put evolutioin drawing out of Draw(), handle history only if enabled

TODO.md

@@ -1,14 +1,10 @@
 - add all other options like size etc
-- do not process history if turned off
 - add gif export
 - add toolbar
 - turn input ifs to switch
-- add insert mode for edit like vi
+- only draw visible part of the world
-- use left mouse to drag grid unless insert mode is active
-- keep supporting middle mouse to drag so that dragging is possible in insert mode
 - print current mode to the bottom like pause, insert and mark
 - add https://www.ibiblio.org/lifepatterns/october1970.html
-- use uint8 or bool, history needs not be larger than 256 anyway
 - history: dont count age but do calc to get index to age tile based on cell age
 - maybe pre calc neighbors as 8 slice of pointers to neighboring cells to faster do the count
 - https://mattnakama.com/blog/go-branchless-coding/

src/play.go

@@ -131,6 +131,7 @@ func (scene *ScenePlay) UpdateCells() {
 			// change state of current cell in next grid
 			scene.Grids[next].Data[y][x] = nextstate
 
+			if scene.Config.ShowEvolution {
 				// set history  to current generation so we  can infer the
 				// age of the cell's state  during rendering and use it to
 				// deduce the color to use if evolution tracing is enabled
@@ -143,6 +144,7 @@ func (scene *ScenePlay) UpdateCells() {
 				//scene.History.Data[y][x] = (state ^ (1 ^ nextstate)) * (scene.Generations - scene.History.Data[y][x])
 			}
 		}
+	}
 
 	// switch grid for rendering
 	scene.Index ^= 1
@@ -459,8 +461,6 @@ func (scene *ScenePlay) Draw(screen *ebiten.Image) {
 	op.GeoM.Translate(0, 0)
 	scene.World.DrawImage(scene.Cache, op)
 
-	var age int64
-
 	for y := 0; y < scene.Config.Height; y++ {
 		for x := 0; x < scene.Config.Width; x++ {
 			op.GeoM.Reset()
@@ -469,14 +469,35 @@ func (scene *ScenePlay) Draw(screen *ebiten.Image) {
 				float64(y*scene.Config.Cellsize),
 			)
 
-			//age = scene.Generations - scene.History.Data[y][x]
+			if scene.Config.ShowEvolution {
-			age = scene.History[y][x]
+				scene.DrawEvolution(screen, x, y, op)
+			} else {
+				if scene.Grids[scene.Index].Data[y][x] {
+					scene.World.DrawImage(scene.Tiles.Black, op)
+				}
+			}
+		}
+	}
+
+	scene.DrawMark(scene.World)
+
+	scene.Camera.Render(scene.World, screen)
+
+	scene.DrawDebug(screen)
+
+	op.GeoM.Reset()
+	op.GeoM.Translate(0, 0)
+
+	scene.Game.Screen.DrawImage(screen, op)
+}
+
+func (scene *ScenePlay) DrawEvolution(screen *ebiten.Image, x, y int, op *ebiten.DrawImageOptions) {
+	age := scene.Generations - scene.History[y][x]
 
 	switch scene.Grids[scene.Index].Data[y][x] {
 	case Alive:
 		if age > 50 && scene.Config.ShowEvolution {
 			scene.World.DrawImage(scene.Tiles.Old, op)
-
 		} else {
 			scene.World.DrawImage(scene.Tiles.Black, op)
 		}
@@ -496,19 +517,6 @@ func (scene *ScenePlay) Draw(screen *ebiten.Image) {
 		}
 	}
 }
-	}
-
-	scene.DrawMark(scene.World)
-
-	scene.Camera.Render(scene.World, screen)
-
-	scene.DrawDebug(screen)
-
-	op.GeoM.Reset()
-	op.GeoM.Translate(0, 0)
-
-	scene.Game.Screen.DrawImage(screen, op)
-}
 
 func (scene *ScenePlay) DrawMark(screen *ebiten.Image) {
 	if scene.Config.Markmode && scene.MarkTaken {