Ticket #15980: textctrl-append_v2.patch

\include/wx/msw/textctrl.h

@@ -285 +285 @@
     int  m_isInkEdit;
 #endif
 
+    // store the expected length of the whole text after append/insert operation
+    int m_expectedTextLen;
 };
 
 #endif // _WX_TEXTCTRL_H_

\src/msw/textctrl.cpp

@@ -226 +226 @@
     m_privateContextMenu = NULL;
     m_updatesCount = -1;
     m_isNativeCaretShown = true;
+    m_expectedTextLen = 0;
 }
 
 wxTextCtrl::~wxTextCtrl()
@@ -1137 +1138 @@
 
         UpdatesCountFilter ucf(m_updatesCount);
 
+        // Expected text length after the operation.
+        m_expectedTextLen = ::GetWindowTextLength(GetHwnd()) + valueDos.length();
         ::SendMessage(GetHwnd(), selectionOnly ? EM_REPLACESEL : WM_SETTEXT,
                       // EM_REPLACESEL takes 1 to indicate the operation should be redoable
                       selectionOnly ? 1 : 0, wxMSW_CONV_LPARAM(valueDos));
+        if( ::GetWindowTextLength(GetHwnd()) < m_expectedTextLen )
+        {
+            // Text size limit has been hit and added text has been truncated.
+            // Text buffer has been increased in the background (EN_MAXTEXT message)
+            // so we can undo the operation and try to add the text again.
+            if( selectionOnly )
+                Undo();
+            ::SendMessage(GetHwnd(), selectionOnly ? EM_REPLACESEL : WM_SETTEXT,
+                          // EM_REPLACESEL takes 1 to indicate the operation should be redoable
+                          selectionOnly ? 1 : 0, wxMSW_CONV_LPARAM(valueDos));
+        }
+        wxASSERT_MSG( ::GetWindowTextLength(GetHwnd()) >= m_expectedTextLen,
+                      wxT("Insufficient text buffer: appended text has been trucated") );
 
         if ( !ucf.GotUpdate() && (flags & SetValue_SendEvent) )
         {
@@ -2119 +2135 @@
     unsigned int len = ::GetWindowTextLength(GetHwnd());
     if ( len >= limit )
     {
-        // increment in 32Kb chunks
-        SetMaxLength(len + 0x8000);
+        unsigned long chunkSize = wxMax(0x8000, m_expectedTextLen - limit);  // at least 32KB
+        chunkSize = (chunkSize + 0x7FFF) & ~0x7FFF; // round up to the nearest 32KB block
+
+        SetMaxLength(len + chunkSize);
     }
 
     // we changed the limit