[FIX/REF] barcodes: don't catch keypress if a control key is pressed

This avoids breaking shortcuts on Firefox, which rely on keypress
events instead of keydown / keyup. The tradeoff is that a barcode
cannot be scanned and interpreted if ctrl, alt or cmd is pressed.
Also don't catch function keys.

addons/barcodes/static/src/js/barcode_events.js

@@ -87,14 +87,15 @@ var BarcodeEvents = core.Class.extend(mixins.PropertiesMixin, {
         return $(element).is('input,textarea,[contenteditable="true"]');
     },
 
-    // This checks that a keypress event is either ESC, TAB or an
-    // arrow key. This is Firefox specific, in Chrom{e,ium}
+    // This checks that a keypress event is either ESC, TAB, an arrow
+    // key or a function key. This is Firefox specific, in Chrom{e,ium}
     // keypress events are not fired for these types of keys, only
     // keyup/keydown.
     is_special_key: function(e) {
         if (e.key === "ArrowLeft" || e.key === "ArrowRight" ||
             e.key === "ArrowUp" || e.key === "ArrowDown" ||
-            e.key === "Escape" || e.key === "Tab") {
+            e.key === "Escape" || e.key === "Tab" ||
+            /F\d\d?/.test(e.key)) {
             return true;
         } else {
             return false;
@@ -117,24 +118,34 @@ var BarcodeEvents = core.Class.extend(mixins.PropertiesMixin, {
     },
 
     handler: function(e){
-        if (! e.dispatched_by_barcode_reader && ! this.is_special_key(e)) {
-            // We only stop events targeting elements that are editable. We
-            // do not stop events targeting other elements because we have
-            // no way of redispatching 'genuine' key events that trigger
-            // native event handlers of elements. So this means that our
-            // fake events will not appear in eg. an <input> element.
-            if (! this.element_is_editable(e.target) || e.target.getAttribute("barcode_events") === "true") {
-                this.buffered_key_events.push(e);
-                e.preventDefault();
-                e.stopImmediatePropagation();
-
-                clearTimeout(this.timeout);
-                if (String.fromCharCode(e.which).match(this.suffix) !== null) {
-                    this.handle_buffered_keys();
-                } else {
-                    this.timeout = setTimeout(this.handle_buffered_keys.bind(this), this.max_time_between_keys_in_ms);
-                }
-            }
+        // Don't catch events we resent
+        if (e.dispatched_by_barcode_reader)
+            return;
+        // Don't catch non-printable keys for which Firefox triggers a keypress
+        if (this.is_special_key(e))
+            return;
+        // Don't catch keypresses which could have a UX purpose (like shortcuts)
+        if (e.ctrlKey || e.metaKey || e.altKey)
+            return;
+        // Don't catch events targeting elements that are editable because we
+        // have no way of redispatching 'genuine' key events. Resent events
+        // don't trigger native event handlers of elements. So this means that
+        // our fake events will not appear in eg. an <input> element.
+        if (this.element_is_editable(e.target) && e.target.getAttribute("barcode_events") !== "true")
+            return;
+
+        // Catch and buffer the event
+        this.buffered_key_events.push(e);
+        e.preventDefault();
+        e.stopImmediatePropagation();
+
+        // Handle buffered keys immediately if the the keypress marks the end
+        // of a barcode or after x milliseconds without a new keypress
+        clearTimeout(this.timeout);
+        if (String.fromCharCode(e.which).match(this.suffix)) {
+            this.handle_buffered_keys();
+        } else {
+            this.timeout = setTimeout(this.handle_buffered_keys.bind(this), this.max_time_between_keys_in_ms);
         }
     },