InputTextMultiline: fixed losing revert value when activating scrollbar. (toward #9308)

docs/CHANGELOG.txt

@@ -86,7 +86,8 @@ Other Changes:
     for vertical scrollbar range would be +1 when the widget is inactive, word-wrap is
     disabled and the text buffer ends with '\n'. Fixed a similar issue related to clipping
     large amount of text.
-  - InputTextMultiline: avoid going through reactivation code when activating scrollbar.
+  - InputTextMultiline: avoid going through reactivation code and fixed losing revert value
+    when activating scrollbar.
 - Style:
   - Border sizes are now scaled (and rounded) by ScaleAllSizes().
   - When using large values with ScallAllSizes(), the following items thickness

imgui_widgets.cpp

@@ -4806,8 +4806,11 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
         // From the moment we focused we are normally ignoring the content of 'buf' (unless we are in read-only mode)
         const int buf_len = (int)ImStrlen(buf);
         IM_ASSERT(((buf_len + 1 <= buf_size) || (buf_len == 0 && buf_size == 0)) && "Is your input buffer properly zero-terminated?");
-        state->TextToRevertTo.resize(buf_len + 1);    // UTF-8. we use +1 to make sure that .Data is always pointing to at least an empty string.
-        memcpy(state->TextToRevertTo.Data, buf, buf_len + 1);
+        if (!user_scroll_finish)
+        {
+            state->TextToRevertTo.resize(buf_len + 1);    // UTF-8. we use +1 to make sure that .Data is always pointing to at least an empty string.
+            memcpy(state->TextToRevertTo.Data, buf, buf_len + 1);
+        }
 
         // Preserve cursor position and undo/redo stack if we come back to same widget
         // FIXME: Since we reworked this on 2022/06, may want to differentiate recycle_cursor vs recycle_undostate?