Add wxWithImages::GetImageCount() and HasImages() helpers

These functions allow avoiding using wxImageList explicitly in a couple
of places.

No real changes, this just prepares for adding new API not based on
wxImageList.

include/wx/withimages.h

@@ -15,7 +15,7 @@
 #include "wx/imaglist.h"
 
 // ----------------------------------------------------------------------------
-// wxWithImages: mix-in class providing access to wxImageList.
+// wxWithImages: mix-in for classes using indices for image access
 // ----------------------------------------------------------------------------
 
 class WXDLLIMPEXP_CORE wxWithImages
@@ -37,6 +37,18 @@ public:
         FreeIfNeeded();
     }
 
+    // Return the number of images, possibly 0.
+    int GetImageCount() const
+    {
+        return m_imageList ? m_imageList->GetImageCount() : 0;
+    }
+
+    // Return true if we have any images at all.
+    bool HasImages() const
+    {
+        return GetImageCount() != 0;
+    }
+
     // Sets the image list to use, it is *not* deleted by the control.
     virtual void SetImageList(wxImageList* imageList)
     {

interface/wx/withimages.h

@@ -18,6 +18,27 @@ public:
     wxWithImages();
     virtual ~wxWithImages();
 
+    /**
+        Return the number of images in this control.
+
+        The returned value may be 0 if there are no images associated with the
+        control.
+
+        @see HasImages()
+
+        @since 3.1.6
+     */
+    int GetImageCount() const;
+
+    /**
+        Return true if the control has any images associated with it.
+
+        @see GetImageCount()
+
+        @since 3.1.6
+     */
+    bool HasImages() const;
+
     /**
         Sets the image list for the page control and takes ownership of the list.
 

samples/notebook/notebook.cpp

@@ -157,9 +157,9 @@ wxPanel *CreateInsertPage(wxBookCtrlBase *parent)
 
 int GetIconIndex(wxBookCtrlBase* bookCtrl)
 {
-    if (bookCtrl && bookCtrl->GetImageList())
+    if (bookCtrl)
     {
-       int nImages = bookCtrl->GetImageList()->GetImageCount();
+       const int nImages = bookCtrl->GetImageCount();
        if (nImages > 0)
        {
            return bookCtrl->GetPageCount() % nImages;

samples/widgets/notebook.cpp

@@ -412,9 +412,9 @@ int BookWidgetsPage::GetTextValue(wxTextCtrl *text) const
 
 int BookWidgetsPage::GetIconIndex() const
 {
-    if ( m_imageList )
+    if ( m_book )
     {
-       int nImages = m_imageList->GetImageCount();
+       const int nImages = m_book->GetImageCount();
        if ( nImages > 0 )
        {
            return m_book->GetPageCount() % nImages;