My custom widget is not shown in Qt Creator / Qt Designer but it is shown when I execute the program

Question

I would like to have a QTabWidget with a tab containing a custom widget.

1. I created a custom Widget (consisting of a .ui, .h and .cpp file)

2. I added this custom Widget to the first page of my QTabWidget, but the content of this Widget is not shown in QtCreator's designer.

3. I promoted my custom Widget as Tab1Custom.

This setup compiles and works as expected when I run the program, but my custom control doesn't show up in QtCreator's designer.

What can I do to make my custom control show up in QtCreator's designer?

Here's the first part of MainWindow.ui:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>my title </string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <widget class="QTabWidget" name="tabWidget">
    <property name="geometry">
     <rect>
      <x>0</x>
      <y>10</y>
      <width>801</width>
      <height>551</height>
     </rect>
    </property>
    <property name="currentIndex">
     <number>0</number>
    </property>
    <widget class="Tab1Custom" name="myTab1">
     <attribute name="title">
      <string>My Tab number 1</string>
     </attribute>
    </widget>
    ....

Answer 1

This is how it works when you use a custom widget and promote it. In order to have your widget drawn with content, you have to create a DLL to extend Qt Designer. Look at "Creating Custom Widgets for Qt Designer" for more information on that.

For the most part, I don't think it's worth the effort to do this; generally speaking, it's fine that it just shows a either a blank widget or whatever base widget you promoted.