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...
Tag: QML
Qt 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...
Using 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...
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...
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...
Responsive QML HMIs with File Selectors
In my previous post, I have shown how to use scaling to adapt QML HMIs to different screen sizes and formats. We reach the limits of scaling if we must change the structure of the HMI or if the HMI must be pixel-perfect. The solution to these problems is to provide a different implementation for...
Responsive QML HMIs with Scaling
The HMIs of in-vehicle infotainment systems, TVs, phones and many other systems must adapt to different screen resolutions and formats. This adaptation should happen with as little duplicate effort as possible. The simplest way of doing this for QML HMIs is to scale the values of all x, y, width, height, margin and border properties...