From 77c7bc9b187450818ec068239a3ae836d01fdebc Mon Sep 17 00:00:00 2001
From: Calvin Morrison <calvin@pobox.com>
Date: Sat, 22 Aug 2026 19:12:01 -0400
Subject: gui: a widget layer, so the next program does not write one

cal9 had grown its own: borders drawn four fills at a time in two
places, a button-3 menu, hit regions, buttons, text wrapping. None of
that is about calendars, and a second program would have written it
again, differently. It lives in gui/ui now.

It is a kit and not a framework. Every call draws a thing and, where it
makes sense, records where it drew it; the program keeps its own event
loop and its own idea of what to redraw. Menu takes a redraw function
rather than calling back into anything. The moment the library owns the
loop it stops being usable by the next program, which was the problem
being fixed.

Body is the fix for two bugs that turned out to be one. rio draws a
window's border into the client's own image and puts corner cursors in
it, taking those clicks before the client sees them: the border is
rio's resize handle. Filling the whole rectangle erased it, so the
border vanished and so did resizing. Drawing inside Body gives both
back, and the drag-to-resize cal9 had grown -- which could only ever
shrink, since a window stops getting mouse events once the pointer
leaves it -- was deleted rather than fixed.

Field is one line of editable text with a cursor, backspace, ^U and a
paste from /dev/snarf. No selection, no mouse placement, no history: a
form asking for a summary and a time needs none of them and each is
somewhere to be subtly wrong.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 gui/ui/menu.go | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 gui/ui/menu.go

(limited to 'gui/ui/menu.go')

diff --git a/gui/ui/menu.go b/gui/ui/menu.go
new file mode 100644
index 0000000..7fe7ff8
--- /dev/null
+++ b/gui/ui/menu.go
@@ -0,0 +1,79 @@
+package ui
+
+import "9front/gui/draw"
+
+// An Item is one line of a menu.
+type Item struct {
+	Label string
+	Do    func()
+}
+
+// Menu pops up at p and tracks until button 3 comes back up, the way
+// page(1) and vdir(1) do it: press 3, drag, release on an item.
+//
+// It keeps itself on the screen, which is the detail everyone forgets
+// until the menu opens near the bottom edge and half of it is missing.
+// redraw is called if the menu is dismissed without a choice.
+func (u *UI) Menu(items []Item, at draw.Point, mc *draw.Mousectl, redraw func()) {
+	if len(items) == 0 {
+		return
+	}
+
+	lh := int32(u.F.Height) + 4
+	var w int32
+	for _, it := range items {
+		if x := u.F.Width(it.Label) + 20; x > w {
+			w = x
+		}
+	}
+	h := lh*int32(len(items)) + 4
+	win := u.Win.Rect()
+	r := draw.Rect(at.X, at.Y, at.X+w, at.Y+h)
+	if r.Max.X > win.Max.X {
+		r = r.Add(draw.Point{X: win.Max.X - r.Max.X})
+	}
+	if r.Max.Y > win.Max.Y {
+		r = r.Add(draw.Point{Y: win.Max.Y - r.Max.Y})
+	}
+
+	sel := -1
+	paint := func() {
+		u.Fill(r, "tag")
+		u.Border(r, "border")
+		for i, it := range items {
+			ir := draw.Rect(r.Min.X+1, r.Min.Y+2+int32(i)*lh,
+				r.Max.X-1, r.Min.Y+2+int32(i+1)*lh)
+			if i == sel {
+				u.Fill(ir, "today")
+			}
+			u.Text(draw.Point{X: ir.Min.X + 8, Y: ir.Min.Y + 2}, "ink", it.Label)
+		}
+		u.D.Flush()
+	}
+	itemAt := func(p draw.Point) int {
+		if p.X < r.Min.X || p.X >= r.Max.X {
+			return -1
+		}
+		i := int((p.Y - r.Min.Y - 2) / lh)
+		if i < 0 || i >= len(items) || p.Y < r.Min.Y+2 {
+			return -1
+		}
+		return i
+	}
+	paint()
+
+	for m := range mc.C {
+		if n := itemAt(m.Point); n != sel {
+			sel = n
+			paint()
+		}
+		if m.Buttons&4 == 0 {
+			if sel >= 0 {
+				items[sel].Do()
+			} else {
+				redraw()
+			}
+			return
+		}
+	}
+}
-- 
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