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How to make `Label`'s font size inside `ViewCell` dependent on the device in Xamarin Forms?

So I have a few custom cells using ViewCell in my app. Inside my ViewCell are Labels. I want the font size of those labels to be dependent on the text size of the device just like how the TextCell's text changes when you adjust the text size of your device.
Below image is using a built-in TextCell.
Below image is using a custom cell ViewCell
Im testing this in an iOS device and the text size is set to the smallest available. Whenever I change the device text size the cells using TextCells will just automatically changed. The labels inside the ViewCell doesn't change at all. Any suggestion pointing me to the right direction is very much appreciated.

Short answer
The TextCell uses the native UITableViewCell on iOS. This native view takes the device accessibility settings into account. When you use the Xamarin Forms Label, it does not. Xamarin Forms does not support iOS Dynamic Type (yet).
Explanation
The Forms Label uses the FontSizeConverter to set the actual font size. This font size defaults to the value -1 if you don't set any value yourself. The value -1 results in the use of NamedSize.Default (see the Font class).
When you take a look at the FontSizeConverter, if it can't parse the value as an absolute value, it will try to convert to a NamedSize value. In that case, it will use Device.GetNamedSize to get the actual size. This is done through the IPlatformServices interface, which converts these to absolute values (see the IOSPlatformServices).
There is also a FontExtensions class, that implements the same conversion from Named Size to an absolute value. Not very DRY at first sight, but there could be a good reason for this, that I'm not aware of.
Unfortunately, both the FontExtensions and the IOSPlatformServices don't take the accessibility options of iOS into account, but just return absolute values.
Possible solution
On iOS, you could use UIKit.UIApplication.SharedApplication.PreferredContentSizeCategory to get the current accessibility category. Based on this value, you could determine a scale for your fonts (use DynamicResource for the font sizes if you use them in XAML, so they can change at runtime).
Or take a look at SushiHangover's answer on a similar question.
See the preferredContentSizeCategory on the Apple Developer API reference.

Getting the largest image from HTML page source in C#

Basically, what I'm trying to do is get an image to represent a page (for quick browsing in a XAML GridView).
I have the pages URL (and it's HTML content), but now I'm not completely sure how to proceed. I could just use the Favicon, but I don't think that would scale well up to the 200x200 box I'm using to display it. The other option (as far as I can think of) is to look through the HTML source and pick out the largest image.
Is there an easier/simpler way to do that in C# other than just using Regexs to find the height/width of all the image tags and then comparing them?
Thanks!

There is no way to know for sure from the HTML source what size the images are. An img tag doesn't require the height and width parameters. If they're not specified, then the image is displayed in its actual size. If all the img tags on the page have their height and width specified, you could pick the one that has the largest values. But those are the display sizes. The actual sizes might be quite different.
The only way to be 100% sure is to download each image and get its size.
By the way, if you're parsing HTML, you probably shouldn't be doing it with regular expressions. I know it seems simple enough, but you're almost certain to get things wrong and not handle some common cases. You'll save yourself a lot of time and frustration by using something like the Html Agility Pack.

you can try
imageObject.ActualWidth
imageObject.ActualHeight
properties

setting maximum web page width

What is the easiest/best way to set the maximum width of a web page. For example assume I don't want to let the user to expand the width beyond 400px. HTML code, CSS, C#?
I am using Visual Studio 2008 C# environment.
Thanks
Bruce

If you want to limit the browser width, well you can't do that :P
Alternatively, if you want to limit a certain element's width, such as a div with an ID of #container, then you would use CSS:
#container {
max-width:400px;
}

Wrap the content of the page is some sort of container (a <div>) is usually suitable. Apply the max-width property to it.

Simply make a fixed width CSS layout set at 400px.
Trying to prevent the browser window to be greater than 400px is horrible idea, and will fail in more ways than it will work (mobile, etc).

Calculate area of HTML element on website?

I'm trying to figure out if it's possible to calculate the area of a HTML element on a website? In pixels, as a percentage or whatever.
My first thoughts have been to make the assumption that the element is 100% in width and height, and then try to retrieve the size through a mapping between the HTML and CSS.
So if there's a width/height attribute in the referenced CSS-file I could possibly say that
the body element is covered by a column that takes 25% of the area (everything is based on your screen resolution of course - and I'm still trying to figure out how I'd be able to do this programmatically).
Or whether I should render the website and do my calculations based on an image with the most common screen resolution at the time).
Are there any more possible solutions?
(Currently I'm trying to solve this in Perl, but I suppose any language that's got a library for this purpose would be appreciated to know about!)
EDIT: I need to retrieve the visual area for every single element on a page.
For example; if there are elements on top of the <body> element, that covers it visually, I want to exclude that area from the <body>'s and so on. A simple raytracing to find the visible area for every element on a page.
EDIT: Let's say we exclude JavaScript - any other approaches possible?

Personally, I would use jQuery - even if you don't use a library, your best bet will be a JavaScript solution.
var $elt = $('#some-element-id'),
height = $elt.height(),
width = $elt.width(),
area = height * width; // contains the area in px^2
http://api.jquery.com/height and http://api.jquery.com/width

This is such a simple problem I don't think JQuery is necessary if you are not already using it.
Try running this:
<div id="myParent">
What's up?
<div id="myDiv">Hello there!</div>
</div>
With
var myDiv = document.getElementById("myDiv");
alert(myDiv.offsetHeight);
alert(myDiv.offsetWidth);
var myParent = myDiv.parentNode;
alert(myParent.offsetHeight);
alert(myParent.offsetWidth);
Divide resulting widths to get % of space the element takes in it's parent, or simply use the absolute pixel values.

I would recommend using jQuery to do it if possible.
alert('Size: ' + $('li').size());
http://api.jquery.com/size/

Would it be feasible to use javascript? If so you can get the width/height with something like this:
document.getElementById(YourElementsId).style.height;
document.getElementById(YourElementsId).style.width;
However this does depening on how the elements are sytled in the first place. Another option would be
document.getElementById(YourElementsId).clientHeight;
document.getElementById(YourElementsId).clientWidth;

How do you draw a string to a Bitmap in Silverlight?

In normal C# it is easy to draw to a bitmap using the Grpahics.DrawString() method. Silverlight seems to have done away with Bitmap objects and Graphics is no longer available either. So...How am I meant to manipulate/create a bitmap when using Silverlight? If it helps, I am using Silverlight 3.
Let me tell you what I am doing. I am being given a template, basically a pre-rendered image. The user is then able to select from multiple images and enter the deisred text. I then render it to the image, adjusting size etc... within bounds and centering it in the pre-defined area of the image. If I can calculate the size (as in the MeasureString method) and then draw the string (as in the Graphics.DrawString method) that would be fine. The real question, no matter why I want to be able to do this, is can it be done?

The question is: why do you want to? Why not just use a TextBlock?
If you are trying to dynamically generate an image, use standard Silverlight/WPF controls (including TextBlock) and render them to a WritableBitmap.
Edit:
Ok, you've updated and expanded, which gives me more to go on. Unfortunately, you're not going to like the answer. First, keep in mind that Silverlight and WPF in general are vector based, and intended to be used as such. Although the Canvas allows you to do pseudo-pixel manipulations, you cannot be nearly as pixel-accurate as old-school GDI. This is a factor of your medium. If you absolutely have to measure things the way you want to measure them, I suggest you build your images on a remote server and transmit them to your Silverlight app.
You can calculate the size on-screen of the text rendered via a TextBlock using the ActualWidth and ActualHeight properties. But it only works on an already rendered control. Something like MeasureString is simply not available in Silverlight. Based on your description of your app, some user interaction could accomplish what you want. The user selects the image, enters the text, and is shown a preview. The user can then adjust the width and height of the various text areas until satisfied, at which point you can take a snapshot using the render method I liked to above.

The following may work, its a bit nebulous because I haven't tried yet myself.
The object you are looking for is the WritableBitmap.
You create a Visual tree, for example create your self a Grid or Canvas (you're not adding this to the UI). Add to it the selected image and a TextBlock positioned and sized as you prefer.
Create a new WritableBitmap either of a specific size or using the selected image to initialize it.
Use the WritableBitmap Render method passing the above root Grid or Canvas to it.
Now you have a bitmap which you should able to use to do whatever its you needed to do that required all this hoop jumping in the first place.