编程

GetHDSerial编译不通过

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源码参见https://www.codeleading.com/article/62852336906/
提示

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error C2065: “STORAGE_PROPERTY_QUERY”: 未声明的标识符
error C2065: “StorageDeviceProperty”: 未声明的标识符
error C2065: “PropertyStandardQuery”: 未声明的标识符
error C2065: “IOCTL_STORAGE_QUERY_PROPERTY”: 未声明的标识符

按F1在msdn上查到的可能结果为

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#include <Ntddstor.h>

但加了还是编译不通过，其实正确的是只要加入

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#include <WinIoCtl.h>

refer to: https://stackoverflow.com/questions/4420632/i-dont-know-what-problem-it-is-error-error-c2065-storage-property-query

Qt备忘录

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程序启动时去掉dos窗口

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#pragma comment(linker, "/subsystem:windows /entry:mainCRTStartup")

DoModal

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	DlgTst dlg(this);
	int result = dlg.exec();
	if (QDialog::Accepted == result)
		QMessageBox::information(this, "title", "done.");

Modelless

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	DlgTst* dlg2 = new DlgTst(this);
//	dlg2->setModal(Qt::ApplicationModal);
	dlg2->show();

嵌入子对话框

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	setWindowFlags(Qt::CustomizeWindowHint | Qt::FramelessWindowHint);

保持对话框前置，类似于MFC的SetOwner

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	setWindowFlags(Qt::Dialog);

PostMessage
signal slot connect的默认行为类似于SendMessage，如果要实现PostMessage的行为，connect时加参数Qt::QueuedConnection。

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class MainWindow : public QMainWindow
{
	...
private slots:
	void on_pushButton_clicked();
	void on_pushButton_2_clicked();
signals:
	void mySignal1();
};
 
MainWindow::MainWindow(QWidget* parent)
{
	...
	connect(this, SIGNAL(mySignal1()), SLOT(on_pushButton_2_clicked()), Qt::QueuedConnection);
}
 
void MainWindow::on_pushButton_clicked()
{
	QMessageBox::information(this, "title", "on_pushButton_clicked 1");
	emit mySignal1();
	QMessageBox::information(this, "title", "on_pushButton_clicked 2");
}
 
void MainWindow::on_pushButton_2_clicked()
{
	QMessageBox::information(this, "title", "B");
}

安装完qt-vs-tools-msvc2013-2.0.0.vsix后，重启vs2013，工程项目右键菜单上qt功能选项为灰色无效，怎么办？
打开.vcxproj修改

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<Keyword>Win32Proj</Keyword>

为

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<Keyword>Qt4VSv1.0</Keyword>

再重启vs，在工程上右键菜单上点击“Convert Project to Qt VS Tools Project”。

生成要翻译的语言文件

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lupdate hello.pro -ts lang.ts
# or in cmake
add_custom_target(tr COMMAND ${Qt5_LUPDATE_EXECUTABLE} -target-language en ${Srcs} -ts "${CMAKE_CURRENT_SOURCE_DIR}/lang.ts")
lrelease lang.ts -qm lang.qm

窗口上画矩形

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void DlgTst01::paintEvent(QPaintEvent *e)
{
	QPainter painter(this);
	painter.setBrush(Qt::red);
	painter.setPen(Qt::red);
	painter.drawRect(QRect(0, 0, this->width(), this->height()));
}

支持c++20

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# CMakeLists.txt
set(CMAKE_CXX_STANDARD 20)

禁止背景重绘

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ui->widgetVideo->setUpdatesEnabled(false);

皮肤skin
https://blog.csdn.net/weixin_42126427
http://t.zoukankan.com/luoxiang-p-13528745.html

无边框窗体的拖动和改变大小
https://www.cnblogs.com/warmlight/p/12841968.html
https://blog.csdn.net/zhushentian/article/details/82021838

Qt Style Sheets Reference
export QT_DEBUG_PLUGINS=1

refer to:
https://blog.csdn.net/qq_24127015/article/details/95118124
https://blog.csdn.net/zyx4843/article/details/50682212
https://blog.csdn.net/ermzdy2/article/details/99692954
https://blog.csdn.net/aaa123524457/article/details/80582978
http://www.myexception.cn/qt/1119616.html
https://blog.csdn.net/hl1hl/article/details/85244451
https://stackoverflow.com/questions/48187569/qt-translation-file-is-removed-on-make-clean-using-cmake

whether go through tcp or udp using EuhatRtsp

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app/src/main/java/com/euhat/rtsp/euhatrtspdemo/MainActivity.java

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// try to modify the 3rd parameter to 0.
mEuhatPlayer.open(url, 8000, 0, 1000, fps, 300);

How to record the H264 stream using EuhatRtsp lib

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euhatrtsp/livevideo/RtspOp.cpp

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int EuhatRtspOp::decodingProc()
{
…
//frame是原始H264数据，在这里录像最好，此库已经把ffmpeg库编译进去了，直接用ffmpeg库就可以完成录像功能。
//可以网上搜ffmpeg录像api怎么用。
//这就要求会写C++代码，还要加jni接口提供给java端打开或关闭录像功能。
decoder_->decode(frame + 4, *(int *)frame);
…
}

VC编译程序时忽略link警告

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比如在链接时会出现一大堆warning LNK4099，在代码中写

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#pragma warning(disable:4099)

是无法禁止这些警告的，正确方法是在项目属性Properties->Linker->Command Line中添加

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/ignore:4099

popen返回NULL

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当程序写得越来越大，进程占用的内存也就越来越多，调用popen时会返回空的FILE指针，网上说原因是system或popen这样的系统函数，其内部实现是调用fork函数创建子进程，创建过程中会复制父进程堆、栈等资源，这样就容易造成创建失败，返回NULL。

以下是我写的用vfork替换fork调用的Vpopen类。

Vpopen.h

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#pragma once
 
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
 
class Vpopen
{
        FILE *fp_;
        pid_t pid_;
        int pipeFd_[2];
public:
        Vpopen();
        ~Vpopen();
        FILE *open(const char *cmd, const char *flags);
        void close();
};

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win32渐变颜色矩形函数

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#define FILL_STYLE_VERTICAL	0
#define FILL_STYLE_HORIZONTAL	1
 
void fillGradientRect(HDC hdc, RECT *rc, COLORREF fromRGB, COLORREF toRGB, int fillStyle)
{
	BITMAPINFO bmpInfo;
	memset(&bmpInfo, 0, sizeof(bmpInfo));
	bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bmpInfo.bmiHeader.biWidth = rc->right - rc->left;
	bmpInfo.bmiHeader.biHeight = rc->bottom - rc->top;
	bmpInfo.bmiHeader.biPlanes = 1;
	bmpInfo.bmiHeader.biBitCount = 32;
	bmpInfo.bmiHeader.biCompression = BI_RGB;
 
	BYTE *rgbBuffer = (BYTE *)malloc(bmpInfo.bmiHeader.biWidth * bmpInfo.bmiHeader.biHeight * 4);
 
	int width = bmpInfo.bmiHeader.biWidth;
	int height = bmpInfo.bmiHeader.biHeight;
 
	int rStart = fromRGB & 0xFF;
	int rEnd = toRGB & 0xFF;
	int gStart = (fromRGB & 0xFF00) >> 8;
	int gEnd = (toRGB & 0xFF00) >> 8;
	int bStart = (fromRGB & 0xFF0000) >> 16;
	int bEnd = (toRGB & 0xFF0000) >> 16;
	if (FILL_STYLE_VERTICAL == fillStyle)
	{
		double rStep = (rEnd - rStart) * 1.0 / height;
		double gStep = (gEnd - gStart) * 1.0 / height;
		double bStep = (bEnd - bStart) * 1.0 / height;
		for (int y = 0; y < height; y++)
		{
			BYTE r = (BYTE)(rStart + rStep * y);
			BYTE g = (BYTE)(gStart + gStep * y);
			BYTE b = (BYTE)(bStart + bStep * y);
			for (int x = 0; x < width; x++)
			{
				BYTE *p = rgbBuffer + ((height - y) * width - (width - x)) * 4;
				*p++ = b;
				*p++ = g;
				*p++ = r;
			}
		}
	}
	else
	{
		double rStep = (rEnd - rStart) * 1.0 / width;
		double gStep = (gEnd - gStart) * 1.0 / width;
		double bStep = (bEnd - bStart) * 1.0 / width;
		for (int x = 0; x < width; x++)
		{
			BYTE r = (BYTE)(rStart + rStep * x);
			BYTE g = (BYTE)(gStart + gStep * x);
			BYTE b = (BYTE)(bStart + bStep * x);
			for (int y = 0; y < height; y++)
			{
				BYTE *p = rgbBuffer + ((height - y) * width - (width - x)) * 4;
				*p++ = b;
				*p++ = g;
				*p++ = r;
			}
		}
	}
 
	StretchDIBits(hdc, rc->left, rc->top, width, height, 0, 0, width, height, rgbBuffer, &bmpInfo, DIB_RGB_COLORS, SRCCOPY);
 
	free(rgbBuffer);
}
 
void CMFCApplicationDlg::OnPaint()
{
	CPaintDC dc(this);
	CRect rc(50, 50, 200, 200);
	fillGradientRect(dc.m_hDC, rc, RGB(255, 0, 255), RGB(0, 255, 0), FILL_STYLE_HORIZONTAL);
 
	CDialogEx::OnPaint();
}

win32发消息触发窗口拖动

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	::ReleaseCapture();
	::SendMessage(m_hWnd, WM_NCLBUTTONDOWN, HTCAPTION, NULL);
	::SendMessage(m_hWnd, WM_LBUTTONUP, NULL, NULL);