Add wxActivityIndicator control.

This is a simple animated control indicating some program activity.

Provide native GTK+ (for > 2.20) and OS X implementations as well as a generic
one used under MSW.

Update the sample and the documentation.

samples/widgets/activityindicator.cpp

@@ -0,0 +1,151 @@
+/////////////////////////////////////////////////////////////////////////////
+// Program:     wxWidgets Widgets Sample
+// Name:        activityindicator.cpp
+// Purpose:     Part of the widgets sample showing wxActivityIndicator
+// Author:      Vadim Zeitlin
+// Created:     2015-03-06
+// Copyright:   (c) 2015 wxWindows team
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+// ============================================================================
+// declarations
+// ============================================================================
+
+// ----------------------------------------------------------------------------
+// headers
+// ----------------------------------------------------------------------------
+
+// for compilers that support precompilation, includes "wx/wx.h".
+#include "wx/wxprec.h"
+
+#ifdef __BORLANDC__
+    #pragma hdrstop
+#endif
+
+// for all others, include the necessary headers
+#ifndef WX_PRECOMP
+    #include "wx/button.h"
+    #include "wx/sizer.h"
+    #include "wx/stattext.h"
+#endif
+
+#include "wx/activityindicator.h"
+
+#include "widgets.h"
+
+#include "icons/activityindicator.xpm"
+
+// ----------------------------------------------------------------------------
+// constants
+// ----------------------------------------------------------------------------
+
+// Control IDs
+enum
+{
+    ActivityIndicator_Start = wxID_HIGHEST,
+    ActivityIndicator_Stop,
+    ActivityIndicator_IsRunning
+};
+
+// ----------------------------------------------------------------------------
+// ActivityIndicatorWidgetsPage
+// ----------------------------------------------------------------------------
+
+class ActivityIndicatorWidgetsPage : public WidgetsPage
+{
+public:
+    ActivityIndicatorWidgetsPage(WidgetsBookCtrl *book, wxImageList *imaglist)
+        : WidgetsPage(book, imaglist, activityindicator_xpm)
+    {
+        m_indicator = NULL;
+        m_sizerIndicator = NULL;
+    }
+
+    virtual wxControl *GetWidget() const wxOVERRIDE { return m_indicator; }
+    virtual void RecreateWidget() wxOVERRIDE;
+
+    // lazy creation of the content
+    virtual void CreateContent() wxOVERRIDE;
+
+protected:
+    void OnButtonStart(wxCommandEvent&) { m_indicator->Start(); }
+    void OnButtonStop(wxCommandEvent&) { m_indicator->Stop(); }
+
+    void OnUpdateIsRunning(wxUpdateUIEvent& event)
+    {
+        event.SetText(m_indicator && m_indicator->IsRunning()
+                        ? "Indicator is running"
+                        : "Indicator is stopped");
+    }
+
+    // the indicator itself and the sizer it is in
+    wxActivityIndicator *m_indicator;
+    wxSizer *m_sizerIndicator;
+
+private:
+    wxDECLARE_EVENT_TABLE();
+    DECLARE_WIDGETS_PAGE(ActivityIndicatorWidgetsPage)
+};
+
+// ----------------------------------------------------------------------------
+// event tables
+// ----------------------------------------------------------------------------
+
+wxBEGIN_EVENT_TABLE(ActivityIndicatorWidgetsPage, WidgetsPage)
+    EVT_BUTTON(ActivityIndicator_Start,
+               ActivityIndicatorWidgetsPage::OnButtonStart)
+    EVT_BUTTON(ActivityIndicator_Stop,
+               ActivityIndicatorWidgetsPage::OnButtonStop)
+
+    EVT_UPDATE_UI(ActivityIndicator_IsRunning,
+                  ActivityIndicatorWidgetsPage::OnUpdateIsRunning)
+wxEND_EVENT_TABLE()
+
+// ============================================================================
+// implementation
+// ============================================================================
+
+IMPLEMENT_WIDGETS_PAGE(ActivityIndicatorWidgetsPage,
+                       wxT("ActivityIndicator"), NATIVE_CTRLS);
+
+void ActivityIndicatorWidgetsPage::CreateContent()
+{
+    wxSizer* const sizerOper = new wxStaticBoxSizer(wxVERTICAL, this,
+                                                    "&Operations");
+
+    sizerOper->Add(new wxButton(this, ActivityIndicator_Start, "&Start"),
+                   wxSizerFlags().Expand().Border());
+    sizerOper->Add(new wxButton(this, ActivityIndicator_Stop, "&Stop"),
+                   wxSizerFlags().Expand().Border());
+
+    sizerOper->Add(new wxStaticText(this, ActivityIndicator_IsRunning,
+                                    "Indicator is initializing..."),
+                   wxSizerFlags().Expand().Border());
+
+
+    m_sizerIndicator = new wxStaticBoxSizer(wxHORIZONTAL, this,
+                                            "Activity Indicator");
+    RecreateWidget();
+
+
+    wxSizer* const sizerTop = new wxBoxSizer(wxHORIZONTAL);
+    sizerTop->Add(sizerOper, wxSizerFlags().Expand().DoubleBorder());
+    sizerTop->Add(m_sizerIndicator, wxSizerFlags(1).Expand().DoubleBorder());
+
+    SetSizer(sizerTop);
+}
+
+void ActivityIndicatorWidgetsPage::RecreateWidget()
+{
+    m_sizerIndicator->Clear(true /* delete windows */);
+
+    m_indicator = new wxActivityIndicator(this, wxID_ANY,
+                                          wxDefaultPosition, wxDefaultSize,
+                                          GetAttrs().m_defaultFlags);
+
+    m_sizerIndicator->AddStretchSpacer();
+    m_sizerIndicator->Add(m_indicator, wxSizerFlags().Centre());
+    m_sizerIndicator->AddStretchSpacer();
+    m_sizerIndicator->Layout();
+}