tomo/unit.go

97 lines
2.8 KiB
Go

package tomo
import "image"
import "image/color"
// Side represents one side of a rectangle.
type Side int; const (
SideTop Side = iota
SideRight
SideBottom
SideLeft
)
// Inset represents a rectangle inset that can have a different value for each
// side.
type Inset [4]int
// I allows you to create an inset in a CSS-ish way:
//
// - One argument: all sides are set to this value
// - Two arguments: the top and bottom sides are set to the first value, and
// the left and right sides are set to the second value.
// - Three arguments: the top side is set by the first value, the left and
// right sides are set by the second vaue, and the bottom side is set by the
// third value.
// - Four arguments: each value corresponds to a side.
//
// This function will panic if an argument count that isn't one of these is
// given.
func I (sides ...int) Inset {
switch len(sides) {
case 1: return Inset { sides[0], sides[0], sides[0], sides[0] }
case 2: return Inset { sides[0], sides[1], sides[0], sides[1] }
case 3: return Inset { sides[0], sides[1], sides[2], sides[1] }
case 4: return Inset { sides[0], sides[1], sides[2], sides[3] }
default: panic("I: illegal argument count.")
}
}
// Apply returns the given rectangle, shrunk on all four sides by the given
// inset. If a measurment of the inset is negative, that side will instead be
// expanded outward. If the rectangle's dimensions cannot be reduced any
// further, an empty rectangle near its center will be returned.
func (inset Inset) Apply (bigger image.Rectangle) (smaller image.Rectangle) {
smaller = bigger
if smaller.Dx() < inset[3] + inset[1] {
smaller.Min.X = (smaller.Min.X + smaller.Max.X) / 2
smaller.Max.X = smaller.Min.X
} else {
smaller.Min.X += inset[3]
smaller.Max.X -= inset[1]
}
if smaller.Dy() < inset[0] + inset[2] {
smaller.Min.Y = (smaller.Min.Y + smaller.Max.Y) / 2
smaller.Max.Y = smaller.Min.Y
} else {
smaller.Min.Y += inset[0]
smaller.Max.Y -= inset[2]
}
return
}
// Inverse returns a negated version of the inset.
func (inset Inset) Inverse () (prime Inset) {
return Inset {
inset[0] * -1,
inset[1] * -1,
inset[2] * -1,
inset[3] * -1,
}
}
// Horizontal returns the sum of SideRight and SideLeft.
func (inset Inset) Horizontal () int {
return inset[SideRight] + inset[SideLeft]
}
// Vertical returns the sum of SideTop and SideBottom.
func (inset Inset) Vertical () int {
return inset[SideTop] + inset[SideBottom]
}
// Border represents a single border of a box.
type Border struct {
Width Inset
Color [4]color.Color
}
// Align lists basic alignment types.
type Align int; const (
AlignStart Align = iota // similar to left-aligned text
AlignMiddle // similar to center-aligned text
AlignEnd // similar to right-aligned text
AlignEven // similar to justified text
)