【Fr2D开发笔记】二、创建Window

在完成上次的Fr2D的控制台版本后，是时候把它变成一个真正的图形库了。控制台绘制显然是不理想的，因此，我选择了Direct2D。

一、WinAPI

调用Direct2D的前提是创建一个渲染对象窗体。所以，我们需要先使用WindowsAPI创建一个。

#include<windows.h>
#include<tchar.h>

HWND ghMainWnd = 0;

bool InitWindowsApp(HINSTANCE instanceHandle, int show);
int Run();
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR pCmdLine, int nShowCmd) {
    if (!InitWindowsApp(hInstance, nShowCmd))
        return 0;
    return Run();
}

bool InitWindowsApp(HINSTANCE instanceHandle, int show) {
    WNDCLASS wc;
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = instanceHandle;
    wc.hIcon = LoadIcon(0, IDI_APPLICATION);
    wc.hCursor = LoadCursor(0, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wc.lpszMenuName = 0;
    wc.lpszClassName = _T("BasicWndClass");

    if (!RegisterClass(&wc)) {
        MessageBox(0, _T("RegisterClass FAILED"), 0, 0);
        return false;
    }

    ghMainWnd = CreateWindow(
        _T("BasicWndClass"),
        _T("Win32Basic"),
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        0,
        0,
        instanceHandle,
        0
    );

    if (ghMainWnd == 0) {
        MessageBox(0, _T("CreateWindow FAILED"), 0, 0);
        return false;
    }

    ShowWindow(ghMainWnd, show);
    UpdateWindow(ghMainWnd);

    return true;
}

int Run() {
    MSG msg = { 0 };
    while (msg.message != WM_QUIT) {
        if (PeekMessage(&msg, 0, 0, 0, PM_REMOVE)) {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        else {
            //...
        }
    }
    return (int)msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch (msg) {
    case WM_LBUTTONDOWN:
        MessageBox(0, _T("Hello, World"), _T("Hello"), MB_OK);
        return 0;

    case WM_KEYDOWN:
        if (wParam == VK_ESCAPE)
            DestroyWindow(ghMainWnd);
        return 0;

    case WM_KEYUP:
        return 0;

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

    return DefWindowProc(hWnd, msg, wParam, lParam);
}

这就是使用WINAPI创建一个窗体的最简代码了，包括注册这个窗体，获取的窗体句柄，消息循环和窗口过程回调函数。其实在vs中创建windows应用的话，vs会直接生成这些代码，但要便于使用于是将其封装。

二、FrWnd类

这里将创建一个窗体个过程粗暴地封装成了FrWnd类，将窗口过程和Display设计成回调函数，Display函数负责写窗体的绘制语句，在注册新窗体时传入即可。

#include<windows.h>
#include<tchar.h>
#include<functional>

#define WINPARAMETERS HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR pCmdLine, int nShowCmd
#define INITPARAMETERS hInstance, nShowCmd

class FrWnd {
public:
	FrWnd();
	FrWnd(int _height, int _width, WNDPROC proc, std::function<bool()> callback, LPCSTR _name);

	HWND GetHandle();
	bool Create(HINSTANCE instanceHandle, int show);
	int Run();

private:
	HWND hwnd;
	LPCSTR name;
	int height;
	int width;
	WNDPROC proc;
	std::function<bool()> Display;
};

FrWnd::FrWnd() {
	height = 800;
	width = 600;
	name = _T("Test");
}

FrWnd::FrWnd(int _height, int _width, WNDPROC _proc, std::function<bool()> callback, LPCSTR _name = _T("Test")) {
	height = _height;
	width = _width;
	Display = callback;
	name = _name;
	proc = _proc;
}


bool FrWnd::Create(HINSTANCE instanceHandle, int show) {
	WNDCLASS wc;
	wc.style = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc = proc;
	wc.cbClsExtra = 0;
	wc.cbWndExtra = 0;
	wc.hInstance = instanceHandle;
	wc.hIcon = LoadIcon(0, IDI_APPLICATION);
	wc.hCursor = LoadCursor(0, IDC_ARROW);
	wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wc.lpszMenuName = 0;
	wc.lpszClassName = _T("BasicWndClass");

	if (!RegisterClass(&wc)) {
		MessageBox(0, _T("RegisterClass FAILED"), 0, 0);
		return false;
	}

	hwnd = CreateWindow(
		_T("BasicWndClass"),
		name,
		WS_OVERLAPPEDWINDOW,
		CW_USEDEFAULT,
		CW_USEDEFAULT,
		height,
		width,
		0,
		0,
		instanceHandle,
		0
	);

	if (hwnd == 0) {
		MessageBox(0, _T("CreateWindow FAILED"), 0, 0);
		return false;
	}

	ShowWindow(hwnd, show);
	UpdateWindow(hwnd);

	return true;
}

int FrWnd::Run() {
	MSG msg = { 0 };
	while (msg.message != WM_QUIT) {
		if (PeekMessage(&msg, 0, 0, 0, PM_REMOVE)) {
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
		else {
			Display();	//此处为回调函数
		}
	}
	return (int)msg.wParam;
}

HWND FrWnd::GetHandle() {
	return hwnd;
}

示例：

#include"frwnd.h"

LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
	switch (msg) {
	case WM_CLOSE:
		DestroyWindow(hWnd);
		break;
	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hWnd, msg, wParam, lParam);
}

bool Display() {}
FrWnd myWnd(480, 640, WndProc, Display, "test");

int WINAPI WinMain(WINPARAMETERS) {
	if (!myWnd.Create(INITPARAMETERS))
		return 0;
	myWnd.Run();
	return 0;
}

此时，就创建了一个窗体。