Framework: Support RFC 1867 accept attribute for file upload

[vaadin-bot]

Originally by @hesara

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The RFC 1867 accept attribute enables defining which MIME types are selectable in a file upload dialog. While the browser support is limited, many newer versions of browsers do support it. We could add support for setting the attribute in the Upload component, with a warning that not all browsers respect it.

See http://en.wikipedia.org/wiki/File_select#Accept_attribute and the forum thread https://vaadin.com/forum/-/message_boards/view_message/428096 .

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Imported from https://dev.vaadin.com/ issue #8857

[vaadin-bot]

Originally by _phansson_

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All browsers now support this feature. This is low hanging fruit to implement and will improve end-user's experience.

Example:

<input type="file" name="foo" accept=".bar">

The above will - at least on Windows - bring up a file browser that is filtering on *.bar by default. Nice.

In short this is really a matter of Vaadin supporting the GWT InputElement's setAccept() method. Should be easy, I think.

[sirbris]

will this be integrated in Vaadin 8 or is there a workaround maybe?

[focbenz]

Would be a nice feature for guiding the use to select only specified files.

[stale[bot]]

Hello there!

It looks like this issue hasn't progressed lately. There are so many issues that we just can't deal them all within a reasonable timeframe.

There are a couple of things you could help to get things rolling on this issue (this is an automated message, so expect that some of these are already in use):

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Thanks again for your contributions! Even though we haven't been able to get this issue fixed, we hope you to report your findings and enhancement ideas in the future too!

[sirbris]

no workaround at least?

[BenICE]

I guess you already found a way around, but here is how we solved it:

String javascript = "Array.from(document.getElementsByClassName('gwt-FileUpload')).forEach("
        + "function(element, index, array){element.setAttribute('accept', '" + validImageFormats + "')});";
JavaScript javaScript = JavaScript.getCurrent();
javaScript.execute(javascript);

Still I vote to have it properly integrated into vaadin :)

[focbenz]

Nice - accept in Vaadin 8.5.0!