Use qmldir to define QML module with IgnSpinBox (#319)

Signed-off-by: William Wedler <william.wedler@resquared.com>
Co-authored-by: Louise Poubel <louise@openrobotics.org>

include/ignition/gui/Helpers.hh

@@ -79,6 +79,16 @@ namespace ignition
     IGNITION_GUI_VISIBLE
     QStringList worldNames();
 
+
+    /// \brief Import path for ign-gui QML modules added to the Qt resource system
+    /// This helper function returns the QRC resource path where custom ignition QML
+    /// modules can be imported from. To import an ignition QML module, add this path
+    /// to the QML engine's import path list before attempting to load a QML file
+    /// that imports ignition QML modules.
+    /// \return Resousrce path prefix as a string
+    IGNITION_GUI_VISIBLE
+    const QString qmlQrcImportPath();
+
     /// \brief Returns the first element on a QList which matches the given
     /// property.
     /// \param[in] _list The list to search through.

include/ignition/gui/qml/qmldir

@@ -0,0 +1,3 @@
+module ignition.gui
+
+IgnSpinBox 1.0 IgnSpinBox.qml

include/ignition/gui/resources.qrc

@@ -20,4 +20,10 @@
   <file>qml/images/menu.png</file>
   <file>qml/images/search.svg</file>
 </qresource>
+<qresource prefix="ign-gui-qml/ignition/gui">
+    <!-- This qmldir file defines a QML module that can be imported -->
+    <file alias="qmldir">qml/qmldir</file>
+    <!-- Add any QML components referenced in the qmldir file here -->
+    <file alias="IgnSpinBox.qml">qml/IgnSpinBox.qml</file>
+</qresource>
 </RCC>

src/Application.cc

@@ -28,6 +28,7 @@
 #include "ignition/gui/Application.hh"
 #include "ignition/gui/config.hh"
 #include "ignition/gui/Dialog.hh"
+#include "ignition/gui/Helpers.hh"
 #include "ignition/gui/MainWindow.hh"
 #include "ignition/gui/Plugin.hh"
 
@@ -91,6 +92,7 @@ Application::Application(int &_argc, char **_argv, const WindowType _type)
 
   // QML engine
   this->dataPtr->engine = new QQmlApplicationEngine();
+  this->dataPtr->engine->addImportPath(qmlQrcImportPath());
 
   // Install signal handler for graceful shutdown
   this->dataPtr->signalHandler.AddCallback(

src/Helpers.cc

@@ -180,3 +180,9 @@ QStringList ignition::gui::worldNames()
 
   return worldNamesVariant.toStringList();
 }
+
+/////////////////////////////////////////////////
+const QString ignition::gui::qmlQrcImportPath()
+{
+  return "qrc:/ign-gui-qml/";
+}

src/plugins/teleop/Teleop.qml

@@ -20,7 +20,7 @@ import QtQuick.Controls 2.2
 import QtQuick.Controls.Material 2.1
 import QtQuick.Controls.Styles 1.4
 import QtQuick.Layouts 1.3
-import "qrc:/qml"
+import ignition.gui 1.0
 
 Rectangle {
   color:"transparent"