document that CanRead() and GetImageCount() functions of wxImageHandlers do NOT modify the current stream position and that they require seekable streams; rename current GetImageCount() functions to DoGetImageCount() and put save-and-restore stream position logic in GetImageCount(); add comments in the various DoCanRead() and in DoGetImageCount() where the stream position is modified; remove unneeded SeekI(0) calls from DoCanRead() and DoGetImageCount() functions: they didn't allow to load images from non-seekable streams; implement forward-seeking in wxInputStream::SeekI() also for non-seekable streams

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@60852 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/anidecod.h

@@ -44,7 +44,7 @@ public:
     virtual wxColour GetTransparentColour(unsigned int frame) const;
 
     // implementation of wxAnimationDecoder's pure virtuals
-    virtual bool CanRead( wxInputStream& stream ) const;
+    
     virtual bool Load( wxInputStream& stream );
 
     bool ConvertToImage(unsigned int frame, wxImage *image) const;
@@ -55,6 +55,10 @@ public:
         { return wxANIMATION_TYPE_ANI; }
 
 private:
+    // wxAnimationDecoder pure virtual:
+    virtual bool DoCanRead( wxInputStream& stream ) const;
+            // modifies current stream position (see wxAnimationDecoder::CanRead)
+    
     // frames stored as wxImage(s): ANI files are meant to be used mostly for animated
     // cursors and thus they do not use any optimization to encode differences between
     // two frames: they are just a list of images to display sequentially.