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/gifdecod.h

@@ -76,7 +76,6 @@ public:
     void Destroy();
 
     // implementation of wxAnimationDecoder's pure virtuals
-    virtual bool CanRead( wxInputStream& stream ) const;
     virtual bool Load( wxInputStream& stream )
         { return LoadGIF(stream) == wxGIF_OK; }
 
@@ -88,6 +87,15 @@ public:
         { return wxANIMATION_TYPE_GIF; }
 
 private:
+    // wxAnimationDecoder pure virtual
+    virtual bool DoCanRead( wxInputStream& stream ) const;
+        // modifies current stream position (see wxAnimationDecoder::CanRead)
+
+    int getcode(wxInputStream& stream, int bits, int abfin);
+    wxGIFErrorCode dgif(wxInputStream& stream,
+                        GIFImage *img, int interl, int bits);
+
+    
     // array of all frames
     wxArrayPtrVoid m_frames;
 
@@ -98,10 +106,6 @@ private:
     unsigned char m_buffer[256];    // buffer for reading
     unsigned char *m_bufp;          // pointer to next byte in buffer
 
-    int getcode(wxInputStream& stream, int bits, int abfin);
-    wxGIFErrorCode dgif(wxInputStream& stream,
-                        GIFImage *img, int interl, int bits);
-
     wxDECLARE_NO_COPY_CLASS(wxGIFDecoder);
 };