Multiply hover over button colour to support other themes.

Correct, and optimise, maths for non-pre-mul channels.
lunarforge · Feb 24, 2021 · ceff3c9 · ceff3c9
1 parent ffeca25
commit ceff3c9
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Showing 3 changed files with 14 additions and 9 deletions.
diff --git a/widget/button.go b/widget/button.go
@@ -313,17 +313,22 @@ func (r *buttonRenderer) buttonColor() color.Color {
 	case r.button.Disabled():
 		return theme.DisabledButtonColor()
 	case r.button.hovered:
+		bg := theme.ButtonColor()
 		if r.button.Importance == HighImportance {
-			srcR, srcG, srcB, srcA := theme.PrimaryColor().RGBA()
-			dstR, dstG, dstB, dstA := theme.HoverColor().RGBA()
-			alpha := float32(dstA) / 0xFFFF
-			outR := alpha*float32(dstR) + (1-alpha)*float32(srcR)
-			outG := alpha*float32(dstG) + (1-alpha)*float32(srcG)
-			outB := alpha*float32(dstB) + (1-alpha)*float32(srcB)
-			outA := alpha*float32(dstA) + (1-alpha)*float32(srcA)
-			return color.RGBA{R: uint8(uint32(outR) >> 8), G: uint8(uint32(outG) >> 8), B: uint8(uint32(outB) >> 8), A: uint8(uint32(outA) >> 8)}
+			bg = theme.PrimaryColor()
 		}
-		return theme.HoverColor()
+
+		dstR, dstG, dstB, dstA := bg.RGBA()
+		srcR, srcG, srcB, srcA := theme.HoverColor().RGBA()
+		srcAlpha := float32(srcA) / 0xFFFF
+		dstAlpha := float32(dstA) / 0xFFFF
+		targetAlpha := 1 - srcAlpha*dstAlpha
+
+		outAlpha := srcAlpha + targetAlpha
+		outR := (srcAlpha*float32(srcR) + targetAlpha*float32(dstR)) / outAlpha
+		outG := (srcAlpha*float32(srcG) + targetAlpha*float32(dstG)) / outAlpha
+		outB := (srcAlpha*float32(srcB) + targetAlpha*float32(dstB)) / outAlpha
+		return color.RGBA{R: uint8(uint32(outR) >> 8), G: uint8(uint32(outG) >> 8), B: uint8(uint32(outB) >> 8), A: uint8(outAlpha * 0xFF)}
 	case r.button.Importance == HighImportance:
 		return theme.PrimaryColor()
 	default:

diff --git a/widget/testdata/button/high_importance_hovered.png b/widget/testdata/button/high_importance_hovered.png
diff --git a/widget/testdata/button/hovered.png b/widget/testdata/button/hovered.png