Add wxTreeCtrl::GetStateImageCount() and HasStateImages()

Add these functions for consistency with SetStateImages() and to avoid
using GetStateImageList() in the treectrl sample, which can now use
GetStateImageCount() instead.

include/wx/treectrl.h

@@ -62,6 +62,11 @@ public:
         // (for example, checked/unchecked).
     virtual void SetStateImages(const wxVector<wxBitmapBundle>& images) = 0;
 
+        // Simple accessors similar to the inherited from wxWithImages
+        // HasImages() and GetImageCount() for normal images.
+    bool HasStateImages() const { return m_imagesState.HasImages(); }
+    int GetStateImageCount() const { return m_imagesState.GetImageCount(); }
+
         // These functions parallel {Set,Get,Assign}ImageList() methods
         // inherited from wxWithImages, but correspond to SetStateImages().
         // As with the other functions using wxImageList, they still work but

interface/wx/treectrl.h

@@ -699,12 +699,38 @@ public:
     */
     virtual size_t GetSelections(wxArrayTreeItemIds& selection) const;
 
+    /**
+        Returns the number of state images used by the control.
+
+        Returns the number of images passed to the last call to
+        SetStateImages() or 0 if it had been never called.
+
+        @see HasImages()
+
+        @since 3.3.0
+     */
+    int GetStateImageCount() const;
+
     /**
         Returns the state image list (from which application-defined state
         images are taken).
+
+        @see HasStateImages(), GetStateImageCount()
     */
     wxImageList* GetStateImageList() const;
 
+    /**
+        Returns true if the control uses any state images.
+
+        This is equivalent to comparing GetStateImageCount() return value with
+        0 but more clear.
+
+        @see SetStateImages(), GetStateImageCount()
+
+        @since 3.3.0
+     */
+    bool HasStateImages() const;
+
     /**
         Calculates which (if any) item is under the given @a point, returning
         the tree item id at this point plus extra information @a flags. @a flags
@@ -994,6 +1020,8 @@ public:
         resolutions for each state. If the vector is empty, no state images are
         shown.
 
+        @see HasStateImages(), GetStateImageCount()
+
         @since 3.3.0
      */
     virtual void SetStateImages(const wxVector<wxBitmapBundle>& images);

samples/treectrl/treetest.cpp

@@ -1288,7 +1288,7 @@ void MyTreeCtrl::DoToggleState(const wxTreeItemId& item)
 
         srand (time(nullptr));
         do {
-            nState = rand() % GetStateImageList()->GetImageCount();
+            nState = rand() % GetStateImageCount();
         } while (nState == state);
 
         SetItemState(item, nState);