL); } return 0; case WM_PAINT: hdc = BeginPaint(hwnd, &ps); // Get vertical scroll bar position si.cbSize = sizeof (si); si.fMask = SIF_POS; GetScrollInfo(hwnd, SB_VERT, &si); iVertPos = si.nPos; // Get horizontal scroll bar position GetScrollInfo(hwnd, SB_HORZ, &si); iHorzPos = si.nPos; // Find painting limits iPaintBeg = max(0, iVertPos + ps.rcPaint.top / cyChar); iPaintEnd = min(NUMLINES - 1, iVertPos + ps.rcPaint.bottom / cyChar); for (i = iPaintBeg ; i <= iPaintEnd ; i++) { x = cxChar * (1 - iHorzPos); y = cyChar * (i - iVertPos); TextOut (hdc, x, y, sysmetrics[i].szLabel, lstrlen (sysmetrics[i].szLabel)); TextOut (hdc, x + 22 * cxCaps, y, sysmetrics[i].szDesc, lstrlen (sysmetrics[i].szDesc)); SetTextAlign (hdc, TA_RIGHT | TA_TOP); TextOut (hdc, x + 22 * cxCaps + 40 * cxChar, y, szBuffer, wsprintf (szBuffer, TEXT ("%5d"), GetSystemMetrics (sysmetrics[i].iIndex))); SetTextAlign (hdc, TA_LEFT | TA_TOP); } EndPaint (hwnd, &ps); return 0; case WM_DESTROY: PostQuitMessage(0); return 0; } return DefWindowProc(hwnd, message, wParam, lParam); }