Add public API for setting and getting the style from C++

TODO: setup QtLabsControls C++ module docs

Task-number: QTBUG-50787
Change-Id: I382bad34df88d13fb9a74b3d2f9203280dfb4a66
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>

4 files changed, 34 insertions, 10 deletions

diff --git a/src/imports/controls/doc/src/qtlabscontrols-styles.qdoc b/src/imports/controls/doc/src/qtlabscontrols-styles.qdoc
index 46939712..9fa3d78b 100644
--- a/src/imports/controls/doc/src/qtlabscontrols-styles.qdoc
+++ b/src/imports/controls/doc/src/qtlabscontrols-styles.qdoc
@@ -37,9 +37,34 @@
 
     \section1 Usage
 
-    In order to run an application with a specific style, either pass a command
-    line argument, or set an environment variable. Alternatively, the preferred
-    style and style-specific attributes can be specified in a configuration file.
+    In order to run an application with a specific style, either configure the
+    style using \l QQuickStyle in C++, pass a command line argument, or set an
+    environment variable. Alternatively, the preferred style and style-specific
+    attributes can be specified in a configuration file.
+
+    \section2 Using QQuickStyle in C++
+
+    \l QQuickStyle provides API configuring a specific style. The following
+    example runs a Qt Labs Controls application with the Material style:
+
+    \code
+    #include <QGuiApplication>
+    #include <QQmlApplicationEngine>
+    #include <QQuickStyle>
+
+    int main(int argc, char *argv[])
+    {
+        QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+        QGuiApplication app(argc, argv);
+
+        QQuickStyle::setStyle("Material");
+
+        QQmlApplicationEngine engine;
+        engine.load(QUrl("qrc:/main.qml"));
+
+        return app.exec();
+    }
+    \endcode
 
     \section2 Command line argument
 
diff --git a/src/imports/controls/material/qtlabsmaterialstyleplugin.cpp b/src/imports/controls/material/qtlabsmaterialstyleplugin.cpp
index e4b44890..95e09225 100644
--- a/src/imports/controls/material/qtlabsmaterialstyleplugin.cpp
+++ b/src/imports/controls/material/qtlabsmaterialstyleplugin.cpp
@@ -42,7 +42,7 @@
 #include "qquickmaterialprogressstrip_p.h"
 
 #include <QtGui/private/qguiapplication_p.h>
-#include <QtLabsControls/private/qquickstyleselector_p.h>
+#include <QtLabsControls/qquickstyle.h>
 
 static inline void initResources()
 {
@@ -92,8 +92,7 @@ void QtLabsMaterialStylePlugin::initializeEngine(QQmlEngine *engine, const char
 {
     Q_UNUSED(engine);
 
-    QQuickStyleSelector selector;
-    if (selector.style() == QLatin1String("material")) {
+    if (QQuickStyle::name().compare(QLatin1String("material"), Qt::CaseInsensitive) == 0) {
         QPlatformTheme *old = QGuiApplicationPrivate::platform_theme;
         if (old) {
             QQuickProxyTheme *theme = new QQuickMaterialTheme(old);
diff --git a/src/imports/controls/qtlabscontrolsplugin.cpp b/src/imports/controls/qtlabscontrolsplugin.cpp
index 82953850..9196f685 100644
--- a/src/imports/controls/qtlabscontrolsplugin.cpp
+++ b/src/imports/controls/qtlabscontrolsplugin.cpp
@@ -40,6 +40,7 @@
 #include <QtCore/qcoreapplication.h>
 #include <QtCore/private/qfileselector_p.h>
 
+#include <QtLabsControls/qquickstyle.h>
 #include <QtLabsTemplates/private/qquickabstractbutton_p.h>
 #include <QtLabsTemplates/private/qquickbuttongroup_p.h>
 #include <QtLabsTemplates/private/qquickcontainer_p.h>
@@ -90,7 +91,7 @@ void QtLabsControlsPlugin::registerTypes(const char *uri)
     else
         selector.setBaseUrl(baseUrl());
 
-    const QString style = selector.style();
+    const QString style = QQuickStyle::name();
     if (!style.isEmpty())
         QFileSelectorPrivate::addStatics(QStringList() << style);
 
diff --git a/src/imports/controls/universal/qtlabsuniversalstyleplugin.cpp b/src/imports/controls/universal/qtlabsuniversalstyleplugin.cpp
index 51a71ea1..b3bb421e 100644
--- a/src/imports/controls/universal/qtlabsuniversalstyleplugin.cpp
+++ b/src/imports/controls/universal/qtlabsuniversalstyleplugin.cpp
@@ -43,7 +43,7 @@
 
 #include <QtGui/private/qguiapplication_p.h>
 #include <QtLabsControls/private/qquickcolorimageprovider_p.h>
-#include <QtLabsControls/private/qquickstyleselector_p.h>
+#include <QtLabsControls/qquickstyle.h>
 
 static inline void initResources()
 {
@@ -91,8 +91,7 @@ void QtLabsUniversalStylePlugin::registerTypes(const char *uri)
 
 void QtLabsUniversalStylePlugin::initializeEngine(QQmlEngine *engine, const char *uri)
 {
-    QQuickStyleSelector selector;
-    if (selector.style() == QLatin1String("universal")) {
+    if (QQuickStyle::name().compare(QLatin1String("universal"), Qt::CaseInsensitive) == 0) {
         QPlatformTheme *old = QGuiApplicationPrivate::platform_theme;
         if (old) {
             QQuickProxyTheme *theme = new QQuickUniversalTheme(old);