Bug 519376

Created attachment 358708 [details]
fix for refresh of window on top of multi-column characters

This request was evaluated by Red Hat Product Management for
inclusion, but this component is not scheduled to be updated in
the current Red Hat Enterprise Linux release. If you would like
this request to be reviewed for the next minor release, ask your
support representative to set the next rhel-x.y flag to "?".

Several issues reported again by my customer, so a simple fix is not enough. I made a bigger patch for  ncurses-5.5-26.  The patch does the following: 
 1) added PutChar2() to print an isolated Wchar "Ext" as a blank
 2) adjust in EmitRange() so that isolated Wchar "Base" and "Ext" be printed as blanks
 3) adjust in TransformLine() so that Wchar "Base" right before "first char" and Wchar "Ext" right after "last char" be included into PutRange()

--- old/ncurses/tty/tty_update.c        2009-11-07 18:36:16.000000000 +0800
+++ new/ncurses/tty/tty_update.c        2009-11-07 19:02:36.000000000 +0800
@@ -439,6 +439,30 @@
     position_check(SP->_cursrow, SP->_curscol, "PutChar");
 }

+#if USE_WIDEC_SUPPORT
+/* need PutChar2() to print an isolated wide char "Ext" as a blank */
+static NCURSES_INLINE void
+PutChar2(const ARG_CH_T ch, int lastIsWcharBase)
+/* insert character, handling automargin stuff */
+{
+    static const NCURSES_CH_T blank = NewChar(BLANK_TEXT);
+
+    if ( !lastIsWcharBase && isWidecExt(CHDEREF(ch)) ) 
+         ch  = CHREF(blank) ; 
+
+    if (SP->_cursrow == screen_lines - 1 && SP->_curscol == screen_columns - 1)
+        PutCharLR(ch);
+    else
+        PutAttrChar(ch);
+
+    if (SP->_curscol >= screen_columns)
+        wrap_cursor();
+
+    position_check(SP->_cursrow, SP->_curscol, "PutChar");
+}
+
+#endif
+
 /*
  * Check whether the given character can be output by clearing commands.  This
  * includes test for being a space and not including any 'bad' attributes, such
@@ -487,6 +511,10 @@
 EmitRange(const NCURSES_CH_T * ntext, int num)
 {
     int i;
+#if USE_WIDEC_SUPPORT
+    int  lastIsWcharBase=0;
+    static const NCURSES_CH_T myBlank = NewChar(BLANK_TEXT);
+#endif

     TR(TRACE_CHARPUT, ("EmitRange %d:%s", num, _nc_viscbuf(ntext, num)));

@@ -496,13 +524,38 @@
            NCURSES_CH_T ntext0;

            while (num > 1 && !CharEq(ntext[0], ntext[1])) {
-               PutChar(CHREF(ntext[0]));
+#if USE_WIDEC_SUPPORT
+                /* print isolated Wchar "Base" as a blank */
+                if ( isWidecBase(ntext[0]) && ! isWidecExt(ntext[1]) ) 
+                     PutChar(CHREF(myBlank));
+                else
+                     PutChar2(CHREF(ntext[0]), lastIsWcharBase); 
+
+                if ( isWidecBase(ntext[0]) )
+                     lastIsWcharBase = 1;
+                else
+                     lastIsWcharBase = 0;
+#else
+                PutChar(CHREF(ntext[0]));
+#endif
                ntext++;
                num--;
            }
            ntext0 = ntext[0];
            if (num == 1) {
-               PutChar(CHREF(ntext0));
+#if USE_WIDEC_SUPPORT
+                /* print isolated Wchar "Base" as a blank */
+                if ( isWidecBase(ntext[0]) )
+                     PutChar(CHREF(myBlank));
+                else
+                     PutChar2(CHREF(ntext[0]), lastIsWcharBase);
+                if ( isWidecBase(ntext[0]) )
+                     lastIsWcharBase = 1;
+                else
+                     lastIsWcharBase = 0;
+#else
+                PutChar(CHREF(ntext[0]));
+#endif
                return 0;
            }
            runcount = 2;
@@ -549,8 +602,22 @@
                if (wrap_possible)
                    PutChar(CHREF(ntext0));
            } else {
-               for (i = 0; i < runcount; i++)
-                   PutChar(CHREF(ntext[i]));
+               for (i = 0; i < runcount; i++) {
+#if USE_WIDEC_SUPPORT
+                    /* print isolated Wchar "Base" as a blank */
+                    if ( (i< runcount-1) && isWidecBase(ntext[i]) && ! isWidecExt(ntext[i+1]) )
+                         PutChar(CHREF(myBlank));
+                    else
+                         PutChar2(CHREF(ntext[i]), lastIsWcharBase);
+
+                    if ( isWidecBase(ntext[i]) )                
+                         lastIsWcharBase = 1;
+                    else
+                         lastIsWcharBase = 0;
+#else
+                    PutChar(CHREF(ntext[i]));
+#endif
+                }
            }
            ntext += runcount;
            num -= runcount;
@@ -558,8 +625,22 @@
        return 0;
     }

-    for (i = 0; i < num; i++)
+    for (i = 0; i < num; i++) {
+#if USE_WIDEC_SUPPORT
+        /* print isolated Wchar "Base" as a blank */
+        if ( (i< num-1) && isWidecBase(ntext[i]) && ! isWidecExt(ntext[i+1]) )
+             PutChar(CHREF(myBlank));
+        else
+             PutChar2(CHREF(ntext[i]), lastIsWcharBase);
+
+        if ( isWidecBase(ntext[i]) ) 
+             lastIsWcharBase = 1;
+        else
+             lastIsWcharBase = 0;
+#else
        PutChar(CHREF(ntext[i]));
+#endif
+    }
     return 0;
 }

@@ -1285,6 +1366,12 @@
            return;
        }

+#if USE_WIDEC_SUPPORT
+        /* don't let alone a Wchar "Base", even it may be isolated */ 
+        if ( ( firstChar > 0 ) && isWidecBase(newLine[firstChar-1]) ) 
+               firstChar--; 
+#endif
+
        blank = newLine[screen_columns - 1];

        if (!can_clear_with(CHREF(blank))) {
@@ -1295,6 +1382,11 @@
                   && CharEq(newLine[nLastChar], oldLine[nLastChar]))
                nLastChar--;

+#if USE_WIDEC_SUPPORT
+                /* don't let alone a Wchar "Ext", even it may be isolated */
+                if ( ( nLastChar < screen_columns -1 ) &&  isWidecExt(newLine[nLastChar+1]) )
+                     nLastChar++;
+#endif 
            if (nLastChar >= firstChar) {
                GoTo(lineno, firstChar);
                PutRange(oldLine, newLine, lineno, firstChar, nLastChar);

Created attachment 374659 [details]
testing examples codes that can demonstrate the issues

The fixed packages have to make the attached examples work.  The "chinese words" in the codes are in "GB18030" .

I made no fix for ncurses-5.4-15/RHEL4.7.  But we can re-compiled the fixed ncurses-5.5-26 on RHEL4.7 and it works well.

I just noticed this followup last week.  The test-cases
appear to work with ncurses 5.7 (tested with 20100313).
If there are remaining issues with current ncurses code,
it would help to open a separate bug report to cover that.

This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated in the
current release, Red Hat is unfortunately unable to address this
request at this time. Red Hat invites you to ask your support
representative to propose this request, if appropriate and relevant,
in the next release of Red Hat Enterprise Linux.

This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated in the
current release, Red Hat is unfortunately unable to address this
request at this time. Red Hat invites you to ask your support
representative to propose this request, if appropriate and relevant,
in the next release of Red Hat Enterprise Linux.

This request was erroneously denied for the current release of
Red Hat Enterprise Linux.  The error has been fixed and this
request has been re-proposed for the current release.

This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated in the
current release, Red Hat is unfortunately unable to address this
request at this time. Red Hat invites you to ask your support
representative to propose this request, if appropriate and relevant,
in the next release of Red Hat Enterprise Linux.

This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated in the
current release, Red Hat is unfortunately unable to address this
request at this time. Red Hat invites you to ask your support
representative to propose this request, if appropriate and relevant,
in the next release of Red Hat Enterprise Linux.