From d100f6fc24948985a586a332c0e52bcbb4476b25 Mon Sep 17 00:00:00 2001
From: Jakub Sobon <jakub.sobon@elohim.sk>
Date: Wed, 20 Feb 2019 23:35:26 -0500
Subject: [PATCH] Switching termdash test to common spinlock utility.

And delaying redraws to allow fast widgets to process the input event.
---
 event/testevent/testevent.go | 32 +++++++++++++++++++++++++++++
 termdash.go                  |  6 ++++++
 termdash_test.go             | 40 +++++++++++++++---------------------
 3 files changed, 54 insertions(+), 24 deletions(-)
 create mode 100644 event/testevent/testevent.go

diff --git a/event/testevent/testevent.go b/event/testevent/testevent.go
new file mode 100644
index 0000000..9235255
--- /dev/null
+++ b/event/testevent/testevent.go
@@ -0,0 +1,32 @@
+// Package testevent provides utilities for tests that deal with concurrent
+// events.
+package testevent
+
+import (
+	"context"
+	"fmt"
+	"time"
+)
+
+// WaitFor waits until the provided function returns a nil error or the timeout.
+// If the function doesn't return a nil error before the timeout expires,
+// returns the last returned error.
+func WaitFor(timeout time.Duration, fn func() error) error {
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	var err error
+	for {
+		tick := time.NewTimer(5 * time.Millisecond)
+		select {
+		case <-tick.C:
+			if err = fn(); err != nil {
+				continue
+			}
+			return nil
+
+		case <-ctx.Done():
+			return fmt.Errorf("timeout expired, error: %v", err)
+		}
+	}
+}
diff --git a/termdash.go b/termdash.go
index c49aa27..f73d427 100644
--- a/termdash.go
+++ b/termdash.go
@@ -277,6 +277,12 @@ func (td *termdash) redraw() error {
 func (td *termdash) evRedraw() error {
 	td.mu.Lock()
 	defer td.mu.Unlock()
+
+	// Don't redraw immediately, give widgets that are performing enough time
+	// to update.
+	// We don't want to actually synchronize until all widgets update, we are
+	// purposefully leaving slow widgets behind.
+	time.Sleep(25 * time.Millisecond)
 	return td.redraw()
 }
 
diff --git a/termdash_test.go b/termdash_test.go
index 8a02287..d32efcc 100644
--- a/termdash_test.go
+++ b/termdash_test.go
@@ -16,6 +16,7 @@ package termdash
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"image"
 	"sync"
@@ -26,6 +27,7 @@ import (
 	"github.com/mum4k/termdash/canvas/testcanvas"
 	"github.com/mum4k/termdash/container"
 	"github.com/mum4k/termdash/event/eventqueue"
+	"github.com/mum4k/termdash/event/testevent"
 	"github.com/mum4k/termdash/keyboard"
 	"github.com/mum4k/termdash/mouse"
 	"github.com/mum4k/termdash/terminal/faketerm"
@@ -388,8 +390,13 @@ func TestRun(t *testing.T) {
 				return
 			}
 
-			if err := untilEmpty(5*time.Second, eq); err != nil {
-				t.Fatalf("untilEmpty => %v", err)
+			if err := testevent.WaitFor(5*time.Second, func() error {
+				if !eq.Empty() {
+					return errors.New("event queue not empty")
+				}
+				return nil
+			}); err != nil {
+				t.Fatalf("testevent.WaitFor => %v", err)
 			}
 
 			if tc.after != nil {
@@ -569,8 +576,13 @@ func TestController(t *testing.T) {
 				tc.apiEvents(mi)
 			}
 
-			if err := untilEmpty(5*time.Second, eq); err != nil {
-				t.Fatalf("untilEmpty => %v", err)
+			if err := testevent.WaitFor(5*time.Second, func() error {
+				if !eq.Empty() {
+					return errors.New("event queue not empty")
+				}
+				return nil
+			}); err != nil {
+				t.Fatalf("testevent.WaitFor => %v", err)
 			}
 			if tc.controls != nil {
 				if err := tc.controls(ctrl); err != nil {
@@ -585,23 +597,3 @@ func TestController(t *testing.T) {
 		})
 	}
 }
-
-// untilEmpty waits until the queue empties.
-// Waits at most the specified duration.
-func untilEmpty(timeout time.Duration, q *eventqueue.Unbound) error {
-	ctx, cancel := context.WithTimeout(context.Background(), timeout)
-	defer cancel()
-
-	for {
-		tick := time.NewTimer(5 * time.Millisecond)
-		select {
-		case <-tick.C:
-			if q.Empty() {
-				return nil
-			}
-
-		case <-ctx.Done():
-			return fmt.Errorf("while waiting for the event queue to empty: %v", ctx.Err())
-		}
-	}
-}