class TGNumberEntry: public TGCompositeFrame, public TGWidget, public TGNumberFormat

TGNumberEntry, TGNumberEntryField and TGNumberFormat

TGNumberEntry is a number entry input widget with up/down buttons.
TGNumberEntryField is a number entry input widget.
TGNumberFormat contains enum types to specify the numeric format.

The number entry widget is based on TGTextEntry but allows only
numerical input. The widget support numerous formats including
integers, hex numbers, real numbers, fixed fraction reals and
time/date formats. The widget also allows to restrict input values
to non-negative or positive numbers and to specify explicit limits.

The following styles are supported:
kNESInteger:        integer number
kNESRealOne:        real number with one digit (no exponent)
kNESRealTwo:        real number with two digits (no exponent)
kNESRealThree:      real number with three digits (no exponent)
kNESRealFour:       real number with four digits (no exponent)
kNESReal:           arbitrary real number
kNESDegree:         angle in degree:minutes:seconds format
kNESMinSec:         time in minutes:seconds format
kNESHourMin:        time in hour:minutes format
kNESHourMinSec:     time in hour:minutes:seconds format
kNESDayMYear:       date in day/month/year format
kNESMDayYear:       date in month/day/year format
kNESHex:            hex number

The following attributes can be specified:
kNEAAnyNumber:      any number is allowed
kNEANonNegative:    only non-negative numbers are allowed
kNEAPositive:       only positive numbers are allowed

Explicit limits can be specified individually:
kNELNoLimits:       no limits
kNELLimitMin:       lower limit only
kNELLimitMax        upper limit only
kNELLimitMinMax     both lower and upper limits

TGNumberEntryField is a plain vanilla entry field, whereas
TGNumberEntry adds two small buttons to increase and decrease the
numerical value in the field. The number entry widgets also support
using the up and down cursor keys to change the numerical values.
The step size can be selected with control and shift keys:
--                  small step (1 unit/factor of 3)
shift               medium step (10 units/factor of 10)
control             large step (100 units/factor of 30)
shift-control       huge step (1000 units/factor of 100)

The steps are either linear or logarithmic. The default behaviour
is set when the entry field is created, but it can be changed by
pressing the alt key at the same time.

Changing the number in the widget will generate the event:
kC_TEXTENTRY, kTE_TEXTCHANGED, widget id, 0.
Hitting the enter key will generate:
kC_TEXTENTRY, kTE_ENTER, widget id, 0.
Hitting the tab key will generate:
kC_TEXTENTRY, kTE_TAB, widget id, 0.