Widget position and size in grid

Form items render as widgets in the window, at a given position and with a given size.

To render form items, grid-based rendering follows the layout rules described below:

1. The position of the widgets in the virtual grid is defined by the posX and posY AUI tree attributes.
2. The number of virtual grid cells occupied by a widget is defined by the gridWidth and gridHeight AUI tree attributes.
3. The real size (i.e. pixels) of a widget is defined by the width and height AUI tree attributes.
4. Empty lines and empty columns in the form layout definition take a size of 0 pixels.
5. The size of a cell in the virtual grid depends on the real size of the widgets inside the grid.
6. A widget's minimum size is computed via its real size and the SAMPLE attribute.
7. The preferred size of the widget is computed following the SIZEPOLICY attribute.
8. The final widget size is computed depending on the minimum and preferred size, to fill the cells in the grid.
9. A small spacing is applied in non-empty cells.

The next screenshot shows 2 labels and 2 fields placed in a grid.

By default, empty grid rows and empty grid columns get no size when rendered on the front-end. For example, in the above grid sample, the grid columns #10 and #11 are empty.