simple color assignment not working in XTK with GWT (mesh.color = [0.7,0,0]) - xtk

Question

#haehn Hi Haehn (XTK)
I'm using edge-XTK with GWT and trying to render a simple STL. However XTK code fails at the line where we assign color to the mesh.
mesh.color = [0.7,0,0] // this line fails
Error message emitted by XTK code: "Invalid color"
This behavior is observed only when using XTK with GWT.
The error seems to be coming from this XTK code snippet
X.displayable.prototype.__defineSetter__('color', function(color) {
// we accept only numbers as arguments
if (!goog.isDefAndNotNull(color) || !(color instanceof Array) ||
(color.length != 3)) {
throw new Error('Invalid color.');
}
I'm guessing that the issue is with the way GWT builds page with iframes... because of which the above if condition could be failing in GWT. I think if you replace the above check with following snippet (got idea from: here).
It might fix the problem.
use goog.isArray(color) instead of (color instanceof Array)
Can you please investigate and comment?
Edit:
Hi XTK
Here is the code snippet which shows how I'm using XTK with GWT.
public class TestGwtXtk implements EntryPoint {
public void onModuleLoad() {
testXtk();
}
// GWT JSNI method, which allows mixing Java and JS natively.
// it is akin using c++ or c libraries in java or android
private native void testXtk() /*-{
var r = new $wnd.X.renderer3D();
r.container = 'xtk_container'; // div ele
r.config.PROGRESSBAR_ENABLED = false;
r.init();
cube = new $wnd.X.cube();
cube.lengthX = cube.lengthY = cube.lengthZ = 20;
cube.color = [ 1, 1, 1 ]; // fails here in XTK code
cube.center = [ 0, 0, 0 ]; // fails here in XTK code
r.add(cube);
r.render();
}-*/;
}
As noted by the inline comments, use of javascript array fails. Failure is not because js array usage, such as [0,0,0] or new Array(0,0,0) is wrong. Failure is because the way XTK code checks for "instance of Array".
Edit: 2
Dear XTK
I was able to checkout XTK code from git, make changes that I'm proposing, re-build XTK.js and finally test successfully that my fix solves the problem.
for example: in displayable.js I commented one line and added another line thus:
// if (!goog.isDefAndNotNull(color) || !(color instanceof Array) || (color.length != 3)) {
if (!goog.isDefAndNotNull(color) || !(goog.isArray(color)) || (color.length != 3)) {
I made similar changes in couple of other places in the xtk codebase to get my usecase going. Explanation of why this is the right solution is here: Closure: The Definitive Guide. Would you please consider making this fix in the codebase for release 8? Thank you

Answer 1

Using XTK with GWT ? What do you mean ? Did you write your own wrappers to compile code with xtk calls from Java to JavaScript ? Or do you directly use xtk.js in the war file and write manualy some JavaScript using it ? Or do you only use GAE (Google App Engine), the Google environnement for web applications (the ones made with GWT, but also not compiled from Java ones). Could you be more accurate please ?
Here they deal with some issues with GWT and type test, did you try to create your array with the "new" operator ?
var mycolor = new Array(0.7,0,0);
mesh.color = mycolor;