Rework tooltip method in BView again.

Passing NULL or a blank string to SetToolTip(const char*) sets the
tooltip to NULL by calling SetToolTip(BToolTip*) with a NULL argument.

Calling SetToolTip(BToolTip*) with a NULL argument calls HideToolTip()
because sometimes the tool tip can change without the mouse moving,
for example because the user clicked.

Thanks Axeld and Stippi.

src/kits/interface/View.cpp

@@ -4817,6 +4817,11 @@ BView::DoLayout()
 void
 BView::SetToolTip(const char* text)
 {
+	if (text == NULL || text[0] == '\0') {
+		SetToolTip((BToolTip*)NULL);
+		return;
+	}
+
 	if (BTextToolTip* tip = dynamic_cast<BTextToolTip*>(fToolTip))
 		tip->SetText(text);
 	else
@@ -4829,10 +4834,14 @@ BView::SetToolTip(BToolTip* tip)
 {
 	if (fToolTip == tip)
 		return;
+	else if (tip == NULL)
+		HideToolTip();
 
 	if (fToolTip != NULL)
 		fToolTip->ReleaseReference();
+
 	fToolTip = tip;
+
 	if (fToolTip != NULL)
 		fToolTip->AcquireReference();
 }
@@ -4851,13 +4860,6 @@ BView::ShowToolTip(BToolTip* tip)
 	if (tip == NULL)
 		return;
 
-	if (BTextToolTip* textTip = dynamic_cast<BTextToolTip*>(tip)) {
-		const char* text = textTip->Text();
-		// if text is NULL or blank don't show the tooltip
-		if (text == NULL || text[0] == '\0')
-			return;
-	}
-
 	BPoint where;
 	GetMouse(&where, NULL, false);