Rectangular and Multiple Selections

Scintilla supports the now popular ability of making a "rectangular" selection. A user can do this by holding the ALT key when dragging the mouse. This feature is a specialized version of what is more generally known a "multiple selections" in Scintilla. To get the most of our rectangular selections you'll likely want to enable the following features at a minimum:

scintilla.MultipleSelection = true;
scintilla.MouseSelectionRectangularSwitch = true;
scintilla.AdditionalSelectionTyping = true;
scintilla.VirtualSpaceOptions = VirtualSpace.RectangularSelection;

Internally Scintilla handles rectangular selections as a list of multiple selection ranges. When there are multiple selections, one range it is said to be the "main selection" and the others are known as "additional selections". These ranges do not need to be contiguous as they are in a rectangular selection. Once multiple selections are enabled with the MultipleSelection property, a user can hold the CTRL key to select additional, non-continuous ranges of text.

To get information about the current selections you can enumerate the Scintilla.Selections property like so:

foreach (var selection in scintilla.Selections)
{
    // Print the current selection's range
    Debug.WriteLine("Start: " + selection.Start + ", End: " + selection.End);
}

Most of the properties on the enumerated Selection object have setters if you want to modify the bounds of an existing selection.

Selections are only queried through the Scintilla.Selections collection, not created. Selections are created using the Scintilla.SetSelection method to make the main selection and the subsequent calls to the AddSelection method as many times is needed to add additional selections.

If you intend to programmatically create a rectangular selection you can save yourself the time of calling SetSelection and multiple calls to AddSelection by using the RectangularSelection* properties. These allow you to specify the anchor and caret (and virtual space) positions of the rectangle and Scintilla will do the extra work of converting those to multiple selections.

In much the same way that you can customize the appearance of a single selection using the SetSelectionForeColor and SetSelectionBackColor methods, you may use the SetAdditionalSelFore and SetAdditionalSelBack methods to do the same for additional selections. The caret in an additional selection can also be customized using the AdditionalCaret* properties.