Hi, I've been working on a mobile app example for FlexJS as a way to try out the Flex JS in a practical manner with the intent of running the app using PhoneGap. In the course of doing this I've been running into things that need adjustment.
One of them is the box model. Right now FlexJS is sort of a hybrid between ActionScript and JavaScript. I'll use the .width property as an example. In Flex, when you give a component a width of 50 pixels that component is 50 pixels wide. Some components, such as a container, would embed a scrollbar if its content were greater than 50 pixels. But you can be sure that your component is 50 pixels wide and you can position other components knowing that. If you add padding to the component, that will offset the interior by that amount. If you make a Container 200 pixels wide and give it a padding of 10 pixels, positioning a child of that container at (0,0) will render the child 10 pixels in from the left and 10 pixels down from the top. The child thinks it is at (0,0) and the Container will remain 200 pixels wide. In the CSS Box model, things work differently. If you make an HTML element 50 pixels wide and give it a padding of 10 pixels, the overall width of the HTML element will be 70 pixels: the 50 pixels are the width of the content area and 2*10 pixels (left and right) are the padding added to that. HTML goes further and adds on border thickness and margin; Flex doesn't have margins. I was having trouble getting things to align because I would make a ButtonBar 480 pixels wide and it was turning out to be wider than that. When I looked into the code, I saw that making a component 480 pixels was just the start: I was getting that plus a padding on each of the buttons that make up the button bar plus the width of the border around each button. This makes alignment very difficult because you must ask for more than just width (or height). I suggest FlexJS completely adopt the CSS Box Model. This means setting a component's width isn't going to take into account its padding, border thickness, and margin - it is just going to set the component's content area width. For example, if I make a Button's width be 50 pixels, the text will be placed within that 50 pixel content area, but there may be padding, a border, and a margin surrounding the Button. If I want all of my Buttons to align horizontally with no gaps, I should make sure the Buttons do not have any margin. What this means is that .width won't set the overall width of the component. This may affect layout calculations which will have to examine the component's margin, border thickness, and padding values. So I suggest making it simple (height dimension would have similar properties of course): .width is the content area. .padding is the padding around the content area, inside the border. .borderThickness is the thickness of border that surrounds the padding and content area. .margin is space around the component. .x will position a component's upper-left margin. .overallWidth will be .width + 2*.margin + 2*.padding + 2*.borderThickness You can use .overallWidth to position elements in layouts as it will account for all of the extra space in a component's box. Further, for Flex JS 1.0, I suggest we keep it simple to padding, margin, and borderThickness and leave edge specifics (e.g., padding-top, margin-bottom) to another release or a developer can create their component or override functions to account for that. Finally, it should be easier to build applications because you can let CSS have a greater say in the size and positioning of components. For example, if I want to make a row of buttons that are all touching, I just create a Container with a horizontal layout and put the Buttons into it. Then in CSS, I specify that the Buttons have zero margin and if I want them inset within the Container, I give the Container, via CSS, some padding. Thanks for your time, Peter Ent Adobe Systems
