Add first version of wxBitmapBundle and use it in wxToolBar

This first version provides only a generic implementation of
wxBitmapBundle using a collection of bitmaps and only supports using it
in wxToolBar in wxMSW and wxGTK.

More methods of creating wxBitmapBundle will be provided later and more
functions taking wxBitmap will be changed to take wxBitmapBundle later
too and, of course, all the other ports will be updated to use the new
API too.

include/wx/bmpbndl.h

@@ -0,0 +1,120 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/bmpbndl.h
+// Purpose:     Declaration of wxBitmapBundle class.
+// Author:      Vadim Zeitlin
+// Created:     2021-09-22
+// Copyright:   (c) 2021 Vadim Zeitlin <vadim@wxwidgets.org>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_BMPBNDL_H_
+#define _WX_BMPBNDL_H_
+
+#include "wx/bitmap.h"
+#include "wx/object.h"
+#include "wx/vector.h"
+
+class wxBitmapBundleImpl;
+
+// ----------------------------------------------------------------------------
+// wxBitmapBundle provides 1 or more versions of a bitmap, all bundled together
+// ----------------------------------------------------------------------------
+
+// This class has value semantics and can be copied cheaply.
+
+class WXDLLIMPEXP_CORE wxBitmapBundle
+{
+public:
+    // Default ctor constructs an empty bundle which can't be used for
+    // anything, but can be assigned something later.
+    wxBitmapBundle();
+
+    // This conversion ctor from a single bitmap does the same thing as
+    // FromBitmap() and only exists for interoperability with the existing code
+    // using wxBitmap.
+    wxBitmapBundle(const wxBitmap& bitmap);
+
+    // Another conversion ctor from a single image: this one is needed to allow
+    // passing wxImage to the functions that used to take wxBitmap but now take
+    // wxBitmapBundle.
+    wxBitmapBundle(const wxImage& image);
+
+    // Default copy ctor and assignment operator and dtor would be ok, but need
+    // to be defined out of line, where wxBitmapBundleImpl is fully declared.
+
+    wxBitmapBundle(const wxBitmapBundle& other);
+    wxBitmapBundle& operator=(const wxBitmapBundle& other);
+
+    ~wxBitmapBundle();
+
+
+    // Create from the given collection of bitmaps (all of which must be valid,
+    // but if the vector itself is empty, empty bundle is returned).
+    static wxBitmapBundle FromBitmaps(const wxVector<wxBitmap>& bitmaps);
+    static wxBitmapBundle FromBitmaps(const wxBitmap& bitmap1,
+                                      const wxBitmap& bitmap2);
+
+    // Create from a single bitmap (this is only useful for compatibility
+    // with the existing code). Returns empty bundle if bitmap is invalid.
+    static wxBitmapBundle FromBitmap(const wxBitmap& bitmap);
+    static wxBitmapBundle FromImage(const wxImage& image);
+
+
+    // Check if bitmap bundle is non-empty.
+    bool IsOk() const { return m_impl; }
+
+    // Get the size of the bitmap represented by this bundle when using the
+    // default DPI, i.e. 100% scaling. Returns invalid size for empty bundle.
+    wxSize GetDefaultSize() const;
+
+    // Get bitmap of the specified size, creating a new bitmap from the closest
+    // available size by rescaling it if necessary.
+    //
+    // If size == wxDefaultSize, GetDefaultSize() is used for it instead.
+    wxBitmap GetBitmap(const wxSize size) const;
+
+private:
+    typedef wxObjectDataPtr<wxBitmapBundleImpl> wxBitmapBundleImplPtr;
+
+    // Private ctor used by static factory functions to create objects of this
+    // class. It takes ownership of the pointer (which must be non-null).
+    explicit wxBitmapBundle(wxBitmapBundleImpl* impl);
+
+    wxBitmapBundleImplPtr m_impl;
+};
+
+// Inline functions implementation.
+
+/* static */ inline
+wxBitmapBundle wxBitmapBundle::FromBitmaps(const wxBitmap& bitmap1,
+                                           const wxBitmap& bitmap2)
+{
+    wxVector<wxBitmap> bitmaps;
+    if ( bitmap1.IsOk() )
+        bitmaps.push_back(bitmap1);
+    if ( bitmap2.IsOk() )
+        bitmaps.push_back(bitmap2);
+    return FromBitmaps(bitmaps);
+}
+
+/* static */ inline
+wxBitmapBundle wxBitmapBundle::FromBitmap(const wxBitmap& bitmap)
+{
+    if ( !bitmap.IsOk() )
+        return wxBitmapBundle();
+
+    wxVector<wxBitmap> bitmaps;
+    bitmaps.push_back(bitmap);
+    return FromBitmaps(bitmaps);
+}
+
+/* static */ inline
+wxBitmapBundle wxBitmapBundle::FromImage(const wxImage& image)
+{
+    if ( !image.IsOk() )
+        return wxBitmapBundle();
+
+    return FromBitmap(wxBitmap(image));
+}
+
+#endif // _WX_BMPBNDL_H_