rename cache duration, and switch to cleaner time.Add logic

internal/cache/base.go

@@ -8,8 +8,8 @@ import (
 )
 
 var (
-	CacheDuration     = 1 * time.Minute
-	cleanTaskInterval = CacheDuration / 2
+	ValidDuration     = 1 * time.Minute
+	cleanTaskInterval = ValidDuration / 2
 
 	lastClean                     time.Time
 	skippedCleanWithCanvasRefresh = false
@@ -20,8 +20,8 @@ var (
 
 func init() {
 	if t, err := time.ParseDuration(os.Getenv("FYNE_CACHE")); err == nil {
-		CacheDuration = t
-		cleanTaskInterval = CacheDuration / 2
+		ValidDuration = t
+		cleanTaskInterval = ValidDuration / 2
 	}
 }
 
@@ -168,5 +168,5 @@ func (c *expiringCache) isExpired(now time.Time) bool {
 
 // setAlive updates expiration time.
 func (c *expiringCache) setAlive() {
-	c.expires = timeNow().Add(CacheDuration)
+	c.expires = timeNow().Add(ValidDuration)
 }

internal/cache/base_test.go

@@ -189,7 +189,7 @@ func Test_expiringCache(t *testing.T) {
 	assert.False(t, c.isExpired(tm.now))
 
 	tm.setTime(10, 11)
-	tm.now = tm.now.Add(CacheDuration)
+	tm.now = tm.now.Add(ValidDuration)
 	assert.True(t, c.isExpired(tm.now))
 }
 

internal/driver/glfw/loop.go

@@ -83,7 +83,7 @@ func (d *gLDriver) drawSingleFrame() {
 			// cache alive if it hasn't been done recently
 			// n.b. we need to make sure threshold is a bit *after*
 			// time.Now() - CacheDuration()
-			threshold := time.Now().Add(-cache.CacheDuration).Add(1 * time.Second)
+			threshold := time.Now().Add(time.Second - cache.ValidDuration)
 			if w.lastWalked().Before(threshold) {
 				w.canvas.WalkTrees(nil, func(node *common.RenderCacheNode, _ fyne.Position) {
 					// marks canvas for widget cache entry alive