Related
I'm hoping to migrate from using WebUSB to SerialAPI (which is explained nicely here).
Current Code:
try {
let device = await navigator.usb.requestDevice({
filters: [{
usbVendorId: RECEIVER_VENDOR_ID
}]
})
this.connect(device)
} catch (error) {
console.log(DEVICE_NAME + ': Permission Denied')
}
New Code:
try {
let device = await navigator.serial.requestPort({
filters: [{
usbVendorId: RECEIVER_VENDOR_ID
}]
})
this.connect(device)
} catch (error) {
console.log(DEVICE_NAME + ': Permission Denied')
}
The new code appears to work, but I think it's because the browser has already requested the device via the old code.
I've tried restarting Chrome as well as clearing all of the browsing history. Even closed the USB-claiming page and claimed the device with another app (during which it returns the DOMException: Unable to claim interface error), but Chrome doesn't seem to want to ask again. It just happily streams the data with the previous connection.
My hope was that using SerialAPI would be a way to avoid fighting over the USB with other processes, or at least losing to them.
Update
I had forgotten about:
Failed to execute 'requestPort' on 'Serial': "Must be handling a user gesture to show a permission request"
Does this mean that the user will need to use a button to connect to the device via SerialUSB? I think with WebUSB I was able to make the connect window automatically pop up.
For both APIs, as is noted in the update, a user gesture is required in order to call the requestDevice() or requestPort() method. It is not possible to automatically pop up this prompt. (If there is that's a bug so please let the Chrome team know so we can fix it.)
Permissions granted to a site through the WebUSB API and Web Serial API are currently tracked separately so permission to access a device through one will not automatically translate into the other.
There is not currently a way to programatically forget a device permission. That would require the navigator.permissions.revoke() method which has been abandoned. You can however manually revoke permission to access the device by clicking on the "lock" icon in the address bar while visiting the site or going to chrome://settings/content/usbDevices (for USB devices) and chrome://settings/content/serialPorts (for serial ports).
To get Chrome to "forget" the WebUSB device previously paired via navigator.usb.requestDevice API:
Open the page paired to the device you want to forget
Click on the icon in the address bar
Click x next to device. If nothing is listed, then there are no paired devices for this web page.
The new code was NOT working. It just appeared to be because Chrome was already paired with the port via the old code. There is no way the "new code" could have worked because, as noted in Kalido's comment, the SerialAPI (due to its power) requires a user gesture to connect.
The code I'm using to actually connect and get data is basically built up from a few pieces from the above links in the OP:
navigator.serial.addEventListener('connect', e => {
// Add |e.target| to the UI or automatically connect.
console.log("connected");
});
navigator.serial.addEventListener('disconnect', e => {
// Remove |e.target| from the UI. If the device was open the disconnection can
// also be observed as a stream error.
console.log("disconnected");
});
console.log(navigator.serial);
document.addEventListener('DOMContentLoaded', async () => {
const connectButton = document.querySelector('#connect') as HTMLInputElement;
if (connectButton) {
connectButton.addEventListener('click', async () => {
try {
// Request Keiser Receiver from the user.
const port = await navigator.serial.requestPort({
filters: [{ usbVendorId: 0x2341, usbProductId: not_required }]
});
try {
// Open and begin reading.
await port.open({ baudRate: 115200 });
} catch (e) {
console.log(e);
}
while (port.readable) {
const reader = port.readable.getReader();
try {
while (true) {
const { value, done } = await reader.read();
if (done) {
// Allow the serial port to be closed later.
reader.releaseLock();
break;
}
if (value) {
console.log(value);
}
}
} catch (error) {
// TODO: Handle non-fatal read error.
console.log(error);
}
}
} catch (e) {
console.log("Permission to access a device was denied implicitly or explicitly by the user.");
console.log(e);
console.log(port);
}
}
}
The device-specific Vendor and Product IDs would obviously change from device to device. In the above example I have inserted an Arduino vendor ID.
It doesn't answer the question of how to get Chrome to "forget", but I'm not sure if that's relevant when using SerialAPI because of the required gesture.
Hopefully someone with more experience will be able to post a more informative answer.
I'm currently working on a simple share function where I can share a news article via the URL (I.E. https://www.nrps.nl/Nieuws/Nieuwsitem.aspx?ID=812). I'm using React Native Share for this (code below). When sharing on Facebook it shows up as dnndev.me instead of nrps.nl, what I expected it to be. Clicking the dnndev.me link redirects to https://www.nrps.nl/Nieuws/Nieuwsitem.aspx?ID=812&fbclid=IwAR3Eq-j1wX8GUVvSEvhFNu85k8U_vjmV0l4_ycF-AUhoV61YBIieRGJgQg4 instead of https://www.nrps.nl/Nieuws/Nieuwsitem.aspx?ID=812, but the content is the same. (if I shouldn't show any of this, please edit it out. I don't know what the extra string means)
From what I can tell, dnndev.me seems to be a development environment.
The questions:
What is dnndev.me, besides some sort of host?
Can I do anything to work around it showing up as dnndev.me or can I only inform NRPS that they haven't done so already?
RN code:
let message = `${news.Title}\n${news.Image}\n${news.MessageUrl}`
news.title is a simple string. news.image is a URL to an image, news.MessageUrl is the URL of the news article itself. I've tested it with only the MessageUrl and it has the same result.
try {
const result = await Share.share({
message: `${message}`,
});
if (result.action === Share.sharedAction) {
if (result.activityType) {
// shared with activity type of result.activityType
} else {
// shared
}
} else if (result.action === Share.dismissedAction) {
// dismissed
console.log("Sharing dismissed")
}
} catch (e) {
console.log(e);
}
EDIT:
What I want to happen is to have the auto generated square / content field (or however it's called) like follows:
https://imgur.com/EalEbmZ
dnndev.me is a web server. As a web server, it notifies facebook of any problems in managing and operating facebook data and also solves any problems.
webSite of dnndev.me
And the fbclid behind the existing parameters is the visitor tracking system ID.
The acronym for fbclid is: "Facebook Click Identifier". It means a
Facebook click identifier.
It's about Facebook clicks.
These are parameters introduced for accurate statistics from this data.
We're also going to exchange data with Google Annalysis and AdSense.
Make more accurate estimates of visitors.
To share Facebook, you can use the following modules to work around it: This solution is contained in the Facebook developer's official document.
$yarn add react-native-fbsdk or npm install --save react-native-fbsdk
$ react-native link react-native-fbsdk
Note For iOS using cocoapods, run:
$ cd ios/ && pod install
Usage
import { ShareDialog } from 'react-native-fbsdk';
let message = `${news.Title}\n${news.Image}\n${news.MessageUrl}`
const shareLinkContent = {
contentType: 'link',
contentUrl: "https://www.nrps.nl/Nieuws/Nieuwsitem.aspx?ID=812",
contentDescription: message,
};
...
this.state = {shareLinkContent: shareLinkContent,};
...
shareLinkWithShareDialog() {
var tmp = this;
ShareDialog.canShow(this.state.shareLinkContent).then(
function(canShow) {
if (canShow) {
return ShareDialog.show(tmp.state.shareLinkContent);
}
}
).then(
function(result) {
if (result.isCancelled) {
alert('Share operation was cancelled');
} else {
alert('Share was successful with postId: '
+ result.postId);
}
},
function(error) {
alert('Share failed with error: ' + error.message);
}
);
}
I'm using the Office JS library to create an Excel add-in, and the Microsoft object is not being recognized. All the other classes from the library seem to to work fine, but when I call dialog.addEventHandler(Microsoft.Office.WebExtension.EventType.DialogMessageReceived,processMessage the Microsoft object is not evaluated properly. This is despite every other object from this library working fine.
I'm following this tutorial https://learn.microsoft.com/en-us/office/dev/add-ins/tutorials/excel-tutorial
I'm using CDN from this link: https://appsforoffice.microsoft.com/lib/1.1/hosted/office.js
The method that calls Microsoft.Office.WebExtension fails, and I knew it would because WebStorm tells me its not recognized.
All of the other objects from Office JS work fine though...here's an example of working code:
function sortTable() {
Excel.run(function (context) {
// Queue commands to sort the table by merchant name
var currentWorkbook = context.workbook.worksheets.getActiveWorksheet();
var expensesTable = currentWorkbook.tables.getItem('ExpensesTable');
var sortFields = [
{
key: 1,
ascending: false,
}
];
expensesTable.sort.apply(sortFields);
return context.sync();
}).catch(function (error) {
console.log("Error" + error);
if (error instanceof OfficeExtension.Error) {
console.log("Debug info: " + JSON.stringify(error.debugInfo));
}
});
}
I've review in detail the Office JavaScript API documentation: https://learn.microsoft.com/en-us/office/dev/add-ins/reference/overview/excel-add-ins-reference-overview
I've reviewed that there is an older common API: https://learn.microsoft.com/en-us/javascript/api/office?view=word-js-preview
I have suspected that I need access to this older common API, but the only documentation I've found says that you are just supposed to use the office.js library I've linked above.
Here's the whole function I'm trying to use:
function openDialog() {
//Call the Office Common API that opens a dialog
Office.context.ui.displayDialogAsync(
'https://localhost:3000/popup.html',
{height: 45, width:55},
function (result) {
dialog = result.value;
dialog.addEventHandler(Microsoft.Office.WebExtension.EventType.DialogMessageReceived,processMessage);
}
)
}
It does in fact open a dialog box as the Office.context.ui.displayDialogAsync method works. But as soon as you get to Microsoft.Office.WebExtension.EventType.DialogMessageReceived WebStorm tells me that the element Microsoft is an unresolved reference.
And here's the function it should call if it worked, processMessage. Because it does not get this far, the element does not get updated, and the dialog box does not close. I'm near 100% certain the issue is not with the function below, but I'm not ruling it out yet.
function processMessage(arg) {
console.log("made it inside processMessage")
document.getElementById("user-name").innerHTML = arg.message;
console.log("made ti just before dialog.close")
dialog.close();
}
The full name has been shortened to Office.EventType.DialogMessageReceived. Here's the GitHub issue: https://github.com/OfficeDev/office-js-docs-pr/issues/1710
I have created a custom URL protocol handler.
http://
mailto://
custom://
I have registered a WinForms application to respond accordingly. This all works great.
But I would like to be able to gracefully handle the case where the user doesn't have the custom URL protocol handler installed, yet.
In order to be able to do this I need to be able to detect the browser's registered protocol handlers, I would assume from JavaScript. But I have been unable to find a way to poll for the information. I am hoping to find a solution to this problem.
Thanks for any ideas you might be able to share.
This would be a very, very hacky way to do this... but would this work?
Put the link in as normal...
But attach an onclick handler to it, that sets a timer and adds an onblur handler for the window
(in theory) if the browser handles the link (application X) will load stealing the focus from the window...
If the onblur event fires, clear the timer...
Otherwise in 3-5seconds let your timeout fire... and notify the user "Hmm, looks like you don't have the Mega Uber Cool Application installed... would you like to install it now? (Ok) (Cancel)"
Far from bulletproof... but it might help?
There's no great cross-browser way to do this. In IE10+ on Win8+, a new msLaunchUri api enables you to launch a protocol, like so:
navigator.msLaunchUri('skype:123456',
function()
{
alert('success');
},
function()
{
alert('failed');
}
);
If the protocol is not installed, the failure callback will fire. Otherwise, the protocol will launch and the success callback will fire.
I discuss this topic a bit further here:
https://web.archive.org/web/20180308105244/https://blogs.msdn.microsoft.com/ieinternals/2011/07/13/understanding-protocols/
This topic is of recent (2021) interest; see https://github.com/fingerprintjs/external-protocol-flooding for discussion.
HTML5 defines Custom scheme and content handlers (to my knowledge Firefox is the only implementor so far), but unfortunately there is currently no way to check if a handler already exists—it has been proposed, but there was no follow-up. This seems like a critical feature to use custom handlers effectively and we as developers should bring attention to this issue in order to get it implemented.
There seems to be no straightforward way via javascript to detect the presence of an installed app that has registered a protocol handler.
In the iTunes model, Apple provides urls to their servers, which then provide pages that run some javascript:
http://ax.itunes.apple.com/detection/itmsCheck.js
So the iTunes installer apparently deploys plugins for the major browsers, whose presence can then be detected.
If your plugin is installed, then you can be reasonably sure that redirecting to your app-specific url will succeed.
What seams the most easy solution is to ask the user the first time.
Using a Javascript confirm dialog per example:
You need this software to be able to read this link. Did you install it ?
if yes: create a cookie to not ask next time; return false and the link applies
if false: window.location.href = '/downloadpage/'
If you have control of the program you're trying to run (the code), one way to see if the user was successful in running the application would be to:
Before trying to open the custom protocol, make an AJAX request to a server script that saves the user's intent in a database (for example, save the userid and what he wanted to do).
Try to open the program, and pass on the intent data.
Have the program make a request to the server to remove the database entry (using the intent data to find the correct row).
Make the javascript poll the server for a while to see if the database entry is gone. If the entry is gone, you'll know the user was successful in opening the application, otherwise the entry will remain (you can remove it later with cronjob).
I have not tried this method, just thought it.
I was able to finally get a cross-browser (Chrome 32, Firefox 27, IE 11, Safari 6) solution working with a combination of this and a super-simple Safari extension. Much of this solution has been mentioned in one way or another in this and this other question.
Here's the script:
function launchCustomProtocol(elem, url, callback) {
var iframe, myWindow, success = false;
if (Browser.name === "Internet Explorer") {
myWindow = window.open('', '', 'width=0,height=0');
myWindow.document.write("<iframe src='" + url + "'></iframe>");
setTimeout(function () {
try {
myWindow.location.href;
success = true;
} catch (ex) {
console.log(ex);
}
if (success) {
myWindow.setTimeout('window.close()', 100);
} else {
myWindow.close();
}
callback(success);
}, 100);
} else if (Browser.name === "Firefox") {
try {
iframe = $("<iframe />");
iframe.css({"display": "none"});
iframe.appendTo("body");
iframe[0].contentWindow.location.href = url;
success = true;
} catch (ex) {
success = false;
}
iframe.remove();
callback(success);
} else if (Browser.name === "Chrome") {
elem.css({"outline": 0});
elem.attr("tabindex", "1");
elem.focus();
elem.blur(function () {
success = true;
callback(true); // true
});
location.href = url;
setTimeout(function () {
elem.off('blur');
elem.removeAttr("tabindex");
if (!success) {
callback(false); // false
}
}, 1000);
} else if (Browser.name === "Safari") {
if (myappinstalledflag) {
location.href = url;
success = true;
} else {
success = false;
}
callback(success);
}
}
The Safari extension was easy to implement. It consisted of a single line of injection script:
myinject.js:
window.postMessage("myappinstalled", window.location.origin);
Then in the web page JavaScript, you need to first register the message event and set a flag if the message is received:
window.addEventListener('message', function (msg) {
if (msg.data === "myappinstalled") {
myappinstalledflag = true;
}
}, false);
This assumes the application which is associated with the custom protocol will manage the installation of the Safari extension.
In all cases, if the callback returns false, you know to inform the user that the application (i.e., it's custom protocol) is not installed.
You say you need to detect the browser's protocol handlers - do you really?
What if you did something like what happens when you download a file from sourceforge? Let's say you want to open myapp://something. Instead of simply creating a link to it, create a link to another HTML page accessed via HTTP. Then, on that page, say that you're attempting to open the application for them. If it doesn't work, they need to install your application, which they can do by clicking on the link you'll provide. If it does work, then you're all set.
This was a recommended approach for IE by Microsoft support
http://msdn.microsoft.com/en-us/library/ms537503%28VS.85%29.aspx#related_topics
"If you have some control over the binaries being installed on a user’s machine, checking the UA in script seems like a relevant approach:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent\Post Platform
" -- By M$ support
Every web page has access to the userAgent string and if you drop a custom post platform value, detecting this in javascript using navigator.userAgent is quite simple.
Fortunately, other major browsers like Firefox and Chrome (barring Safari :( ), do not throw "page not found" errors when a link with a custom protocol is clicked and the protocol is not installed on the users machine. IE is very unforgiving here, any trick to click in a invisible frame or trap javascript errors does not work and ends up with ugly "webpage cannot be displayed" error. The trick we use in our case is to inform users with browser specific images that clicking on the custom protocol link will open an application. And if they do not find the app opening up, they can click on an "install" page. In terms of XD this wprks way better than the ActiveX approach for IE.
For FF and Chrome, just go ahead and launch the custom protocol without any detection. Let the user tell you what he sees.
For Safari, :( no answers yet
I'm trying to do something similar and I just discovered a trick that works with Firefox. If you combine it with the trick for IE you can have one that works on both main browsers (I'm not sure if it works in Safari and I know it doesn't work in Chrome)
if (navigator.appName=="Microsoft Internet Explorer" && document.getElementById("testprotocollink").protocolLong=="Unknown Protocol") {
alert("No handler registered");
} else {
try {
window.location = "custom://stuff";
} catch(err) {
if (err.toString().search("NS_ERROR_UNKNOWN_PROTOCOL") != -1) {
alert("No handler registered");
}
}
}
In order for this to work you also need to have a hidden link somewhere on the page, like this:
<a id="testprotocollink" href="custom://testprotocol" style="display: none;">testprotocollink</a>
It's a bit hacky but it works. The Firefox version unfortunately still pops up the default alert that comes up when you try to visit a link with an unknown protocol, but it will run your code after the alert is dismissed.
You can try something like this:
function OpenCustomLink(link) {
var w = window.open(link, 'xyz', 'status=0,toolbar=0,menubar=0,height=0,width=0,top=-10,left=-10');
if(w == null) {
//Work Fine
}
else {
w.close();
if (confirm('You Need a Custom Program. Do you want to install?')) {
window.location = 'SetupCustomProtocol.exe'; //URL for installer
}
}
}
This is not a trivial task; one option might be to use signed code, which you could leverage to access the registry and/or filesystem (please note that this is a very expensive option). There is also no unified API or specification for code signing, so you would be required to generate specific code for each target browser. A support nightmare.
Also, I know that Steam, the gaming content delivery system, doesn't seem to have this problem solved either.
Here's another hacky answer that would require (hopefully light) modification to your application to 'phone home' on launch.
User clicks link, which attempts to launch the application. A unique
identifier is put in the link, so that it's passed to the
application when it launches. Web app shows a spinner or something of that nature.
Web page then starts checking for a
'application phone home' event from an app with this same unique ID.
When launched, your application does an HTTP post to your web app
with the unique identifier, to indicate presence.
Either the web page sees that the application launched, eventually, or moves on with a 'please download' page.
I have created a custom URL protocol handler.
http://
mailto://
custom://
I have registered a WinForms application to respond accordingly. This all works great.
But I would like to be able to gracefully handle the case where the user doesn't have the custom URL protocol handler installed, yet.
In order to be able to do this I need to be able to detect the browser's registered protocol handlers, I would assume from JavaScript. But I have been unable to find a way to poll for the information. I am hoping to find a solution to this problem.
Thanks for any ideas you might be able to share.
This would be a very, very hacky way to do this... but would this work?
Put the link in as normal...
But attach an onclick handler to it, that sets a timer and adds an onblur handler for the window
(in theory) if the browser handles the link (application X) will load stealing the focus from the window...
If the onblur event fires, clear the timer...
Otherwise in 3-5seconds let your timeout fire... and notify the user "Hmm, looks like you don't have the Mega Uber Cool Application installed... would you like to install it now? (Ok) (Cancel)"
Far from bulletproof... but it might help?
There's no great cross-browser way to do this. In IE10+ on Win8+, a new msLaunchUri api enables you to launch a protocol, like so:
navigator.msLaunchUri('skype:123456',
function()
{
alert('success');
},
function()
{
alert('failed');
}
);
If the protocol is not installed, the failure callback will fire. Otherwise, the protocol will launch and the success callback will fire.
I discuss this topic a bit further here:
https://web.archive.org/web/20180308105244/https://blogs.msdn.microsoft.com/ieinternals/2011/07/13/understanding-protocols/
This topic is of recent (2021) interest; see https://github.com/fingerprintjs/external-protocol-flooding for discussion.
HTML5 defines Custom scheme and content handlers (to my knowledge Firefox is the only implementor so far), but unfortunately there is currently no way to check if a handler already exists—it has been proposed, but there was no follow-up. This seems like a critical feature to use custom handlers effectively and we as developers should bring attention to this issue in order to get it implemented.
There seems to be no straightforward way via javascript to detect the presence of an installed app that has registered a protocol handler.
In the iTunes model, Apple provides urls to their servers, which then provide pages that run some javascript:
http://ax.itunes.apple.com/detection/itmsCheck.js
So the iTunes installer apparently deploys plugins for the major browsers, whose presence can then be detected.
If your plugin is installed, then you can be reasonably sure that redirecting to your app-specific url will succeed.
What seams the most easy solution is to ask the user the first time.
Using a Javascript confirm dialog per example:
You need this software to be able to read this link. Did you install it ?
if yes: create a cookie to not ask next time; return false and the link applies
if false: window.location.href = '/downloadpage/'
If you have control of the program you're trying to run (the code), one way to see if the user was successful in running the application would be to:
Before trying to open the custom protocol, make an AJAX request to a server script that saves the user's intent in a database (for example, save the userid and what he wanted to do).
Try to open the program, and pass on the intent data.
Have the program make a request to the server to remove the database entry (using the intent data to find the correct row).
Make the javascript poll the server for a while to see if the database entry is gone. If the entry is gone, you'll know the user was successful in opening the application, otherwise the entry will remain (you can remove it later with cronjob).
I have not tried this method, just thought it.
I was able to finally get a cross-browser (Chrome 32, Firefox 27, IE 11, Safari 6) solution working with a combination of this and a super-simple Safari extension. Much of this solution has been mentioned in one way or another in this and this other question.
Here's the script:
function launchCustomProtocol(elem, url, callback) {
var iframe, myWindow, success = false;
if (Browser.name === "Internet Explorer") {
myWindow = window.open('', '', 'width=0,height=0');
myWindow.document.write("<iframe src='" + url + "'></iframe>");
setTimeout(function () {
try {
myWindow.location.href;
success = true;
} catch (ex) {
console.log(ex);
}
if (success) {
myWindow.setTimeout('window.close()', 100);
} else {
myWindow.close();
}
callback(success);
}, 100);
} else if (Browser.name === "Firefox") {
try {
iframe = $("<iframe />");
iframe.css({"display": "none"});
iframe.appendTo("body");
iframe[0].contentWindow.location.href = url;
success = true;
} catch (ex) {
success = false;
}
iframe.remove();
callback(success);
} else if (Browser.name === "Chrome") {
elem.css({"outline": 0});
elem.attr("tabindex", "1");
elem.focus();
elem.blur(function () {
success = true;
callback(true); // true
});
location.href = url;
setTimeout(function () {
elem.off('blur');
elem.removeAttr("tabindex");
if (!success) {
callback(false); // false
}
}, 1000);
} else if (Browser.name === "Safari") {
if (myappinstalledflag) {
location.href = url;
success = true;
} else {
success = false;
}
callback(success);
}
}
The Safari extension was easy to implement. It consisted of a single line of injection script:
myinject.js:
window.postMessage("myappinstalled", window.location.origin);
Then in the web page JavaScript, you need to first register the message event and set a flag if the message is received:
window.addEventListener('message', function (msg) {
if (msg.data === "myappinstalled") {
myappinstalledflag = true;
}
}, false);
This assumes the application which is associated with the custom protocol will manage the installation of the Safari extension.
In all cases, if the callback returns false, you know to inform the user that the application (i.e., it's custom protocol) is not installed.
You say you need to detect the browser's protocol handlers - do you really?
What if you did something like what happens when you download a file from sourceforge? Let's say you want to open myapp://something. Instead of simply creating a link to it, create a link to another HTML page accessed via HTTP. Then, on that page, say that you're attempting to open the application for them. If it doesn't work, they need to install your application, which they can do by clicking on the link you'll provide. If it does work, then you're all set.
This was a recommended approach for IE by Microsoft support
http://msdn.microsoft.com/en-us/library/ms537503%28VS.85%29.aspx#related_topics
"If you have some control over the binaries being installed on a user’s machine, checking the UA in script seems like a relevant approach:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent\Post Platform
" -- By M$ support
Every web page has access to the userAgent string and if you drop a custom post platform value, detecting this in javascript using navigator.userAgent is quite simple.
Fortunately, other major browsers like Firefox and Chrome (barring Safari :( ), do not throw "page not found" errors when a link with a custom protocol is clicked and the protocol is not installed on the users machine. IE is very unforgiving here, any trick to click in a invisible frame or trap javascript errors does not work and ends up with ugly "webpage cannot be displayed" error. The trick we use in our case is to inform users with browser specific images that clicking on the custom protocol link will open an application. And if they do not find the app opening up, they can click on an "install" page. In terms of XD this wprks way better than the ActiveX approach for IE.
For FF and Chrome, just go ahead and launch the custom protocol without any detection. Let the user tell you what he sees.
For Safari, :( no answers yet
I'm trying to do something similar and I just discovered a trick that works with Firefox. If you combine it with the trick for IE you can have one that works on both main browsers (I'm not sure if it works in Safari and I know it doesn't work in Chrome)
if (navigator.appName=="Microsoft Internet Explorer" && document.getElementById("testprotocollink").protocolLong=="Unknown Protocol") {
alert("No handler registered");
} else {
try {
window.location = "custom://stuff";
} catch(err) {
if (err.toString().search("NS_ERROR_UNKNOWN_PROTOCOL") != -1) {
alert("No handler registered");
}
}
}
In order for this to work you also need to have a hidden link somewhere on the page, like this:
<a id="testprotocollink" href="custom://testprotocol" style="display: none;">testprotocollink</a>
It's a bit hacky but it works. The Firefox version unfortunately still pops up the default alert that comes up when you try to visit a link with an unknown protocol, but it will run your code after the alert is dismissed.
You can try something like this:
function OpenCustomLink(link) {
var w = window.open(link, 'xyz', 'status=0,toolbar=0,menubar=0,height=0,width=0,top=-10,left=-10');
if(w == null) {
//Work Fine
}
else {
w.close();
if (confirm('You Need a Custom Program. Do you want to install?')) {
window.location = 'SetupCustomProtocol.exe'; //URL for installer
}
}
}
This is not a trivial task; one option might be to use signed code, which you could leverage to access the registry and/or filesystem (please note that this is a very expensive option). There is also no unified API or specification for code signing, so you would be required to generate specific code for each target browser. A support nightmare.
Also, I know that Steam, the gaming content delivery system, doesn't seem to have this problem solved either.
Here's another hacky answer that would require (hopefully light) modification to your application to 'phone home' on launch.
User clicks link, which attempts to launch the application. A unique
identifier is put in the link, so that it's passed to the
application when it launches. Web app shows a spinner or something of that nature.
Web page then starts checking for a
'application phone home' event from an app with this same unique ID.
When launched, your application does an HTTP post to your web app
with the unique identifier, to indicate presence.
Either the web page sees that the application launched, eventually, or moves on with a 'please download' page.