Restore AbstractButton::checkable

In 7a8f055, we hid the checkable property from QQuickAbstractButton and
exposed it only in QQuickButton and QQuickMenuItem. The reasoning was
that QQuickCheckBox, QQuickRadioButton, QQuickSwitch and their delegate
counterparts are inherently checkable, so having the checkable property
available in QML didn't seem to make sense.

While this still holds true, there are other factors to take into
consideration. AbstractButton is meant to be a generic base class for
all types of buttons, but the lack of a checkable property makes it
unusable as a base class for custom QML-based checkable buttons.

If we want to a hide the checkable property from CheckBox, RadioButton,
and Switch to avoid having it popup in the auto-completion list, we can
probably do it in a less disruptive way via tooling.

[ChangeLog][Controls][AbstractButton] The checkable property has been
made accessible from QML. Previously it was only exposed for Button and
MenuItem, but it is now available for any AbstractButton to make it
possible to create custom QML-based checkable buttons.

Task-number: QTBUG-51554
Change-Id: I19e29fc87cd15811c43c9b9ebb29701d66cde72f
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

6 files changed, 20 insertions, 49 deletions

diff --git a/src/quicktemplates2/qquickabstractbutton.cpp b/src/quicktemplates2/qquickabstractbutton.cpp
index e7c34065..2615608f 100644
--- a/src/quicktemplates2/qquickabstractbutton.cpp
+++ b/src/quicktemplates2/qquickabstractbutton.cpp
@@ -330,6 +330,8 @@ void QQuickAbstractButton::setPressed(bool isPressed)
     \qmlproperty bool QtQuick.Controls::AbstractButton::checked
 
     This property holds whether the button is checked.
+
+    \sa checkable
 */
 bool QQuickAbstractButton::isChecked() const
 {
@@ -352,11 +354,21 @@ void QQuickAbstractButton::setChecked(bool checked)
     emit checkedChanged();
 }
 
-// We define these in QQuickAbstractButton without exposing checkable as a
-// property, and instead expose it as a property in QQuickButton.
-// QQuickRadioButton, QQuickSwitch and QQuickCheckBox are checkable by default,
-// but if we removed the checkable code from here, they'd each have to
-// duplicate it.
+/*!
+    \qmlproperty bool QtQuick.Controls::AbstractButton::checkable
+
+    This property holds whether the button is checkable.
+
+    A checkable button toggles between checked (on) and unchecked (off) when
+    the user clicks on it or presses the space bar while the button has active
+    focus.
+
+    Setting \l checked to \c true forces this property to \c true.
+
+    The default value is \c false.
+
+    \sa checked
+*/
 bool QQuickAbstractButton::isCheckable() const
 {
     Q_D(const QQuickAbstractButton);
@@ -372,6 +384,7 @@ void QQuickAbstractButton::setCheckable(bool checkable)
     d->checkable = checkable;
     setAccessibleProperty("checkable", checkable);
     checkableChange();
+    emit checkableChanged();
 }
 
 /*!
diff --git a/src/quicktemplates2/qquickabstractbutton_p.h b/src/quicktemplates2/qquickabstractbutton_p.h
index 779739de..97b5c06b 100644
--- a/src/quicktemplates2/qquickabstractbutton_p.h
+++ b/src/quicktemplates2/qquickabstractbutton_p.h
@@ -61,6 +61,7 @@ class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickAbstractButton : public QQuickContr
     Q_PROPERTY(bool down READ isDown WRITE setDown NOTIFY downChanged RESET resetDown FINAL)
     Q_PROPERTY(bool pressed READ isPressed NOTIFY pressedChanged FINAL)
     Q_PROPERTY(bool checked READ isChecked WRITE setChecked NOTIFY checkedChanged FINAL)
+    Q_PROPERTY(bool checkable READ isCheckable WRITE setCheckable NOTIFY checkableChanged FINAL)
     Q_PROPERTY(bool autoExclusive READ autoExclusive WRITE setAutoExclusive NOTIFY autoExclusiveChanged FINAL)
     Q_PROPERTY(QQuickItem *indicator READ indicator WRITE setIndicator NOTIFY indicatorChanged FINAL)
 
@@ -107,6 +108,7 @@ Q_SIGNALS:
     void downChanged();
     void pressedChanged();
     void checkedChanged();
+    void checkableChanged();
     void autoExclusiveChanged();
     void indicatorChanged();
 
diff --git a/src/quicktemplates2/qquickbutton.cpp b/src/quicktemplates2/qquickbutton.cpp
index 3d00e40c..b11d2179 100644
--- a/src/quicktemplates2/qquickbutton.cpp
+++ b/src/quicktemplates2/qquickbutton.cpp
@@ -96,28 +96,6 @@ QQuickButton::QQuickButton(QQuickButtonPrivate &dd, QQuickItem *parent) :
 }
 
 /*!
-    \qmlproperty bool QtQuick.Controls::Button::checkable
-
-    This property holds whether the button is checkable.
-
-    A checkable button toggles between checked (on) and unchecked (off) when
-    the user clicks on it or presses the space bar while the button has active
-    focus.
-
-    Setting \l {AbstractButton::}{checked} to \c true forces this property to
-    \c true.
-
-    The default value is \c false.
-
-    \sa CheckBox, Switch
-*/
-
-void QQuickButton::checkableChange()
-{
-    emit checkableChanged();
-}
-
-/*!
     \qmlproperty bool QtQuick.Controls::Button::autoRepeat
 
     This property holds whether the button repeats
diff --git a/src/quicktemplates2/qquickbutton_p.h b/src/quicktemplates2/qquickbutton_p.h
index 95f94f10..5edbbe4e 100644
--- a/src/quicktemplates2/qquickbutton_p.h
+++ b/src/quicktemplates2/qquickbutton_p.h
@@ -57,7 +57,6 @@ class QQuickButtonPrivate;
 class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickButton : public QQuickAbstractButton
 {
     Q_OBJECT
-    Q_PROPERTY(bool checkable READ isCheckable WRITE setCheckable NOTIFY checkableChanged FINAL)
     Q_PROPERTY(bool autoRepeat READ autoRepeat WRITE setAutoRepeat NOTIFY autoRepeatChanged FINAL)
     Q_PROPERTY(bool highlighted READ isHighlighted WRITE setHighlighted NOTIFY highlightedChanged FINAL)
     Q_PROPERTY(bool flat READ isFlat WRITE setFlat NOTIFY flatChanged FINAL)
@@ -72,7 +71,6 @@ public:
     void setFlat(bool flat);
 
 Q_SIGNALS:
-    void checkableChanged();
     void autoRepeatChanged();
     void highlightedChanged();
     void flatChanged();
@@ -80,7 +78,6 @@ Q_SIGNALS:
 protected:
     QQuickButton(QQuickButtonPrivate &dd, QQuickItem *parent);
 
-    void checkableChange() override;
     void autoRepeatChange() override;
 
     QFont defaultFont() const override;
diff --git a/src/quicktemplates2/qquickmenuitem.cpp b/src/quicktemplates2/qquickmenuitem.cpp
index 564d3f38..cb23df07 100644
--- a/src/quicktemplates2/qquickmenuitem.cpp
+++ b/src/quicktemplates2/qquickmenuitem.cpp
@@ -110,22 +110,6 @@ QQuickMenuItem::QQuickMenuItem(QQuickItem *parent) :
     connect(this, &QQuickAbstractButton::clicked, this, &QQuickMenuItem::triggered);
 }
 
-/*!
-    \qmlproperty bool QtQuick.Controls::MenuItem::checkable
-
-    This property holds whether the menu item is checkable.
-
-    A checkable menu item toggles between checked (on) and unchecked (off) when
-    the user clicks on it or interacts with it via the keyboard.
-
-    \sa {AbstractButton::}{checked}
-*/
-
-void QQuickMenuItem::checkableChange()
-{
-    emit checkableChanged();
-}
-
 QFont QQuickMenuItem::defaultFont() const
 {
     return QQuickControlPrivate::themeFont(QPlatformTheme::MenuItemFont);
diff --git a/src/quicktemplates2/qquickmenuitem_p.h b/src/quicktemplates2/qquickmenuitem_p.h
index 6c717e13..258a096f 100644
--- a/src/quicktemplates2/qquickmenuitem_p.h
+++ b/src/quicktemplates2/qquickmenuitem_p.h
@@ -57,7 +57,6 @@ class QQuickMenuItemPrivate;
 class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickMenuItem : public QQuickAbstractButton
 {
     Q_OBJECT
-    Q_PROPERTY(bool checkable READ isCheckable WRITE setCheckable NOTIFY checkableChanged FINAL)
     Q_PROPERTY(bool highlighted READ isHighlighted WRITE setHighlighted NOTIFY highlightedChanged FINAL)
 
 public:
@@ -67,12 +66,10 @@ public:
     void setHighlighted(bool highlighted);
 
 Q_SIGNALS:
-    void checkableChanged();
     void triggered();
     void highlightedChanged();
 
 protected:
-    void checkableChange() override;
     QFont defaultFont() const override;
 
 #ifndef QT_NO_ACCESSIBILITY