Backend unsets style attributes if they are no longer specified

go.mod

@@ -3,7 +3,7 @@ module git.tebibyte.media/tomo/backend
 go 1.20
 
 require (
-	git.tebibyte.media/tomo/tomo v0.42.0
+	git.tebibyte.media/tomo/tomo v0.45.0
 	git.tebibyte.media/tomo/typeset v0.7.1
 	git.tebibyte.media/tomo/xgbkb v1.0.1
 	github.com/jezek/xgb v1.1.1

go.sum

@@ -1,6 +1,6 @@
 git.tebibyte.media/sashakoshka/xgbkb v1.0.0/go.mod h1:pNcE6TRO93vHd6q42SdwLSTTj25L0Yzggz7yLe0JV6Q=
-git.tebibyte.media/tomo/tomo v0.42.0 h1:yaEUnURYrvBdMdcajrFhpd83TNzyQyBB+jOxvIyQTkU=
+git.tebibyte.media/tomo/tomo v0.45.0 h1:fQH0WIPidW275hOq9dE6R7p064xG1RGx2QU68Avlr84=
-git.tebibyte.media/tomo/tomo v0.42.0/go.mod h1:WrtilgKB1y8O2Yu7X4mYcRiqOlPR8NuUnoA/ynkQWrs=
+git.tebibyte.media/tomo/tomo v0.45.0/go.mod h1:WrtilgKB1y8O2Yu7X4mYcRiqOlPR8NuUnoA/ynkQWrs=
 git.tebibyte.media/tomo/typeset v0.7.1 h1:aZrsHwCG5ZB4f5CruRFsxLv5ezJUCFUFsQJJso2sXQ8=
 git.tebibyte.media/tomo/typeset v0.7.1/go.mod h1:PwDpSdBF3l/EzoIsa2ME7QffVVajnTHZN6l3MHEGe1g=
 git.tebibyte.media/tomo/xgbkb v1.0.1 h1:b3HDUopjdQp1MZrb5Vpil4bOtk3NnNXtfQW27Blw2kE=

internal/system/box.go

@@ -27,15 +27,12 @@ type box struct {
 	focusQueued *bool
 
 	attrColor       attrHierarchy[tomo.AttrColor]
-	attrIcon        attrHierarchy[tomo.AttrIcon]
 	attrTexture     attrHierarchy[tomo.AttrTexture]
 	attrTextureMode attrHierarchy[tomo.AttrTextureMode]
 	attrBorder      attrHierarchy[tomo.AttrBorder]
 	attrMinimumSize attrHierarchy[tomo.AttrMinimumSize]
 	attrPadding     attrHierarchy[tomo.AttrPadding]
 
-	icon canvas.Texture
-
 	dndData   data.Data
 	dndAccept []data.Mime
 	focusable bool
@@ -195,11 +192,6 @@ func (this *box) setAttr (attr tomo.Attr, user bool) {
 			this.invalidateDraw()
 		}
 		
-	case tomo.AttrIcon:
-		if this.attrIcon.Set(attr, user) {
-			this.handleIconChange()
-		}
-		
 	case tomo.AttrTexture:
 		if this.attrTexture.Set(attr, user) {
 			this.invalidateDraw()
@@ -235,11 +227,6 @@ func (this *box) unsetAttr (kind tomo.AttrKind, user bool) {
 			this.invalidateDraw()
 		}
 		
-	case tomo.AttrKindIcon:
-		if this.attrIcon.Unset(user) {
-			this.handleIconChange()
-		}
-		
 	case tomo.AttrKindTexture:
 		if this.attrTexture.Unset(user) {
 			this.invalidateDraw()
@@ -438,11 +425,6 @@ func (this *box) Draw (can canvas.Canvas) {
 	if textureMode == tomo.TextureModeCenter && texture != nil {
 		this.centeredTexture(can, texture)
 	}
-
-	// centered icon
-	if this.icon != nil {
-		this.centeredTexture(can, this.icon)
-	}
 }
 
 func (this *box) centeredTexture (can canvas.Canvas, texture canvas.Texture) {
@@ -600,15 +582,6 @@ func (this *box) handleBorderChange (previousBorderSum tomo.Inset, different boo
 	}
 }
 
-func (this *box) handleIconChange () {
-	this.icon = nil
-	hierarchy := this.getHierarchy()
-	if hierarchy == nil { return }	
-	icon := this.attrIcon.Value()
-	if icon.Icon == tomo.IconUnknown { return }
-	this.icon = hierarchy.getIconSet().Icon(icon.Icon, icon.Size)
-}
-
 func (this *box) invalidateStyle () {
 	hierarchy := this.getHierarchy()
 	if hierarchy == nil { return }
@@ -635,7 +608,8 @@ func (this *box) invalidateMinimum () {
 }
 
 func (this *box) recursiveReApply () {
-	if this.getHierarchy() == nil { return }
+	hierarchy := this.getHierarchy()
+	if hierarchy == nil { return }
 	
 	// re-apply styling, icons *if needed*
 
@@ -647,7 +621,7 @@ func (this *box) recursiveReApply () {
 		// information about the boxes they're linked to (like all rules
 		// with a matching role).
 		this.lastStyleNonce = hierarchyStyleNonce
-		this.styleApplicator = this.getHierarchy().newStyleApplicator()
+		this.styleApplicator = hierarchy.newStyleApplicator()
 		this.invalidateStyle()
 		this.on.styleChange.Broadcast()
 	}

internal/system/style.go

@@ -4,9 +4,10 @@ import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/backend/style"
 
 type styleApplicator struct {
-	style *style.Style
+	style      *style.Style
-	role  tomo.Role
+	role       tomo.Role
-	rules []style.Rule
+	rules      []style.Rule
+	currentSet style.AttrSet
 }
 
 func (this *styleApplicator) apply (box anyBox) {
@@ -41,7 +42,18 @@ func (this *styleApplicator) apply (box anyBox) {
 		}
 	}
 
+	// reset an attribute if it is no longer specified
+	if this.currentSet != nil {
+		for kind := range this.currentSet {
+			_, exists := attrs[kind]
+			if !exists {
+				box.unsetAttr(kind, false)
+			}
+		}
+	}
+
 	// apply that list of attributes
+	this.currentSet = attrs
 	for _, attr := range attrs {
 		box.setAttr(attr, false)
 	}

internal/system/textbox.go

@@ -493,9 +493,9 @@ func (this *textBox) scrollToDot () {
 
 func (this *textBox) handleFaceChange () {
 	hierarchy := this.getHierarchy()
-	if hierarchy != nil { return }
+	if hierarchy == nil { return }
 	faceSet := hierarchy.getFaceSet()
-	if faceSet != nil { return }
+	if faceSet == nil { return }
 	
 	face := faceSet.Face(tomo.Face(this.attrFace.Value()))
 	this.face.Set(face, face)
@@ -503,3 +503,23 @@ func (this *textBox) handleFaceChange () {
 	this.invalidateMinimum()
 	this.invalidateLayout()
 }
+
+func (this *textBox) recursiveReApply () {
+	this.box.recursiveReApply()
+	
+	hierarchy := this.getHierarchy()
+	if hierarchy == nil { return }
+	
+	previousFace := this.face.Value()
+	if previousFace == nil {
+		faceSet := hierarchy.getFaceSet()
+		if faceSet == nil { return }
+		face := faceSet.Face(tomo.Face(this.attrFace.Value()))
+		if face != previousFace {
+			this.face.Set(face, face)
+			this.drawer.SetFace(face)
+			this.invalidateMinimum()
+			this.invalidateLayout()
+		}
+	}
+}

x/canvas/canvas.go

@@ -132,3 +132,32 @@ func convertColor (c color.Color) xgraphics.BGRA {
 		A: uint8(a >> 8),
 	}
 }
+
+// For some reason, xgraphics.BGRA does not specify whether or not it uses
+// premultiplied alpha, and information regarding this is contradictory.
+// Basically:
+//   - BGRAModel just takes the result of c.RGBA and bit shifts it, without
+//     un-doing the aplha premultiplication that is required by Color.RGBA,
+//     suggesting that xgraphics.BGRA stores alpha-premultiplied color.
+//   - xgraphics.BlendBGRA lerps between dest and src using only the alpha of
+//     src (temporarily converting the colors to fucking floats for some reason)
+//     which seems to suggest that xgraphics.BGRA *does not* store alpha-
+//     premultiplied color.
+// There is no issues page on xgbutil so we may never get an answer to this
+// question. However, in this package we just use xgraphics.BGRA to store alpha-
+// premultiplied color anyway because its way faster, and I would sooner eat
+// spaghetti with a spoon than convert to and from float64 to blend pixels.
+func blendPremultipliedBGRA (dst, src xgraphics.BGRA) xgraphics.BGRA {
+	// https://en.wikipedia.org/wiki/Alpha_compositing
+	return xgraphics.BGRA {
+		B: blendPremultipliedChannel(dst.B, src.B, src.A),
+		G: blendPremultipliedChannel(dst.G, src.G, src.A),
+		R: blendPremultipliedChannel(dst.R, src.R, src.A),
+		A: blendPremultipliedChannel(dst.A, src.A, src.A),
+	}
+}
+
+func blendPremultipliedChannel (dst, src, a uint8) uint8 {
+	dst16, src16, a16 := uint16(dst), uint16(src), uint16(a)
+	return uint8(src16 + ((dst16 * (255 - a16)) >> 8))
+}

x/canvas/draw.go

@@ -46,7 +46,7 @@ func (this *pen) textureRectangleTransparent (bounds image.Rectangle) {
 		srcPos := pos.Add(offset)
 		dstIndex := this.image.PixOffset(pos.X, pos.Y)
 		srcIndex := this.texture.PixOffset(srcPos.X, srcPos.Y)
-		pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
+		pixel := blendPremultipliedBGRA(xgraphics.BGRA {
 			B: dst[dstIndex + 0],
 			G: dst[dstIndex + 1],
 			R: dst[dstIndex + 2],
@@ -93,7 +93,7 @@ func (this *pen) fillRectangleTransparent (c xgraphics.BGRA, bounds image.Rectan
 	for pos.Y = bounds.Min.Y; pos.Y < bounds.Max.Y; pos.Y ++ {
 	for pos.X = bounds.Min.X; pos.X < bounds.Max.X; pos.X ++ {
 		index := this.image.PixOffset(pos.X, pos.Y)
-		pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
+		pixel := blendPremultipliedBGRA(xgraphics.BGRA {
 			B: this.image.Pix[index + 0],
 			G: this.image.Pix[index + 1],
 			R: this.image.Pix[index + 2],
@@ -256,7 +256,7 @@ func (context *fillingContext) fillPolygonHotTransparent () {
 			// fill pixels in between
 			for x := left; x < right; x ++ {
 				index := context.image.PixOffset(x, context.y)
-				pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
+				pixel := blendPremultipliedBGRA(xgraphics.BGRA {
 					B: context.image.Pix[index + 0],
 					G: context.image.Pix[index + 1],
 					R: context.image.Pix[index + 2],

x/canvas/plot.go

@@ -32,7 +32,7 @@ func (context plottingContext) plot (center image.Point) {
 		for y := square.Min.Y; y < square.Max.Y; y ++ {
 		for x := square.Min.X; x < square.Max.X; x ++ {
 			index := context.image.PixOffset(x, y)
-			pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
+			pixel := blendPremultipliedBGRA(xgraphics.BGRA {
 				B: context.image.Pix[index + 0],
 				G: context.image.Pix[index + 1],
 				R: context.image.Pix[index + 2],