From ca75748dff369a6507883e544c663914aeab075f Mon Sep 17 00:00:00 2001
From: Trevor Slocum <trevor@rocketnine.space>
Date: Sun, 6 Jun 2021 20:35:05 -0700
Subject: [PATCH] Update Application.Draw to accept one or more primitives to
 draw instead of the whole screen

---
 CHANGELOG      |  1 +
 application.go | 29 ++++++++++++++++++++++++-----
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index cdfa792..d761022 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -6,6 +6,7 @@ v1.5.6 (WIP)
 - Add DropDown.SetAlwaysDrawDropDownSymbol (DropDown symbols are now shown only when focused by default)
 - Add DropDown.SetDropDownOpenSymbolRune
 - Draw additional accents when rendering a list divider
+- Update Application.Draw to accept one or more primitives to draw instead of the whole screen
 - Update List, Table and TreeView to not handle Tab or Backtab
 - Allow specifying TabbedPanels switcher height
 - Change default colors (fields and buttons are now green)
diff --git a/application.go b/application.go
index de2cec5..2d23995 100644
--- a/application.go
+++ b/application.go
@@ -611,12 +611,31 @@ func (a *Application) Suspend(f func()) bool {
 	return true
 }
 
-// Draw refreshes the screen (during the next update cycle). It calls the Draw()
-// function of the application's root primitive and then syncs the screen
-// buffer.
-func (a *Application) Draw() {
+// Draw draws the provided primitives on the screen, or when no primitives are
+// provided, draws the application's root primitive (i.e. the entire screen).
+//
+// When one or more primitives are supplied, the Draw functions of the
+// primitives are called. Handlers set via BeforeDrawFunc and AfterDrawFunc are
+// not called.
+//
+// When no primitives are provided, the Draw function of the application's root
+// primitive is called. This results in drawing the entire screen. Handlers set
+// via BeforeDrawFunc and AfterDrawFunc are also called.
+func (a *Application) Draw(p ...Primitive) {
 	a.QueueUpdate(func() {
-		a.draw()
+		if len(p) == 0 {
+			a.draw()
+			return
+		}
+
+		a.Lock()
+		if a.screen != nil {
+			for _, primitive := range p {
+				primitive.Draw(a.screen)
+			}
+			a.screen.Show()
+		}
+		a.Unlock()
 	})
 }