Fix ChangeGC.

lib/corereqs.js

@@ -765,13 +765,9 @@ var templates = {
            var vals = packValueMask('CreateGC', values);
            var packetLength = 3 + (values ? vals[2].length : 0);
            var args = [56, packetLength, cid];
-           args.push(vals[0]);     // values bitmask
-           var valArr = vals[1];
-           for (var v in valArr)
-           {
-               format += 'L'; // TODO: we know format string length in advance and += inefficient for string
-               args.push(valArr[v]);
-           }
+           format += vals[0]
+           args.push(vals[1]);     // values bitmask
+           args = args.concat(vals[2])
            return [format, args];
         }
    ],

test/changeGC.js

@@ -0,0 +1,54 @@
+var x11 = require('../lib');
+var should = require('should');
+
+describe('CreateGC', function() {
+    before(function(done) {
+        var self = this;
+        this.client = x11.createClient(function(err, dpy) {
+            should.not.exist(err);
+            self.X = dpy.client;
+            self.root = dpy.screen[0].root;
+            self.white = dpy.screen[0].white_pixel;
+            self.black = dpy.screen[0].black_pixel;
+            self.wid = self.X.AllocID();
+            self.X.CreateWindow(self.wid, self.root, 0, 0, 1, 1); // 1x1 pixel window
+            self.X.MapWindow(self.wid);
+            self.X.QueryTree(self.root, function(err, list) {
+                should.not.exist(err);
+                list.children.indexOf(self.wid).should.not.equal(-1);
+                done();
+            });
+        });
+    });
+
+    it('should create a Graphic Context correctly', function() {
+        var self = this;
+        this.client.on('error', function(err) {
+            should.not.exist(err);
+        });
+
+        this.gc = this.X.AllocID();
+        this.X.CreateGC(this.gc,
+                        this.wid,
+                        {
+                            foreground: this.black,
+                            background: this.white,
+                            lineStyle : 0
+                        }
+        );
+
+        this.X.ChangeGC(this.gc,
+                        {
+                            foreground: 0xffff00,
+                            background: 0x0000ff,
+                            lineStyle : 2
+                        }
+        );
+    });
+
+    after(function(done) {
+        this.X.DestroyWindow(this.wid);
+        this.X.on('end', done);
+        this.X.terminate();
+    });
+});