2 files changed, 27 insertions, 35 deletions
diff --git a/generic/tkTextBTree.c b/generic/tkTextBTree.c
index 005ce46..67ff79d 100644
--- a/generic/tkTextBTree.c
+++ b/generic/tkTextBTree.c
@@ -1991,17 +1991,37 @@ TkBTreeLinesTo(
 	    index += nodePtr2->numLines;
 	}
     }
-    if (textPtr != NULL && textPtr->start != NULL) {
-	index -= TkBTreeLinesTo(NULL, textPtr->start);
-        if (index < 0) {
-            /* One should panic here!
-            Tcl_Panic("TkBTreeLinesTo: linePtr comes before -startline");
-             */
+    if (textPtr != NULL) {
+        /* 
+         * The index to return must be relative to textPtr, not to the entire
+         * tree. Take care to never return a negative index when linePtr
+         * denotes a line before -startline, or an index larger than the
+         * number of lines in textPtr when linePtr is a line past -endline.
+         */
+
+        int indexStart, indexEnd;
+
+        if (textPtr->start != NULL) {
+            indexStart = TkBTreeLinesTo(NULL, textPtr->start);
+        } else {
+            indexStart = 0;
+        }
+        if (textPtr->end != NULL) {
+            indexEnd = TkBTreeLinesTo(NULL, textPtr->end);
+        } else {
+            indexEnd = TkBTreeNumLines(textPtr->sharedTextPtr->tree, NULL);
+        }
+        if (index < indexStart) {
+            index = 0;
+        } else if (index > indexEnd) {
+            index = TkBTreeNumLines(textPtr->sharedTextPtr->tree, textPtr);
+        } else {
+            index -= indexStart;
         }
     }
     return index;
 }
-
+
 /*
  *----------------------------------------------------------------------
  *
diff --git a/generic/tkTextDisp.c b/generic/tkTextDisp.c
index f674b75..61fb76e 100644
--- a/generic/tkTextDisp.c
+++ b/generic/tkTextDisp.c
@@ -3219,34 +3219,6 @@ TextInvalidateLineMetrics(
     int fromLine;
     TextDInfo *dInfoPtr = textPtr->dInfoPtr;
 
-    /*
-     * All lines to invalidate must be inside the -startline/-endline range.
-     */
-
-    if (linePtr != NULL) {
-        int start;
-        TkTextLine *toLinePtr;
-        if (textPtr->start != NULL) {
-            fromLine = TkBTreeLinesTo(NULL, linePtr);
-            start = TkBTreeLinesTo(NULL, textPtr->start);
-            if (fromLine < start) {
-                lineCount -= start - fromLine;
-                linePtr = textPtr->start;
-            }
-        }
-        if (textPtr->end != NULL) {
-            int count = 0;
-            toLinePtr = linePtr;
-            while (count < lineCount && toLinePtr != NULL) {
-                toLinePtr = TkBTreeNextLine(textPtr, toLinePtr);
-                count++;
-            }
-            if (toLinePtr == NULL) {
-                lineCount = count;
-            }
-        }
-    }
-
     if (linePtr != NULL) {
 	int counter = lineCount;