Widgets are not placed as expected in Qt Designer - qt

Question

I created the custom widget which has buttons in a horizontal layout.
But buttons are not placed correctly and shrink.
I can avoid this by setting the button size manually.
Is there any way to avoid this behavior automatically?
.ui XML code:
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>VideoPlaybackWidgetBase</class>
<widget class="QWidget" name="VideoPlaybackWidgetBase">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>790</width>
<height>58</height>
</rect>
</property>
<property name="sizePolicy">
<sizepolicy hsizetype="Minimum" vsizetype="Minimum">
<horstretch>1</horstretch>
<verstretch>1</verstretch>
</sizepolicy>
</property>
<property name="minimumSize">
<size>
<width>0</width>
<height>0</height>
</size>
</property>
<property name="maximumSize">
<size>
<width>16777215</width>
<height>58</height>
</size>
</property>
<property name="windowTitle">
<string>Form</string>
</property>
<layout class="QHBoxLayout" name="horizontalLayout_2">
<item>
<widget class="QFrame" name="horizontalFrame">
<layout class="QHBoxLayout" name="horizontalLayout">
<item>
<widget class="QPushButton" name="moveFirstButton">
<property name="sizePolicy">
<sizepolicy hsizetype="Maximum" vsizetype="Maximum">
<horstretch>0</horstretch>
<verstretch>0</verstretch>
</sizepolicy>
</property>
<property name="text">
<string>PushButton</string>
</property>
</widget>
</item>
<item>
<widget class="QPushButton" name="movePrevButton">
<property name="sizePolicy">
<sizepolicy hsizetype="Maximum" vsizetype="Maximum">
<horstretch>0</horstretch>
<verstretch>0</verstretch>
</sizepolicy>
</property>
<property name="text">
<string>PushButton</string>
</property>
</widget>
</item>
<item>
<widget class="QPushButton" name="playButton">
<property name="sizePolicy">
<sizepolicy hsizetype="Maximum" vsizetype="Maximum">
<horstretch>0</horstretch>
<verstretch>0</verstretch>
</sizepolicy>
</property>
<property name="text">
<string>PushButton</string>
</property>
</widget>
</item>
<item>
<widget class="QPushButton" name="moveNextButton">
<property name="sizePolicy">
<sizepolicy hsizetype="Maximum" vsizetype="Maximum">
<horstretch>0</horstretch>
<verstretch>0</verstretch>
</sizepolicy>
</property>
<property name="text">
<string>PushButton</string>
</property>
</widget>
</item>
<item>
<widget class="QPushButton" name="moveLastButton">
<property name="sizePolicy">
<sizepolicy hsizetype="Maximum" vsizetype="Maximum">
<horstretch>0</horstretch>
<verstretch>0</verstretch>
</sizepolicy>
</property>
<property name="text">
<string>PushButton</string>
</property>
</widget>
</item>
</layout>
</widget>
</item>
</layout>
</widget>
<resources/>
<connections/>
</ui>

Answer 1

I see Maximum size policy in the XML. Go to buttons' properties in Designer, and change size policy for example to Expanding. Also make sure the button widths are same (or with the right ratio if you want different width buttons).
Alternatively, you can keep the Maximum policy and just increase the width to what ever you want to be the maximum button width, like 2000 to allow for 10000 pixel wide future displays... There are many ways to achieve desired sizing behavior. Choose what best describes what you want, in this case perhaps MinimumExpanding.
See QSizePolicy docs.