centreforelearning

Exporting & Saving One thing that SVG can’t do is save the resulting image as a bitmap. It’s easy for <canvas> because the element is already a bitmap in the first place! The canvas can export its image to a data URL (e.g., data:image/png;base64,iVBORw0KGg...). This data may then be rendered in the browser, which could then be saved or dragged to the desktop, used in a new canvas, and so on. The browser must support PNG images, and it may have varying support for GIF and JPG. For our example, we’ll stick with PNG since it supports alpha transparency, and where we haven’t drawn on the canvas, it’ll be transparent. To get the data URL, we simply call canvas.toDataURL('image/png'). Note that we’re calling toDataURL() on the <canvas> element, not on the 2D context. This is because we’re getting all the pixels in the canvas, not just the pixels in a particular context. So taking the example we’ve put together already, we’ll make the browser redirect to a PNG version of the image when a user clicks on the <canvas> element (a contrived example, I know!): canvas.onclick = function () {  window.location = canvas.toDataURL('image/png');};

Press the Home and Sleep Buttons Simultaneously to Take a Screenshot

Enable International Keyboards for International TLDs

Hold Home and Sleep to Reboot

Scrolling Long Lists Another big problem with iPhone web apps is presenting very long lists efficiently. Digg has this problem with their stories and comments and they work around it by breaking stories into pages of ten and omitting all but the top five comments. Apple solves this problem nicely in their Mail app by loading 25 messages at a time and putting a link to get more at the end. Clicking it loads those messages and appends them to the end of the list, allowing you to use the joyous flick gesture to scroll the complete list at once. In my view, this is nicer than breaking the list up into separate pages. iUI makes it easy for you to use this convention in your own web apps. Simply create a link with target="_replace" and iUI will load the URL it and replace the <a> with the contents of the URL. Again, the URL should not point to a complete HTML document, but only the fragment you want to replace the "Get More" link with. For an example of incrementally loaded lists, look at the Digg demo again. Scroll to the bottom of the stories list and click on the "Get 10 More Stories..." link.