Unlike the single touch gestures, which state which gesture you have just entered, the multi-touch gestures are events that fire whenever you have more than one finger on the touchscreen. The plugin tracks up to five contact points, if 6 or more are present they will simply be ignored by the plugin. The events the plugin listens to are gre.press, gre.release, and gre.motion to track the touchscreen info while only one finger is present and gre.mtpress, gre.mtrelease, and gre.mtmotion, to track the touchscreen info while multiple touches are present. Note when using a multi-touch enabled device single the press, release and motion events will be sent only while there is only one touch point present. As soon as there are multiple touch points present, all events will be mt events.

After listening to the events, if more than one touch point is present and one or more touch points move, the plugin will do an update where it compares the old touch locations to the updated touch locations and generates the related multi-touch gesture events. These events are all of the form gre.mtXaction, where X is the number of touch points present (between 2 and 5), and action is the name of the event, which will be one of, move, pinch or rotate.

All multi-touch gesture events have the same format of a gre pointer event, with a few extra data fields.

gre.mtXmove

This event has an x_move and y_move data field, which will be the difference in x and y of the midpoint of all present touch touches between the current and last event sent from the touchscreen.

gre.mtXpinch

This event has a value data field, which will be the scale factor of the average spacing from all current touch points compared to the spacing of all the old touch points. The scale factor is calculated by newspacing/oldspacing, so a value of 1.1 indicates a growth of 10% and a value of 0.9 indicates a shrink of 10%

gre.mtXrotate

This event has a value data field, which will be the difference in rotation between the average angle of all current touch points compared to the average angle of all the previous touch points. The value will be in degrees.