Developing a QML Keypad with TDD
Although Qt comes with a unit-test framework QuickTest for QML code, hardly any QML GUIs are unit-tested, let alone developed with TDD (test-driven development). One… Read More »Developing a QML Keypad with TDD
QML
Detecting Overdraw in QML HMIs with GammaRay
Overdraw happens when one QML item fully eclipses another QML item. The QML renderer always draws both items, although there is no need to draw the eclipsed item. You must help out the renderer by explicitly setting visible: false on the eclipsed item.
On embedded systems, heavy overdraw makes animations or flicking jerky. In the worst case, it freezes your HMI. Fortunately, the Qt experts at KDAB developed a tool, GammaRay, which makes detecting overdraw a piece of cake. I’ll show you how to build GammaRay, how to detect overdraw in the home screen of a harvester HMI, and how to fix the overdraw.
Read More »Detecting Overdraw in QML HMIs with GammaRayQt Quick 2D Renderer: Under LGPLv3 since Qt 5.8
I know that this is pretty old news. Unfortunately, it is not very well known. I have been asked half a dozen times over the last two months, whether the QML software renderer – officially known as the Qt Quick 2D renderer – is available under LGPLv3. Nobody belives me, when I answer with a firm “Yes!”.
Read More »Qt Quick 2D Renderer: Under LGPLv3 since Qt 5.8Using Qt 5.6 and Later under LGPL
Up to Qt 5.3, things were pretty simple. Most modules were under LGPLv2.1 with the exception of some commercial modules. Starting with Qt 5.4, new Qt modules were published under LGPLv3 and old modules additionally under LGPLv3. With Qt 5.6, we now have quite a patchwork of modules under different licenses. Qt 5.7 will drop LGPLv2.1 completely. Some companies stay on Qt 5.3, because they are afraid of LGPLv3. Let me bring some clarity into this patchwork and explain how you can still use Qt under LGPL and sleep well.
Read More »Using Qt 5.6 and Later under LGPL
Remote Support for Harvester Terminal via VNC
The maize harvest is in full swing. The harvester runs nearly 24/7. The driver notices a drop in the area cut per hour. He calls tech support and starts sharing the screen of the terminal in the harvester. The support technician guides guides the driver through changing some machine parameters. All is fine again. My Italian business partner, Ispirata, and I developed a VNC server for the Freescale i.MX53 terminal of Krone’s BiGX forage harvester – to make this scenario possible.
Read More »Remote Support for Harvester Terminal via VNC
Running a QML HMI on an ARM11 without OpenGL
Recently, I brought up Qt 5.5 on a Freescale i.MX35, which has an ARM11 CPU but no OpenGL support. Despite the missing OpenGL, I wanted to write the HMI with QML. The additional challenge was that the cross-compilation toolchain was 32-bit, but I wanted to use my standard 64-bit Ubuntu. I’ll show in this post how to set up the 32-bit toolchain and rootfs on my 64-bit Ubuntu machine, how to configure and build Qt 5.5 from the sources, and how to run a hello-world application written in QML on the i.MX35.Read More »Running a QML HMI on an ARM11 without OpenGL