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### Dynamic Layout Properties

Layout dynamics refer to the effects of window operations on the spatial properties of windows on the layout. In Elastic Windows, when a window is resized, opened, closed, packed, etc. the surrounding windows are also resized in an elastic space-filling manner. Groups of windows stretch like an elastic material as they are being resized, and other windows shrink to make space. When a window is packed, the emerging space is filled with the surrounding windows proportionally.

The effects of the operations are split proportionally according to the window sizes. A resize operation, depending on the border dragged and the direction of drag, is either a push or pull operation (Figure ). In the example, the push operation on window B does not affect window A but windows C and D proportionally shrunk. Calculations are as shown below:

Elastic layout dynamics can also be described by a transformation function. A transformation (T) basically determines the mapping from the original layout to the new layout. The transformation function of the push operation in the previous example coincides with the diagonal line for window A and has a constant larger slope (;SPMgt;1) for window B, and smaller slope (;SPMlt;1) for windows C and D. In two-dimensions, simply two transformation functions are used for each dimension of the layout.

Effects of the window operations are limited to the windows in the current group and their subwindows recursively. Limiting the extent of the operation to the group window may be beneficial in that it prevents disorientation when a large portion of the screen is updated and minimizes unintentional effects.

Typically, when a large portion of the screen is updated, users may get disoriented. In order to reorient themselves, users typically look for associations between the previous and the new layout. Associations can be based on spatial (e.g. absolute and relative location, size, shape, etc.) and visual (e.g. color, images, structure, etc.) properties.

In order to minimize the effects of disorientation, the required properties of elastic window operations can be listed as below:

• R1. Keep windows non-overlapping
• R2. Keep sides orthogonal
• R3. Keep all windows in view at all times
• R4. Preserve relative locations of windows
• R5. Preserve the structure of windows
• R6. Be simple to perceive and easy to undo

Space-filling elastic layout dynamics in Elastic Windows satisfy all the above requirements and provide a space-efficient, highly visible and orienting layout. However, elastic dynamics do not preserve aspect ratios of windows. This could be a disadvantage, if the content of windows are not reformatted or rescaled based on the new window size.

Next: Alternatives Up: Space-filling Tiled Layout and Previous: Static Layout Properties

Eser Kandogan
Sun Sep 13 18:34:46 EDT 1998

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