From 02b4fc79179d14e1c8d9e29bac75e3beac7c1b82 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Wed, 28 Feb 2018 22:58:23 +0900
Subject: [PATCH] graphics: Reduce num of Image.Clear() calls

---
 graphicscontext.go           |  5 ++++-
 internal/restorable/image.go | 13 ++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/graphicscontext.go b/graphicscontext.go
index 5597a41df..fe0101ffc 100644
--- a/graphicscontext.go
+++ b/graphicscontext.go
@@ -87,7 +87,6 @@ func (c *graphicsContext) Update(afterFrameUpdate func()) error {
 		return err
 	}
 	for i := 0; i < updateCount; i++ {
-		restorable.ClearVolatileImages()
 		setRunningSlowly(i < updateCount-1)
 		if err := hooks.Run(); err != nil {
 			return err
@@ -98,6 +97,10 @@ func (c *graphicsContext) Update(afterFrameUpdate func()) error {
 		afterFrameUpdate()
 	}
 	if 0 < updateCount {
+		// Call ClearFramebuffer instead of c.screen.Clear()
+		// to clear the whole region including fullscreen's padding.
+		c.screen.restorable.ClearFramebuffer()
+
 		dw, dh := c.screen.Size()
 		sw, _ := c.offscreen.Size()
 		scale := float64(dw) / float64(sw)
diff --git a/internal/restorable/image.go b/internal/restorable/image.go
index 38ae12e4a..0ab17579b 100644
--- a/internal/restorable/image.go
+++ b/internal/restorable/image.go
@@ -90,7 +90,7 @@ func NewImage(width, height int, volatile bool) *Image {
 func NewScreenFramebufferImage(width, height int) *Image {
 	i := &Image{
 		image:    graphics.NewScreenFramebufferImage(width, height),
-		volatile: true,
+		volatile: false,
 		screen:   true,
 	}
 	theImages.add(i)
@@ -129,6 +129,10 @@ func (i *Image) clearIfVolatile() {
 	if !i.volatile {
 		return
 	}
+	i.ClearFramebuffer()
+}
+
+func (i *Image) ClearFramebuffer() {
 	i.basePixels = nil
 	i.drawImageHistory = nil
 	i.stale = false
@@ -167,7 +171,7 @@ func (i *Image) DrawImage(img *Image, sx0, sy0, sx1, sy1 int, geom *affine.GeoM,
 		return
 	}
 	theImages.makeStaleIfDependingOn(i)
-	if img.stale || img.volatile || !IsRestoringEnabled() {
+	if img.stale || img.volatile || i.screen || !IsRestoringEnabled() {
 		i.makeStale()
 	} else {
 		i.appendDrawImageHistory(img, vs, colorm, mode, filter)
@@ -177,7 +181,7 @@ func (i *Image) DrawImage(img *Image, sx0, sy0, sx1, sy1 int, geom *affine.GeoM,
 
 // appendDrawImageHistory appends a draw-image history item to the image.
 func (i *Image) appendDrawImageHistory(image *Image, vertices []float32, colorm *affine.ColorM, mode opengl.CompositeMode, filter graphics.Filter) {
-	if i.stale || i.volatile {
+	if i.stale || i.volatile || i.screen {
 		return
 	}
 	if len(i.drawImageHistory) > 0 {
@@ -253,6 +257,9 @@ func (i *Image) resolveStale() error {
 	if i.volatile {
 		return nil
 	}
+	if i.screen {
+		return nil
+	}
 	if !i.stale {
 		return nil
 	}