allow 0-width 0-height elements. see slap-editor/slap#153.

lib/widget.js

@@ -2821,6 +2821,8 @@ Element.prototype.__defineGetter__('visible', function() {
   do {
     if (el.detached) return false;
     if (el.hidden) return false;
+    // if (!el.lpos) return false;
+    // if (el.position.width === 0 || el.position.height === 0) return false;
   } while (el = el.parent);
   return true;
 });
@@ -3154,7 +3156,7 @@ Element.prototype._getPos = function() {
 
 Element.prototype._getWidth = function(get) {
   var parent = get ? this.parent._getPos() : this.parent
-    , width = this.position.width || 0
+    , width = this.position.width
     , left
     , expr;
 
@@ -3174,7 +3176,7 @@ Element.prototype._getWidth = function(get) {
   // the content width, and the content width is initially
   // decided by the width the element, so it needs to be
   // calculated here.
-  if (!width) {
+  if (width == null) {
     left = this.position.left || 0;
     if (typeof left === 'string') {
       if (left === 'center') left = '50%';
@@ -3203,7 +3205,7 @@ Element.prototype.__defineGetter__('width', function() {
 
 Element.prototype._getHeight = function(get) {
   var parent = get ? this.parent._getPos() : this.parent
-    , height = this.position.height || 0
+    , height = this.position.height
     , top
     , expr;
 
@@ -3223,7 +3225,7 @@ Element.prototype._getHeight = function(get) {
   // the content width, and the content width is initially
   // decided by the width the element, so it needs to be
   // calculated here.
-  if (!height) {
+  if (height == null) {
     top = this.position.top || 0;
     if (typeof top === 'string') {
       if (top === 'center') top = '50%';
@@ -3950,6 +3952,16 @@ Element.prototype.render = function() {
     return;
   }
 
+  if (coords.xl - coords.xi <= 0) {
+    coords.xl = Math.max(coords.xl, coords.xi);
+    return;
+  }
+
+  if (coords.yl - coords.yi <= 0) {
+    coords.yl = Math.max(coords.yl, coords.yi);
+    return;
+  }
+
   var lines = this.screen.lines
     , xi = coords.xi
     , xl = coords.xl

test/widget.js

@@ -175,6 +175,33 @@ var stext = blessed.scrollabletext({
   }
 });
 
+setTimeout(function() {
+  stext.width = 0;
+  screen.render();
+  setTimeout(function() {
+    stext.width = '50%';
+    screen.render();
+    setTimeout(function() {
+      stext.height = 0;
+      screen.render();
+      setTimeout(function() {
+        stext.height = 6;
+        screen.render();
+        setTimeout(function() {
+          stext.width = 0;
+          stext.height = 0;
+          screen.render();
+          setTimeout(function() {
+            stext.width = '50%';
+            stext.height = 6;
+            screen.render();
+          }, 1000);
+        }, 1000);
+      }, 1000);
+    }, 1000);
+  }, 1000);
+}, 1000);
+
 screen.append(stext);
 stext.on('keypress', function(ch, key) {
   if (key.name === 'up' || key.name === 'k') {