I posted a question previously that got off topic, I'm reposting with better code that I have VERIFIED is compatible with iPhone (it works with mine anyway!)
I just want to apply background-position coordinates to
the body element and call
the script conditionally for iPhone, iPod, & iPad. Here's my conditional call for those devices:
var deviceAgent = navigator.userAgent.toLowerCase();
var agentID = deviceAgent.match(/(iphone|ipod|ipad)/);
if (agentID) {
// do something
} else {
//do this
}
Now, I've found this excellent script that sets
the "top: x" dynamically on
the basis of scroll
position. Everyone has told me (and ALL of
the tutorials and Google search results as well) that it's impossible to set scroll
position dynamically for iPhone because of
the viewport issue. HOWEVER, they are wrong because if you scroll to
the bottom of
the page and view this javascript demo on iPhone, you can scroll and
the
<div style="background-position: fixed; top: x (variable)"></div>
div DOES stay centered on iPhone. I really hope this question helps alot of people, I thought it was impossible, but it's NOT... I just need help stitching it together!
The original code (you can test it on iPhone yourself) is here:
http://stevenbenner.com/2010/04/calculate-page-size-and-view-port-position-in-javascript/
So I just need help getting
the following code to apply
the dynamic "background-position: 0 x" to
the BODY tag where x is centered and relative to
the viewport
position. Also, needs to be nested inside
the above code that is conditional for iPhone and similar devices.
// Page Size and View Port Dimension Tools
// http://stevenbenner.com/2010/04/calculate-page-size-and-view-port-position-in-javascript/
if (!sb_windowTools) { var sb_windowTools = new Object(); };
sb_windowTools = {
scrollBarPadding: 17, // padding to assume for scroll bars
// EXAMPLE METHODS
// center an element in
the viewport
centerElementOnScreen: function(element) {
var pageDimensions = this.updateDimensions();
element.style.top = ((this.pageDimensions.verticalOffset() + this.pageDimensions.windowHeight() / 2) - (this.scrollBarPadding + element.offsetHeight / 2)) + 'px';
element.style.left = ((this.pageDimensions.windowWidth() / 2) - (this.scrollBarPadding + element.offsetWidth / 2)) + 'px';
element.style.
position = 'absolute';
},
// INFORMATION GETTERS
// load
the page size, view port
position and vertical scroll offset
updateDimensions: function() {
this.updatePageSize();
this.updateWindowSize();
this.updateScrollOffset();
},
// load page size information
updatePageSize: function() {
// document dimensions
var viewportWidth, viewportHeight;
if (window.innerHeight && window.scrollMaxY) {
viewportWidth = document.body.scrollWidth;
viewportHeight = window.innerHeight + window.scrollMaxY;
} else if (document.body.scrollHeight > document.body.offsetHeight) {
// all but explorer mac
viewportWidth = document.body.scrollWidth;
viewportHeight = document.body.scrollHeight;
} else {
// explorer mac...would also work in explorer 6 strict, mozilla and safari
viewportWidth = document.body.offsetWidth;
viewportHeight = document.body.offsetHeight;
};
this.pageSize = {
viewportWidth: viewportWidth,
viewportHeight: viewportHeight
};
},
// load window size information
updateWindowSize: function() {
// view port dimensions
var windowWidth, windowHeight;
if (self.innerHeight) {
// all except explorer
windowWidth = self.innerWidth;
windowHeight = self.innerHeight;
} else if (document.documentElement && document.documentElement.clientHeight) {
// explorer 6 strict mode
windowWidth = document.documentElement.clientWidth;
windowHeight = document.documentElement.clientHeight;
} else if (document.body) {
// other explorers
windowWidth = document.body.clientWidth;
windowHeight = document.body.clientHeight;
};
this.windowSize = {
windowWidth: windowWidth,
windowHeight: windowHeight
};
},
// load scroll offset information
updateScrollOffset: function() {
// viewport vertical scroll offset
var horizontalOffset, verticalOffset;
if (self.pageYOffset) {
horizontalOffset = self.pageXOffset;
verticalOffset = self.pageYOffset;
} else if (document.documentElement && document.documentElement.scrollTop) {
// Explorer 6 Strict
horizontalOffset = document.documentElement.scrollLeft;
verticalOffset = document.documentElement.scrollTop;
} else if (document.body) {
// all other Explorers
horizontalOffset = document.body.scrollLeft;
verticalOffset = document.body.scrollTop;
};
this.scrollOffset = {
horizontalOffset: horizontalOffset,
verticalOffset: verticalOffset
};
},
// INFORMATION CONTAINERS
// raw data containers
pageSize: {},
windowSize: {},
scrollOffset: {},
// combined dimensions object with bounding logic
pageDimensions: {
pageWidth: function() {
return sb_windowTools.pageSize.viewportWidth > sb_windowTools.windowSize.windowWidth ?
sb_windowTools.pageSize.viewportWidth :
sb_windowTools.windowSize.windowWidth;
},
pageHeight: function() {
return sb_windowTools.pageSize.viewportHeight > sb_windowTools.windowSize.windowHeight ?
sb_windowTools.pageSize.viewportHeight :
sb_windowTools.windowSize.windowHeight;
},
windowWidth: function() {
return sb_windowTools.windowSize.windowWidth;
},
windowHeight: function() {
return sb_windowTools.windowSize.windowHeight;
},
horizontalOffset: function() {
return sb_windowTools.scrollOffset.horizontalOffset;
},
verticalOffset: function() {
return sb_windowTools.scrollOffset.verticalOffset;
}
}
};
