Develop Reference

Qt function runJavaScript() does not execute JavaScript code

I am trying to implement the displaying of a web page in Qt. I chose to use the Qt WebEngine to achieve my task. Here's what I did :
Wrote a sample web page consisting of a empty form.
Wrote a JS file with just an API to create a radio button inside the form.
In my code, it looks like this :
View = new QWebEngineView(this);
// read the js file using qfile
file.open("path to jsFile");
myJsApi = file.Readall();
View->page()->runjavascript (myjsapi);
View->page()->runjavascript ("createRadioButton(\"button1\");");
I find that the runJavaScript() function has no effect on the web page. I can see the web page in the output window, but the radio button I expected is not present. What am I doing wrong?

I think you will have to connect the signal loadFinished(bool) of your page() to a slot, then execute runJavaScript() in this slot.
void yourClass::mainFunction()
{
View = new QWebEngineView(this);
connect( View->page(), SIGNAL(loadFinished(bool)), this, SLOT(slotForRunJS(bool)));
}
void yourClass::slotForRunJS(bool ok)
{
// read the js file using qfile
file.open("path to jsFile");
myJsApi = file.Readall();
View->page()->runJavaScript(myjsapi);
View->page()->runJavaScript("createRadioButton(\"button1\");");
}

I had this problem, runJavascript didn't have any effect. I had to put some html content into the view (with page().setHtml("") before running it.

Check the application output, it might contain JavaScript errors. Even if your JS code is valid, you might encounter the situation where the script is run before DOMContentLoaded event, that is document.readyState == 'loading'. Therefore, the DOM might not be available yet, as well as variables or functions provided by other scripts. If you depend on them for your code to run, when you detect this readyState, either wait for the event or try calling the function later, after a timeout. The second approach with timeout might be needed if you need to get the result of the code execution, as this can be done only synchronously.

Timing React.js Application

I am working with a 3rd party APM tool which provides a javascript agent to give insight into the visibility of UI rendering times.
Understanding that that React.js doesn't really map well to the browser timings API, can anyone shed any insight into when I would measure the below metrics? I included the available API calls that the vendor provides.
Metrics to report
End User Response Time - virtualPageStart() to virtualPageEnd()
HTML Download Time - viewChangeStart() to viewChangeEnd()
HTML Download & DOM Building Time - viewChangeStart() to viewDOMLoaded()
DOM Building Time - viewChangeEnd() to viewDOMLoaded()
DOM Ready Time - viewChangeStart to viewDOMLoaded
Available API Calls
markViewChangeStart() Sets the view change start time.
markViewChangeEnd() Sets the view change end time.
markViewDOMLoaded() Sets the view DOM loaded time.
markXhrRequestsCompleted() Sets the XHR requests completed time.
markViewResourcesLoaded() Sets the view resources loaded time.
markVirtualPageStart() Sets the virtual page start time.
markVirtualPageEnd() Sets the virtual page end time.
THANKS!!!

For most of these items, you are actually not affected by React itself. You can record the changestart/changeend events with your routing library. If you don't use any routing library, your pseudocode would look like this:
markViewChangeStart();
ReactROM.render(component, domNode, function() {
markViewChangeEnd();
});
For DOM loaded, you can use the first time markViewChangeEnd is called:
markViewChangeStart();
ReactROM.render(component, domNode, function() {
if (!window.rendered) {
markViewDOMLoaded();
window.rendered = true;
}
markViewChangeEnd();
});
For the RequestsComplete event, you can hold a global variable to mark you have started making requests, an when all of your requests are resolved, call the RequestsCompleted() event.
I think page start and end events can be called at the same place with changeend and change start.
For the ResourcesLoaded, I'm not sure how it could be handled.

Since Meteor upgrade to 0.8.0, Template "rendered" callback is not fired when Session variable dependancy changes

I'm stuck with a problem since I upgraded to 0.8.0.
The Template rendered is not being fired anymore (except the first time).
I followed the recommendations as in:
https://github.com/avital/meteor-ui-new-rendered-callback/blob/master/new2/client/each.js
This didn't helped, and so I finally made this small piece of code (by modifying the new2 example).
The main difference is that the update is triggered by a Session variable change instead of a DB change.
This perfectly shows the problem, as rendered is fired only twice with this example:
client/each.js
Template.list.items = function () {
return (Session.get('items') || 'None')
};
var renderCount = 1;
var logRender = function () {
console.log("rendered #" + renderCount);
renderCount++;
};
Template.list.rendered = function () {
logRender();
};
Template.justName.rendered = function () {
logRender();
};
setInterval(function () {
Session.set('items', {name: Random.choice(["one", "two", "three"])});
}, 1000);
client/each.html
<body>
{{> list}}
</body>
<template name="list">
{{#with items}}
{{> justName}}
{{/with}}
</template>
<template name="justName">
{{name}}
</template>
How can I do to get the Template.justName.rendered callback properly fired when content update is triggered by a Session.set?
Thanks,

I do have an instant solution for you, but it probably requires a tiny bit of re-thinking your actual code. This is by the way the same problem as here:
Meteor 0.8.0 - Failed to operate DOM in rendered callback
But the question is posed in such a different context that it makes sense to answer it twice.
So why does it not trigger the rendered callback? Because it does not re-render.
Blaze treats the whole thing of "how to react on a changed dependencies" very differently, "better" one might say: it will identify the DOM node where your "one", "two" or "three" (in your case it's the template itself) was stored in and just replace the part that has changed, which is the text content "one", "two" or "three". The DOM node itself as well as the template stay completely intact. That also means, that everything you could have been doing with this DOM node won't have to be re-done in almost every practical scenario. I.e. if you animate it, change it's text color using jQuery, the color and animation will just stay on the screen, so you won't need the rendered callback to re-do that.
In your case, the problem is easily solved by just rearanging what you want to do on "rerender":
var whatever = function(){
// whatever you want to do on data-change, in your case calling "logRender" (which needs to be renamed with Blaze, anyway..)
logRender();
}
And then the only thing you have to do is firing it whenever your data change, either manually, like this:
setInterval(function () {
Session.set('items', {name: Random.choice(["one", "two", "three"])});
// calling the function when changing the data, knowing that it WON'T destroy the DOM node it affects
whatever();
}, 1000);
or reactively, like this:
Deps.autorun(function(){
Session.get("items"); // our dependency, just has to be there, but you can also use it
whatever(); // will be fired whenever dependency changes
});
The core idea is to eliminate the need to re-do something you did in the rendered callback, since the DOM and the identity of its objects (and all the beautiful jQuery effects) are still intact. So all that is left to re-do is something that only would depend on the particular reactive data-change, which is why there is the Deps.autorun().
In your particular example, your "logRender" function did not have any reactive dependencies, but if you add some and put it into the Deps.autorun(), it will be reliably re-run whenever the dependency changes.
As a conclusion, Meteor 0.7.x and below drove us to make the mistake of treating the "rendered" callback function as a general purpose autorun function, which is why we are running into trouble now and have to fix our apps.

As noted in the comments, this is a indeed a design change with Meteor.
Prior to Meteor 0.8, a template was a function that generated HTML. This function would be re-computed whenever any of its reactive dependencies changed, which resulted in a recreation of all the DOM nodes generated by the template (apart from any sub-templates or isolated nodes). Whenever this re-draw happened, the rendered callback was triggered.
This behavior creates quite a performance hit because it requires re-rendering of potentially a lot of HTML, including for identifiers and helpers depending on data that hadn't changed. Additionally, it made it difficult to use other libraries like jQuery to modify the DOM elements that were created, because Meteor basically had control of the entire process and the jQuery code would have to be carefully re-run each time.
Meteor 0.8 fixes this by only rendering the pieces of the DOM that have actually changed, down to the granularity of the identifiers in your template - it is much more fine-grained. As a result, the template's rendered callback is only triggered once when your template hits the page, and is never called again afterward. This solves a lot of performance issues and allows jQuery and other DOM manipulations to work seamlessly with Meteor, but also means that you won't get the automatic callback signalling when something has changed. You can, however, achieve this with helpers that use reactive variables for specific things that change.
For a more detailed listing of how Spacebars, the new Handlebars replacement, works, see https://github.com/meteor/meteor/blob/devel/packages/spacebars/README.md
See also the new documentation about the rendered callback: http://docs.meteor.com/#template_rendered

So, I was doing a lot of digging yesterday to try and figure out basically the exact same issues you are having. I am still digging, but I did come across this Devshop Talk about Integrating Other Clientside JS Libraries. In it Ted Blackman describes a package he made to trigger events when a Session variable changed. It sounds like what you need. This talk was given prior to 0.8.0 so I am not sure how the package would be effected, but it might be worth a shot.
Devshop Talk - https://www.youtube.com/watch?v=NdBPY98o6eM
Session Extras - https://atmospherejs.com/package/session-extras
Event Horizon - https://atmospherejs.com/package/event-horizon

Call javascript function from objective C on orientation change

First off I would like to say I am an absolute Objective C novice.
I have been looking everywhere for a solution for this, but somehow I cannot seem to get it to work.
All I want is to run a Javascript function from Objective C when an orientation change event occurs, seeing how this is the only way to execute Javascript before the orientation change animation starts.
I have been able to get a NSLog to show when an orientation change occurs, but no matter what I try, I am unable to execute any Javascript. Not even a console.log() or an alert(), let alone the actual function I want to trigger.
Could anyone please save me another afternoon of trial and error?
SOLVED
Place this in didFinishLaunchingWithOptions (AppDelegate.m):
[[NSNotificationCenter defaultCenter] addObserver: self
selector: #selector(orientationDidChange:)
name: UIApplicationDidChangeStatusBarOrientationNotification
object: nil];
And this just below
- (void) orientationDidChange: (NSNotification *) note
{
[self.viewController.webView stringByEvaluatingJavaScriptFromString:#"hideContentsDuringOrientationChange();"];
}

You should be able to do this:
- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
[(UIWebView *)self.visibleViewController.view stringByEvaluatingJavaScriptFromString:#"someGlobalJSFunction();"];
}
Your reference to the UIWebView may have to change based on how your project is setup.
You can use didRotateFromInterfaceOrientation for an event after the rotation is complete. I've found this sometimes fires just a bit early for the JS to redraw, though. I fixed that by putting a short timeout in the JS function it calls.

Event handling in Dojo

Taking Jeff Atwood's advice, I decided to use a JavaScript library for the very basic to-do list application I'm writing. I picked the Dojo toolkit, version 1.1.1. At first, all was fine: the drag-and-drop code I wrote worked first time, you can drag tasks on-screen to change their order of precedence, and each drag-and-drop operation calls an event handler that sends an AJAX call to the server to let it know that order has been changed.
Then I went to add in the email tracking functionality. Standard stuff: new incoming emails have a unique ID number attached to their subject line, all subsequent emails about that problem can be tracked by simply leaving that ID number in the subject when you reply. So, we have a list of open tasks, each with their own ID number, and each of those tasks has a time-ordered list of associated emails. I wanted the text of those emails to be available to the user as they were looking at their list of tasks, so I made each task box a Dijit "Tree" control - top level contains the task description, branches contain email dates, and a single "leaf" off of each of those branches contains the email text.
First problem: I wanted the tree view to be fully-collapsed by default. After searching Google quite extensively, I found a number of solutions, all of which seemed to be valid for previous versions of Dojo but not the one I was using. I eventually figured out that the best solution would seem to be to have a event handler called when the Tree control had loaded that simply collapsed each branch/leaf. Unfortunately, even though the Tree control had been instantiated and its "startup" event handler called, the branches and leaves still hadn't loaded (the data was still being loaded via an AJAX call). So, I modified the system so that all email text and Tree structure is added server-side. This means the whole fully-populated Tree control is available when its startup event handler is called.
So, the startup event handler fully collapses the tree. Next, I couldn't find a "proper" way to have nice formatted text for the email leaves. I can put the email text in the leaf just fine, but any HTML gets escaped out and shows up in the web page. Cue more rummaging around Dojo's documentation (tends to be out of date, with code and examples for pre-1.0 versions) and Google. I eventually came up with the solution of getting JavaScript to go and read the SPAN element that's inside each leaf node and un-escape the escaped HTML code in it's innerHTML. I figured I'd put code to do this in with the fully-collapse-the-tree code, in the Tree control's startup event handler.
However... it turns out that the SPAN element isn't actually created until the user clicks on the expando (the little "+" symbol in a tree view you click to expand a node). Okay, fair enough - I'll add the re-formatting code to the onExpand() event handler, or whatever it's called. Which doesn't seem to exist. I've searched to documentation, I've searched Google... I'm quite possibly mis-understanding Dojo's "publish/subscribe" event handling system, but I think that mainly because there doesn't seem to be any comprehensive documentation for it anywhere (like, where do I find out what events I can subscribe to?).
So, in the end, the best solution I can come up with is to add an onClick event handler (not a "Dojo" event, but a plain JavaScript event that Dojo knows nothing about) to the expando node of each Tree branch that re-formats the HTML inside the SPAN element of each leaf. Except... when that is called, the SPAN element still doesn't exist (sometimes - other times it's been cached, just to further confuse you). Therefore, I have the event handler set up a timer that periodically calls a function that checks to see if the relevant SPAN element has turned up yet before then re-formatting it.
// An event handler called whenever a "email title" tree node is expanded.
function formatTreeNode(nodeID) {
if (dijit.byId(nodeID).getChildren().length != 0) {
clearInterval(nodeUpdateIntervalID);
messageBody = dijit.byId(nodeID).getChildren()[0].labelNode.innerHTML
if (messageBody.indexOf("<b>Message text:</b>") == -1) {
messageBody = messageBody.replace(/>/g, ">");
messageBody = messageBody.replace(/</g, "<");
messageBody = messageBody.replace(/&/g, "&");
dijit.byId(nodeID).getChildren()[0].labelNode.innerHTML = "<b>Message text:</b><div style=\"font-family:courier\">"+messageBody+"</div>";
}
}
}
// An event handler called when a tree node has been set up - we changed the default fully-expanded to fully-collapsed.
function setupTree(theTree) {
dijit.byId("tree-"+theTree).rootNode.collapse();
messageNode = dijit.byId("tree-"+theTree).rootNode.getChildren();
for (pl = 0; pl < messageNode.length; pl++) {
messageNode[pl].collapse();
messageNode[pl].expandoNode.onclick = eval("nodeUpdateIntervalID = setInterval(\"formatTreeNode('"+messageNode[pl].id+"')\",200); formatTreeNode('"+messageNode[pl].id+"');");
}
}
The above has the feel of a truly horrible hack, and I feel sure I must have taken a wrong turn somewhere early on in my thought process. Can someone please tell me:
The correct way to go about putting nicely-formatted text inside a Dojo/Dijit Tree control.
The correct way to handle Dojo events, like where I can figure out what events are available for me to subscribe to.
A better JavaScript library to use (can I do what I want to with JQuery and avoid the all-around-the-houses approach seen above?).
PS: If you're naming a software project, give thought to its name's uniqueness in Google - I'm sure searching for "Dojo" documentation in Google would be easier without all the martial arts results getting in the way.
PPS: Firefox spellchecker knows how to spell "Atwood", correcting me when I put two 'T's instead of one. Is Jeff just that famous now?

I assume that you followed the dijit.Tree and dojo.data in Dojo 1.1 tutorial which directed you to pass the data to the tree control using a data store. That had me banging my head of a brick wall for a while.
Its not really a great approach and the alternative is not really well documented. You need to create a use model instead. I have included an example below of a tree model that I created for displaying the structure of an LDAP directory.
You will find the default implementation of the model in your dojo distribution at ./dijit/_tree/model.js. The comments should help you understand the functions supported by the model.
The IDirectoryService class the code below are stubs for server-side Java POJOs generated by Direct Web Remoting (DWR). I highly recommend DWR if you going to be doing a lot of client-server interaction.
dojo.declare("LDAPDirectoryTreeModel", [ dijit.tree.model ], {
getRoot : function(onItem) {
IDirectoryService.getRoots( function(roots) {
onItem(roots[0])
});
},
mayHaveChildren : function(item) {
return true;
},
getChildren : function(parentItem, onComplete) {
IDirectoryService.getChildrenImpl(parentItem, onComplete);
},
getIdentity : function(item) {
return item.dn;
},
getLabel : function(item) {
return item.rdn;
}
});
And here is an extract from the my JSP page where I created the model and used it to populate the tree control.
<div
dojoType="LDAPDirectoryTreeModel"
jsid="treeModel"
id="treeModel">
</div>
<div
jsid="tree"
id="tree"
dojoType="dijit.Tree" model="treeModel"
labelAttr="name"
label="${directory.host}:${directory.port}">
</div>