From 6e1065830aebbef76ad787b982af5064ac584b55 Mon Sep 17 00:00:00 2001
From: Raphael 'kena' Poss <knz@thaumogen.net>
Date: Thu, 25 Aug 2022 19:13:30 +0200
Subject: [PATCH] feat: support a Clear command

---
 nil_renderer.go      |  1 +
 renderer.go          |  3 +++
 screen.go            | 14 ++++++++++++++
 standard_renderer.go |  8 ++++++++
 tea.go               |  3 +++
 5 files changed, 29 insertions(+)

diff --git a/nil_renderer.go b/nil_renderer.go
index 37b3c45..a022636 100644
--- a/nil_renderer.go
+++ b/nil_renderer.go
@@ -7,6 +7,7 @@ func (n nilRenderer) stop()                   {}
 func (n nilRenderer) kill()                   {}
 func (n nilRenderer) write(v string)          {}
 func (n nilRenderer) repaint()                {}
+func (n nilRenderer) clearScreen()            {}
 func (n nilRenderer) altScreen() bool         { return false }
 func (n nilRenderer) enterAltScreen()         {}
 func (n nilRenderer) exitAltScreen()          {}
diff --git a/renderer.go b/renderer.go
index a975e33..a6f4162 100644
--- a/renderer.go
+++ b/renderer.go
@@ -21,6 +21,9 @@ type renderer interface {
 	// in succession.
 	repaint()
 
+	// Clears the terminal.
+	clearScreen()
+
 	// Whether or not the alternate screen buffer is enabled.
 	altScreen() bool
 	// Enable the alternate screen buffer.
diff --git a/screen.go b/screen.go
index e8df7b1..5780290 100644
--- a/screen.go
+++ b/screen.go
@@ -9,6 +9,20 @@ type WindowSizeMsg struct {
 	Height int
 }
 
+// ClearScreen is a special command that tells the program to clear the screen
+// before the next update. This can be used to move the cursor to the top left
+// of the screen and clear visual clutter when the alt screen is not in use.
+//
+// Note that it should never be necessary to call ClearScreen() for regular
+// redraws.
+func ClearScreen() Msg {
+	return clearScreenMsg{}
+}
+
+// clearScreenMsg is an internal message that signals to clear the screen.
+// You can send a clearScreenMsg with ClearScreen.
+type clearScreenMsg struct{}
+
 // EnterAltScreen is a special command that tells the Bubble Tea program to
 // enter the alternate screen buffer.
 //
diff --git a/standard_renderer.go b/standard_renderer.go
index feafb82..4edf214 100644
--- a/standard_renderer.go
+++ b/standard_renderer.go
@@ -245,6 +245,14 @@ func (r *standardRenderer) repaint() {
 	r.lastRender = ""
 }
 
+func (r *standardRenderer) clearScreen() {
+	r.mtx.Lock()
+	defer r.mtx.Unlock()
+
+	r.out.ClearScreen()
+	r.out.MoveCursor(1, 1)
+}
+
 func (r *standardRenderer) altScreen() bool {
 	return r.altScreenActive
 }
diff --git a/tea.go b/tea.go
index c561c2d..9b38062 100644
--- a/tea.go
+++ b/tea.go
@@ -378,6 +378,9 @@ func (p *Program) StartReturningModel() (Model, error) {
 				p.shutdown(false)
 				return model, nil
 
+			case clearScreenMsg:
+				p.renderer.clearScreen()
+
 			case enterAltScreenMsg:
 				p.renderer.enterAltScreen()