MFC第二十二天 三种绘图句柄与三大坐标系（三大CDC派生类）简介以及应用、Invalidate刷新函数的功能和用法简介

三种绘图句柄与三大坐标系（三大CDC派生类）简介以及应用

三种HDC句柄

a)标准绘图消息WM_PAINT：，必须使用BeginPaint和EndPaint来绘图。
BeginPaint和EndPaint只能在WM_PAINT中使用。
b)在其他任何消息中使用的绘图句柄叫做临时绘图句柄。
（GetDC和ReleaseDC）
c)标准非客户户区绘图：（不推荐使用）
GetWindowDC和ReleaseDC

非客户区如同一个桌子的桌面，桌面上有桌布，露出了四角就是。
这里要说明的问题是：非客户区不是只有四角。

三大CDC派生类

a)客户区标准绘图：必须由CPaintDC派生类来调用，不能直接调用由CDC基类；
因为CPaintDC类构造函数是调用::BeginPaint，析构函数调用::EndPaint；
CPaintDC类必须在WM_PAINT消息中使用

CPaintDC::CPaintDC(CWnd* pWnd)
{
	ASSERT_VALID(pWnd);
	ASSERT(::IsWindow(pWnd->m_hWnd));
	if (!Attach(::BeginPaint(m_hWnd = pWnd->m_hWnd, &m_ps)))
		AfxThrowResourceException();
}
CPaintDC::~CPaintDC()
{
	ASSERT(m_hDC != NULL);
	ASSERT(::IsWindow(m_hWnd));
	::EndPaint(m_hWnd, &m_ps);
	Detach();
}

b)非客户区标准绘图，必须由CWindowDC来调用，必须在WM_NCPAINT下执行；
（不推荐使用）内部是构造函数调用GetWindowDC，析构函数调用ReleaseDC

CWindowDC::CWindowDC(CWnd* pWnd)
{
	ASSERT(pWnd == NULL || ::IsWindow(pWnd->m_hWnd));

	if (!Attach(::GetWindowDC(m_hWnd = pWnd->GetSafeHwnd())))
		AfxThrowResourceException();
}
CWindowDC::~CWindowDC()
{
	ASSERT(m_hDC != NULL);
	::ReleaseDC(m_hWnd, Detach());
}

c)客户区临时绘图除了以上两个消息之外，客户区的其他消息都调用CClientDC来执行绘图；
内部是构造函数调用GetDC，析构函数调用RleaseDC。

CClientDC::CClientDC(CWnd* pWnd)
{
	ASSERT(pWnd == NULL || ::IsWindow(pWnd->m_hWnd));

	if (!Attach(::GetDC(m_hWnd = pWnd->GetSafeHwnd())))
		AfxThrowResourceException();
}
CClientDC::~CClientDC()
{
	ASSERT(m_hDC != NULL);
	::ReleaseDC(m_hWnd, Detach());
}

什么是放泄露架构

利用析构函数，无论任何条件返回，析构函数都系统帮你防止泄露

class CPaintDC : public CDC
{// Attributes
protected:
	HWND m_hWnd;
public:
	explicit CPaintDC(CWnd* pWnd);   // BeginPaint

public:
	PAINTSTRUCT m_ps;       // actual paint struct!
// Implementation
public:
	virtual ~CPaintDC();

};

使用HDC句柄进行常见图形绘制演示

HPEN和HBRUSH句柄

a)HPEN是修饰边框，HBRUSH是修饰填充；
b)HPEN可修饰闭合和非闭合图形，HBRUSH只能修饰闭合图形；
c)所有GDI对象的摧毁用DeleteObject，所有GDI对象句柄的信息获取都用GetObject。
d)GetObject反函数是，由详细信息创建句柄，CreateXXXIndirect
！！关注：SelectObject的返回值，是旧对象（OldPen，OldBrush，OldFont等等）

GetObject支持哪些句柄（对应的结构体）
LOGPEN,LOGBRUSH,LOGFONT,BITMAP,

LOGBRUSH logBrush;
GetObject(hBrush, sizeof(LOGBRUSH), &logBrush);

HPEN的创建

HPEN CreatePen(   int fnPenStyle,   int nWidth,   COLORREF crColor);
HPEN CreatePenIndirect(  const LOGPEN* lplgpn);
typedef struct tagLOGPEN
 { 
  UINT lopnStyle; 
  POINT lopnWidth; 
  COLORREF lopnColor; 
} LOGPEN;

PS_SOLID   Creates a solid pen.
PS_DASH  Creates a dashed pen. Valid only when the pen width is 1 or less, in device units.
PS_DOT  Creates a dotted pen. Valid only when the pen width is 1 or less, in device units.
PS_DASHDOT   
Creates a pen with alternating dashes and dots. Valid only when the pen width is 1 or less, in device units.
PS_DASHDOTDOT   
Creates a pen with alternating dashes and double dots. Valid only when the pen width is 1 or less, in device units.
PS_NULL   Creates a null pen.

PS_INSIDEFRAME   Creates a pen that draws a line inside the frame of closed shapes produced by the Windows GDI output functions that specify a bounding rectangle (for example, the Ellipse, Rectangle, RoundRect, Pie, and Chord member functions). When this style is used with Windows GDI output functions that do not specify a bounding rectangle (for example, the LineTo member function), the drawing area of the pen is not limited by a frame.

Invalidate刷新函数的功能和用法简介

InvalidateRect函数用于使指定的矩形区域失效，从而触发重绘操作。其刷新原理如下：

a) InvalidateRect函数会发送WM_PAINT消息给窗口，告诉窗口需要进行绘图操作。窗口收到WM_PAINT消息后，会调用窗口过程中的处理函数，进行标准的绘图操作。

b) 在进行绘图之前，窗口会接收到WM_ERASEBKGND消息，用于擦除当前窗口的背景。这个消息会导致窗口的背景被擦除，以准备进行绘图操作。

c) InvalidateRect函数的第三个参数可以是TRUE或FALSE。当为TRUE时，表示需要同时刷新前景和背景；当为FALSE时，表示只刷新前景。默认情况下，第三个参数为TRUE。

d) UpdateWindow函数用于立即执行窗口的重绘操作，类似于SendMessage函数。它会强制窗口立即进行绘图操作，而不需要等待下一次消息循环。这样可以立即刷新窗口的内容。与之相对，InvalidateRect函数只是标记了指定区域为失效，需要等待下一次绘图消息的到来才会进行绘图操作。

	case WM_SIZE:
	{
		//FALSE  前景覆盖 （WM_PAINT）单层覆盖 TRUE 前景和背景(WM_EARSEBGGND)同时刷新 双层覆盖
		RECT rect{ 300,200,100,200 };
		InvalidateRect(hDlg, NULL, FALSE);
		 //当窗口大小发生变化时 对其刷新 第二个参数为NULL 代表全区域刷新  CRect 可指定
	}
	break;

应用

Win32下

#include
#include
#include
#include "resource.h"
void OnPaint(HWND hDlg, HDC hdc)
{
	RECT rect;
	GetClientRect(hDlg, &rect);

	HBRUSH hbr = CreateSolidBrush(RGB(102, 250, 230));
	SelectObject(hdc, hbr);
 
	Rectangle(hdc, rect.left, rect.top, rect.right, rect.bottom);

	DeleteObject(hbr);

	hbr = CreateSolidBrush(RGB(0, 0, 230));
	SelectObject(hdc, hbr);
	Ellipse(hdc, 10, 10, 300, 200);
	DeleteObject(hbr);

	hbr = CreateSolidBrush(RGB(0, 250, 0));
	SelectObject(hdc, hbr);
	RoundRect(hdc, 300, 300, 500, 400, 50, 50);

	DeleteObject(hbr);

	hbr = CreateSolidBrush(RGB(255, 250, 0));
	SelectObject(hdc, hbr);
	POINT pts[] = { {433,221},{444,555},{777,544} ,{877,444} };
	Polygon(hdc, pts, _countof(pts)); //闭合图形
	DeleteObject(hbr);

	hbr = CreateSolidBrush(RGB(255, 250, 0));
	SelectObject(hdc, hbr);
	POINT pts2[] = { {733,521},{244,155},{377,744} ,{277,244}, {733,521}};
	Polyline(hdc, pts2, _countof(pts2));//非闭合图形 填充颜色也无效

	DeleteObject(hbr);
	SetBkMode(hdc, TRANSPARENT);
	DrawText(hdc, _T("这世间本没有控件"), 8, &rect, DT_CENTER | DT_SINGLELINE | DT_VCENTER);
}

INT_PTR CALLBACK theProc(HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	switch (uMsg)
	{
	case WM_LBUTTONDOWN:
	{
		int x = LOWORD(lParam);
		int y = HIWORD(lParam);
		HDC hdc = GetDC(hDlg); //临时绘图DC 会被冲毁
		Rectangle(hdc, x - 5, y - 5, x + 5, y + 5);
		ReleaseDC(hDlg, hdc);
		return TRUE;
	}
	case WM_PAINT:
	{
		PAINTSTRUCT ps;
		HDC hdc = BeginPaint(hDlg, &ps);  //hdc 理解为绘图句柄  绑定什么 就绘图什么

		OnPaint(hDlg,hdc);
		//TextOut(hdc,_T("这世间本没有控件"),8);
		EndPaint(hDlg, &ps);  //成对使用
	}
	return TRUE;
	case WM_SIZE:
	{
		//FALSE  前景覆盖 （WM_PAINT）单层覆盖 TRUE 前景和背景(WM_EARSEBGGND)同时刷新 双层覆盖
		RECT rect{ 300,200,100,200 };
		InvalidateRect(hDlg, NULL, FALSE);  
		//当窗口大小发生变化时 对其刷新 第二个参数为NULL 代表全区域刷新  CRect 可指定
	}
	break;
	case WM_COMMAND:
	{
		if (LOWORD(wParam) == IDCANCEL)
			EndDialog(hDlg, IDCANCEL);
	}
	break;
	}
	return FALSE;//return 0代表系统默认要执行的 return 1代表执行系统以外的
}
int CALLBACK WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
	DialogBox(hInstance, MAKEINTRESOURCE(IDD_GDI_DLG), NULL, theProc);
	return 0;
}

MFC下

#include "pch.h"
#include "framework.h"
#include "MFC_GDI.h"
#include "CMainDlg.h"
#include "afxdialogex.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#endif
CMainDlg::CMainDlg(CWnd* pParent /*=nullptr*/)
	: CDialogEx(IDD_MFC_GDI_DIALOG, pParent)
{
	m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void CMainDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialogEx::DoDataExchange(pDX);
}

BEGIN_MESSAGE_MAP(CMainDlg, CDialogEx)
	ON_WM_PAINT()
	ON_WM_QUERYDRAGICON()
	ON_WM_SIZE()
	ON_WM_LBUTTONDOWN()
END_MESSAGE_MAP()

BOOL CMainDlg::OnInitDialog()
{
	CDialogEx::OnInitDialog();
	SetIcon(m_hIcon, TRUE);			// 设置大图标
	SetIcon(m_hIcon, FALSE);		// 设置小图标
	return TRUE;  // 除非将焦点设置到控件，否则返回 TRUE
}

void CMainDlg::OnPaint()
{
	CPaintDC dc(this); // 用于绘制的设备上下文 不用请不要删掉
	RECT rect;
	GetClientRect(&rect);
	CPen p1,p2,p3;
	p1.CreatePen(PS_SOLID, 5, RGB(255, 0, 255));
	auto hOldPen = dc.SelectObject(p1);

	LOGPEN logPen;
	p1.GetObject(sizeof(logPen), &logPen);

	HBRUSH hbr = CreateSolidBrush(RGB(102, 250, 230));
	dc.SelectObject( hbr);
 
	dc.Rectangle(rect.left, rect.top, rect.right, rect.bottom);
	dc.SelectObject(hOldPen);//恢复

	DeleteObject(hbr);

	hbr = CreateSolidBrush(RGB(0, 0, 230));
	dc.SelectObject(hbr);
	dc.Ellipse( 10, 10, 300, 200);
	DeleteObject(hbr);

 
	LOGPEN lp{ PS_NULL };
	p3.CreatePenIndirect(&lp);
	dc.SelectObject(p3);
	dc.RoundRect( 300, 300, 500, 400, 50, 50);


	p2.CreatePen(PS_DASHDOTDOT, 1, RGB(255, 0, 255));
	dc.SelectObject(p2);
	GetObject(p2, sizeof(logPen), &logPen);
	dc.SelectObject(hOldPen);//恢复

	hbr = CreateSolidBrush(RGB(255, 250, 0));
	dc.SelectObject( hbr);
	POINT pts[] = { {433,221},{444,555},{777,544} ,{877,444} };
	dc.Polygon(  pts, _countof(pts)); //闭合图形
	DeleteObject(hbr);

	hbr = CreateSolidBrush(RGB(255, 250, 0));
	dc.SelectObject(  hbr);
	POINT pts2[] = { {733,521},{244,155},{377,744} ,{277,244}, {733,521} };
	dc.Polyline( pts2, _countof(pts2));//非闭合图形 填充颜色也无效

	DeleteObject(hbr);
	dc.SetBkMode(TRANSPARENT);
	dc.DrawText( _T("这世间本没有控件"), 8, &rect, DT_CENTER | DT_SINGLELINE | DT_VCENTER);
}

HCURSOR CMainDlg::OnQueryDragIcon()
{
	return static_cast<HCURSOR>(m_hIcon);
}
void CMainDlg::OnSize(UINT nType, int cx, int cy)
{
	CDialogEx::OnSize(nType, cx, cy);
	this->Invalidate(FALSE);
}

void CMainDlg::OnLButtonDown(UINT nFlags, CPoint point)
{
	CDialogEx::OnLButtonDown(nFlags, point);
	CClientDC dc(this);
	dc.Rectangle(point.x - 10, point.y - 10, point.x + 10, point.y + 10);
}

附录

DrawText() Format Flags
 
#define DT_TOP                      0x00000000
#define DT_LEFT                     0x00000000
#define DT_CENTER                   0x00000001
#define DT_RIGHT                    0x00000002
#define DT_VCENTER                  0x00000004
#define DT_BOTTOM                   0x00000008
#define DT_WORDBREAK                0x00000010  过长折回
#define DT_SINGLELINE               0x00000020 单行