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 // Copyright 2016 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package theme import ( "testing" "golang.org/x/exp/shiny/unit" "golang.org/x/image/math/fixed" ) func approxEqual(x, y, tolerance float64) bool { delta := x - y return -tolerance < delta && delta < +tolerance } func TestThemeIsAUnitConverter(t *testing.T) { // 1.5 inches (at the default 72 DPI) should be 108 pixels. c := unit.Converter(Default) got := c.Pixels(unit.Inches(1.5)) want := fixed.I(108) if got != want { t.Errorf("1 inch in pixels: got %v, want %v", got, want) } // 3 em (at inconsolata.Regular8x16's 16 pixel em-height) should be 48 // pixels, regardless of the DPI. That font face is based on a bitmap font, // not a vector font, so its height does not depend on the DPI. 48 pixels // is 48 points at 72 DPI, and 48 pixels is 21.6 points at 160 DPI. for _, dpi := range []float64{72, 160} { c := unit.Converter(&Theme{ DPI: dpi, }) got := c.Convert(unit.Ems(3), unit.Pt) want := unit.Points(3 * 16 * unit.PointsPerInch / dpi) if got.U != want.U || !approxEqual(got.F, want.F, 1e-10) { t.Errorf("dpi=%v: 3 em in points: got %v, want %v", dpi, got, want) } } }