<div>SUMMARY</div><div><br></div><div>The HTML 5 spec defines the event-based drag-and-drop mechanism that could cross the browser boundary. If a draggable element contains a URL, dragging it out of the browser will only copy the URL value. However, in some scenarios, we really want to download the data file from the specified URL, instead of copying the value. Here we propose a way to allow dragging a virtual file denoted by an URL out of the browser boundary.</div>
<div><br></div><div><span class="Apple-style-span" style="border-collapse: collapse; ">USE CASES</span></div><div><span class="Apple-style-span" style="border-collapse: collapse;"><br></span></div><div><span class="Apple-style-span" style="border-collapse: collapse;">In order to download the attachment from an Internet mail application, the user will have to click the attachment link and a "save" dialog will pop up to let the user select the destination folder. This will normally involves multiple clicks. Native application, like Outlook, can let the user drag attachments directly into the destination place, i.e. desktop, which is really convenient. </span></div>
<div><span class="Apple-style-span" style="border-collapse: collapse; "><br></span></div><div><span class="Apple-style-span" style="border-collapse: collapse;">WORKAROUNDS</span></div><div><span class="Apple-style-span" style="border-collapse: collapse;"><br>
</span></div><div><span class="Apple-style-span" style="border-collapse: collapse;">Currently there is no direct support in HTML 5 to support such dragging of the virtual file. To work around this, a plugin with such capability has to be installed and used.</span></div>
<div><span class="Apple-style-span" style="border-collapse: collapse;"><br></span></div><div><span class="Apple-style-span" style="border-collapse: collapse;">PROPOSAL</span></div><div><span class="Apple-style-span" style="border-collapse: collapse;"><br>
</span></div><div><span class="Apple-style-span" style="border-collapse: collapse;"><div>We propose adding a specific format string to the DataTransfer object: "DownloadURL". The data associated with the "DownloadURL" format should be parsed similar to the "URL" format. When the drag ends in another application, the remote file described in the associated data URL should be downloaded and provided to the target application.</div>
<div><br></div><div>For example, here's how one can create a draggable image that results in a file when dragged:</div><div><br></div><div>var dragTarget = document.createElement("img");</div><div>dragTarget.src = "<a href="http://example.com/example-attachment.gif">http://example.com/example-attachment.gif</a>";</div>
<div>document.body.insertBefore(dragTarget, document.body.firstChild);</div><div>dragTarget.addEventListener("dragstart", function(event) {</div><div> event.dataTransfer.setData("DownloadURL", "<a href="http://example.com/example-download-attachment">http://example.com/example-download-attachment</a>");</div>
<div>}, false);</div><div><br></div><div><div>Traditionally allowing the non-image file to be dragged out of the browser is considered bad. The main danger here is that the user might unknowingly drag a file that will auto-execute. To address this issue, the browser needs to mark the dragged file to indicate that it is coming from the Internet. With this zone marker, the user will be prompted with a security warning dialog when the dropped file is launched. If a specific platform does not support zone identifier marker, this feature should be turned off by default.</div>
<div><br></div><div>We should consider allowing only http and https typed URL in the associated data for the "DownloadURL" format. Should we further restrict the download URL to the same origin?</div><div><br></div>
<div>If the filename is provided in the Content-Disposition header, it should always be used. Otherwise, it is up to the browser to decide how the filename is generated from the URL. But once it is chosen, it cannot be changed.</div>
<div><br></div><div>The drag-and-drop feedback might be decorated with the filename and the domain from which the file is downloaded. However, the real filename might be only available when we initiate the download and get back the response header. To address this, we can download the response header after the drag is initiated and then update the feedback image based on the filename retrieved from the Content-Disposition header. This might not be possible for certain platform because changing the drag meta-data might not be allowed.</div>
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