How do you read localsettings variables in default.css file in a windows store app? - windows-8

Question

I am building a windows store app that has a default css and a default font size in that css. I am allowing the user to customize the font size from settings screen and that preference gets stored in local settings. How do I update my app to reflect the new font size? Are there any current patterns? This is a Html5/js app. Can I simply reload the css value from the change event?

Answer 1

When your app launches, read the font size from local settings and then set the document's font size with JavaScript:
document.body.style.fontSize = fontSizeFromSettings;
When the app is running and the user changes the font size, also call the above line. You could do this right after your code which saves the font size to local settings.
Naturally, you can also change the font size of individual elements using document.getElementById("myId").style.fontSize.

Answer 2

I read this as the OP having a class selector already defined, like
.myclass
{
font-size: 36px;
}
and wanting to modify all elements with the .myclass selector to be a new value, say 72px. If that's the intent, then you can dynamically modify the CSS.
Here's a simple (and fragile, not-suitable-for-production) function that looks for a specific style selector in a known CSS file and modifies it on the fly. You could probably generalize this, take a look at Changing External Stylesheets and How to change CSS Stylesheets with JavaScript for more details.
function updateFontSize(newFontSize) {
for (var i = 0; i < document.styleSheets.length; i++) {
if (document.styleSheets[i].href.indexOf("default.css") >= 0) {
var mySheet = document.styleSheets[i];
for (var r in mySheet.cssRules) {
if (mySheet.cssRules[r].selectorText == ".myclass") {
var myRule = mySheet.cssRules[r];
myRule.style.fontSize = newFontSize;
return;
}
}
}
}
};
Then somewhere you call it like (without hardcoding the value, of course):
updateFontSize("128px");