Fix bug [b2dd3b4fe8] (text-11a.41 sometimes hangs) by reworking how the

<<WidgetViewSync>> event is handled.

4 files changed, 179 insertions, 134 deletions

diff --git a/generic/tkText.c b/generic/tkText.c
index ff773a1..6c1512d 100644
--- a/generic/tkText.c
+++ b/generic/tkText.c
@@ -406,7 +406,6 @@ static Tcl_Obj *	TextGetText(const TkText *textPtr,
 static void		GenerateModifiedEvent(TkText *textPtr);
 static void		GenerateUndoStackEvent(TkText *textPtr);
 static void		UpdateDirtyFlag(TkSharedText *sharedPtr);
-static void		RunAfterSyncCmd(ClientData clientData);
 static void		TextPushUndoAction(TkText *textPtr,
 			    Tcl_Obj *undoString, int insert,
 			    const TkTextIndex *index1Ptr,
@@ -1547,7 +1546,7 @@ TextWidgetObjCmd(
 		textPtr->afterSyncCmd = cmd;
 	    } else {
 		textPtr->afterSyncCmd = cmd;
-		Tcl_DoWhenIdle(RunAfterSyncCmd, (ClientData) textPtr);
+		Tcl_DoWhenIdle(TkTextRunAfterSyncCmd, (ClientData) textPtr);
 	    }
 	    break;
 	} else if (objc != 2) {
@@ -1559,7 +1558,7 @@ TextWidgetObjCmd(
 	    Tcl_DecrRefCount(textPtr->afterSyncCmd);
 	}
 	textPtr->afterSyncCmd = NULL;
-	TkTextUpdateLineMetrics(textPtr, 1,
+	TkTextUpdateLineMetrics(textPtr, 0,
 		TkBTreeNumLines(textPtr->sharedTextPtr->tree, textPtr), -1);
 	break;
     }
@@ -5506,7 +5505,7 @@ UpdateDirtyFlag(
 /*
  *----------------------------------------------------------------------
  *
- * RunAfterSyncCmd --
+ * TkTextRunAfterSyncCmd --
  *
  *	This function is called by the event loop and executes the command
  *      scheduled by [.text sync -command $cmd].
@@ -5520,8 +5519,8 @@ UpdateDirtyFlag(
  *----------------------------------------------------------------------
  */
 
-static void
-RunAfterSyncCmd(
+void
+TkTextRunAfterSyncCmd(
     ClientData clientData)		/* Information about text widget. */
 {
     register TkText *textPtr = (TkText *) clientData;
diff --git a/generic/tkText.h b/generic/tkText.h
index 5d88784..4703703 100644
--- a/generic/tkText.h
+++ b/generic/tkText.h
@@ -1070,7 +1070,7 @@ MODULE_SCOPE int	TkTextGetObjIndex(Tcl_Interp *interp, TkText *textPtr,
 MODULE_SCOPE int	TkTextSharedGetObjIndex(Tcl_Interp *interp,
 			    TkSharedText *sharedTextPtr, Tcl_Obj *idxPtr,
 			    TkTextIndex *indexPtr);
-MODULE_SCOPE const TkTextIndex *TkTextGetIndexFromObj(Tcl_Interp *interp,
+MODULE_SCOPE const	TkTextIndex *TkTextGetIndexFromObj(Tcl_Interp *interp,
 			    TkText *textPtr, Tcl_Obj *objPtr);
 MODULE_SCOPE TkTextTabArray *TkTextGetTabs(Tcl_Interp *interp,
 			    TkText *textPtr, Tcl_Obj *stringPtr);
@@ -1159,7 +1159,7 @@ MODULE_SCOPE int	TkTextYviewCmd(TkText *textPtr, Tcl_Interp *interp,
 			    int objc, Tcl_Obj *const objv[]);
 MODULE_SCOPE void	TkTextWinFreeClient(Tcl_HashEntry *hPtr,
 			    TkTextEmbWindowClient *client);
-
+MODULE_SCOPE void       TkTextRunAfterSyncCmd(ClientData clientData);
 #endif /* _TKTEXT */
 
 /*
diff --git a/generic/tkTextDisp.c b/generic/tkTextDisp.c
index 7e1a88e..cde30e1 100644
--- a/generic/tkTextDisp.c
+++ b/generic/tkTextDisp.c
@@ -497,13 +497,15 @@ static TkTextDispChunk *baseCharChunkPtr = NULL;
  *				different character might be under the mouse
  *				cursor now). Need to recompute the current
  *				character before the next redisplay.
+ * OUT_OF_SYNC                  1 means that the last <<WidgetViewSync>> event had
+ *                              value 0, indicating that the widget is out of sync.
  */
 
 #define DINFO_OUT_OF_DATE	1
 #define REDRAW_PENDING		2
 #define REDRAW_BORDERS		4
 #define REPICK_NEEDED		8
-
+#define OUT_OF_SYNC             16
 /*
  * Action values for FreeDLines:
  *
@@ -681,7 +683,7 @@ TkTextCreateDInfo(
     dInfoPtr->scanTotalYScroll = 0;
     dInfoPtr->scanMarkY = 0;
     dInfoPtr->dLinesInvalidated = 0;
-    dInfoPtr->flags = DINFO_OUT_OF_DATE;
+    dInfoPtr->flags = 0;
     dInfoPtr->topPixelOffset = 0;
     dInfoPtr->newTopPixelOffset = 0;
     dInfoPtr->currentMetricUpdateLine = -1;
@@ -3070,10 +3072,13 @@ AsyncUpdateLineMetrics(
 	 * We have looped over all lines, so we're done. We must release our
 	 * refCount on the widget (the timer token was already set to NULL
 	 * above). If there is a registered aftersync command, run that first.
+	 * Cancel any pending idle task which would try to run the command
+	 * after the afterSyncCmd pointer had been set to NULL.
 	 */
 
         if (textPtr->afterSyncCmd) {
             int code;
+	    Tcl_CancelIdleCall(TkTextRunAfterSyncCmd, textPtr);
             Tcl_Preserve((ClientData) textPtr->interp);
             code = Tcl_EvalObjEx(textPtr->interp, textPtr->afterSyncCmd,
                     TCL_EVAL_GLOBAL);
@@ -3091,7 +3096,6 @@ AsyncUpdateLineMetrics(
          * with its internal data (actually it will be after the next trip
          * through the event loop, because the widget redraws at idle-time).
          */
-
         GenerateWidgetViewSyncEvent(textPtr, 1);
 
 	if (textPtr->refCount-- <= 1) {
@@ -3115,8 +3119,14 @@ AsyncUpdateLineMetrics(
  * GenerateWidgetViewSyncEvent --
  *
  *      Send the <<WidgetViewSync>> event related to the text widget
- *      line metrics asynchronous update.
- *      This is equivalent to:
+ *      line metrics asynchronous update.  These events should only
+ *      be sent when the sync status has changed.  So this function
+ *      compares the requested state with the state saved in the
+ *      TkText structure, and only generates the event if they are
+ *      different.  This means that it is safe to call this function
+ *      at any time when the state is known.
+ *
+ *      If an event is sent, the effect is equivalent to:
  *         event generate $textWidget <<WidgetViewSync>> -data $s
  *      where $s is the sync status: true (when the widget view is in
  *      sync with its internal data) or false (when it is not).
@@ -3132,9 +3142,12 @@ AsyncUpdateLineMetrics(
 
 static void
 GenerateWidgetViewSyncEvent(
-    TkText *textPtr,		/* Information about text widget. */
-    Bool InSync)                /* true if in sync, false otherwise */
+    TkText *textPtr,	  /* Information about text widget. */
+    Bool InSync)          /* true if becoming in sync, false otherwise */
 {
+    Bool NewSyncState = (InSync != 0); /* ensure 0 or 1 value */
+    Bool OldSyncState = !(textPtr->dInfoPtr->flags & OUT_OF_SYNC);
+    
     /*
      * OSX 10.14 needs to be told to display the window when the Text Widget
      * is in sync.  (That is, to run DisplayText inside of the drawRect
@@ -3147,8 +3160,15 @@ GenerateWidgetViewSyncEvent(
 	FORCE_DISPLAY(textPtr->tkwin);
     }
 
-    TkSendVirtualEvent(textPtr->tkwin, "WidgetViewSync",
-        Tcl_NewBooleanObj(InSync));
+    if (NewSyncState != OldSyncState) {
+	if (NewSyncState) {
+	    textPtr->dInfoPtr->flags &= ~OUT_OF_SYNC;
+	} else {
+	    textPtr->dInfoPtr->flags |= OUT_OF_SYNC;
+	}
+        TkSendVirtualEvent(textPtr->tkwin, "WidgetViewSync",
+                           Tcl_NewBooleanObj(NewSyncState));
+    }
 }
 
 /*
@@ -3191,6 +3211,9 @@ TkTextUpdateLineMetrics(
     TkTextLine *linePtr = NULL;
     int count = 0;
     int totalLines = TkBTreeNumLines(textPtr->sharedTextPtr->tree, textPtr);
+    int fullUpdateRequested = (lineNum == 0 &&
+                               endLine == totalLines &&
+                               doThisMuch == -1);
 
     if (totalLines == 0) {
 	/*
@@ -3201,6 +3224,7 @@ TkTextUpdateLineMetrics(
     }
 
     while (1) {
+
 	/*
 	 * Get a suitable line.
 	 */
@@ -3227,6 +3251,7 @@ TkTextUpdateLineMetrics(
 	     */
 
 	    if (textPtr->dInfoPtr->metricEpoch == -1 && lineNum == endLine) {
+
 		/*
 		 * We have looped over all lines, so we're done.
 		 */
@@ -3250,10 +3275,12 @@ TkTextUpdateLineMetrics(
 
 	    if (TkBTreeLinePixelEpoch(textPtr, linePtr)
 		    == textPtr->dInfoPtr->lineMetricUpdateEpoch) {
+
 		/*
 		 * This line is already up to date. That means there's nothing
 		 * to do here.
 		 */
+
 	    } else if (doThisMuch == -1) {
 		count += 8 * TkTextUpdateOneLine(textPtr, linePtr, 0,NULL,0);
 	    } else {
@@ -3275,6 +3302,7 @@ TkTextUpdateLineMetrics(
 		    indexPtr = &textPtr->dInfoPtr->metricIndex;
 		    pixelHeight = textPtr->dInfoPtr->metricPixelHeight;
 		} else {
+
 		    /*
 		     * We must reset the partial line height calculation data
 		     * here, so we don't use it when it is out of date.
@@ -3298,6 +3326,7 @@ TkTextUpdateLineMetrics(
 			pixelHeight, indexPtr, 1);
 
 		if (indexPtr->linePtr == linePtr) {
+
 		    /*
 		     * We didn't complete the logical line, because it
 		     * produced very many display lines, which must be because
@@ -3306,6 +3335,7 @@ TkTextUpdateLineMetrics(
 		     */
 
 		    if (pixelHeight == 0) {
+
 			/*
 			 * These have already been stored, unless we just
 			 * started the new line.
@@ -3327,6 +3357,7 @@ TkTextUpdateLineMetrics(
 		textPtr->dInfoPtr->metricEpoch = -1;
 	    }
 	} else {
+
 	    /*
 	     * We must never recalculate the height of the last artificial
 	     * line. It must stay at zero, and if we recalculate it, it will
@@ -3351,13 +3382,21 @@ TkTextUpdateLineMetrics(
 	}
     }
     if (doThisMuch == -1) {
+
 	/*
-	 * If we were requested to provide a full update, then also update the
-	 * scrollbar.
+	 * If we were requested to update the entire range, then also update
+	 * the scrollbar.
 	 */
 
 	GetYView(textPtr->interp, textPtr, 1);
     }
+    if (fullUpdateRequested) {
+        TextDInfo *dInfoPtr = textPtr->dInfoPtr;
+
+        dInfoPtr->lastMetricUpdateLine = lineNum;
+        dInfoPtr->currentMetricUpdateLine = lineNum;
+        GenerateWidgetViewSyncEvent(textPtr, 1);
+    }
     return lineNum;
 }
 
@@ -3526,8 +3565,12 @@ TextInvalidateLineMetrics(
 	textPtr->refCount++;
 	dInfoPtr->lineUpdateTimer = Tcl_CreateTimerHandler(1,
 		AsyncUpdateLineMetrics, textPtr);
-        GenerateWidgetViewSyncEvent(textPtr, 0);
     }
+
+    /*
+     * The widget is out of sync: send a <<WidgetViewSync>> event.
+     */
+    GenerateWidgetViewSyncEvent(textPtr, 0);
 }
 
 /*
@@ -5269,9 +5312,7 @@ TkTextRelayoutWindow(
 	    inSync = 0;
 	}
 
-	if (!inSync) {
-	    GenerateWidgetViewSyncEvent(textPtr, 0);
-	}
+        GenerateWidgetViewSyncEvent(textPtr, inSync);
     }
 }
 
@@ -6296,11 +6337,7 @@ TkTextPendingsync(
 {
     TextDInfo *dInfoPtr = textPtr->dInfoPtr;
 
-    return (
-        (!(dInfoPtr->flags & REDRAW_PENDING) &&
-	 (dInfoPtr->metricEpoch == -1) &&
-         (dInfoPtr->lastMetricUpdateLine == dInfoPtr->currentMetricUpdateLine)) ?
-        0 : 1);
+    return ((dInfoPtr->flags & OUT_OF_SYNC) != 0);
 }
 
 /*
diff --git a/tests/text.test b/tests/text.test
index 988417e..aaddc2c 100644
--- a/tests/text.test
+++ b/tests/text.test
@@ -2936,11 +2936,13 @@ test text-11a.1 {TextWidgetCmd procedure, "pendingsync" option} -setup {
 } -cleanup {
     destroy .yt
 } -result {1 {wrong # args: should be ".yt pendingsync"}}
+
 test text-11a.2 {TextWidgetCmd procedure, "pendingsync" option} -setup {
     destroy .top.yt .top
 } -body {
     toplevel .top
     pack [text .top.yt]
+    update
     set content {}
     for {set i 1} {$i < 300} {incr i} {
         append content [string repeat "$i " 15] \n
@@ -2978,9 +2980,11 @@ test text-11a.12 {TextWidgetCmd procedure, "sync" option} -setup {
 } -body {
     toplevel .top
     pack [text .top.yt]
+    update
     set content {}
+    # Use long lines so the line metrics will need updating.
     for {set i 1} {$i < 30} {incr i} {
-        append content [string repeat "$i " 15] \n
+        append content [string repeat "$i " 200] \n
     }
     .top.yt insert 1.0 $content
     # wait for end of line metrics calculation to get correct $fraction1
@@ -3053,19 +3057,18 @@ test text-11a.31 {"<<WidgetViewSync>>" event} -setup {
     for {set i 1} {$i < 300} {incr i} {
         append content [string repeat "$i " 15] \n
     }
-    .top.yt insert 1.0 $content
+    # Sync the widget and process <<WidgetViewSync>> events before binding.
+    .top.yt sync
     update
     bind .top.yt <<WidgetViewSync>> { if {%d} {set yud(%W) 1} }
-    # wait for end of line metrics calculation to get correct $fraction1
-    # as a reference
-    if {[.top.yt pendingsync]} {vwait yud(.top.yt)}
+    .top.yt insert 1.0 $content
     .top.yt yview moveto 1
     set fraction1 [lindex [.top.yt yview] 0]
     set res [expr {$fraction1 > 0}]
     .top.yt delete 1.0 end
     .top.yt insert 1.0 $content
     # synchronously wait for completion of line metrics calculation
-    # and ensure the test is relevant
+    # and verify that the fractions agree.
     set waited 0
     if {[.top.yt pendingsync]} {set waited 1 ; vwait yud(.top.yt)}
     lappend res $waited
@@ -3079,7 +3082,6 @@ test text-11a.31 {"<<WidgetViewSync>>" event} -setup {
 test text-11a.41 {"sync" "pendingsync" and <<WidgetViewSync>>} -setup {
     destroy .top.yt .top
 } -body {
-    set res {}
     toplevel .top
     pack [text .top.yt]
     update
@@ -3087,15 +3089,21 @@ test text-11a.41 {"sync" "pendingsync" and <<WidgetViewSync>>} -setup {
     for {set i 1} {$i < 300} {incr i} {
         append content [string repeat "$i " 50] \n
     }
+    # Sync the widget and process all <<WidgetViewSync>> events before binding. 
+    .top.yt sync
+    update
     bind .top.yt <<WidgetViewSync>> {lappend res Sync:%d}
+    set res {}
+    # The next line triggers <<WidgetViewSync>> with %d==0 i.e. out of sync.
     .top.yt insert 1.0 $content
-    vwait res  ; # event dealt with by the event loop, with %d==0 i.e. we're out of sync
-    # ensure the test is relevant
+    vwait res
+    # Verify that the line metrics are not up-to-date (pendingsync is 1).
     lappend res "Pending:[.top.yt pendingsync]"
-    # - <<WidgetViewSync>> fires when sync returns if there was pending syncs 
-    # - there is no more any pending sync after running 'sync'
+    # Update all line metrics by calling the sync command.
     .top.yt sync
-    vwait res  ; # event dealt with by the event loop, with %d==1 i.e. we're in sync again
+    # <<WidgetViewSync>> should fire with %d==1 i.e. back in sync.
+    vwait res
+    # At this time the line metrics should be up-to-date (pendingsync is 0).
     lappend res "Pending:[.top.yt pendingsync]"
     set res
 } -cleanup {
@@ -3110,6 +3118,7 @@ test text-11a.51 {<<WidgetViewSync>> calls TkSendVirtualEvent(),
     set res {}
     toplevel .top
     pack [text .top.t]
+    update
     for {set i 1} {$i < 10000} {incr i} {
         .top.t insert end "Hello world!\n" 
     }
@@ -7356,6 +7365,100 @@ test text-32.1 {line heights on creation} -setup {
     destroy .t
 } -result {1}
 
+test text-32.2 {peer widget -start, -end and deletion (bug 1630262)} -setup {
+    destroy .t .pt
+    set res {}
+} -body {
+    text .t
+    .t peer create .pt
+    for {set i 1} {$i < 100} {incr i} {
+      .t insert end "Line $i\n"
+    }
+    .t configure -startline 5
+    # none of the following delete shall crash
+    # (all did before fixing bug 1630262)
+    # 1. delete on the same line: line1 == line2 in DeleteIndexRange,
+    #    and resetView is true neither for .t not for .pt
+    .pt delete 2.0 2.2
+    # 2. delete just one line: line1 < line2 in DeleteIndexRange,
+    #    and resetView is true only for .t, not for .pt
+    .pt delete 2.0 3.0
+    # 3. delete several lines: line1 < line2 in DeleteIndexRange,
+    #    and resetView is true only for .t, not for .pt
+    .pt delete 2.0 5.0
+    # 4. delete to the end line: line1 < line2 in DeleteIndexRange,
+    #    and resetView is true only for .t, not for .pt
+    .pt delete 2.0 end
+    # this test succeeds provided there is no crash
+    set res 1
+} -cleanup {
+    destroy .pt
+} -result {1}
+
+test text-32.3 {peer widget -start, -end and deletion (bug 1630262)} -setup {
+    destroy .t .pt
+    set res {}
+} -body {
+    text .t
+    .t peer create .pt
+    for {set i 1} {$i < 100} {incr i} {
+      .t insert end "Line $i\n"
+    }
+    .t configure -startline 5
+    .pt configure -startline 3
+    # the following delete shall not crash
+    # (it did before fixing bug 1630262)
+    .pt delete 2.0 3.0
+    # moreover -startline shall be correct
+    # (was wrong before fixing bug 1630262)
+    lappend res [.t cget -start] [.pt cget -start]
+} -cleanup {
+    destroy .pt
+} -result {4 3}
+
+test text-32.4 {peer widget -start, -end and deletion (bug 1630262)} -setup {
+    destroy .t .pt
+    set res {}
+} -body {
+    text .t
+    .t peer create .pt
+    for {set i 1} {$i < 100} {incr i} {
+      .t insert end "Line $i\n"
+    }
+    .t configure -startline 5 -endline 15
+    .pt configure -startline 8 -endline 12
+    # .pt now shows a range entirely inside the range of .pt
+    # from .t, delete lines located after [.pt cget -end]
+    .t delete 9.0 10.0
+    # from .t, delete lines straddling [.pt cget -end]
+    .t delete 6.0 9.0
+    lappend res [.t cget -start] [.t cget -end] [.pt cget -start] [.pt cget -end]
+    .t configure -startline 5 -endline 12
+    .pt configure -startline 8 -endline 12
+    # .pt now shows again a range entirely inside the range of .pt
+    # from .t, delete lines located before [.pt cget -start]
+    .t delete 2.0 3.0
+    # from .t, delete lines straddling [.pt cget -start]
+    .t delete 2.0 5.0
+    lappend res [.t cget -start] [.t cget -end] [.pt cget -start] [.pt cget -end]
+    .t configure -startline 22 -endline 31
+    .pt configure -startline 42 -endline 51
+    # .t now shows a range entirely before the range of .pt
+    # from .t, delete some lines, then do it from .pt
+    .t delete 2.0 3.0
+    .t delete 2.0 5.0
+    .pt delete 2.0 5.0
+    lappend res [.t cget -start] [.t cget -end] [.pt cget -start] [.pt cget -end]
+    .t configure -startline 55 -endline 75
+    .pt configure -startline 60 -endline 70
+    # .pt now shows a range entirely inside the range of .t
+    # from .t, delete a range straddling the entire range of .pt
+    .t delete 3.0 18.0
+    lappend res [.t cget -start] [.t cget -end] [.pt cget -start] [.pt cget -end]
+} -cleanup {
+    destroy .pt .t
+} -result {5 11 8 10 5 8 6 8 22 27 38 44 55 60 57 57}
+
 
 test text-33.1 {TextWidgetCmd procedure, "peer" option} -setup {
     text .t
@@ -7488,100 +7591,6 @@ test text-34.1 {peer widget -start, -end and selection} -setup {
     destroy .t
 } -result {{10.0 20.0} {6.0 16.0} {6.0 11.0} {1.0 6.0} {1.0 2.0} {} {10.0 20.0}}
 
-test text-32.2 {peer widget -start, -end and deletion (bug 1630262)} -setup {
-    destroy .t .pt
-    set res {}
-} -body {
-    text .t
-    .t peer create .pt
-    for {set i 1} {$i < 100} {incr i} {
-      .t insert end "Line $i\n"
-    }
-    .t configure -startline 5
-    # none of the following delete shall crash
-    # (all did before fixing bug 1630262)
-    # 1. delete on the same line: line1 == line2 in DeleteIndexRange,
-    #    and resetView is true neither for .t not for .pt
-    .pt delete 2.0 2.2
-    # 2. delete just one line: line1 < line2 in DeleteIndexRange,
-    #    and resetView is true only for .t, not for .pt
-    .pt delete 2.0 3.0
-    # 3. delete several lines: line1 < line2 in DeleteIndexRange,
-    #    and resetView is true only for .t, not for .pt
-    .pt delete 2.0 5.0
-    # 4. delete to the end line: line1 < line2 in DeleteIndexRange,
-    #    and resetView is true only for .t, not for .pt
-    .pt delete 2.0 end
-    # this test succeeds provided there is no crash
-    set res 1
-} -cleanup {
-    destroy .pt
-} -result {1}
-
-test text-32.3 {peer widget -start, -end and deletion (bug 1630262)} -setup {
-    destroy .t .pt
-    set res {}
-} -body {
-    text .t
-    .t peer create .pt
-    for {set i 1} {$i < 100} {incr i} {
-      .t insert end "Line $i\n"
-    }
-    .t configure -startline 5
-    .pt configure -startline 3
-    # the following delete shall not crash
-    # (it did before fixing bug 1630262)
-    .pt delete 2.0 3.0
-    # moreover -startline shall be correct
-    # (was wrong before fixing bug 1630262)
-    lappend res [.t cget -start] [.pt cget -start]
-} -cleanup {
-    destroy .pt
-} -result {4 3}
-
-test text-32.4 {peer widget -start, -end and deletion (bug 1630262)} -setup {
-    destroy .t .pt
-    set res {}
-} -body {
-    text .t
-    .t peer create .pt
-    for {set i 1} {$i < 100} {incr i} {
-      .t insert end "Line $i\n"
-    }
-    .t configure -startline 5 -endline 15
-    .pt configure -startline 8 -endline 12
-    # .pt now shows a range entirely inside the range of .pt
-    # from .t, delete lines located after [.pt cget -end]
-    .t delete 9.0 10.0
-    # from .t, delete lines straddling [.pt cget -end]
-    .t delete 6.0 9.0
-    lappend res [.t cget -start] [.t cget -end] [.pt cget -start] [.pt cget -end]
-    .t configure -startline 5 -endline 12
-    .pt configure -startline 8 -endline 12
-    # .pt now shows again a range entirely inside the range of .pt
-    # from .t, delete lines located before [.pt cget -start]
-    .t delete 2.0 3.0
-    # from .t, delete lines straddling [.pt cget -start]
-    .t delete 2.0 5.0
-    lappend res [.t cget -start] [.t cget -end] [.pt cget -start] [.pt cget -end]
-    .t configure -startline 22 -endline 31
-    .pt configure -startline 42 -endline 51
-    # .t now shows a range entirely before the range of .pt
-    # from .t, delete some lines, then do it from .pt
-    .t delete 2.0 3.0
-    .t delete 2.0 5.0
-    .pt delete 2.0 5.0
-    lappend res [.t cget -start] [.t cget -end] [.pt cget -start] [.pt cget -end]
-    .t configure -startline 55 -endline 75
-    .pt configure -startline 60 -endline 70
-    # .pt now shows a range entirely inside the range of .t
-    # from .t, delete a range straddling the entire range of .pt
-    .t delete 3.0 18.0
-    lappend res [.t cget -start] [.t cget -end] [.pt cget -start] [.pt cget -end]
-} -cleanup {
-    destroy .pt .t
-} -result {5 11 8 10 5 8 6 8 22 27 38 44 55 60 57 57}
-
 test text-35.1 {widget dump -command alters tags} -setup {
      proc Dumpy {key value index} {
 #puts "KK: $key, $value"