头文件：sysmets.h

作用：存储打印信息

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/*-----------------------------------------------
   SYSMETS.H -- System metrics display structure
  -----------------------------------------------*/
#define NUMLINES ((int) (sizeof sysmetrics / sizeof sysmetrics [0]))

struct
{ 
     int     iIndex ;
     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")
} ;

程序文件：

分析

Windows 负责：

  • 处理滚动条中的所有鼠标消息
  • 当用户单击滚动条时，提供一种反向显示的闪烁
  • 当用户拖动滑块时，在滚动条内移动滑块
  • 向拥有滚动条的窗口的窗口过程发送滚动条消

代码需要负责：

  • 初始化滚动条的范围和位置
  • 处理传送给窗口过程的滚动条消息
  • 更新滑块的位置
  • 根据滚动条的变化更新客户区的内容

实现

1. 使用 SetScrollRange 函数来设置滚动条的范围

ps：这里所说的范围是指滑块的位置所能移动的范围，例如一个范围是 0~100 的滚动条，那么它的滑块就有 101 个位置可以移动。

2. TextOut 函数的第三个参数决定文本显示的位置

3. 如何看待滚动条

当用户拉动滚动条向下滚动时，他们希望是看到文件中下方的内容。而我们设计程序，则是需要将文件相对于窗口向上移动。从这个角度来说，是相反的。

4. 需要系统发送 WM_PAINT 消息重绘窗口，可以使用 InvalidateRect 函数使得客户区失效

ps：使用 InvalidateRect 使客户区失效，Windows 会在应用程序的消息队列为空的时候才发送 WM_PAINT 消息，也就意味着，如果你的程序很忙，那么刷新这一操作就会有所延迟，那么客户看到的就可能是程序一卡一卡的。因此，如果你想立刻更新无效区域，则可以在调用 InvalidateRect 函数后随即调用 UpdateWindow 函数。因为如果客户区有任何一部分是无效的，UpdateWindow 函数将绕过消息队列，直接给窗口过程发一个 WM_PAINT 消息。

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#include <windows.h>
#include "strsafe.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("MyWindows");
	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("这个程序需要在 Windows NT 才能执行！"), szAppName, MB_ICONERROR);
		return 0;
	}

	hwnd = CreateWindow(szAppName,
		TEXT("快乐小凳凳"),
		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)
{
	HDC hdc;
	PAINTSTRUCT ps;
	TEXTMETRIC tm;
	TCHAR szBuffer[10];
	static int cxChar, cxCaps, cyChar, cxClient, cyClient, iVscrollPos;
	size_t iTarget;
	int i, y;

	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, 0, TRUE);
		return 0;

	case WM_SIZE:
		cxClient = LOWORD(lParam);
		cyClient = HIWORD(lParam);
         return 0;

	case WM_VSCROLL:
		hdc = GetDC(hwnd);
		SetTextAlign(hdc, TA_TOP | TA_RIGHT);

		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;
		}

		ReleaseDC(hwnd, hdc);

		iVscrollPos = max(0, min(iVscrollPos, NUMLINES - 1));

		if (iVscrollPos != GetScrollPos(hwnd, SB_VERT))
		{
			SetScrollPos(hwnd, SB_VERT, iVscrollPos, TRUE);
			InvalidateRect(hwnd, NULL, TRUE);
			UpdateWindow(hwnd);
		}
		return 0;

	case WM_PAINT:
		hdc = BeginPaint(hwnd, &ps);

		for (i = 0; i < NUMLINES; i++)
		{
			y = cyChar * (i - iVscrollPos);

			StringCchLength(sysmetrics[i].szLabel, 1024, &iTarget);
			TextOut(hdc, 0, y, sysmetrics[i].szLabel, iTarget);

			StringCchLength(sysmetrics[i].szDesc, 1024, &iTarget);
			TextOut(hdc, 22 * cxCaps, y, sysmetrics[i].szDesc, iTarget);

			SetTextAlign(hdc, TA_RIGHT | TA_TOP);
			StringCchPrintf(szBuffer, 10, TEXT("%5d"), GetSystemMetrics(sysmetrics[i].iIndex));
			StringCchLength(szBuffer, 10, &iTarget);
			TextOut(hdc, 22 * cxCaps + 40 * cxChar, y, szBuffer, iTarget);

			SetTextAlign(hdc, TA_LEFT | TA_TOP);
		}

		EndPaint(hwnd, &ps);
		return 0;

	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}

	return DefWindowProc(hwnd, message, wParam, lParam);
}