fix(core): preserve untouched tiles across border rounding

commit: 02f2bf5cf610c9c53374607e445f82305463d72e
author: brice · 41h ago · 2026-10-21 05:26 UTC
committer: brice · 40h ago · 2026-10-21 07:11 UTC
parent: 5932e6b
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

2 files · +41 -2

M internal/core/border.go +24 -2


@@ -29,7 +29,7 @@ func borderZone(a, b, pad int) (int, int) {
29	29		}
30	30
31	31		func (w *Workspace) borderAt(x, y, pad int) (border, bool) {
32		-	if w.fullscreen != 0 {
	32	+	if w.fullscreen != 0 \|\| !borderContains(w.Usable, x, y) {
33	33		return border{}, false
34	34		}
35	35		// Overview and preview are Monitor presentation, not Workspace state. Their

@@ -101,6 +101,8 @@ func (w *Workspace) setBorder(b border, pos int) {
101	101		c.Shares = make([]int, len(rows))
102	102		used := 0
103	103		for i := range rows {
	104	+	// Stamp the middle of the pixel bucket, leaving room for
	105	+	// pair-preserving rounding on subsequent resizes.
104	106		c.Shares[i] = (rows[i].H*10000 + 5000) / avail
105	107		used += c.Shares[i]
106	108		}

@@ -112,6 +114,9 @@ func (w *Workspace) setBorder(b border, pos int) {
112	114		}
113	115		target := pixelShare(pos-w.gap()/2-rows[b.row].Y, avail)
114	116		target = min(max(target, minShare), pair-minShare)
	117	+	if b.row+1 < len(rows)-1 {
	118	+	target = pairPixelShare(target, pair, avail, rows[b.row].H+rows[b.row+1].H, minShare)
	119	+	}
115	120		c.Shares[b.row], c.Shares[b.row+1] = target, pair-target
116	121		return
117	122		}

@@ -129,7 +134,7 @@ func (w *Workspace) setBorder(b border, pos int) {
129	134		if !w.validSpans(first, last) {
130	135		used := 0
131	136		for i := first; i <= last; i++ {
132		-	w.Columns[i].Span = max(pixelShare(rs[i].W, avail), 1)
	137	+	w.Columns[i].Span = max((rs[i].W*10000+5000)/avail, 1)
133	138		w.Columns[i].spanLane = last - first + 1
134	139		used += w.Columns[i].Span
135	140		}

@@ -148,6 +153,9 @@ func (w *Workspace) setBorder(b border, pos int) {
148	153		return
149	154		}
150	155		target = min(max(target, minimum), pair-minimum)
	156	+	if b.col+1 < last {
	157	+	target = pairPixelShare(target, pair, avail, rs[b.col].W+rs[b.col+1].W, minimum)
	158	+	}
151	159		w.Columns[b.col].Span, w.Columns[b.col+1].Span = target, pair-target
152	160		}
153	161

@@ -162,3 +170,17 @@ func (w *Workspace) resetBorder(b border) {
162	170		w.Columns[b.col].Shares = nil
163	171		}
164	172		}
	173	+
	174	+	// pairPixelShare keeps the pair's combined integer width unchanged as well as
	175	+	// its basis-point sum. Independent floors can otherwise shift later tiles by
	176	+	// one pixel even when the sum of the two shares is constant.
	177	+	func pairPixelShare(target, pair, avail, pixels, minimum int) int {
	178	+	left := avail * target / 10000
	179	+	right := pixels - left
	180	+	lo := max(pixelShare(left, avail), pair-pixelShare(right+1, avail)+1, minimum)
	181	+	hi := min(pixelShare(left+1, avail)-1, pair-pixelShare(right, avail), pair-minimum)
	182	+	if lo <= hi {
	183	+	return min(max(target, lo), hi)
	184	+	}
	185	+	return target
	186	+	}

 }
 func (w *Workspace) borderAt(x, y, pad int) (border, bool) {
-	if w.fullscreen != 0 {
+	if w.fullscreen != 0 || !borderContains(w.Usable, x, y) {
 		return border{}, false
 	}
 	// Overview and preview are Monitor presentation, not Workspace state. Their
 			c.Shares = make([]int, len(rows))
 			used := 0
 			for i := range rows {
+				// Stamp the middle of the pixel bucket, leaving room for
+				// pair-preserving rounding on subsequent resizes.
 				c.Shares[i] = (rows[i].H*10000 + 5000) / avail
 				used += c.Shares[i]
 			}
 		}
 		target := pixelShare(pos-w.gap()/2-rows[b.row].Y, avail)
 		target = min(max(target, minShare), pair-minShare)
+		if b.row+1 < len(rows)-1 {
+			target = pairPixelShare(target, pair, avail, rows[b.row].H+rows[b.row+1].H, minShare)
+		}
 		c.Shares[b.row], c.Shares[b.row+1] = target, pair-target
 		return
 	}
 	if !w.validSpans(first, last) {
 		used := 0
 		for i := first; i <= last; i++ {
-			w.Columns[i].Span = max(pixelShare(rs[i].W, avail), 1)
+			w.Columns[i].Span = max((rs[i].W*10000+5000)/avail, 1)
 			w.Columns[i].spanLane = last - first + 1
 			used += w.Columns[i].Span
 		}
 		return
 	}
 	target = min(max(target, minimum), pair-minimum)
+	if b.col+1 < last {
+		target = pairPixelShare(target, pair, avail, rs[b.col].W+rs[b.col+1].W, minimum)
+	}
 	w.Columns[b.col].Span, w.Columns[b.col+1].Span = target, pair-target
 }
 		w.Columns[b.col].Shares = nil
 	}
 }
+// pairPixelShare keeps the pair's combined integer width unchanged as well as
+// its basis-point sum. Independent floors can otherwise shift later tiles by
+// one pixel even when the sum of the two shares is constant.
+func pairPixelShare(target, pair, avail, pixels, minimum int) int {
+	left := avail * target / 10000
+	right := pixels - left
+	lo := max(pixelShare(left, avail), pair-pixelShare(right+1, avail)+1, minimum)
+	hi := min(pixelShare(left+1, avail)-1, pair-pixelShare(right, avail), pair-minimum)
+	if lo <= hi {
+		return min(max(target, lo), hi)
+	}
+	return target
+}

M internal/core/border_test.go +17 -0


@@ -176,3 +176,20 @@ func TestSetRowBorder(t *testing.T) {
176	176		t.Fatal("reset")
177	177		}
178	178		}
	179	+
	180	+	func TestBorderPixelRemainders(t *testing.T) {
	181	+	for width := 997; width <= 1003; width++ {
	182	+	w := spanWorkspace(OverflowFixed, 3)
	183	+	w.SetOutput(width, 800)
	184	+	before := w.columnRects()
	185	+	b := border{kind: borderColumn, col: 0}
	186	+	for delta := -20; delta <= 20; delta++ {
	187	+	pos := before[0].X + before[0].W + 5 + delta
	188	+	w.setBorder(b, pos)
	189	+	after := w.columnRects()
	190	+	if after[2].X != before[2].X \|\| after[0].X+after[0].W+5 != pos {
	191	+	t.Fatal(width, delta, before, after)
	192	+	}
	193	+	}
	194	+	}
	195	+	}


@@ -176,3 +176,20 @@ func TestSetRowBorder(t *testing.T) {
176	t.Fatal("reset")	176		t.Fatal("reset")
177	}	177		}
178	}	178		}
		179	+
		180	+	func TestBorderPixelRemainders(t *testing.T) {
		181	+	for width := 997; width <= 1003; width++ {
		182	+	w := spanWorkspace(OverflowFixed, 3)
		183	+	w.SetOutput(width, 800)
		184	+	before := w.columnRects()
		185	+	b := border{kind: borderColumn, col: 0}
		186	+	for delta := -20; delta <= 20; delta++ {
		187	+	pos := before[0].X + before[0].W + 5 + delta
		188	+	w.setBorder(b, pos)
		189	+	after := w.columnRects()
		190	+	if after[2].X != before[2].X \|\| after[0].X+after[0].W+5 != pos {
		191	+	t.Fatal(width, delta, before, after)
		192	+	}
		193	+	}
		194	+	}
		195	+	}