pcb-rnd knowledge pool

Abstract: A positive direction selection box will select any object that is fully enclosed by the box; a negative direction box will select any object that touches the box.

  When a selection is made using drag&drop (box selection), depending on the direction the rule for object selection differ:

• drag from top-left towards bottom-right (positive sized box): select objects that are fully contained in the box (original behaviour)
• drag in any other direction (e.g. bottom-left to top-right, or bottom-right to top-left; negative sized box): select objects that are even partially within the box or merely touch the edge of the box

As an example, we look at the features in the following layout, which will be subsequently combined to form a footprint for a B7G thermionic valve. Using a click and drag selection box going from the top left and then down and rightwards to the middle of the set of features, as follows:

we obtain the following selection, namely, only objects that lie entirely within the selection box, which in this case is only a single pin:

If we now use a click and drag selection box going from the bottom right to the middle of the set of features, as follows:

we obtain the following selection, namely, any objects which lie partly or entirely within the selection box, which includes the silk circle, the text, the hole and two of the pins:

This feature is of most use on crowded layouts or when selecting from amongst closely spaced features.

The feature can be disabled using the editor/selection/disable_negative conf setting.

It's possible to limit the feature so that only horizontal-negative is considered negative size (i.e. only right-to-left dragging), using the editor/selection/symmetric_negative conf setting.