Qt widget not updating

15-Mar-2020 23:14 by 8 Comments

Qt widget not updating - 101 rules for dating

Without this, we will not see the LED widget in the Designer palette.

On lines 173 to 178, we set the final color of the gradient to black if the state variable is false (off), or to the value of the color property. Finally, on lines 185 to 188, we turn on a timer to the flash rate property value if the flash property is true, or we turn off the timer if the flash property is false. We can insert it into layouts programmatically and we can use promotion in Qt Designer to place LED widgets into designs.

The problem with using promotion is that the appearance and behavior of the promoted widget doesn't appear in Designer.

We have to actually compile and run our form to see how the LED lays out.

The example we will work through is an LED (Light Emitting Diode) object.

It is designed to be a realistic representation of the real thing: The diameter of the LED is measured in millimeters (like real LEDs) and can be any color you want ( real LEDs).

This blog post will describe how to write a custom Qt widget and how to integrate it into Qt Designer so that you can drag and drop it onto your designs.

It will also provide an understanding of important differences between Qt 4 and Qt 5 when it comes to creating designable widgets.

More importantly for our purposes, properties are exposed in the Qt Designer property editor.

Lines 13 to 18 specify six properties of the LED widget.

The last item we need to look at is our qmake file, 5 greater Than(QT_MAJOR_VERSION, 4) 8 9 less Than(QT_MAJOR_VERSION, 5) 12 13 CONFIG = plugin release 14 15 TEMPLATE = lib 16 TARGET = $$qt Library Target($$TARGET) 17 = $$[QT_INSTALL_PLUGINS]/designer 18 INSTALLS = target 19 20 INCLUDEPATH = .

21 22 # Input 23 HEADERS = LED.h LEDPlugin.h 24 SOURCES = needs to be added to the CONFIG variable.

In Qt 5, it needs to be added to the QT variable instead.