C++ 改變螢幕解析度

Change Screen Resolution in Windows using C++

主要使用 Windows API
ChangeDisplaySettings
及
EnumDisplaySettings

首先使用 EnumDisplaySettings 取得目前的螢幕設定值
然後修改解析度的寬高
最後使用 ChangeDisplaySettings 更新螢幕設定值

=== 程式範例
#include "windows.h"
#include <string>
#include <iostream>

int main(int argc, char* argv[])
{
if (argc == 3)
{
try
{
unsigned long width = std::stoul(argv[1]);
unsigned long height = std::stoul(argv[2]);


DEVMODE *dm = new DEVMODE();
EnumDisplaySettings(NULL, ENUM_CURRENT_SETTINGS, dm);
dm->dmPelsWidth = width;
dm->dmPelsHeight = height;
ChangeDisplaySettings(dm, CDS_UPDATEREGISTRY);
}
catch (std::invalid_argument e)
{
std::cout << e.what() << std::endl;
}
}

return 0;
}



=== 資料來源
How to change screen resolution using QT, OpenGL, C++, and Linux?
http://stackoverflow.com/questions/11387724/how-to-change-screen-resolution-using-qt-opengl-c-and-linux

How to change screen resolution in Windows using Qt
http://eastfist.com/qt_tutorials/how-to-change-screen-resolution-in-windows-using-qt/

ChangeDisplaySettings function
https://msdn.microsoft.com/en-us/library/dd183411(VS.85).aspx

Qt 如何將 UTF-8 檔案轉存為 UTF-16

之前的文章介紹如何讀取 UTF-8 檔案。
Qt 如何從檔案讀取 UTF-8 的中文
這次介紹如何將 UTF-8 檔案轉存為 UTF-16。

使用 QFile 開啟檔案，
使用 QTextStream 處理編碼，

=== 完整範例
QFile fileIn("input.txt");
if (!fileIn.open(QIODevice::ReadOnly | QIODevice::Text))
{
qDebug() << "fileIn opne fail.";
return;
}

QFile fileOut("output.txt");
if (!fileOut.open(QIODevice::WriteOnly | QIODevice::Text))
{
qDebug() << "fileOut opne fail.";
return;
}

QTextStream in(&fileIn);
in.setCodec("UTF-8");
QTextStream out(&fileOut);
out.setCodec("UTF-16");

while (!in.atEnd()) {
QString line = in.readLine();
out << changeText(line);
}

fileIn.close();
fileOut.close();

qDebug() << "done";

=== 資料來源
Qt Documentation - QTextStream Class
http://doc.qt.io/qt-5/qtextstream.html

Qt PostgreSQL 範例

Qt PostgreSQL 範例

=== 測試環境
OS: Windows 7
Qt Verstion: 5.5.0
Compiler: Visual Studio 2013

OS: Arch Linux 4.1.6
Qt Version: 5.5.0
Compiler: GCC 5.2.0

=== 程式範例

	QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
	db.setHostName("127.0.0.1");
	db.setDatabaseName("FirstDB");
	db.setUserName("demo");
	db.setPassword("password");
	bool ok = db.open();
	if (ok)
	{
	QSqlQuery query("SELECT \"SID\", \"Account\", \"CreateDate\", \"LoginTimes\" FROM \"Account\"");
	while (query.next())
	{
	qWarning() << query.value(0).toString();
	qWarning() << query.value(1).toString();
	qWarning() << query.value(2).toString();
	qWarning() << query.value(3).toString();
	}
	qDebug() << query.lastError().text();
	}

view raw sql.cpp hosted with ❤ by GitHub

=== 錯誤訊息
QSqlDatabase: QPSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QODBC QODBC3 QPSQL QPSQL7

在 Windows，確認下列檔案
MyAppDir\sqldrivers\qsqlpsql.dll
MyAppDir\libpq.dll
MyAppDir\libeay32.dll
MyAppDir\ssleay32.dll

在 linux，確認 qt project file 加上
INCLUDEPATH+=/usr/include/pgsql
LIBS+=-L/usr/lib -lpq

=== 資料來源
Qt Documentation - SQL Database Drivers
http://doc.qt.io/qt-5/sql-driver.html

Qt: SELECT-Query to PostgreSQL-Server always responses with NULL
http://stackoverflow.com/questions/13633055/qt-select-query-to-postgresql-server-always-responses-with-null

QT5: Failed to load psql driver in windows
http://stackoverflow.com/questions/20884010/qt5-failed-to-load-psql-driver-in-windows