Modifier Keys

What are Modifier Keys?

Modifiers keys are the keys Ctrl, Shift, Alt, and, sometimes, the key between Ctrl and Alt, called the Windows key (WinKey), Super key, or Meta key. Modifier keys are so-called because they "modify" the effect of other user input. For example, normally pressing the left arrow key while typing something moves the text cursor one character to the left, but if you do so while you hold the Ctrl key, it moves one whole word to the left. In complex editing applications, it's common for tools and functions activated with mouse buttons to have different effects while specific modifier keys are held.

Some examples:

• In file managers, holding modifier keys while moving a file from one folder to another can change the operation from "move file" to "copy file" or "create shortcut." Similar functionality can be found in other interfaces that display lists of items, such as panels for layers in a document.
• When using selection tools in image editors, some modifiers keys change the Boolean operation from "replace current selection" to "add to the current selection" or "subtract to the current selection," allowing you modify the currently selected area. In Krita, the modifiers would be Shift and Alt, respectively.
• When drawing shapes in image editors, like rectangles and circles, or when using a transform tool to resize parts of the image, it's possible to constrain the aspect ratio or change the origin of the transformation by holding a modifier key. In Krita, if you use the rectangle tool and hold Shift, you will always draw a square (1:1 aspect ratio) instead of an arbitrary rectangle. Holding Alt moves the rectangle you drew so far without resizing it, and holding Shift makes resizing symmetrical (origin at center instead of at starting point).