Qt widget not updating

25 Jan

For each property, we define "setter" and "getter" methods using the WRITE and READ parameters (leaving out the WRITE parameter makes the property read-only).

Additional parameters are described in the Qt documentation. accessor) methods are very simple - they just return the value of internal private variables. First, we handle the alignment property which specifies how the LED should fit into the space allocated to it by whatever layout within which the LED widget is contained (lines 149 to 168).

This macro allows us to add any sort of metadata we like to an object.

In this case, the Qt 5 Designer executable will not load your plug-in unless it sees the IID, a unique identifier for your plug-in.

This pulls in everything needed to make the widget designable. Properties are an important feature of the Qt meta-object system.

A property is a value that can be read and (optionally) written.

We'll start by looking at portions of the header for the LED.

The plugin implementation is almost trivial: 6 LEDPlugin:: 7 LEDPlugin(QObject* parent) : 8 QObject(parent), 9 initialized(false) 10 12 13 QString LEDPlugin:: 14 name() const 15 18 19 QString LEDPlugin:: 20 group() const 21 24 25 QString LEDPlugin:: 26 tool Tip() const 27 30 31 QString LEDPlugin:: 32 whats This() const 33 36 37 QString LEDPlugin:: 38 include File() const 39 42 43 QIcon LEDPlugin:: 44 icon() const 45 48 49 bool LEDPlugin:: 50 is Container() const 51 54 55 QWidget * LEDPlugin:: 56 create Widget(QWidget *parent) 57 60 61 #if QT_VERSION to obtain an instance of the LED widget, We simply allocate a new instance on the heap and return it. The Q_EXPORT_PLUGIN2 macro ensures that the Qt 4 Designer will see our plug-in.

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.

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.