fix(io): auto-scale the default pinch distance to the screen

cli/io.go

@@ -294,7 +294,7 @@ func init() {
 	ioKeyboardHideCmd.Flags().StringVar(&deviceId, "device", "", "ID of the device to hide keyboard on")
 	ioPinchCmd.Flags().StringVar(&deviceId, "device", "", "ID of the device to pinch on")
 	ioPinchCmd.Flags().StringVar(&pinchDirection, "direction", "", "\"in\" to zoom out or \"out\" to zoom in (required)")
-	ioPinchCmd.Flags().IntVar(&pinchDistance, "distance", 200, "pixels each finger travels")
+	ioPinchCmd.Flags().IntVar(&pinchDistance, "distance", 0, "pixels each finger travels (0 = auto, scaled to the screen)")
 	ioPinchCmd.Flags().IntVar(&pinchDuration, "duration", 300, "duration of the finger movement in milliseconds")
 	cobra.CheckErr(ioPinchCmd.MarkFlagRequired("direction"))
 }

commands/input.go

@@ -72,9 +72,13 @@ const (
 	PinchDirectionIn  = "in"
 	PinchDirectionOut = "out"
 
-	defaultPinchDistance   = 200
 	defaultPinchDurationMs = 300
 
+	// minPinchDistance is the smallest travel an auto-scaled pinch uses, so a
+	// pinch centered close to the left edge still moves a little rather than
+	// collapsing to nothing.
+	minPinchDistance = 20
+
 	// pinchStartGap is how far from the center each finger touches down (or
 	// lifts, for "in"), so the two fingers never share a point.
 	pinchStartGap = 30
@@ -84,6 +88,20 @@ const (
 	pinchPressHoldMs = 50
 )
 
+// autoPinchDistance picks a travel that keeps the inner finger on-screen when no
+// distance is given. The binding constraint is the left edge (far = pinchStartGap
+// + distance must not exceed x), so a fixed default like 200 overflowed a pinch
+// centered at x≈200 on a narrow phone. Deriving it from x scales with the screen
+// without needing the screen size (which mobilecli only knows in the natural
+// orientation), and leaves the far edges to the device like the rest of pinch.
+func autoPinchDistance(x int) int {
+	d := (x - pinchStartGap) * 4 / 5
+	if d < minPinchDistance {
+		d = minPinchDistance
+	}
+	return d
+}
+
 // pinchActions lays two fingers on the horizontal line through (x, y), each
 // pinchStartGap from the center, and moves them distance pixels away from it
 // ("out", zooms in) or toward it ("in", zooms out) over duration milliseconds.
@@ -97,7 +115,7 @@ const (
 // screen.
 func pinchActions(x, y int, direction string, distance, duration int) ([]devicekit.TapAction, error) {
 	if distance <= 0 {
-		distance = defaultPinchDistance
+		distance = autoPinchDistance(x)
 	}
 	if duration <= 0 {
 		duration = defaultPinchDurationMs

commands/input_test.go

@@ -61,3 +61,28 @@ func TestNormalizeButtonNameIsCaseInsensitiveAndTrimmed(t *testing.T) {
 		}
 	}
 }
+
+func TestAutoPinchDistanceKeepsInnerFingerOnScreen(t *testing.T) {
+	// For a centered pinch, far = pinchStartGap + distance must not pass the
+	// left edge (x - far >= 0). The old fixed default of 200 failed at x≈201.
+	for _, x := range []int{201, 180, 300, 540, 640} {
+		d := autoPinchDistance(x)
+		far := pinchStartGap + d
+		if x-far < 0 {
+			t.Errorf("autoPinchDistance(%d)=%d -> far=%d puts the inner finger at x=%d (off-screen left)", x, d, far, x-far)
+		}
+		if d < minPinchDistance {
+			t.Errorf("autoPinchDistance(%d)=%d is below the minimum %d", x, d, minPinchDistance)
+		}
+	}
+}
+
+func TestPinchActionsAutoDistanceSucceedsAtNarrowCenter(t *testing.T) {
+	// A default pinch centered on a 402pt-wide screen (x=201) used to error with
+	// "past the left edge"; with the auto distance it must build valid actions.
+	for _, dir := range []string{PinchDirectionOut, PinchDirectionIn} {
+		if _, err := pinchActions(201, 437, dir, 0, 0); err != nil {
+			t.Errorf("pinchActions at a narrow center (%s) returned error: %v", dir, err)
+		}
+	}
+}

commands/pinch_test.go

@@ -57,8 +57,10 @@ func TestPinchAppliesDefaultDistanceAndDuration(t *testing.T) {
 	actions, err := pinchActions(640, 1428, PinchDirectionOut, 0, 0)
 	require.NoError(t, err)
 
+	// with no distance given, the travel auto-scales to the center so the inner
+	// finger stays on-screen
 	leftStart, leftEnd := fingerPath(t, actions, 0)
-	assert.Equal(t, defaultPinchDistance, leftStart-leftEnd)
+	assert.Equal(t, autoPinchDistance(640), leftStart-leftEnd)
 
 	for _, a := range actions {
 		if a.Type == pointerMove && a.Duration != 0 {

test/simulator.spec.ts

@@ -336,6 +336,15 @@ test.describe('iOS Simulator Tests', () => {
 				}
 			});
 
+			test('should pinch at the screen center with the default distance', async () => {
+				test.skip(!simulatorId, 'simulator not found');
+
+				// the default distance used to overflow a narrow screen's left edge
+				// ("would put the left finger at x=-29"); it now scales to the center
+				mobilecli(['io', 'pinch', '--direction', 'out', '--device', simulatorId]);
+				mobilecli(['io', 'pinch', '--direction', 'in', '--device', simulatorId]);
+			});
+
 			test.skip('should test device lifecycle: boot, reboot, shutdown', async () => {
 				// shutdown simulator using simctl to get it offline
 				shutdownSimulator(simulatorId);