layout_policy.go RawHistoryFolder

1package core
2
3// layoutAxis is a logical navigation axis, independent of rendering.
4type layoutAxis uint8
5
6const (
7	verticalAxis layoutAxis = iota
8	horizontalAxis
9)
10
11func (a layoutAxis) span(r Rect) int {
12	if a == verticalAxis {
13		return r.H
14	}
15	return r.W
16}
17func (a layoutAxis) offset(r *Rect, pixels int) {
18	if a == verticalAxis {
19		r.Y += pixels
20	} else {
21		r.X += pixels
22	}
23}
24
25// layoutPolicy keeps geometry capabilities distinct from workspace navigation.
26// Window state remains owned by Workspace; policies contain no mutable state.
27type layoutPolicy struct {
28	content, workspace layoutAxis
29	equalCells, wraps  bool
30}
31
32// maximizeHides reports whether a maximized column hides the others, so
33// it is a transient state that focus changes undo: fixed overflow. In
34// scroll overflow and cascade it is a lasting state of its column (a
35// cascade band packs a maximized column alone).
36func (p layoutPolicy) maximizeHides() bool { return p.equalCells && !p.wraps }
37
38// workspaceStep is the workspace step a directional focus past the content
39// edge takes along axis: dir when axis is the workspace axis, else 0.
40func (p layoutPolicy) workspaceStep(axis layoutAxis, dir int) int {
41	if axis == p.workspace {
42		return dir
43	}
44	return 0
45}
46
47func (w *Workspace) policy() layoutPolicy {
48	if w.Overflow == OverflowCascade {
49		return layoutPolicy{content: verticalAxis, workspace: horizontalAxis, equalCells: true, wraps: true}
50	}
51	if w.Overflow == OverflowFixed {
52		return layoutPolicy{content: horizontalAxis, workspace: verticalAxis, equalCells: true}
53	}
54	return layoutPolicy{content: horizontalAxis, workspace: verticalAxis}
55}
56
57// validSpans requires a complete, exclusive lane stamp: every column has
58// a positive span and the same nonzero identity, with no members elsewhere
59// in the workspace. Equal-cell lanes must also sum to 10000 basis points.
60func (w *Workspace) validSpans(first, last int) bool {
61	if first > last || w.Overflow == OverflowFixed && !w.laneRow() {
62		return false
63	}
64	stamp := w.Columns[first].spanStamp
65	if stamp == 0 {
66		return false
67	}
68	total := 0
69	for i := first; i <= last; i++ {
70		c := w.Columns[i]
71		if c.Span <= 0 || c.spanStamp != stamp {
72			return false
73		}
74		total += c.Span
75	}
76	count := 0
77	for _, c := range w.Columns {
78		if c.spanStamp == stamp {
79			count++
80		}
81	}
82	return count == last-first+1 && (!w.policy().equalCells || total == 10000)
83}
84
85// dropStaleSpans runs before scroll measures mutated layout geometry. Decide
86// validity before clearing any stamps, so shared identities cannot become
87// valid merely because an earlier invalid lane was cleared.
88func (w *Workspace) dropStaleSpans() {
89	stamped := false
90	for _, c := range w.Columns {
91		if c.Span != 0 || c.spanStamp != 0 {
92			stamped = true
93			break
94		}
95	}
96	if !stamped {
97		return
98	}
99	// A nil stale slice does not allocate, so valid lanes cost nothing here.
100	var stale []int
101	for first := 0; first < len(w.Columns); {
102		_, last := w.laneBounds(w.laneOf(first))
103		if !w.validSpans(first, last) {
104			for i := first; i <= last; i++ {
105				stale = append(stale, i)
106			}
107		}
108		first = last + 1
109	}
110	for _, i := range stale {
111		w.Columns[i].Span, w.Columns[i].spanStamp = 0, 0
112	}
113}
114
115func (w *Workspace) clearSpans(col int) {
116	if col < 0 || col >= len(w.Columns) {
117		return
118	}
119	first, last := w.laneBounds(w.laneOf(col))
120	for i := first; i <= last; i++ {
121		w.Columns[i].Span = 0
122		w.Columns[i].spanStamp = 0
123	}
124}