panel: a click that moves a point or two is still a click

any pointer movement between press and release started a panel drag and
swallowed the click, so clicking a row often did nothing and had to be
repeated: in a logged session, 12 of 17 clicks were taken as drags. the
5 that counted waited at most 4 ms and ran `dingger focus` in 60-120 ms.
a drag now needs more than 4 points of movement (isDrag, selftest).

2 files changed, 14 insertions, 2 deletions

diff --git a/menubar/main.swift b/menubar/main.swift
index c37386e..1b6ce4f 100644
--- a/menubar/main.swift
+++ b/menubar/main.swift
@@ -408,6 +408,8 @@ if arguments.contains("--selftest") {
     if importanceListed != importanceExpected {
         failures.append("order: status first, then importance, then time: \(importanceListed)")
     }
+    if isDrag(from: .zero, to: NSPoint(x: 2, y: 3)) { failures.append("click: a few points of jitter is a click") }
+    if !isDrag(from: .zero, to: NSPoint(x: 0, y: 5)) { failures.append("click: moving 5 points is a drag") }
     let high = Row(paneId: "%1", agent: "pi", name: "Fix it", status: .done, session: "s", window: "w", since: 1, importance: .high)
     if rowTitle(high).string != "✓  ! Fix it" || rowTitlePrefix(high) != "✓  ! " {
         failures.append("title: a high agent is marked: \(rowTitle(high).string)")
diff --git a/menubar/panel.swift b/menubar/panel.swift
index 8edab70..6619dc0 100644
--- a/menubar/panel.swift
+++ b/menubar/panel.swift
@@ -194,10 +194,17 @@ func darkHUD() -> NSVisualEffectView {
     return effect
 }
 
+/// Whether the pointer moved far enough from where the button went down to
+/// be a drag: a click on a trackpad or mouse moves it a point or two.
+func isDrag(from down: NSPoint, to now: NSPoint) -> Bool {
+    hypot(now.x - down.x, now.y - down.y) > 4
+}
+
 /// A click target that does not swallow drags: a drag moves the panel.
 class ClickView: NSView {
     var onClick: () -> Void = {}
     private var dragged = false
+    private var downAt = NSPoint.zero
     var hovered = false { didSet { needsDisplay = true; hoverChanged() } }
 
     func hoverChanged() {}
@@ -222,10 +229,13 @@ class ClickView: NSView {
 
     override func mouseEntered(with event: NSEvent) { hovered = true }
     override func mouseExited(with event: NSEvent) { hovered = false }
-    override func mouseDown(with event: NSEvent) { dragged = false }
+    override func mouseDown(with event: NSEvent) {
+        dragged = false
+        downAt = NSEvent.mouseLocation
+    }
 
     override func mouseDragged(with event: NSEvent) {
-        if !dragged {
+        if !dragged, isDrag(from: downAt, to: NSEvent.mouseLocation) {
             dragged = true
             window?.performDrag(with: event)
         }