layout,f32: add convenience functions for rectangles and points

layout.FRect, layout.FPt for converting from integer to floating point,
useful for drawing operations.

f32.Pt is a shorthand that mirrors image.Pt.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

f32/f32.go

@@ -33,9 +33,9 @@ func (r Rectangle) String() string {
 	return r.Min.String() + "-" + r.Max.String()
 }
 
-// Rect is a shorthand to Rectangle{Point{x0, y0}, Point{x1, y1}}.
+// Rect is a shorthand for Rectangle{Point{x0, y0}, Point{x1, y1}}.
 // The returned Rectangle has x0 and y0 swapped if necessary so that
-// it's correctly formed
+// it's correctly formed.
 func Rect(x0, y0, x1, y1 float32) Rectangle {
 	if x0 > x1 {
 		x0, x1 = x1, x0
@@ -46,6 +46,11 @@ func Rect(x0, y0, x1, y1 float32) Rectangle {
 	return Rectangle{Point{x0, y0}, Point{x1, y1}}
 }
 
+// Pt is shorthand for Point{X: x, Y: y}.
+func Pt(x, y float32) Point {
+	return Point{X: x, Y: y}
+}
+
 // Add return the point p+p2.
 func (p Point) Add(p2 Point) Point {
 	return Point{X: p.X + p2.X, Y: p.Y + p2.Y}

layout/layout.go

@@ -5,6 +5,7 @@ package layout
 import (
 	"image"
 
+	"gioui.org/f32"
 	"gioui.org/op"
 	"gioui.org/unit"
 )
@@ -66,6 +67,20 @@ func Exact(size image.Point) Constraints {
 	}
 }
 
+// FPt converts an point to a f32.Point.
+func FPt(p image.Point) f32.Point {
+	return f32.Point{
+		X: float32(p.X), Y: float32(p.Y),
+	}
+}
+
+// FRect converts a rectangle to a f32.Rectangle.
+func FRect(r image.Rectangle) f32.Rectangle {
+	return f32.Rectangle{
+		Min: FPt(r.Min), Max: FPt(r.Max),
+	}
+}
+
 // Constrain a size so each dimension is in the range [min;max].
 func (c Constraints) Constrain(size image.Point) image.Point {
 	if min := c.Min.X; size.X < min {