I have a gwt app that need to display images thats hosted by other server, i used the Image(url) to create those icon, but it's unbearably slow, (need to display up to 50 images on one page), is there any way i can speed up? i looked a bit of image bundle but seems it only works for the images hosted on my own server.
here is my code:
for (int i = 0 ; i < 50; i++) {
item = items.get(i);
icon = new Image(ROOT_URL + item.getIconURI());
....
}
1) If there is not security concern ( just images right ) ensure that you are not requesting over https.
2) Use Chrome Dev Tools - Network Profiler to monitor the page load and http requests. Tune your application using the profiler suggestions.
3) Try precaching the images ( i.e ) fetch them before the user navigates to the page in the background.
4) You can also try requesting the image host to send compressed images if they are not compressed already.
The above suggestion have very little to do with GWT.
Related
We are running 2 servers. Server 1 hosts a react application. Server 2 hosts a webcomponent exposed as a single javascript bundle along with some assets such as images. We are dynamically loading the webcomponent Javascript hosted on Server 2 in our react app hosted on Server 1. The fact that it is a webcomponent might or might not affect the issue.
What's happening is that the webcomponent makes uses of assets such as images that are located on Server 2. But when the react app loads the webcomponent, the images are not found as its looking for the images locally on Server 1.
We can fix this in many ways. I am looking for the simplest fix. Since Server 1 app and Server 2 apps are being developed by different teams both should be able to develop in the most natural way possible without making allowances for their app being potentially loaded by other apps.
The fixes that I could think of was:
Making use of absolute URLs to load assets - Need to know the deployed location in advance .
Adding a reverse proxy to Server 1 to redirect to Server 2 whenever a particular path is hit - Need to configure this. The React app could load hundreds of webcomponents, viz we need add a lot of reverse proxies.
Embed all assets into the single javascript on Server 2, like embed svgs into the javascript. - Too limiting. If the SVGs are huge and will make the bundle size bigger.
I was hoping to implement something like -
Since the react app knows where to hit Server 2, can't we write some clever javascript that will make the browser go to Server 2 whenever assets are requested by a Javascript loaded by Server 2.
If you download your Web Component via a classic script (<script> with default type="text/javascript") you can retrieve the URL of the loaded file by using document.currentScript.src.
If you download the file as a module script (<script> with type="module"), you can retrieve the URL by using import.meta.url.
Parse then the property to extract the base path to the Web Component.
Example of Web Component Javascript file:
( function ( path ) {
var base = path.slice( 0, path.lastIndexOf( '/' ) )
customElements.define( 'my-comp', class extends HTMLElement {
constructor() {
super()
this.attachShadow( { mode: 'open' } )
.innerHTML = `<img src="${base}/image.png">`
}
} )
} ) ( document.currentScript ? document.currentScript.src : import.meta.url )
How about uploading all required assets to a 3rd location, or maybe an AWS S3 bucket, Google Drive, Dropbox etc.? That way those assets always have a unique, known URL, and both teams can access them independently. As long as the names remain the same, so will the URLs.
Im creating a web extension and porting from XUL. I used to be able to easily read files with
var dJsm = Components.utils.import("resource://gre/modules/Downloads.jsm").Downloads;
var tJsm = Components.utils.import("resource://gre/modules/Task.jsm").Task;
var fuJsm = Components.utils.import("resource://gre/modules/FileUtils.jsm").FileUtils;
var nsiPromptService = Components.classes["#mozilla.org/embedcomp/prompt-service;1"].getService(Components.interfaces.nsIPromptService);
....
NetUtil.asyncFetch(file, function(inputStream, status) {
if (!Components.isSuccessCode(status)) {
return;
}
var data = NetUtil.readInputStreamToString(inputStream, inputStream.available());
var data = window.btoa(data);
var encoded_data_to_send_via_xmlhttp = encodeURIComponent(data);
...
});
This above will be deprecated.
I can use the downloads.download() to know what was the last download but I can NOT read the file and then get the equivalent for encoded_data_to_send_via_xmlhttp
Also in Firefox 57 onwards, means that I have to try to fake a user action by a button click or something, or upload a file.
Access to file:// URLs or reading files without any explicit user input
isnt there an easy way to read the last downloaded file?
The WebExtension API won't allow extensions to read local files anymore. You could let the extension get CORS privilege and read the content directly from the URL via fetch() or XMLHttpRequest() as blob and store directly to IndexedDB or memory, then encode and send to server. This comes with many restrictions and limitations such as to which origin you can read from and so forth.
Also, this would add potentially many unneeded steps. If the purpose is, as it seem to be in the question at the moment, to share the downloaded file with a server, I would instead suggest that you obtain the last DownloadItem object, extract the URL (.url) from that object and send the URL back to server.
This way the server can load directly from that URL (and encode it on server if needed). The network load will be about the same (a little less actually since there is no Base64 encoding involved which adds 33% to the size), and much less load on the client. The server would read the data as a binary/byte data stream; about the same as if the data was sent directly from the extension.
To obtain the last downloaded file you would do the following from a privileged script:
browser.downloads.search({
limit: 1,
orderBy: ["-startTime"]
})
.then(getLastDownload);
function getLastDownload(downloads) {
if (downloads.length) {
var url = downloads[0].url;
// ... send url to the server and let server fetch the data from it directly
}
}
According to this support mozilla question.
(2) Local file security
Firefox limits access from pages on web servers to pages on local disk or UNC paths. [...]).
Which solution ?
Use local-filesystem-links firefox addon (not tested)
and/or
run a small local webserver on client side, supposing server was run with sufficient privileges, you may finally access any local content via http:// (but still cannot with file:///)
I am trying to make a playground like plunker. I just noticed a very odd behavior on production (with active mode in Cloudflare), whereas it works well in localhost.
By iframe, the playground previews index_internal.html which may contain links to other files (eg, .html, .js, .css). iframe is able to interpret external links such as <script src="script.js"></script>.
So each time a user modifies their file (eg, script.js) on the editor, my program saves the new file into a temporary folder on the server, then refresh the iframe by iframe.src = iframe.src, it works well on localhost.
However, I realized that, in production, the browser always keeps loading the initial script.js, even though users modify it in the editor and a new version is written in the folder in the server. For example, what I see in Dev Tools ==> Network is always the initial version of script.js, whereas I can check the new version of script.js saved in the server by less on the left hand.
Does anyone know why it is like this? And how to fix it?
Edit 1:
I tried the following, which did not work with script.js:
var iframe = document.getElementById('myiframe');
iframe.contentWindow.location.reload(true);
iframe.contentDocument.location.reload(true);
iframe.contentWindow.location.href = iframe.contentWindow.location.href
iframe.contentWindow.src = iframe.contentWindow.src
iframe.contentWindow.location.replace(iframe.contentWindow.location.href)
I tried to add a version, it worked with index_internal.html, but did not reload script.js:
var newSrc = iframe.src.split('?')[0]
iframe.src = newSrc + "?uid=" + Math.floor((Math.random() * 100000) + 1);
If I turn Cloudflare to development mode, script.js is reloaded, but I do want to keep Cloudflare in active mode.
I found it.
We can create a custom rule for caching in CloudFlare:
https://support.cloudflare.com/hc/en-us/articles/200168306-Is-there-a-tutorial-for-Page-Rules-#cache
For example, I could set Bypass as Cache Level for the folder www.mysite.com/tmp/*.
I am having an erratic problem using Azure blob storage where my images do not load consistently. The problem is that sometimes when I load a web page, the browser will not show the image, but if I refresh it will load correctly.
When the image doesn't load, the browser shows the default image placeholder. Here is an example:
If I check the hyperlink for the image placeholder, I find that it is the same as the when the image loads successfully, except the Shared Access Signature is different.
Sometimes the same image will fail to load for one link but load successfully for another link even in the same page and same page load. The only difference in the URL is the Shared Access Signature.
Here is my code to build the URL with the shared signature
// Get reference to blob (file) that is to be downloaded
blob = blobContainer.GetBlobReference(blobURL.ToString());
// Get shared access signature to download file from azure blob (valid upto "active duration" minutes) from now
signature = blob.GetSharedAccessSignature(new SharedAccessPolicy()
{
SharedAccessStartTime = null,
SharedAccessExpiryTime = DateTime.UtcNow.AddMinutes(60),
Permissions = SharedAccessPermissions.Read
});
// Append signature query string to blob / file that is to be downloaded
downloadURL = string.Format("{0}{1}", blob.Uri.AbsoluteUri, signature);
This is the final HTML image link on the web page, i.e. if I show source on the web page in the browser:
<img alt="Profile Picture" src="https://mystorageaccount2.blob.core.windows.net/abcdefg1-hi23-40b5-86de-a20b568f5626/1601/1234d664d1b74ce1aebf4403e5b74af7.jpg?se=2015-10-31T11%3A38%3A39Z&sr=b&sp=r&sig=SaiUToJg%5Ab3zcdef8EeOq84urHf6HQqS%2BAFt1dEQMNI%3D">
Has anyone else seen this problem? Any recommendations on what I might be doing wrong?
I suspect this could be related to the expiry period which you have set on your image blob's shared access signature (SAS). Is there any good reason where you need to set the SAS to 1 minute when you have set it's permission to read-only?
I am automating Internet Explorer using SHDocVW.dll and MSHTML with C#, and I wish to save an image from the page to the disk (JPEG format).
I can't use the WebClient class to download the image; if I do it, I end up downloading the site's login page. I can't print the screen either, because the browser has to remain invisible during this process, running in the background.
I have tried to do the following:
IHTMLImgElement imgElement = ...;
IHTMLControlRange imgRange = ...;
imgRange.add(imgElement as IHTMLControlElement);
imgRange.execCommand( "copy", false, null );
This does nothing. I am not able to extract anything from the clipboard. Every solution I found didn't work for me.
Your webclient approach is probably missing cookies... see How do I log into a site with WebClient? for an example that handles cookies.
your code looks fine except the user has to change the security setting to enable clipboard access. If the image is cached on disk you can dig the WinInet cache after parsing the page for the image location.