windows滚动条
今天自己写了《windows程序设计》184页的用键盘控制滚动条显示程序，对滚动条显示有点感悟，留个纪念！
代码如下：
#include
#include
#include "SYSMETS.h"
LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam);
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,PSTR szCmdLine,int iCmdShow)
{
static TCHAR szAppName[]=TEXT("First Program");
MSG msg;
HWND hwnd;
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(hwnd,TEXT("Error exists!"),TEXT("Error!"),MB_ICONERROR);
return 0;
}
hwnd=CreateWindow(szAppName,TEXT("Hello World!"),WS_OVERLAPPEDWINDOW|WS_HSCROLL|WS_VSCROLL,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,
CW_USEDEFAULT,NULL,NULL,hInstance,NULL);
ShowWindow(hwnd,iCmdShow);
UpdateWindow(hwnd);
while (GetMessage(&msg,hwnd,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam)
{
static int cxChar,cyChar,cxCaps,cxClient,cyClient;
int iVertPos,x,y,i,iPaintBeg,iPaintEnd;
TCHAR szBuffer[20];
HDC hdc;
PAINTSTRUCT ps;
TEXTMETRIC tm;
SCROLLINFO si;
switch(message)
{
case WM_CREATE:
hdc=GetDC(hwnd);
GetTextMetrics(hdc,&tm);
cxChar=tm.tmAveCharWidth;
cyChar=tm.tmHeight+tm.tmExternalLeading;
cxCaps=(tm.tmPitchAndFamily&1?3:2)*cxChar/2;
ReleaseDC(hwnd,hdc);
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);
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_PAGEUP:
si.nPos-=si.nPage;
break;
case SB_PAGEDOWN:
si.nPos+=si.nPage;
break;
case SB_LINEUP:
si.nPos-=1;
break;
case SB_LINEDOWN:
si.nPos+=1;
break;
case SB_THUMBTRACK:
si.nPos=si.nTrackPos;
break;
default:
break;
}
si.cbSize=sizeof(si);
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_KEYDOWN:
switch(wParam)
{
case VK_UP:
SendMessage(hwnd,WM_VSCROLL,SB_LINEUP,0);
break;
case VK_DOWN:
SendMessage(hwnd,WM_VSCROLL,SB_LINEDOWN,0);
break;
case VK_PRIOR:
SendMessage(hwnd,WM_VSCROLL,SB_PAGEUP,0);
break;
case VK_NEXT:
SendMessage(hwnd,WM_VSCROLL,SB_PAGEDOWN,0);
break;
default:
break;
}
return 0;
//关键代码
case WM_PAINT:
si.cbSize=sizeof(si);
si.fMask=SIF_ALL;
GetScrollInfo(hwnd,SB_VERT,&si);
iVertPos=si.nPos;
hdc=BeginPaint(hwnd,&ps);
iPaintBeg=max(0,si.nPos+ps.rcPaint.top/cyChar);
iPaintEnd=min(si.nMax,si.nPos+ps.rcPaint.bottom/cyChar);
for (i=iPaintBeg;i<=iPaintEnd;i++)
{
y=cyChar*(i-iVertPos);
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_TOP|TA_RIGHT);
TextOut(hdc,60*cxCaps,y,szBuffer,wsprintf(szBuffer,TEXT("%5d"),GetSystemMetrics(sysmetrics[i].Index)));
SetTextAlign(hdc,TA_LEFT|TA_TOP);
}
EndPaint(hwnd,&ps);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd,message,wParam,lParam);
}
原来我老是有个疑问：
1、iPaintBeg=max(0,si.nPos+ps.rcPaint.top/cyChar);
iPaintEnd=min(si.nMax,si.nPos+ps.rcPaint.bottom/cyChar);
这两句是干嘛用的？
2、为什么是for (i=iPaintBeg;i<=iPaintEnd;i++)这样循环？
3、y=cyChar*(i-iVertPos);
为什么是i-iVertPos？
今天调试了一下，颇有感悟！
调试时滚动条下拉了一行！
首先给出调试时一些参数，是我写的一张图：
得出了一些结论：
1、下拉滚动条时，只更新时新出现的客户区，这个矩形的具体参数存数在ps.rcPaint中。
更新起点iPaintBeg是需更新矩形的顶部所在的行数，iPaintEnd是底部所在的行数。即图中新出现一行的顶部和底部。
2、for循环就是输出这些新出现的文本
3、i-iVerPos就是以新客户区的顶部为起点更新客户区