Small Step Systems

Latest posts — page 13

Using Qt under LGPLv3

At Qt Day 2019 in Florence, Italy, I gave a talk Using Qt under LGPLv3. In the first part The obligations of Qt LGPLv3: made understandable, I explain in detail, how you must provide the source code, the license texts,

Using Docker Containers for Yocto Builds

We want to build a custom Linux image with Yocto for the Raspberry Pi 3 model B (BCM2837). The Linux image contains a very simple Internet radio application using Qt 5.11 and the eglfs graphics backend. Our colleagues shall

Tremendous Speed-Up with SQL Transactions

The function CustomerDatabase::importCustomers reads 500 customers from the list c_customers, creates an SQL query cmd for each customer and inserts each customer into the Customers table of the SQL database db. void CustomerDatabase::importCustomers() { auto db = QSqlDatabase::database(

Emitting Signals during Construction or Destruction

In the beginning, the application shows the Main Screen. When the user clicks on the Open button, the application will show a second screen. The second screen creates a C++ model when opened and destroys this model when closed. As

Monitoring Sys Files with QFileSystemWatcher

When the driver turns off the ignition in a vehicle, display computers like terminals in harvesters or infotainment systems in cars should be notified. The display computers should save important data and shut down orderly. When the display computer runs

QML Engine Deletes C++ Objects Still In Use

Correction: In the original post, I stated that ownership is transferred from C++ to QML by READ functions of Q_PROPERTYs. This is wrong. Ownership is only transferred by Q_INVOKABLE functions and slots, which return a QObject pointer. I

Converting a QByteArray into an Unsigned Integer

My program received messages from a network as an array of bytes. The sender of the messages encoded integers in Big Endian format. So, the hex number 0x1540 arrived in the sequence [0x15, 0x40]. I wrote the following function, which