widget: add Fit for scaling widgets

Currently adds four different variants Unscaled, Contain, Cover, ScaleDown and Fill. Signed-off-by: Egon Elbre <egonelbre@gmail.com>
2026-07-01 07:35:40 +00:00 · 2021-02-28 16:54:13 +02:00
parent 9e85b43b0c
commit 2c5daf10a2
2 changed files with 223 additions and 0 deletions
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package widget
+
+import (
+	"bytes"
+	"encoding/binary"
+	"image"
+	"math"
+	"testing"
+
+	"gioui.org/f32"
+	"gioui.org/layout"
+	"gioui.org/op"
+)
+
+func TestFit(t *testing.T) {
+	type test struct {
+		Dims   image.Point
+		Scale  f32.Point
+		Result image.Point
+	}
+
+	fittests := [...][]test{
+		Unscaled: {
+			{
+				Dims:   image.Point{0, 0},
+				Scale:  f32.Point{X: 1, Y: 1},
+				Result: image.Point{X: 0, Y: 0},
+			}, {
+				Dims:   image.Point{50, 25},
+				Scale:  f32.Point{X: 1, Y: 1},
+				Result: image.Point{X: 50, Y: 25},
+			}, {
+				Dims:   image.Point{50, 200},
+				Scale:  f32.Point{X: 1, Y: 1},
+				Result: image.Point{X: 50, Y: 100},
+			}},
+		Contain: {
+			{
+				Dims:   image.Point{50, 25},
+				Scale:  f32.Point{X: 2, Y: 2},
+				Result: image.Point{X: 100, Y: 50},
+			}, {
+				Dims:   image.Point{50, 200},
+				Scale:  f32.Point{X: 0.5, Y: 0.5},
+				Result: image.Point{X: 25, Y: 100},
+			}},
+		Cover: {
+			{
+				Dims:   image.Point{50, 25},
+				Scale:  f32.Point{X: 4, Y: 4},
+				Result: image.Point{X: 100, Y: 100},
+			}, {
+				Dims:   image.Point{50, 200},
+				Scale:  f32.Point{X: 2, Y: 2},
+				Result: image.Point{X: 100, Y: 100},
+			}},
+		ScaleDown: {
+			{
+				Dims:   image.Point{50, 25},
+				Scale:  f32.Point{X: 1, Y: 1},
+				Result: image.Point{X: 50, Y: 25},
+			}, {
+				Dims:   image.Point{50, 200},
+				Scale:  f32.Point{X: 0.5, Y: 0.5},
+				Result: image.Point{X: 25, Y: 100},
+			}},
+		Fill: {
+			{
+				Dims:   image.Point{50, 25},
+				Scale:  f32.Point{X: 2, Y: 4},
+				Result: image.Point{X: 100, Y: 100},
+			}, {
+				Dims:   image.Point{50, 200},
+				Scale:  f32.Point{X: 2, Y: 0.5},
+				Result: image.Point{X: 100, Y: 100},
+			}},
+	}
+
+	for fit, tests := range fittests {
+		fit := Fit(fit)
+		for i, test := range tests {
+			ops := new(op.Ops)
+			gtx := layout.Context{
+				Ops: ops,
+				Constraints: layout.Constraints{
+					Max: image.Point{X: 100, Y: 100},
+				},
+			}
+
+			result := fit.scale(gtx, layout.NW, layout.Dimensions{Size: test.Dims})
+
+			if test.Scale.X != 1 || test.Scale.Y != 1 {
+				opsdata := gtx.Ops.Data()
+				scaleX := float32Bytes(test.Scale.X)
+				scaleY := float32Bytes(test.Scale.Y)
+				if !bytes.Contains(opsdata, scaleX) {
+					t.Errorf("did not find scale.X:%v (%x) in ops: %x", test.Scale.X, scaleX, opsdata)
+				}
+				if !bytes.Contains(opsdata, scaleY) {
+					t.Errorf("did not find scale.Y:%v (%x) in ops: %x", test.Scale.Y, scaleY, opsdata)
+				}
+			}
+
+			if result.Size != test.Result {
+				t.Errorf("fit %v, #%v: expected %#v, got %#v", fit, i, test.Result, result.Size)
+			}
+		}
+	}
+}
+
+func float32Bytes(v float32) []byte {
+	var dst [4]byte
+	binary.LittleEndian.PutUint32(dst[:], math.Float32bits(v))
+	return dst[:]
+}