Merge lp:~zsombi/ubuntu-ui-toolkit/theming-attached into lp:ubuntu-ui-toolkit/staging

[Zsombor Egri]

Detaching theming management from StyledItem to be reused in other cpp types.

[Zsombor Egri (zsombi)]

StyledItem was registered twice with the revision 2, so the 1.3 appeared twice in the API file. I fixed that as well.

[PS Jenkins bot (ps-jenkins)]

FAILED: Continuous integration, rev:1583
http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-ci/2071/
Executed test runs:
    FAILURE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-amd64-ci/799/console
    FAILURE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-armhf-ci/801/console
    FAILURE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-i386-ci/798/console

Click here to trigger a rebuild:
http://s-jenkins.ubuntu-ci:8080/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-ci/2071/rebuild

review: Needs Fixing (continuous-integration)

[lp:~zsombi/ubuntu-ui-toolkit/theming-attached]

1584. By Zsombor Egri on 2015-07-30

segfault fixed

[PS Jenkins bot (ps-jenkins)]

FAILED: Continuous integration, rev:1584
http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-ci/2073/
Executed test runs:
    UNSTABLE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-amd64-ci/801
    SUCCESS: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-armhf-ci/803
        deb: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-armhf-ci/803/artifact/work/output/*zip*/output.zip
    UNSTABLE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-i386-ci/800

Click here to trigger a rebuild:
http://s-jenkins.ubuntu-ci:8080/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-ci/2073/rebuild

review: Needs Fixing (continuous-integration)

[Cris Dywan (kalikiana)]

As discussed, there is no effective change in functionality in StyledItemBase so it's already covered by unit tests. We won't really know if it exposes the theming correctly until we have the first real word user of it, which is going to be the Label in C++ which can't currently inherit from StyledItemBase, so this should be the prerequisite branch.

review: Approve

[lp:~zsombi/ubuntu-ui-toolkit/theming-attached]

1585. By Zsombor Egri on 2015-08-05

staging sync

[PS Jenkins bot (ps-jenkins)]

FAILED: Continuous integration, rev:1585
http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-ci/2085/
Executed test runs:
    UNSTABLE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-amd64-ci/813
    SUCCESS: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-armhf-ci/815
        deb: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-armhf-ci/815/artifact/work/output/*zip*/output.zip
    UNSTABLE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-i386-ci/812

Click here to trigger a rebuild:
http://s-jenkins.ubuntu-ci:8080/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-ci/2085/rebuild

review: Needs Fixing (continuous-integration)

[lp:~zsombi/ubuntu-ui-toolkit/theming-attached]

1586. By Zsombor Egri on 2015-08-06

simplifying the use of theming

1587. By Zsombor Egri on 2015-08-06

staging sync

[PS Jenkins bot (ps-jenkins)]

FAILED: Continuous integration, rev:1587
http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-ci/2100/
Executed test runs:
    UNSTABLE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-amd64-ci/828
    SUCCESS: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-armhf-ci/830
        deb: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-armhf-ci/830/artifact/work/output/*zip*/output.zip
    UNSTABLE: http://jenkins.qa.ubuntu.com/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-vivid-i386-ci/827

Click here to trigger a rebuild:
http://s-jenkins.ubuntu-ci:8080/job/ubuntu-sdk-team-ubuntu-ui-toolkit-staging-ci/2100/rebuild

review: Needs Fixing (continuous-integration)

Unmerged revisions

1587. By Zsombor Egri on 2015-08-06

staging sync

1586. By Zsombor Egri on 2015-08-06

simplifying the use of theming

1585. By Zsombor Egri on 2015-08-05

staging sync

1584. By Zsombor Egri on 2015-07-30

segfault fixed

1583. By Zsombor Egri on 2015-07-30

renaming styling to theming

1582. By Zsombor Egri on 2015-07-30

API file fixed

1581. By Zsombor Egri on 2015-07-30

staging merge

1580. By Zsombor Egri on 2015-07-29

separation completed

1579. By Zsombor Egri on 2015-07-28

staging sync

=== modified file 'components.api'
--- components.api	2015-08-04 20:07:41 +0000
+++ components.api	2015-08-06 18:06:52 +0000
@@ -878,7 +878,7 @@
 Ubuntu.Components.StateSaver 1.0 0.1: QtObject
 Ubuntu.Components.StyleHints 1.3: QtObject
     property bool ignoreUnknownProperties
-Ubuntu.Components.StyledItem 1.3 1.3 1.1 1.0 0.1: Item
+Ubuntu.Components.StyledItem 1.3 1.1 1.0 0.1: Item
     property bool activeFocusOnPress 1.3
     function bool requestFocus(Qt.FocusReason reason) 1.3
     function bool requestFocus() 1.3
@@ -1238,6 +1238,7 @@
 UCStateSaverAttached: QtObject
     property bool enabled
     property string properties
+UCThemingAttached: QtObject
 Ubuntu.Components.UCUnits 1.0 0.1: QtObject
     property float gridUnit
     function float dp(float value)

=== modified file 'src/Ubuntu/Components/plugin/plugin.cpp'
--- src/Ubuntu/Components/plugin/plugin.cpp	2015-07-23 11:49:38 +0000
+++ src/Ubuntu/Components/plugin/plugin.cpp	2015-08-06 18:06:52 +0000
@@ -22,6 +22,7 @@
 
 #include "plugin.h"
 #include "uctheme.h"
+#include "ucthemingattached.h"
 #include "ucdeprecatedtheme.h"
 
 #include <QtQml/QQmlContext>
@@ -208,11 +209,11 @@
     qmlRegisterType<UCUbuntuShapeOverlay>(uri, 1, 2, "UbuntuShapeOverlay");
 
     // register 1.3 API
+    qmlRegisterType<UCThemingAttached>();
     qmlRegisterType<UCListItem13>(uri, 1, 3, "ListItem");
     qmlRegisterType<UCTheme>(uri, 1, 3, "ThemeSettings");
     qmlRegisterType<UCStyledItemBase, 2>(uri, 1, 3, "StyledItem");
     qmlRegisterSingletonType<UCNamespaceV13>(uri, 1, 3, "Ubuntu", registerUbuntuNamespace13);
-    qmlRegisterType<UCStyledItemBase, 2>(uri, 1, 3, "StyledItem");
     qmlRegisterCustomType<UCStyleHints>(uri, 1, 3, "StyleHints", new UCStyleHintsParser);
     qmlRegisterType<UCAction, 1>(uri, 1, 3, "Action");
     qmlRegisterType<UCUbuntuShape, 2>(uri, 1, 3, "UbuntuShape");

=== modified file 'src/Ubuntu/Components/plugin/plugin.pri'
--- src/Ubuntu/Components/plugin/plugin.pri	2015-07-30 09:57:45 +0000
+++ src/Ubuntu/Components/plugin/plugin.pri	2015-08-06 18:06:52 +0000
@@ -76,7 +76,8 @@
     $$PWD/ucnamespace.h \
     $$PWD/ucdeprecatedtheme.h \
     $$PWD/ucdefaulttheme.h \
-    $$PWD/ucstylehints.h
+    $$PWD/ucstylehints.h \
+    $$PWD/ucthemingattached.h
 
 SOURCES += $$PWD/plugin.cpp \
     $$PWD/uctheme.cpp \
@@ -125,7 +126,8 @@
     $$PWD/ucnamespace.cpp \
     $$PWD/ucdeprecatedtheme.cpp \
     $$PWD/ucdefaulttheme.cpp \
-    $$PWD/ucstylehints.cpp
+    $$PWD/ucstylehints.cpp \
+    $$PWD/ucthemingattached.cpp
 
 # adapters
 SOURCES += $$PWD/adapters/alarmsadapter_organizer.cpp

=== modified file 'src/Ubuntu/Components/plugin/ucstyleditembase.cpp'
--- src/Ubuntu/Components/plugin/ucstyleditembase.cpp	2015-07-29 11:41:16 +0000
+++ src/Ubuntu/Components/plugin/ucstyleditembase.cpp	2015-08-06 18:06:52 +0000
@@ -18,18 +18,16 @@
 
 #include "ucstyleditembase.h"
 #include "ucstyleditembase_p.h"
+#include "ucthemingattached.h"
 #include "uctheme.h"
 #include "ucstylehints.h"
 #include <QtQml/QQmlEngine>
 #include <QtQuick/private/qquickanchors_p.h>
 
 UCStyledItemBasePrivate::UCStyledItemBasePrivate()
-    : activeFocusOnPress(false)
-    , styleComponent(0)
-    , styleItemContext(0)
+    : styleComponent(0)
     , styleItem(0)
-    , theme(0)
-    , parentStyledItem(0)
+    , activeFocusOnPress(false)
 {
 }
 
@@ -41,10 +39,6 @@
 {
     Q_Q(UCStyledItemBase);
     q->setFlag(QQuickItem::ItemIsFocusScope);
-    QObject::connect(&UCTheme::defaultTheme(), SIGNAL(nameChanged()),
-                     q, SLOT(_q_reloadStyle()));
-    QObject::connect(&UCTheme::defaultTheme(), SIGNAL(versionChanged()),
-                     q, SLOT(_q_reloadStyle()));
 }
 
 
@@ -455,75 +449,14 @@
  */
 UCTheme *UCStyledItemBasePrivate::getTheme() const
 {
-    if (theme) {
-        return theme;
-    } else if (!parentStyledItem.isNull()) {
-        return UCStyledItemBasePrivate::get(parentStyledItem)->getTheme();
-    }
-    return &UCTheme::defaultTheme();
+    return theming ? theming->getTheme() : &UCTheme::defaultTheme();
 }
 void UCStyledItemBasePrivate::setTheme(UCTheme *newTheme)
 {
-    Q_Q(UCStyledItemBase);
-    if (theme == newTheme) {
+    if (theming && !theming->setTheme(newTheme)) {
         return;
     }
 
-    // preform pre-theme change tasks
-    preThemeChanged();
-
-    // disconnect from the previous set
-    UCTheme *connectedSet = theme ?
-                                theme :
-                                (!parentStyledItem ? &UCTheme::defaultTheme() : NULL);
-    if (connectedSet) {
-        QObject::disconnect(connectedSet, SIGNAL(nameChanged()),
-                            q, SLOT(_q_reloadStyle()));
-        QObject::disconnect(connectedSet, SIGNAL(versionChanged()),
-                            q, SLOT(_q_reloadStyle()));
-    }
-
-    UCTheme *prevSet = theme;
-
-    // resolve new theme
-    if (theme && newTheme) {
-        // no need to redo the parentStack, simply set the theme and leave
-        theme = newTheme;
-    } else {
-        theme = newTheme;
-        if (!newTheme) {
-            // redo the parent chanin
-            disconnectTillItem(0);
-            connectParents(0);
-        }
-    }
-
-    // connect to the new set
-    connectedSet = theme ?
-                    theme :
-                    (!parentStyledItem ? &UCTheme::defaultTheme() : NULL);
-    if (connectedSet) {
-        QObject::connect(connectedSet, SIGNAL(nameChanged()),
-                         q, SLOT(_q_reloadStyle()));
-        QObject::connect(connectedSet, SIGNAL(versionChanged()),
-                         q, SLOT(_q_reloadStyle()));
-    }
-    // detach previous set and attach the new one
-    if (prevSet) {
-        Q_EMIT prevSet->parentThemeChanged();
-    }
-    if (theme) {
-        // re-parent theme to make sure we have it
-        // for the entire lifetime of the styled item
-        theme->setParent(q);
-        Q_EMIT theme->parentThemeChanged();
-    }
-
-    // perform post-theme changes, update internal styling
-    postThemeChanged();
-
-    Q_EMIT q->themeChanged();
-
     // perform style reload
     if (!styleComponent) {
         preStyleChanged();
@@ -533,102 +466,22 @@
 }
 void UCStyledItemBasePrivate::resetTheme()
 {
-    setTheme(NULL);
-}
-
-// link/unlink all ascendant items until we reach a StyledItem, returns true if the
-// theme change signal emission is justified
-bool UCStyledItemBasePrivate::connectParents(QQuickItem *fromItem)
-{
-    Q_Q(UCStyledItemBase);
-    QQuickItem *item = fromItem ? fromItem : parentItem;
-    while (item) {
-        // push the item onto the stack
-        parentStack.push(QPointer<QQuickItem>(item));
-        UCStyledItemBase *styledItem = qobject_cast<UCStyledItemBase*>(item);
-        if (styledItem) {
-            // this is the closest StyledItem, connect its themeChanged() signal
-            QObject::connect(styledItem, SIGNAL(themeChanged()),
-                             q, SLOT(_q_parentStyleChanged()), Qt::DirectConnection);
-            // set the current style set to the one in the parent's one if differs
-            return setParentStyled(styledItem);
-        } else {
-            // connect to the item's parentChanged() signal so we can detect when the parent changes
-            QObject::connect(item, SIGNAL(parentChanged(QQuickItem*)),
-                             q, SLOT(_q_ascendantChanged(QQuickItem*)), Qt::DirectConnection);
-        }
-        item = item->parentItem();
-    }
-    return false;
-}
-
-// set the used parent styled item's style; returns true if the parent styled got changed
-bool UCStyledItemBasePrivate::setParentStyled(UCStyledItemBase *styledItem)
-{
-    if (parentStyledItem == styledItem) {
-        return false;
-    }
-    parentStyledItem = styledItem;
-    if (theme) {
-        Q_EMIT theme->parentThemeChanged();
-    }
-    return (theme == NULL);
-}
-
-// disconnect parent stack till item is reached; all the stack if item == 0
-void UCStyledItemBasePrivate::disconnectTillItem(QQuickItem *item)
-{
-    Q_Q(UCStyledItemBase);
-    while (!parentStack.isEmpty() && item != parentStack.top()) {
-        QPointer<QQuickItem> stackItem = parentStack.pop();
-        // the topmost item can be the only one which is a StyledItem
-        UCStyledItemBase *styledItem = qobject_cast<UCStyledItemBase*>(stackItem.data());
-        if (styledItem) {
-            QObject::disconnect(styledItem, SIGNAL(themeChanged()),
-                                q, SLOT(_q_parentStyleChanged()));
-        } else if (!stackItem.isNull()) {
-            QObject::disconnect(stackItem.data(), SIGNAL(parentChanged(QQuickItem*)),
-                                q, SLOT(_q_ascendantChanged(QQuickItem*)));
-        }
-    }
-}
-
-// captures ascendant change signal, the sender is the one which counts!
-void UCStyledItemBasePrivate::_q_ascendantChanged(QQuickItem *ascendant)
-{
-    Q_Q(UCStyledItemBase);
-    QQuickItem *sender = static_cast<QQuickItem*>(q->sender());
-    if (!sender) {
-        // cannot detect the sender, leave!
-        return;
-    }
-    if (ascendant) {
-        // disconnect from the previous ones
-        disconnectTillItem(sender);
-        parentStyledItem.clear();
-        // traverse ascendants till we reach a StyledItem or root and push them into the stack
-        if (connectParents(ascendant)) {
-            Q_EMIT q->themeChanged();
-        }
-    }
-}
-
-// syncs the ascendant StyledItem's style
-void UCStyledItemBasePrivate::_q_parentStyleChanged()
-{
-    // do not trigger themeChanged() on this item if we have a
-    // custom one, but resolve its eventual parent change!
-    if (theme) {
-        Q_EMIT theme->parentThemeChanged();
-        return;
-    }
-    Q_Q(UCStyledItemBase);
-    UCStyledItemBase *styledItem = static_cast<UCStyledItemBase*>(q->sender());
-    if (!styledItem) {
-        return;
-    }
-    setParentStyled(styledItem);
-    Q_EMIT q->themeChanged();
+    theming->setTheme(Q_NULLPTR);
+}
+
+
+void UCStyledItemBase::classBegin()
+{
+    QQuickItem::classBegin();
+
+    Q_D(UCStyledItemBase);
+    // attach theming
+    d->theming = UCThemingAttached::attachTheming(this);
+    if (d->theming) {
+        d->theming->setListener(d);
+        connect(d->theming.data(), SIGNAL(themeChanged()),
+                         this, SLOT(_q_reloadStyle()));
+    }
 }
 
 void UCStyledItemBase::componentComplete()
@@ -667,20 +520,4 @@
     return QQuickItem::childMouseEventFilter(child, event);
 }
 
-// catch parent change event so we can lookup for the parent chain theme
-void UCStyledItemBase::itemChange(ItemChange change, const ItemChangeData &data)
-{
-    QQuickItem::itemChange(change, data);
-    if (change == ItemParentHasChanged) {
-        Q_D(UCStyledItemBase);
-        // clean stack
-        d->disconnectTillItem(0);
-        // make sure we reset parent StyledItem
-        d->parentStyledItem.clear();
-        // build the stack - if possible
-        d->connectParents(0);
-        Q_EMIT themeChanged();
-    }
-}
-
 #include "moc_ucstyleditembase.cpp"

=== modified file 'src/Ubuntu/Components/plugin/ucstyleditembase.h'
--- src/Ubuntu/Components/plugin/ucstyleditembase.h	2015-06-02 12:37:41 +0000
+++ src/Ubuntu/Components/plugin/ucstyleditembase.h	2015-08-06 18:06:52 +0000
@@ -53,16 +53,14 @@
 protected:
     UCStyledItemBase(UCStyledItemBasePrivate &, QQuickItem *parent);
 
+    void classBegin();
     void componentComplete();
     void mousePressEvent(QMouseEvent *event);
     bool childMouseEventFilter(QQuickItem *child, QEvent *event);
-    void itemChange(ItemChange, const ItemChangeData &);
 
 private:
     Q_DECLARE_PRIVATE(UCStyledItemBase)
     Q_PRIVATE_SLOT(d_func(), void _q_styleResized())
-    Q_PRIVATE_SLOT(d_func(), void _q_ascendantChanged(QQuickItem*))
-    Q_PRIVATE_SLOT(d_func(), void _q_parentStyleChanged())
     Q_PRIVATE_SLOT(d_func(), void _q_reloadStyle())
 };
 

=== modified file 'src/Ubuntu/Components/plugin/ucstyleditembase_p.h'
--- src/Ubuntu/Components/plugin/ucstyleditembase_p.h	2015-06-02 12:37:41 +0000
+++ src/Ubuntu/Components/plugin/ucstyleditembase_p.h	2015-08-06 18:06:52 +0000
@@ -21,10 +21,11 @@
 
 #include <QtQuick/private/qquickitem_p.h>
 #include "ucstyleditembase.h"
+#include "ucthemingattached.h"
 
 class QQuickMouseArea;
 class UCStyledItemBase;
-class UCStyledItemBasePrivate : public QQuickItemPrivate
+class UCStyledItemBasePrivate : public QQuickItemPrivate, public UCThemeChangeListener
 {
     Q_DECLARE_PUBLIC(UCStyledItemBase)
 public:
@@ -35,8 +36,6 @@
 
     void _q_reloadStyle();
     void _q_styleResized();
-    void _q_ascendantChanged(QQuickItem *ascendant);
-    void _q_parentStyleChanged();
 
     UCStyledItemBasePrivate();
     virtual ~UCStyledItemBasePrivate();
@@ -61,25 +60,19 @@
     void setTheme(UCTheme *theme);
     void resetTheme();
 
-    virtual void preThemeChanged(){}
-    virtual void postThemeChanged(){}
+    void preThemeChanged(){}
+    void postThemeChanged(){}
 
 public:
-    bool activeFocusOnPress:1;
     QString styleDocument;
+    QPointer<UCThemingAttached> theming;
+    QPointer<QQmlContext> styleItemContext;
     QQmlComponent *styleComponent;
-    QPointer<QQmlContext> styleItemContext;
     QQuickItem *styleItem;
-    UCTheme *theme;
-    QPointer<UCStyledItemBase> parentStyledItem;
+    bool activeFocusOnPress:1;
 
 protected:
-    QStack< QPointer<QQuickItem> > parentStack;
-
     void connectStyleSizeChanges(bool attach);
-    bool connectParents(QQuickItem *fromItem);
-    bool setParentStyled(UCStyledItemBase *styledItem);
-    void disconnectTillItem(QQuickItem *item);
 };
 
 #endif // UCSTYLEDITEMBASE_P_H

=== modified file 'src/Ubuntu/Components/plugin/uctheme.cpp'
--- src/Ubuntu/Components/plugin/uctheme.cpp	2015-07-20 12:56:17 +0000
+++ src/Ubuntu/Components/plugin/uctheme.cpp	2015-08-06 18:06:52 +0000
@@ -24,6 +24,7 @@
 #include "i18n.h"
 #include "ucfontutils.h"
 #include "ucstyleditembase_p.h"
+#include "ucthemingattached.h"
 
 #include <QtQml/qqml.h>
 #include <QtQml/qqmlinfo.h>
@@ -422,10 +423,9 @@
  */
 UCTheme *UCTheme::parentTheme()
 {
-    UCStyledItemBase *owner = qobject_cast<UCStyledItemBase*>(parent());
-    UCStyledItemBasePrivate *pOwner = owner ? UCStyledItemBasePrivate::get(owner) : NULL;
-    if (pOwner && pOwner->theme == this && pOwner->parentStyledItem) {
-        return UCStyledItemBasePrivate::get(pOwner->parentStyledItem)->getTheme();
+    UCThemingAttached *theming = itemTheming(static_cast<QQuickItem*>(parent()));
+    if (theming && theming->m_theme == this && theming->m_parentTheming) {
+        return theming->m_parentTheming->getTheme();
     }
     return NULL;
 }

=== added file 'src/Ubuntu/Components/plugin/ucthemingattached.cpp'
--- src/Ubuntu/Components/plugin/ucthemingattached.cpp	1970-01-01 00:00:00 +0000
+++ src/Ubuntu/Components/plugin/ucthemingattached.cpp	2015-08-06 18:06:52 +0000
@@ -0,0 +1,257 @@
+/*
+ * Copyright 2015 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; version 3.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Zsombor Egri <[e-mail]>
+ */
+
+#include "ucthemingattached.h"
+#include <QtQuick/QQuickItem>
+#include "uctheme.h"
+
+/*
+ * UCThemingAttached is an attached object to all themable components. It is used
+ * internally by those components which need theme access thru the theme property.
+ * Components which want to use this should do the following:
+ * - attach the object in classBegin() function
+ * - expose a theme property
+ * - getter should use the getTheme() attached function
+ * - setter/reset should use the setTheme() attached function
+ * - themeChanged() signal must be connected to the property change signal
+ *
+ * The theme change is notified through listener callbacks. Registering listener
+ * is not mandatory.
+ */
+
+UCThemingAttached *itemTheming(QQuickItem *item)
+{
+    return qobject_cast<UCThemingAttached*>(
+                qmlAttachedPropertiesObject<UCThemingAttached>(item, false));
+}
+
+UCThemingAttached::UCThemingAttached(QObject *parent)
+    : QObject(parent)
+    , m_theme(Q_NULLPTR)
+    , m_listener(Q_NULLPTR)
+    , m_ownerItem(static_cast<QQuickItem*>(parent))
+{
+}
+
+UCThemingAttached *UCThemingAttached::qmlAttachedProperties(QObject *owner)
+{
+    UCThemingAttached *theming = new UCThemingAttached(owner);
+    // the theme is the default one at this stage, so connect all the necessary signals
+    // owner must have theme signal
+    theming->connectThemeSignals(theming->getTheme(), true);
+    // connect parentChanged of owner to know when its parent is changed
+    connect(theming->m_ownerItem, &QQuickItem::parentChanged,
+            theming, &UCThemingAttached::itemParentChanged, Qt::DirectConnection);
+    return theming;
+}
+
+UCThemingAttached *UCThemingAttached::attachTheming(QObject *owner)
+{
+    return qobject_cast<UCThemingAttached*>(
+                qmlAttachedPropertiesObject<UCThemingAttached>(owner, true));
+}
+
+void UCThemingAttached::connectThemeSignals(UCTheme *theme, bool connect)
+{
+    if (connect) {
+        QObject::connect(theme, SIGNAL(nameChanged()), this, SIGNAL(themeChanged()), Qt::DirectConnection);
+        QObject::connect(theme, SIGNAL(versionChanged()), this, SIGNAL(themeChanged()), Qt::DirectConnection);
+    } else {
+        QObject::disconnect(theme, SIGNAL(nameChanged()), this, SIGNAL(themeChanged()));
+        QObject::disconnect(theme, SIGNAL(versionChanged()), this, SIGNAL(themeChanged()));
+    }
+}
+
+// link/unlink all ascendant items until we reach a StyledItem, returns true if the
+// theme change signal emission is justified
+bool UCThemingAttached::connectParents(QQuickItem *fromItem)
+{
+    QQuickItem *item = fromItem ? fromItem : m_ownerItem->parentItem();
+    while (item) {
+        // push the item onto the stack
+        m_parentStack.push(QPointer<QQuickItem>(item));
+        UCThemingAttached *styling = itemTheming(item);
+        if (styling) {
+            // this is the closest StyledItem, connect its themeChanged() signal
+            QObject::connect(styling, SIGNAL(themeChanged()),
+                             this, SLOT(parentStyleChanged()), Qt::DirectConnection);
+            // set the current style set to the one in the parent's one if differs
+            return setParentStyled(styling);
+        } else {
+            // connect to the item's parentChanged() signal so we can detect when the parent changes
+            QObject::connect(item, SIGNAL(parentChanged(QQuickItem*)),
+                             this, SLOT(ascendantChanged(QQuickItem*)), Qt::DirectConnection);
+        }
+        item = item->parentItem();
+    }
+    return false;
+}
+
+// disconnect parent stack till item is reached; all the stack if item == 0
+void UCThemingAttached::disconnectTillItem(QQuickItem *item)
+{
+    while (!m_parentStack.isEmpty() && item != m_parentStack.top()) {
+        QPointer<QQuickItem> stackItem = m_parentStack.pop();
+        // the topmost item can be the only one which is a StyledItem
+        UCThemingAttached *styling = itemTheming(stackItem.data());
+        if (styling) {
+            QObject::disconnect(styling, SIGNAL(themeChanged()),
+                                this, SLOT(parentStyleChanged()));
+            // clear parent styling as well
+            if (styling == m_parentTheming) {
+                m_parentTheming.clear();
+            }
+        } else if (!stackItem.isNull()) {
+            QObject::disconnect(stackItem.data(), SIGNAL(parentChanged(QQuickItem*)),
+                                this, SLOT(ascendantChanged(QQuickItem*)));
+        }
+    }
+}
+
+// set the used parent styled item's style; returns true if the parent styled got changed
+bool UCThemingAttached::setParentStyled(UCThemingAttached *newStyling)
+{
+    if (m_parentTheming == newStyling) {
+        return false;
+    }
+    m_parentTheming = newStyling;
+    if (m_theme) {
+        Q_EMIT themeChanged();
+    }
+    return (m_theme == NULL);
+}
+
+UCTheme *UCThemingAttached::getTheme()
+{
+    if (m_theme) {
+        return m_theme;
+    } else if (!m_parentTheming.isNull()) {
+        return m_parentTheming->getTheme();
+    }
+    return &UCTheme::defaultTheme();
+}
+
+bool UCThemingAttached::setTheme(UCTheme *newTheme)
+{
+    if (m_theme == newTheme) {
+        return false;
+    }
+
+    // preform pre-theme change tasks
+    if (m_listener) {
+        m_listener->preThemeChanged();
+    }
+
+    // disconnect from the previous set
+    UCTheme *connectedSet = m_theme ?
+                                m_theme :
+                                (!m_parentTheming ? &UCTheme::defaultTheme() : NULL);
+    if (connectedSet) {
+        connectThemeSignals(connectedSet, false);
+    }
+
+    UCTheme *prevSet = m_theme;
+
+    // resolve new theme
+    if (m_theme && newTheme) {
+        // no need to redo the parentStack, simply set the theme and leave
+        m_theme = newTheme;
+    } else {
+        m_theme = newTheme;
+        if (!newTheme) {
+            // redo the parent chanin
+            disconnectTillItem(0);
+            connectParents(0);
+        }
+    }
+
+    // connect to the new set
+    connectedSet = m_theme ?
+                    m_theme :
+                    (!m_parentTheming ? &UCTheme::defaultTheme() : NULL);
+    if (connectedSet) {
+        connectThemeSignals(connectedSet, true);
+    }
+    // detach previous set and attach the new one
+    if (prevSet) {
+        Q_EMIT prevSet->parentThemeChanged();
+    }
+    if (m_theme) {
+        // re-parent theme to make sure we have it
+        // for the entire lifetime of the styled item
+        m_theme->setParent(parent());
+        Q_EMIT m_theme->parentThemeChanged();
+    }
+
+    // perform post-theme changes, update internal styling
+    if (m_listener) {
+        m_listener->postThemeChanged();
+    }
+
+    Q_EMIT themeChanged();
+    return true;
+}
+
+// lookup for the parent chain theme
+void UCThemingAttached::itemParentChanged()
+{
+    // clean stack
+    disconnectTillItem(0);
+    // make sure we reset parent StyledItem
+    m_parentTheming.clear();
+    // build the stack - if possible
+    connectParents(0);
+    Q_EMIT themeChanged();
+}
+
+// captures ascendant change signal, the sender is the one which counts!
+void UCThemingAttached::ascendantChanged(QQuickItem *ascendant)
+{
+    QQuickItem *sender = static_cast<QQuickItem*>(this->sender());
+    if (!sender) {
+        // cannot detect the sender, leave!
+        return;
+    }
+    if (ascendant) {
+        // disconnect from the previous ones
+        disconnectTillItem(sender);
+        m_parentTheming.clear();
+        // traverse ascendants till we reach a StyledItem or root and push them into the stack
+        if (connectParents(ascendant)) {
+            Q_EMIT themeChanged();
+        }
+    }
+}
+
+// syncs the ascendant styled item's styles
+void UCThemingAttached::parentStyleChanged()
+{
+    // do not trigger themeChanged() on this item if we have a
+    // custom one, but resolve its eventual parent change!
+    if (m_theme) {
+        Q_EMIT m_theme->parentThemeChanged();
+        return;
+    }
+
+    UCThemingAttached *styling = static_cast<UCThemingAttached*>(sender());
+    if (!styling) {
+        return;
+    }
+    setParentStyled(styling);
+    Q_EMIT themeChanged();
+}

=== added file 'src/Ubuntu/Components/plugin/ucthemingattached.h'
--- src/Ubuntu/Components/plugin/ucthemingattached.h	1970-01-01 00:00:00 +0000
+++ src/Ubuntu/Components/plugin/ucthemingattached.h	2015-08-06 18:06:52 +0000
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2015 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; version 3.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Zsombor Egri <[e-mail]>
+ */
+
+#ifndef UCTHEMINGATTACHED_H
+#define UCTHEMINGATTACHED_H
+
+#include <QtCore/QObject>
+#include <QtCore/QPointer>
+#include <QtQml>
+
+class UCTheme;
+class QQuickItem;
+
+class UCThemeChangeListener {
+public:
+    virtual void preThemeChanged() = 0;
+    virtual void postThemeChanged() = 0;
+};
+
+class UCThemingAttached : public QObject
+{
+    Q_OBJECT
+public:
+    explicit UCThemingAttached(QObject *parent = 0);
+
+    static UCThemingAttached *qmlAttachedProperties(QObject *owner);
+    static UCThemingAttached *attachTheming(QObject *owner);
+
+    void setListener(UCThemeChangeListener *listener)
+    {
+        m_listener = listener;
+    }
+    UCTheme *getTheme();
+    bool setTheme(UCTheme *theme);
+
+Q_SIGNALS:
+    void themeChanged();
+
+public Q_SLOTS:
+
+    void ascendantChanged(QQuickItem *ascendant);
+    void parentStyleChanged();
+    void itemParentChanged();
+
+protected:
+    friend class UCTheme;
+
+    QStack< QPointer<QQuickItem> > m_parentStack;
+    QPointer<UCThemingAttached> m_parentTheming;
+    UCTheme *m_theme;
+    UCThemeChangeListener *m_listener;
+    QQuickItem *m_ownerItem;
+
+    void connectThemeSignals(UCTheme *theme, bool connect);
+
+    bool connectParents(QQuickItem *fromItem);
+    void disconnectTillItem(QQuickItem *item);
+    bool setParentStyled(UCThemingAttached *newStyling);
+
+};
+QML_DECLARE_TYPEINFO(UCThemingAttached, QML_HAS_ATTACHED_PROPERTIES)
+
+UCThemingAttached *itemTheming(QQuickItem *item);
+
+
+#endif // UCTHEMINGATTACHED_H