From 066029539e3ab6e88a3585db2b2394a2f04aeac6 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Fri, 28 Oct 2022 19:07:33 +0900
Subject: [PATCH] internal/ui: clean-up code

A callback is preferred to a dirty flag.

Updates #2341
---
 internal/ui/context.go | 10 ++++++++--
 internal/ui/image.go   | 14 ++++++++++----
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/internal/ui/context.go b/internal/ui/context.go
index 054b2c665..54285a8ff 100644
--- a/internal/ui/context.go
+++ b/internal/ui/context.go
@@ -54,6 +54,8 @@ type context struct {
 	outsideWidth  float64
 	outsideHeight float64
 
+	isOffscreenDirty bool
+
 	skipCount int
 }
 
@@ -165,14 +167,15 @@ func (c *context) drawGame(graphicsDriver graphicsdriver.Graphics, forceDraw boo
 		c.offscreen.clear()
 	}
 
-	c.offscreen.dirty = false
+	// isOffscreenDirty is updated when an offscreen's drawCallback.
+	c.isOffscreenDirty = false
 	if err := c.game.DrawOffscreen(); err != nil {
 		return err
 	}
 
 	const maxSkipCount = 3
 
-	if !forceDraw && !theGlobalState.isScreenClearedEveryFrame() && !c.offscreen.dirty {
+	if !forceDraw && !theGlobalState.isScreenClearedEveryFrame() && !c.isOffscreenDirty {
 		if c.skipCount < maxSkipCount {
 			c.skipCount++
 		}
@@ -234,6 +237,9 @@ func (c *context) layoutGame(outsideWidth, outsideHeight float64, deviceScaleFac
 	}
 	if c.offscreen == nil {
 		c.offscreen = c.game.NewOffscreenImage(ow, oh)
+		c.offscreen.drawCallback = func() {
+			c.isOffscreenDirty = true
+		}
 	}
 
 	return ow, oh
diff --git a/internal/ui/image.go b/internal/ui/image.go
index 10e10aadf..457d38095 100644
--- a/internal/ui/image.go
+++ b/internal/ui/image.go
@@ -46,7 +46,9 @@ type Image struct {
 	bigOffscreenBufferBlend graphicsdriver.Blend
 	bigOffscreenBufferDirty bool
 
-	dirty bool
+	// drawCallback is a callback called when DrawTriangles or WritePixels is called.
+	// drawCallback is useful to detect whether the image is manipulated or not after a certain time.
+	drawCallback func()
 }
 
 func NewImage(width, height int, imageType atlas.ImageType) *Image {
@@ -70,11 +72,13 @@ func (i *Image) MarkDisposed() {
 	i.mipmap.MarkDisposed()
 	i.mipmap = nil
 	i.dotsBuffer = nil
-	i.dirty = false
+	i.drawCallback = nil
 }
 
 func (i *Image) DrawTriangles(srcs [graphics.ShaderImageCount]*Image, vertices []float32, indices []uint16, blend graphicsdriver.Blend, dstRegion, srcRegion graphicsdriver.Region, subimageOffsets [graphics.ShaderImageCount - 1][2]float32, shader *Shader, uniforms [][]float32, evenOdd bool, canSkipMipmap bool, antialias bool) {
-	i.dirty = true
+	if i.drawCallback != nil {
+		i.drawCallback()
+	}
 
 	if antialias {
 		// Flush the other buffer to make the buffers exclusive.
@@ -146,7 +150,9 @@ func (i *Image) DrawTriangles(srcs [graphics.ShaderImageCount]*Image, vertices [
 }
 
 func (i *Image) WritePixels(pix []byte, x, y, width, height int) {
-	i.dirty = true
+	if i.drawCallback != nil {
+		i.drawCallback()
+	}
 
 	if width == 1 && height == 1 {
 		// Flush the other buffer to make the buffers exclusive.