Merged TIP #446 accepted by TCT vote. This fixes [1273358] - Ask a text widget for the depth of its undo and redo stacks.

6 files changed, 233 insertions, 23 deletions

diff --git a/doc/event.n b/doc/event.n
index 045339e..54ad42e 100644
--- a/doc/event.n
+++ b/doc/event.n
@@ -352,6 +352,10 @@ user-driven
 .QW "tab to widget"
 action.
 .TP
+\fB<<UndoStack>>\fR
+This is sent to a text widget when its undo stack or redo stack becomes
+empty or unempty.
+.TP
 \fB<<WidgetViewSync>>\fR
 This is sent to a text widget when its internal data become obsolete,
 and again when these internal data are back in sync with the widget
diff --git a/doc/text.n b/doc/text.n
index 9ec8f74..e2bb01f 100644
--- a/doc/text.n
+++ b/doc/text.n
@@ -897,6 +897,9 @@ separator is already present at the top of the undo stack no other will be
 inserted. That means that two separators on the undo stack are always
 separated by at least one insert or delete action.
 .PP
+The \fB<<UndoStack>>\fR virtual event is generated every time the undo stack
+or the redo stack becomes empty or unempty.
+.PP
 The undo mechanism is also linked to the modified flag. This means that
 undoing or redoing changes can take a modified text widget back to the
 unmodified state or vice versa. The modified flag will be set automatically to
@@ -1282,6 +1285,16 @@ behavior of the command depends on the \fIoption\fR argument that follows the
 supported:
 .RS
 .TP
+\fIpathName \fBedit canredo\fR
+.
+Returns a boolean true if redo is possible, i.e. when the redo stack is not
+empty. Otherwise returns false.
+.TP
+\fIpathName \fBedit canundo\fR
+.
+Returns a boolean true if undo is possible, i.e. when the undo stack is not
+empty. Otherwise returns false.
+.TP
 \fIpathName \fBedit modified \fR?\fIboolean\fR?
 .
 If \fIboolean\fR is not specified, returns the modified flag of the widget.
diff --git a/generic/tkText.c b/generic/tkText.c
index 3e8d625..b610844 100644
--- a/generic/tkText.c
+++ b/generic/tkText.c
@@ -401,6 +401,7 @@ static Tcl_Obj *	TextGetText(const TkText *textPtr,
 			    const TkTextIndex *index1,
 			    const TkTextIndex *index2, int visibleOnly);
 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,
@@ -2093,7 +2094,7 @@ ConfigureText(
     textPtr->sharedTextPtr->maxUndo = textPtr->maxUndo;
     textPtr->sharedTextPtr->autoSeparators = textPtr->autoSeparators;
 
-    TkUndoSetDepth(textPtr->sharedTextPtr->undoStack,
+    TkUndoSetMaxDepth(textPtr->sharedTextPtr->undoStack,
 	    textPtr->sharedTextPtr->maxUndo);
 
     /*
@@ -2769,6 +2770,7 @@ TextPushUndoAction(
 				/* Index describing second location. */
 {
     TkUndoSubAtom *iAtom, *dAtom;
+    int canUndo, canRedo;
 
     /*
      * Create the helpers.
@@ -2855,6 +2857,9 @@ TextPushUndoAction(
     Tcl_DecrRefCount(index1Obj);
     Tcl_DecrRefCount(index2Obj);
 
+    canUndo = TkUndoCanUndo(textPtr->sharedTextPtr->undoStack);
+    canRedo = TkUndoCanRedo(textPtr->sharedTextPtr->undoStack);
+
     /*
      * Depending whether the action is to insert or delete, we provide the
      * appropriate second and third arguments to TkUndoPushAction. (The first
@@ -2866,6 +2871,10 @@ TextPushUndoAction(
     } else {
 	TkUndoPushAction(textPtr->sharedTextPtr->undoStack, dAtom, iAtom);
     }
+
+    if (!canUndo || canRedo) {
+        GenerateUndoStackEvent(textPtr);
+    }
 }
 
 /*
@@ -5155,11 +5164,16 @@ TextEditCmd(
     Tcl_Obj *const objv[])	/* Argument objects. */
 {
     int index, setModified, oldModified;
+    int canRedo = 0;
+    int canUndo = 0;
+
     static const char *const editOptionStrings[] = {
-	"modified", "redo", "reset", "separator", "undo", NULL
+	"canundo", "canredo", "modified", "redo", "reset", "separator",
+        "undo", NULL
     };
     enum editOptions {
-	EDIT_MODIFIED, EDIT_REDO, EDIT_RESET, EDIT_SEPARATOR, EDIT_UNDO
+	EDIT_CANUNDO, EDIT_CANREDO, EDIT_MODIFIED, EDIT_REDO, EDIT_RESET,
+	EDIT_SEPARATOR, EDIT_UNDO
     };
 
     if (objc < 3) {
@@ -5173,6 +5187,26 @@ TextEditCmd(
     }
 
     switch ((enum editOptions) index) {
+    case EDIT_CANREDO:
+        if (objc != 3) {
+            Tcl_WrongNumArgs(interp, 3, objv, NULL);
+             return TCL_ERROR;
+        }
+        if (textPtr->sharedTextPtr->undo) {
+            canRedo = TkUndoCanRedo(textPtr->sharedTextPtr->undoStack);
+        }
+        Tcl_SetObjResult(interp, Tcl_NewBooleanObj(canRedo));
+        break;
+    case EDIT_CANUNDO:
+        if (objc != 3) {
+            Tcl_WrongNumArgs(interp, 3, objv, NULL);
+             return TCL_ERROR;
+        }
+        if (textPtr->sharedTextPtr->undo) {
+            canUndo = TkUndoCanUndo(textPtr->sharedTextPtr->undoStack);
+        }
+        Tcl_SetObjResult(interp, Tcl_NewBooleanObj(canUndo));
+        break;
     case EDIT_MODIFIED:
 	if (objc == 3) {
 	    Tcl_SetObjResult(interp,
@@ -5206,29 +5240,36 @@ TextEditCmd(
 	 */
 
 	if ((!oldModified) != (!setModified)) {
-            for (textPtr = textPtr->sharedTextPtr->peers; textPtr != NULL;
-                    textPtr = textPtr->next) {
-                GenerateModifiedEvent(textPtr);
-            }
+            GenerateModifiedEvent(textPtr);
 	}
 	break;
     case EDIT_REDO:
-	if (objc != 3) {
+        if (objc != 3) {
 	    Tcl_WrongNumArgs(interp, 3, objv, NULL);
 	    return TCL_ERROR;
 	}
-	if (TextEditRedo(textPtr)) {
+	canUndo = TkUndoCanUndo(textPtr->sharedTextPtr->undoStack);
+        if (TextEditRedo(textPtr)) {
 	    Tcl_SetObjResult(interp, Tcl_NewStringObj("nothing to redo", -1));
 	    Tcl_SetErrorCode(interp, "TK", "TEXT", "NO_REDO", NULL);
 	    return TCL_ERROR;
 	}
+        canRedo = TkUndoCanRedo(textPtr->sharedTextPtr->undoStack);
+        if (!canUndo || !canRedo) {
+            GenerateUndoStackEvent(textPtr);
+        }
 	break;
     case EDIT_RESET:
 	if (objc != 3) {
 	    Tcl_WrongNumArgs(interp, 3, objv, NULL);
 	    return TCL_ERROR;
 	}
+        canUndo = TkUndoCanUndo(textPtr->sharedTextPtr->undoStack);
+        canRedo = TkUndoCanRedo(textPtr->sharedTextPtr->undoStack);
 	TkUndoClearStacks(textPtr->sharedTextPtr->undoStack);
+        if (canUndo || canRedo) {
+            GenerateUndoStackEvent(textPtr);
+        }
 	break;
     case EDIT_SEPARATOR:
 	if (objc != 3) {
@@ -5238,15 +5279,20 @@ TextEditCmd(
 	TkUndoInsertUndoSeparator(textPtr->sharedTextPtr->undoStack);
 	break;
     case EDIT_UNDO:
-	if (objc != 3) {
+        if (objc != 3) {
 	    Tcl_WrongNumArgs(interp, 3, objv, NULL);
 	    return TCL_ERROR;
 	}
+        canRedo = TkUndoCanRedo(textPtr->sharedTextPtr->undoStack);
 	if (TextEditUndo(textPtr)) {
 	    Tcl_SetObjResult(interp, Tcl_NewStringObj("nothing to undo", -1));
 	    Tcl_SetErrorCode(interp, "TK", "TEXT", "NO_UNDO", NULL);
 	    return TCL_ERROR;
 	}
+        canUndo = TkUndoCanUndo(textPtr->sharedTextPtr->undoStack);
+        if (!canRedo || !canUndo) {
+            GenerateUndoStackEvent(textPtr);
+        }
 	break;
     }
     return TCL_OK;
@@ -5341,7 +5387,8 @@ TextGetText(
  *
  *	Send an event that the text was modified. This is equivalent to:
  *	   event generate $textWidget <<Modified>>
- *
+  *	for all peers of $textWidget.
+*
  * Results:
  *	None
  *
@@ -5355,8 +5402,41 @@ static void
 GenerateModifiedEvent(
     TkText *textPtr)	/* Information about text widget. */
 {
-    Tk_MakeWindowExist(textPtr->tkwin);
-    TkSendVirtualEvent(textPtr->tkwin, "Modified", NULL);
+    for (textPtr = textPtr->sharedTextPtr->peers; textPtr != NULL;
+            textPtr = textPtr->next) {
+        Tk_MakeWindowExist(textPtr->tkwin);
+        TkSendVirtualEvent(textPtr->tkwin, "Modified", NULL);
+    }
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * GenerateUndoStackEvent --
+ *
+ *	Send an event that the undo or redo stack became empty or unempty.
+ *	This is equivalent to:
+ *	   event generate $textWidget <<UndoStack>>
+ *	for all peers of $textWidget.
+ *
+ * Results:
+ *	None
+ *
+ * Side effects:
+ *	May force the text window (and all peers) into existence.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static void
+GenerateUndoStackEvent(
+    TkText *textPtr)	/* Information about text widget. */
+{
+    for (textPtr = textPtr->sharedTextPtr->peers; textPtr != NULL;
+            textPtr = textPtr->next) {
+        Tk_MakeWindowExist(textPtr->tkwin);
+        TkSendVirtualEvent(textPtr->tkwin, "UndoStack", NULL);
+    }
 }
 
 /*
@@ -5380,7 +5460,6 @@ UpdateDirtyFlag(
     TkSharedText *sharedTextPtr)/* Information about text widget. */
 {
     int oldDirtyFlag;
-    TkText *textPtr;
 
     /*
      * If we've been forced to be dirty, we stay dirty (until explicitly
@@ -5411,10 +5490,7 @@ UpdateDirtyFlag(
     }
 
     if (sharedTextPtr->isDirty == 0 || oldDirtyFlag == 0) {
-	for (textPtr = sharedTextPtr->peers; textPtr != NULL;
-		textPtr = textPtr->next) {
-	    GenerateModifiedEvent(textPtr);
-	}
+        GenerateModifiedEvent(sharedTextPtr->peers);
     }
 }
 
diff --git a/generic/tkUndo.c b/generic/tkUndo.c
index 8359e0a..c66905d 100644
--- a/generic/tkUndo.c
+++ b/generic/tkUndo.c
@@ -353,7 +353,7 @@ TkUndoInitStack(
 /*
  *----------------------------------------------------------------------
  *
- * TkUndoSetDepth --
+ * TkUndoSetMaxDepth --
  *
  *	Set the maximum depth of stack.
  *
@@ -368,7 +368,7 @@ TkUndoInitStack(
  */
 
 void
-TkUndoSetDepth(
+TkUndoSetMaxDepth(
     TkUndoRedoStack *stack,	/* An Undo/Redo stack */
     int maxdepth)		/* The maximum stack depth */
 {
@@ -478,6 +478,52 @@ TkUndoFreeStack(
 /*
  *----------------------------------------------------------------------
  *
+ * TkUndoCanRedo --
+ *
+ *	Returns true if redo is possible, i.e. if the redo stack is not empty.
+ *
+ * Results:
+ *	 A boolean.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+TkUndoCanRedo(
+    TkUndoRedoStack *stack)	/* An Undo/Redo stack */
+{
+    return stack->redoStack != NULL;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TkUndoCanUndo --
+ *
+ *	Returns true if undo is possible, i.e. if the undo stack is not empty.
+ *
+ * Results:
+ *	 A boolean.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+TkUndoCanUndo(
+    TkUndoRedoStack *stack)	/* An Undo/Redo stack */
+{
+    return stack->undoStack != NULL;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * TkUndoInsertUndoSeparator --
  *
  *	Insert a separator on the undo stack, indicating a border for an
@@ -498,7 +544,7 @@ TkUndoInsertUndoSeparator(
 {
     if (TkUndoInsertSeparator(&stack->undoStack)) {
 	stack->depth++;
-	TkUndoSetDepth(stack, stack->maxdepth);
+	TkUndoSetMaxDepth(stack, stack->maxdepth);
     }
 }
 
diff --git a/generic/tkUndo.h b/generic/tkUndo.h
index e63aac4..490ede9 100644
--- a/generic/tkUndo.h
+++ b/generic/tkUndo.h
@@ -96,9 +96,11 @@ MODULE_SCOPE void	TkUndoClearStack(TkUndoAtom **stack);
  */
 
 MODULE_SCOPE TkUndoRedoStack *TkUndoInitStack(Tcl_Interp *interp, int maxdepth);
-MODULE_SCOPE void	TkUndoSetDepth(TkUndoRedoStack *stack, int maxdepth);
+MODULE_SCOPE void	TkUndoSetMaxDepth(TkUndoRedoStack *stack, int maxdepth);
 MODULE_SCOPE void	TkUndoClearStacks(TkUndoRedoStack *stack);
 MODULE_SCOPE void	TkUndoFreeStack(TkUndoRedoStack *stack);
+MODULE_SCOPE int	TkUndoCanRedo(TkUndoRedoStack *stack);
+MODULE_SCOPE int	TkUndoCanUndo(TkUndoRedoStack *stack);
 MODULE_SCOPE void	TkUndoInsertUndoSeparator(TkUndoRedoStack *stack);
 MODULE_SCOPE TkUndoSubAtom *TkUndoMakeCmdSubAtom(Tcl_Command command,
 			    Tcl_Obj *actionScript, TkUndoSubAtom *subAtomList);
diff --git a/tests/text.test b/tests/text.test
index f217bcf..0ec69d0 100644
--- a/tests/text.test
+++ b/tests/text.test
@@ -6207,7 +6207,7 @@ test text-27.2 {TextEditCmd procedure, argument parsing} -body {
     .t edit gorp
 } -cleanup {
     destroy .t
-} -returnCodes {error} -result {bad edit option "gorp": must be modified, redo, reset, separator, or undo}
+} -returnCodes {error} -result {bad edit option "gorp": must be canundo, canredo, modified, redo, reset, separator, or undo}
 test text-27.3 {TextEditUndo procedure, undoing changes} -body {
     text .t -undo 1
     pack .t
@@ -6494,6 +6494,75 @@ test text-27.22 {patch 1669632 (v) - <<Clear>> is atomic} -setup {
 } -cleanup {
     destroy .top.t .top
 } -result "This A an example text"
+test text-27.24 {TextEditCmd procedure, canundo and canredo} -setup {
+    destroy .t
+    set res {}
+} -body {
+    text .t -undo false -autoseparators false
+    lappend res [.t edit canundo] [.t edit canredo]
+    .t configure -undo true
+    lappend res [.t edit canundo] [.t edit canredo]
+    .t insert end "DO\n"
+    .t edit separator
+    .t insert end "IT\n"
+    .t insert end "YOURSELF\n"
+    .t edit separator
+    lappend res [.t edit canundo] [.t edit canredo]
+    .t edit undo
+    lappend res [.t edit canundo] [.t edit canredo]
+    .t configure -undo false
+    lappend res [.t edit canundo] [.t edit canredo]
+    .t configure -undo true
+    lappend res [.t edit canundo] [.t edit canredo]
+    .t edit redo
+    lappend res [.t edit canundo] [.t edit canredo]
+} -cleanup {
+    destroy .t
+} -result {0 0 0 0 1 0 1 1 0 0 1 1 1 0}
+test text-27.25 {<<UndoStack>> virtual event} -setup {
+    destroy .t
+    set res {}
+    set nbUS 0
+} -body {
+    text .t -undo false -autoseparators false
+    bind .t <<UndoStack>> {incr nbUS}
+    update ; lappend res $nbUS
+    .t configure -undo true
+    update ; lappend res $nbUS
+    .t insert end "DO\n"
+    .t edit separator
+    .t insert end "IT\n"
+    .t insert end "YOURSELF\n"
+    .t edit separator
+    .t insert end "MAN\n"
+    .t edit separator
+    update ; lappend res $nbUS
+    .t edit undo
+    update ; lappend res $nbUS
+    .t edit redo
+    update ; lappend res $nbUS
+    .t edit undo
+    update ; lappend res $nbUS
+    .t edit undo
+    update ; lappend res $nbUS
+    .t edit undo
+    update ; lappend res $nbUS
+    .t edit redo
+    update ; lappend res $nbUS
+    .t edit redo
+    update ; lappend res $nbUS
+    .t edit redo
+    update ; lappend res $nbUS
+    .t edit undo
+    update ; lappend res $nbUS
+    .t edit undo
+    update ; lappend res $nbUS
+    .t edit reset
+    update ; lappend res $nbUS
+} -cleanup {
+    destroy .t
+} -result {0 0 1 2 3 4 4 5 6 6 7 8 8 9}
+
 
 test text-28.1 {bug fix - 624372, ControlUtfProc long lines} -body {
     pack [text .t -wrap none]