本文的程序来自《windows程序设计(第五版)》
设计滚动条的初衷,是因为客户区需要显示的东西太多了,在这个头文件中,我们包含了一大堆的系统的信息:
-
- #define NUMLINES ((int) (sizeof sysmetrics / sizeof sysmetrics [0]))
-
- struct
- {
- int Index ;
- TCHAR* szLabel;
- TCHAR* szDesc ;
-
- }
-
- sysmetrics [] =
-
- {
-
- SM_CXSCREEN, TEXT ("SM_CXSCREEN"), TEXT ("Screen width in pixels"),
- SM_CYSCREEN, TEXT ("SM_CYSCREEN"), TEXT ("Screen height in pixels"),
- SM_CXVSCROLL, TEXT ("SM_CXVSCROLL"), TEXT ("Vertical scroll width"),
- SM_CYHSCROLL, TEXT ("SM_CYHSCROLL"), TEXT ("Horizontal scroll height"),
- SM_CYCAPTION, TEXT ("SM_CYCAPTION"), TEXT ("Caption bar height"),
- SM_CXBORDER, TEXT ("SM_CXBORDER"), TEXT ("Window border width"),
- SM_CYBORDER, TEXT ("SM_CYBORDER"), TEXT ("Window border height"),
- SM_CXFIXEDFRAME, TEXT ("SM_CXFIXEDFRAME"), TEXT ("Dialog window frame width"),
- SM_CYFIXEDFRAME, TEXT ("SM_CYFIXEDFRAME"), TEXT ("Dialog window frame height"),
- SM_CYVTHUMB, TEXT ("SM_CYVTHUMB"), TEXT ("Vertical scroll thumb height"),
- SM_CXHTHUMB, TEXT ("SM_CXHTHUMB"), TEXT ("Horizontal scroll thumb width"),
- SM_CXICON, TEXT ("SM_CXICON"), TEXT ("Icon width"),
- SM_CYICON, TEXT ("SM_CYICON"), TEXT ("Icon height"),
- SM_CXCURSOR, TEXT ("SM_CXCURSOR"), TEXT ("Cursor width"),
- SM_CYCURSOR, TEXT ("SM_CYCURSOR"), TEXT ("Cursor height"),
- SM_CYMENU, TEXT ("SM_CYMENU"), TEXT ("Menu bar height"),
- SM_CXFULLSCREEN, TEXT ("SM_CXFULLSCREEN"), TEXT ("Full screen client area width"),
- SM_CYFULLSCREEN, TEXT ("SM_CYFULLSCREEN"), TEXT ("Full screen client area height"),
- SM_CYKANJIWINDOW, TEXT ("SM_CYKANJIWINDOW"), TEXT ("Kanji window height"),
- SM_MOUSEPRESENT, TEXT ("SM_MOUSEPRESENT"), TEXT ("Mouse present flag"),
- SM_CYVSCROLL, TEXT ("SM_CYVSCROLL"), TEXT ("Vertical scroll arrow height"),
- SM_CXHSCROLL, TEXT ("SM_CXHSCROLL"), TEXT ("Horizontal scroll arrow width"),
- SM_DEBUG, TEXT ("SM_DEBUG"), TEXT ("Debug version flag"),
- SM_SWAPBUTTON, TEXT ("SM_SWAPBUTTON"), TEXT ("Mouse buttons swapped flag"),
- SM_CXMIN, TEXT ("SM_CXMIN"), TEXT ("Minimum window width"),
- SM_CYMIN, TEXT ("SM_CYMIN"), TEXT ("Minimum window height"),
- SM_CXSIZE, TEXT ("SM_CXSIZE"), TEXT ("Min/Max/Close button width"),
- SM_CYSIZE, TEXT ("SM_CYSIZE"), TEXT ("Min/Max/Close button height"),
- SM_CXSIZEFRAME, TEXT ("SM_CXSIZEFRAME"), TEXT ("Window sizing frame width"),
- SM_CYSIZEFRAME, TEXT ("SM_CYSIZEFRAME"), TEXT ("Window sizing frame height"),
- SM_CXMINTRACK, TEXT ("SM_CXMINTRACK"), TEXT ("Minimum window tracking width"),
- SM_CYMINTRACK, TEXT ("SM_CYMINTRACK"), TEXT ("Minimum window tracking height"),
- SM_CXDOUBLECLK, TEXT ("SM_CXDOUBLECLK"), TEXT ("Double click x tolerance"),
- SM_CYDOUBLECLK, TEXT ("SM_CYDOUBLECLK"), TEXT ("Double click y tolerance"),
- SM_CXICONSPACING, TEXT ("SM_CXICONSPACING"), TEXT ("Horizontal icon spacing"),
- SM_CYICONSPACING, TEXT ("SM_CYICONSPACING"), TEXT ("Vertical icon spacing"),
- SM_MENUDROPALIGNMENT, TEXT ("SM_MENUDROPALIGNMENT"), TEXT ("Left or right menu drop"),
- SM_PENWINDOWS, TEXT ("SM_PENWINDOWS"), TEXT ("Pen extensions installed"),
- SM_DBCSENABLED, TEXT ("SM_DBCSENABLED"), TEXT ("Double-Byte Char Set enabled"),
- SM_CMOUSEBUTTONS, TEXT ("SM_CMOUSEBUTTONS"), TEXT ("Number of mouse buttons"),
- SM_SECURE, TEXT ("SM_SECURE"), TEXT ("Security present flag"),
- SM_CXEDGE, TEXT ("SM_CXEDGE"), TEXT ("3-D border width"),
- SM_CYEDGE, TEXT ("SM_CYEDGE"), TEXT ("3-D border height"),
- SM_CXMINSPACING, TEXT ("SM_CXMINSPACING"), TEXT ("Minimized window spacing width"),
- SM_CYMINSPACING, TEXT ("SM_CYMINSPACING"), TEXT ("Minimized window spacing height"),
- SM_CXSMICON, TEXT ("SM_CXSMICON"), TEXT ("Small icon width"),
- SM_CYSMICON, TEXT ("SM_CYSMICON"), TEXT ("Small icon height"),
- SM_CYSMCAPTION, TEXT ("SM_CYSMCAPTION"), TEXT ("Small caption height"),
- SM_CXSMSIZE, TEXT ("SM_CXSMSIZE"), TEXT ("Small caption button width"),
- SM_CYSMSIZE, TEXT ("SM_CYSMSIZE"), TEXT ("Small caption button height"),
- SM_CXMENUSIZE, TEXT ("SM_CXMENUSIZE"), TEXT ("Menu bar button width"),
- SM_CYMENUSIZE, TEXT ("SM_CYMENUSIZE"), TEXT ("Menu bar button height"),
- SM_ARRANGE, TEXT ("SM_ARRANGE"), TEXT ("How minimized windows arranged"),
- SM_CXMINIMIZED, TEXT ("SM_CXMINIMIZED"), TEXT ("Minimized window width"),
- SM_CYMINIMIZED, TEXT ("SM_CYMINIMIZED"), TEXT ("Minimized window height"),
- SM_CXMAXTRACK, TEXT ("SM_CXMAXTRACK"), TEXT ("Maximum draggable width"),
- SM_CYMAXTRACK, TEXT ("SM_CYMAXTRACK"), TEXT ("Maximum draggable height"),
- SM_CXMAXIMIZED, TEXT ("SM_CXMAXIMIZED"), TEXT ("Width of maximized window"),
- SM_CYMAXIMIZED, TEXT ("SM_CYMAXIMIZED"), TEXT ("Height of maximized window"),
- SM_NETWORK, TEXT ("SM_NETWORK"), TEXT ("Network present flag"),
- SM_CLEANBOOT, TEXT ("SM_CLEANBOOT"), TEXT ("How system was booted"),
- SM_CXDRAG, TEXT ("SM_CXDRAG"), TEXT ("Avoid drag x tolerance"),
- SM_CYDRAG, TEXT ("SM_CYDRAG"), TEXT ("Avoid drag y tolerance"),
- SM_SHOWSOUNDS, TEXT ("SM_SHOWSOUNDS"), TEXT ("Present sounds visually"),
- SM_CXMENUCHECK, TEXT ("SM_CXMENUCHECK"), TEXT ("Menu check-mark width"),
- SM_CYMENUCHECK, TEXT ("SM_CYMENUCHECK"), TEXT ("Menu check-mark height"),
- SM_SLOWMACHINE, TEXT ("SM_SLOWMACHINE"), TEXT ("Slow processor flag"),
- SM_MIDEASTENABLED, TEXT ("SM_MIDEASTENABLED"), TEXT ("Hebrew and Arabic enabled flag"),
- SM_MOUSEWHEELPRESENT, TEXT ("SM_MOUSEWHEELPRESENT"), TEXT ("Mouse wheel present flag"),
- SM_XVIRTUALSCREEN, TEXT ("SM_XVIRTUALSCREEN"), TEXT ("Virtual screen x origin"),
- SM_YVIRTUALSCREEN, TEXT ("SM_YVIRTUALSCREEN"), TEXT ("Virtual screen y origin"),
- SM_CXVIRTUALSCREEN, TEXT ("SM_CXVIRTUALSCREEN"), TEXT ("Virtual screen width"),
- SM_CYVIRTUALSCREEN, TEXT ("SM_CYVIRTUALSCREEN"), TEXT ("Virtual screen height"),
- SM_CMONITORS, TEXT ("SM_CMONITORS"), TEXT ("Number of monitors"),
- SM_SAMEDISPLAYFORMAT, TEXT ("SM_SAMEDISPLAYFORMAT"), TEXT ("Same color format flag")
-
- } ;
第一行定义的,是数组有多少个元素。之后我们定义了结构体数组。元素个数很多,一行显示不下,那么如何添加滚动条呢?
我们先看程序:
- #include <windows.h>
- #include "sysmets.h"
-
- LRESULT CALLBACK WndProc (HWND,UINT,WPARAM,LPARAM);
-
- int WINAPI WinMain(HINSTANCE hInstance,
- HINSTANCE hPrevInstance,
- LPSTR lpCmdLine,
- int iCmdShow)
- {
- static TCHAR szAppName[] = TEXT("显示系统内容");
-
- 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))
- {
- return -1;
- }
-
-
- hwnd = CreateWindow(szAppName,
- TEXT("系统内容"),
- WS_OVERLAPPEDWINDOW | WS_VSCROLL,
- 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 ;
-
- static int cxClient, cyClient ;
-
- static int iVscrollPos;
- HDC hdc;
-
- int i;
-
- int y;
-
- PAINTSTRUCT ps;
-
- 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);
-
-
- SetScrollRange (hwnd, SB_VERT, 0, NUMLINES - 1, FALSE);
-
- SetScrollPos (hwnd, SB_VERT, iVscrollPos, TRUE);
-
- return 0;
- case WM_SIZE:
- cxClient = LOWORD (lParam) ;
- cyClient = HIWORD (lParam) ;
- return 0;
- case WM_PAINT:
- hdc = BeginPaint (hwnd, &ps) ;
- for(i = 0;i < NUMLINES;i++ )
- {
-
-
- y = cyChar * (i - iVscrollPos) ;
-
-
-
- TextOut(hdc,0, y,sysmetrics[i].szLabel,lstrlen(sysmetrics[i].szLabel));
-
- TextOut(hdc,22*cxCaps, y,sysmetrics[i].szDesc,lstrlen(sysmetrics[i].szDesc));
-
- SetTextAlign(hdc,TA_RIGHT | TA_TOP);
-
-
-
- TextOut(hdc,22*cxCaps+40*cxChar,y,szBuffer,wsprintf(szBuffer,TEXT("%5d"),GetSystemMetrics (sysmetrics[i].Index)));
-
- SetTextAlign(hdc,TA_LEFT | TA_TOP);
- }
- EndPaint (hwnd, &ps) ;
- return 0;
-
-
- case WM_VSCROLL:
-
-
- switch(LOWORD (wParam))
- {
-
- case SB_LINEUP:
- iVscrollPos -=1;
- break;
-
- case SB_LINEDOWN:
- iVscrollPos +=1;
- break;
-
- case SB_PAGEUP:
- iVscrollPos -= cyClient / cyChar ;
- break;
-
- case SB_PAGEDOWN:
- iVscrollPos += cyClient / cyChar ;
- break;
-
- case SB_THUMBPOSITION:
- iVscrollPos = HIWORD (wParam) ;
- break;
- default:
- break;
- }
-
-
- iVscrollPos = max (0, min (iVscrollPos, NUMLINES - 1)) ;
-
-
- if (iVscrollPos != GetScrollPos (hwnd, SB_VERT))
- {
-
- SetScrollPos (hwnd, SB_VERT, iVscrollPos, TRUE) ;
-
- InvalidateRect (hwnd, NULL, TRUE) ;
- }
-
- return 0;
-
-
- case WM_DESTROY:
- PostQuitMessage(0);
- return 0;
- }
- return DefWindowProc (hwnd, message, wParam, lParam) ;
-
- }
程序的思路是这样的:在创建窗口时,就要告诉系统你要加一个滚动条(垂直的),在WM_CREATE消息中,就要对滚动条进行一些基本的设置。WM_VSCROLL对滚动条做出相应,可以分为3部分:第一部分接收滚动条的消息;第二部分是让滚动条的那个小方块滚动到特定的位置,第三部分是页面的文字出现“滚动”的效果。
先看第一部分:滚动条的作用是什么:当点击一下向上或者向下的按钮时,会滚动一行文字;当点击滚动的小方块的上面或者下面时,会滚动一页文字;而拖着滚动条走,能滚动到指定的地方。到底是这几种操作的哪一种,是通过WM_VSCROLL消息的wParam的低字节传过来的。在程序中,使用iVscrollPos这个全局变量来记录滚动的位置,每一次对滚动条都会改变位置。
iVscrollPos = max (0, min (iVscrollPos, NUMLINES - 1)) ;是为了不让滚动条的位置超出一定为范围,大家可以把它屏蔽之后,将滚动条向上或者向下滚,就可以理解结果了。
而通过SetScrollPos (hwnd, SB_VERT, iVscrollPos, TRUE) ;就将滚动条的方块放到了可定位位置。而第三部分让页面滚动,则是WM_PAINT的作用了:其实当你看到第二行显示在原来第一行为位置上时,其实并不是系统没有输出第一行,而是第一行输出的位置已经到了客户区的上面,所以你看不到!第二行紧跟在第一行下面,刚好就放到了开始的位置。
这个滚动条有一个明显的缺点,就是他并不是我们希望看到的那样:滚动条的长度反应的当前页面占显示的内容总的内容的百分比,具体的说,就是:
页面方块的大小/滚动的长度=页面大小/整个范围=显示文件的数量/整个文件的数量
别看这只是一点小小的改动,但是他的实现方法却与上面的差别很大。总体上来说,他需要使用SCROLLINFO结构来记录滚动条的信息,然后使用GetScrollInfo获取信息,通过SetScrollInfo设置信息。在对滚动条的响应消息中,通过ScrollWindow来实现内容的滚动(而不像前面那个程序,在WM_PAINT消息下实现)。
我们在看看程序:
- #include <windows.h>
- #include "sysmets.h"
-
- LRESULT CALLBACK WndProc (HWND,UINT,WPARAM,LPARAM);
-
- int WINAPI WinMain(HINSTANCE hInstance,
- HINSTANCE hPrevInstance,
- LPSTR lpCmdLine,
- int iCmdShow)
- {
- static TCHAR szAppName[] = TEXT("显示系统内容");
-
- 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))
- {
- return -1;
- }
-
-
- hwnd = CreateWindow(szAppName,
- TEXT("系统内容"),
- 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 ;
-
- static int cxClient, cyClient ;
-
- static int iMaxWidth;
-
- static int iVertPos,iHorzPos,iPaintBeg,iPaintEnd;
- HDC hdc;
-
- int i;
-
- int x,y;
-
- 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);
-
- iMaxWidth = 40*cxChar+22*cxCaps;
- return 0;
- case WM_SIZE:
- cxClient = LOWORD (lParam) ;
- cyClient = HIWORD (lParam) ;
-
-
- si.cbSize = sizeof(si);
-
- si.fMask = SIF_RANGE | SIF_PAGE ;
-
- si.nMin = 0;
-
- si.nMax = NUMLINES - 1 ;
-
- si.nPage = cyClient / cyChar ;
-
- SetScrollInfo(hwnd, SB_VERT,&si,TRUE);
-
-
- 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_PAINT:
- hdc = BeginPaint (hwnd, &ps) ;
-
- si.cbSize = sizeof(si);
- si.fMask = SIF_POS;
- GetScrollInfo(hwnd,SB_VERT,&si);
- iVertPos = si.nPos;
- GetScrollInfo(hwnd,SB_HORZ,&si);
- iHorzPos = si.nPos;
-
-
- iPaintBeg = max(0,iVertPos);
-
- 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].Index)));
- SetTextAlign(hdc,TA_LEFT | TA_TOP);
- }
- EndPaint (hwnd, &ps) ;
- return 0;
-
-
- case WM_VSCROLL:
-
-
- si.cbSize = sizeof(si);
-
- si.fMask = SIF_ALL;
- GetScrollInfo(hwnd,SB_VERT,&si);
-
- 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;
- case SB_PAGEUP:
- si.nPage -= si.nPage;
- break;
- case SB_PAGEDOWN:
- si.nPos +=si.nPage;
- break;
- case SB_THUMBTRACK:
- si.nPos = si.nTrackPos;
- break;
- default:
- break;
- }
-
-
- si.fMask = SIF_POS;
- SetScrollInfo(hwnd,SB_VERT,&si,TRUE);
- GetScrollInfo(hwnd,SB_VERT,&si);
- if(si.nPos != iVertPos)
- {
-
- ScrollWindow(hwnd,0,cyChar*(iVertPos-si.nPos),NULL,NULL);
- UpdateWindow(hwnd);
- }
- return 0;
-
- case WM_HSCROLL:
- si.cbSize = sizeof(si);
- si.fMask = SIF_ALL;
- 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;
-
- }
- si.fMask = SIF_POS;
- SetScrollInfo(hwnd,SB_HORZ,&si,TRUE);
- GetScrollInfo(hwnd,SB_HORZ,&si);
- if(si.nPos != iHorzPos)
- {
- ScrollWindow(hwnd,cxChar*(iHorzPos-si.nPos),0,NULL,NULL);
-
-
- }
- return 0;
- case WM_DESTROY:
- PostQuitMessage(0);
- return 0;
- }
- return DefWindowProc (hwnd, message, wParam, lParam) ;
-
- }
程序中有几点需要注意:
1.程序中设置了垂直滚动条和水平滚动条。在WM_SIZE消息中,随着窗口的变化,滚动条的那个小方块的大小也在变化。
2.在每次使用GetScrollInfo或者SetScrollInfo之前,都必须有si.cbSize = sizeof(si);这是因为兼容的缘故。而且还得指明操作的是SCROLLINFO中的哪些内容,这通过fMask来控制。
3.程序中有几行代码很费解:
iPaintBeg = max(0,iVertPos+ps.rcPaint.top/cyChar);实际上,由于ps.rcPaint.top=0,这行代码也可以写为:iPaintBeg = max(0,iVertPos);
iPaintEnd = min(NUMLINES -1,iVertPos+ps.rcPaint.bottom/cyChar);画图的结束位置=滚动条当前的位置+绘制的行数,而行数=客户区宽度/每一行的宽度;
x = cxChar * (1 - iHorzPos) ;绘图的x坐标,那个1是为了不是太“顶格”,你也可以把它设置大一点,结果就很明显了。
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