iOS Web Inspector

If you are using iOS 6 and Safari 6, you can inspect web pages shown in Mobile Safari or in WebViews of applications like those created with ADF Mobile. This can either be in the iOS Simulator or on a device (iPhone, iPad, iPod touch) connected over USB.

In Safari 6, enable the “Develop” menu:

From that menu, your connected devices and iOS Simulator will display as submenus. Each submenu will list all of the WebViews that you are able to inspect (if you are not sure which one you want, a highlight will appear on your device or in the simulator as you hover over each menu item):

A web inspector window will open:

In the first column, the panel with a document icon (1) is where you can browse the DOM, look at scripts, style sheets, etc.  When the HTML page is selected, the middle panel will show you the DOM tree (3) which you can manually browse for an element. Alternatively, you can use the hand tool (2) to click on the screen (of the actual device or the simulator) to pick an element that you want to inspect.

With an element selected, you can then use the “{}” icon (4) of the right panel to view the element’s style properties.  This will show you the exact selectors that are providing each style to the element (5). This is incredibly valuable, particularly when multiple selectors are competing (a line will strike out any styles that lose due to some other more specific selector). You can also edit those values directly or add additional properties and see the change immediately take effect on the screen. Unfortunately, there’s no way to save off any changes you’ve made. If you are trying to create a custom style sheet, you’ll need to jot down elsewhere the changes you’ve made; if you leave the page or close the app, you’ll lose your changes.

CSS Shorthand Tokens

In CSS, you will come across some shorthand notation for the margin, border-color, border-style, border-width, and padding properties. It isn’t obvious or easy to remember which token in the value applies to which side of the element so here’s a handy list of the 4 possible varieties:

1. One token — all-sides-use-the-same-value
2. Two tokens — top-and-bottom right-and-left
3. Three tokens — top right-and-left bottom
4. Four tokens — top right bottom left

At least the four-token example can be remembered by associating the element with a clock where time progresses clockwise.

Decrypting Margin, Border, and Padding Styles

When working with ADF Faces skins, JSF inlineStyles, or just CSS in general, you may have come across some explicit style definitions like this which is very easy to understand:

padding-top: 15px;

However, you may have also come across more cryptic style definitions like these but wonder which measurement applies to which side of the element:

padding: 1px 2px 3px 4px;
padding: 5px 6px 7px;
padding: 8px 9px;
padding: 10px;

Here’s a key for decoding these definitions:

padding:   top   right   bottom   left;
padding:   top   right/left   bottom;
padding:   top/bottom   right/left;
padding:   top/bottom/right/left;

This same pattern applies to margins and borders.

Aside from the cryptic definitions, see my other post displaying how the CSS Box Model treats margins, borders, and padding with respect to width and height dimensions.  If you are an ADF Faces application developer be sure to also read the Layout Basics page.

Visualizing the CSS Box Model

Since the way web browsers deal with width and height is so non-intuitive, I’ve created this a handy guide showing how the CSS (Cascading Style Sheets) box model applies widths and heights when scrolling, margins, borders, and padding are involved: