Improve behavior of font size detection when editors have changing visibility

- Allow on-demand checking of text layer character sizes
- Disregard character measurements that result in width or height of 0

lib/ace/layer/text.js

@@ -50,7 +50,7 @@ var Text = function(parentEl) {
     this.element.className = "ace_layer ace_text-layer";
     parentEl.appendChild(this.element);
 
-    this.$characterSize = this.$measureSizes();
+    this.$characterSize = this.$measureSizes() || {width: 0, height: 0};
     this.$pollSizeChanges();
 };
 
@@ -75,14 +75,18 @@ var Text = function(parentEl) {
         return this.$characterSize.width || 1;
     };
 
+    this.checkForSizeChanges = function() {
+        var size = this.$measureSizes();
+        if (size && (this.$characterSize.width !== size.width || this.$characterSize.height !== size.height)) {
+            this.$characterSize = size;
+            this._dispatchEvent("changeCharaterSize", {data: size});
+        }
+    };
+
     this.$pollSizeChanges = function() {
         var self = this;
         setInterval(function() {
-            var size = self.$measureSizes();
-            if (self.$characterSize.width !== size.width || self.$characterSize.height !== size.height) {
-                self.$characterSize = size;
-                self._dispatchEvent("changeCharaterSize", {data: size});
-            }
+            self.checkForSizeChanges();
         }, 500);
     };
 
@@ -92,7 +96,7 @@ var Text = function(parentEl) {
         fontWeight : 1,
         fontStyle : 1,
         lineHeight : 1
-    },
+    };
 
     this.$measureSizes = function() {
         var n = 1000;
@@ -134,6 +138,12 @@ var Text = function(parentEl) {
             height: this.$measureNode.offsetHeight,
             width: this.$measureNode.offsetWidth / (n * 2)
         };
+
+        // Size and width can be null if the editor is not visible or
+        // detached from the document
+        if (size.width == 0 && size.height == 0)
+            return null;
+
         return size;
     };
 

lib/ace/virtual_renderer.js

@@ -192,6 +192,10 @@ var VirtualRenderer = function(container, theme) {
         this.$loop.schedule(this.CHANGE_FULL);
     };
 
+    this.updateFontSize = function() {
+        this.$textLayer.checkForSizeChanges();
+    };
+
     /**
      * Triggers resize of the editor
      */