Define LogoSetter interface and BestFit selection helper

src/gopheros/device/video/console/device.go

@@ -2,6 +2,7 @@ package console
 
 import (
 	"gopheros/device/video/console/font"
+	"gopheros/device/video/console/logo"
 	"image/color"
 )
 
@@ -68,3 +69,11 @@ type Device interface {
 type FontSetter interface {
 	SetFont(*font.Font)
 }
+
+// LogoSetter is an interface implemented by console devices that
+// support drawing of logo images.
+//
+// SetLogo selects the logo to be drawn by the console.
+type LogoSetter interface {
+	SetLogo(*logo.Image)
+}

src/gopheros/device/video/console/logo/logo.go

@@ -3,9 +3,10 @@ package logo
 
 import "image/color"
 
-// ConsoleLogo defines the logo used by framebuffer consoles. If set to nil
-// then no logo will be displayed.
-var ConsoleLogo *Image
+var (
+	// The list of available logos.
+	availableLogos []*Image
+)
 
 // Alignment defines the supported horizontal alignments for a console logo.
 type Alignment uint8
@@ -42,3 +43,29 @@ type Image struct {
 	// represents an index in the logo palette.
 	Data []uint8
 }
+
+// BestFit returns the best logo from the available logo list given the
+// specified console dimensions.
+func BestFit(consoleWidth, consoleHeight uint32) *Image {
+	var (
+		best                *Image
+		bestDelta, absDelta uint32
+		threshold           = consoleHeight / 10
+	)
+
+	for _, l := range availableLogos {
+		if l.Height > threshold {
+			absDelta = l.Height - threshold
+		} else {
+			absDelta = threshold - l.Height
+		}
+
+		if best == nil || absDelta < bestDelta {
+			best = l
+			bestDelta = absDelta
+			continue
+		}
+	}
+
+	return best
+}

src/gopheros/device/video/console/logo/logo_test.go

@@ -0,0 +1,39 @@
+package logo
+
+import "testing"
+
+func TestBestFit(t *testing.T) {
+	defer func(origList []*Image) {
+		availableLogos = origList
+	}(availableLogos)
+
+	availableLogos = []*Image{
+		&Image{Height: 64},
+		&Image{Height: 96},
+		&Image{Height: 128},
+	}
+
+	specs := []struct {
+		consW, consH uint32
+		expIndex     int
+	}{
+		{320, 200, 0},
+		{800, 600, 0},
+		{1024, 768, 0},
+		{1280, 1024, 1},
+		{3000, 3000, 2},
+		{2500, 1600, 2},
+	}
+
+	for specIndex, spec := range specs {
+		got := BestFit(spec.consW, spec.consH)
+		if got == nil {
+			t.Errorf("[spec %d] unable to find a logo", specIndex)
+			continue
+		}
+
+		if got.Height != availableLogos[spec.expIndex].Height {
+			t.Errorf("[spec %d] expected to get logo with height %d; got %d", specIndex, availableLogos[spec.expIndex].Height, got.Height)
+		}
+	}
+}