Drag/Drop

The drag/drop mechanism is used to specify most of the aspects of a map. The simplest operation is to drag an input map element to an output map element. If the output map element had no previous value expression, this creates a value expression that copies the input to the output.

Here are the different possibilities for drag/drop when editing a map:

• Drag from input map element to:

  • An output map element - If no value expression is present, creates a value expression copying input to output.

  • An empty value expression panel - Behaves identically to dragging to the output map element (assuming the value expression tab is enabled, which occurs when you have previously selected the output map element).

  • An expression - Adds the input map element as the last child of the expression. If the expression is a function argument, only one child to a function argument is allowed.

• Drag a function to:

  • An output map element - If no value expression is present, the function becomes the root of the value expression tree. Otherwise, has no effect.

  • An empty value expression Panel - Behaves identically to dragging to the output map element (assuming the value expression tab is enabled, which occurs when you have previously selected the output map element).

  • An expression - Adds the function as the last child of the expression. If the expression is a function argument, only one child to a function argument is allowed.

• Drag an expression to:

  • Another expression - Adds the source expression as the last child of the target expression, and removes the source expression. This is because a drag/drop is identical to a cut/paste operation. A copy/paste will do the same thing, except it will not remove the source expression.

• Drag from an output map element to:

  • An output map element - Creates a value expression in the destination output with a reference to the source output, unless a value expression is already present in the destination output.

  • An empty value expression Panel - Behaves identically to dragging to the output map element (assuming the value expression tab is enabled, which occurs when you have previously selected the output map element).

  • An expression - Adds the output map element as the last child of the expression. If the expression is a function argument, only one child to a function argument is allowed.

• Drag from an value map element (input or output) to:

  • An output map element - Creates a Constant expression with the specified value.

  • An empty value expression Panel - Creates a Constant expression with the specified value.

  • An expression - Creates a Constant expression with the specified value.

No other drag/drop operations have any effect when editing a map.