Environmental variables for Calligra

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PWD_DIR=/home/work/kde/calligra/build
INST_DIR=$PWD_DIR/installed
 
export XDG_DATA_DIRS=$INST_DIR/share:$XDG_DATA_DIRS
export XDG_CONFIG_DIRS=$INST_DIR/etc/xdg:$XDG_CONFIG_DIRS
export PATH=$INST_DIR/bin:$PATH
export QT_PLUGIN_PATH=$INST_DIR/lib64/plugins:$INST_DIR/lib/plugins:$INST_DIR/lib/x86_64-linux-gnu/plugins:$QT_PLUGIN_PATH
export QML_IMPORT_PATH=$INST_DIR/lib64/qml:$INST_DIR/lib/qml:$INST_DIR/lib/x86_64-linux-gnu/qml
export QML2_IMPORT_PATH=$INST_DIR/lib64/qml:$INST_DIR/lib/qml:$INST_DIR/lib/x86_64-linux-gnu/qml
 
export XDG_CONFIG_HOME=$HOME/kde/Settings
export KDETMP=/tmp/kdedev-$USER
export KDEVARTMP=/var/tmp/kdedev-$USER
export KDESYCOCA=$KDEVARTMP/ksycoca
 
mkdir -p $KDETMP
mkdir -p $KDEVARTMP

refer to:
https://community.kde.org/Calligra/Building/3

ERROR 2003 (HY000): Can't connect to MySQL server on ... 113

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telnet 192.168.1.165 3306
 
# firewall in ubuntu
sudo ufw disable
 
# or found ip changed
vi /etc/mysql/mysql.conf.d/mysqld.cnf
systemctl restart mysql
systemctl status mysql

refer to:
https://blog.csdn.net/zhangasas/article/details/89432832

Recording video or audio in Windows

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ffmpeg -f dshow -list_devices true -i dummy
 
# can only play one instance simultaneously
ffplay -f dshow -i video="Integrated Webcam"
 
# can play multiple instances
ffmpeg -f dshow -i audio="Microphone (Realtek(R) Audio)" out2.wav
 
# record screen sound,
# if "Stereo Mix..." is not displayed, activate it in Sound Settings of Windows Control Panel.
ffmpeg -f dshow -i audio="Stereo Mix (Realtek Audio)" C:\Users\fatiw\Desktop\Audio\output.mp3

refer to:
https://blog.csdn.net/qq_43627907/article/details/124416450
compiled ok in Qt5.15.2.

https://blog.csdn.net/how0723/article/details/77418421
https://zhuanlan.zhihu.com/p/31348306
search 'QAudioOutput' in Qt Creator Examples.

https://blog.csdn.net/jlf521521/article/details/106689503
QT5使用QCustomplot绘制频谱瀑布图并封快速傅里叶变换fft类
https://blog.csdn.net/u013915524/article/details/122288358

https://www.addictivetips.com/windows-tips/record-system-sound-with-ffmpeg-on-windows-10/

Compile gdb

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./configure --prefix=`pwd`/installed --with-python=/usr/bin/python3
make -j 16
make install
cp -Rf /usr/share/gdb/auto-load `pwd`/installed/share/gdb/

Remote desktop between Ubuntus

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sudo apt install tigervnc-common
sudo apt install tigervnc-standalone-server
#vncpasswd
vncserver -localhost no -geometry 1280x720 :1
vncserver -list

Authentication required?

Empty ~/.vnc/passwd and

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#/etc/xdg/autostart$ sudo vi org.gnome.SettingsDaemon.Color.desktop
X-GNOME-Autostart-enabled=false

then reboot the server.

refer to:
https://blog.csdn.net/Naisu_kun/article/details/123007055