reduce flicker without worrying about carriage returns

2 files changed, 21 insertions, 7 deletions

diff --git a/pkg/gui/tasks_adapter.go b/pkg/gui/tasks_adapter.go
index bc2fb8a24..71cde5b00 100644
--- a/pkg/gui/tasks_adapter.go
+++ b/pkg/gui/tasks_adapter.go
@@ -83,13 +83,23 @@ func (gui *Gui) getManager(view *gocui.View) *tasks.ViewBufferManager {
 			gui.Log,
 			view,
 			func() {
-				view.Clear()
+				// we could clear here, but that actually has the effect of causing a flicker
+				// where the view may contain no content momentarily as the gui refreshes.
+				// Instead, we're rewinding the write pointer so that we will just start
+				// overwriting the existing content from the top down. Once we've reached
+				// the end of the content do display, we call view.FlushStaleCells() to
+				// clear out the remaining content from the previous render.
+				view.Reset()
 			},
 			func() {
 				gui.g.Update(func(*gocui.Gui) error {
 					return nil
 				})
-			})
+			},
+			func() {
+				view.FlushStaleCells()
+			},
+		)
 		gui.viewBufferManagerMap[view.Name()] = manager
 	}
 
diff --git a/pkg/tasks/tasks.go b/pkg/tasks/tasks.go
index 5854b4f46..8287b3927 100644
--- a/pkg/tasks/tasks.go
+++ b/pkg/tasks/tasks.go
@@ -33,12 +33,13 @@ type ViewBufferManager struct {
 	readLines    chan int
 
 	// beforeStart is the function that is called before starting a new task
-	beforeStart func()
-	refreshView func()
+	beforeStart     func()
+	refreshView     func()
+	flushStaleCells func()
 }
 
-func NewViewBufferManager(log *logrus.Entry, writer io.Writer, beforeStart func(), refreshView func()) *ViewBufferManager {
-	return &ViewBufferManager{Log: log, writer: writer, beforeStart: beforeStart, refreshView: refreshView, readLines: make(chan int, 1024)}
+func NewViewBufferManager(log *logrus.Entry, writer io.Writer, beforeStart func(), refreshView func(), flushStaleCells func()) *ViewBufferManager {
+	return &ViewBufferManager{Log: log, writer: writer, beforeStart: beforeStart, refreshView: refreshView, flushStaleCells: flushStaleCells, readLines: make(chan int, 1024)}
 }
 
 func (m *ViewBufferManager) ReadLines(n int) {
@@ -75,7 +76,7 @@ func (m *ViewBufferManager) NewCmdTask(r io.Reader, cmd *exec.Cmd, prefix string
 			loaded := false
 
 			go utils.Safe(func() {
-				ticker := time.NewTicker(time.Millisecond * 100)
+				ticker := time.NewTicker(time.Millisecond * 200)
 				defer ticker.Stop()
 				select {
 				case <-ticker.C:
@@ -114,6 +115,9 @@ func (m *ViewBufferManager) NewCmdTask(r io.Reader, cmd *exec.Cmd, prefix string
 						default:
 						}
 						if !ok {
+							// if we're here then there's nothing left to scan from the source
+							// so we're at the EOF and can flush the stale content
+							m.flushStaleCells()
 							m.refreshView()
 							break outer
 						}