fix error with opening autosave file; more tug of war example graph i…

…mprovements

marbles/graphs/tug-of-war.json

@@ -1 +1 @@
-{"Params":{"NMarbles":100,"MarbleStartX":{"Expr":"if(rand\u003c0.5, 5(rand+0.1), 5(rand-1.1))"},"MarbleStartY":{"Expr":"10-2n/nmarbles"},"StartVelocityY":{"Expr":{"Expr":"0"}},"StartVelocityX":{"Expr":{"Expr":"0"}},"UpdateRate":{"Expr":{"Expr":".02"}},"TimeStep":{"Expr":{"Expr":"0.01"}},"YForce":{"Expr":{"Expr":"-0.1"}},"XForce":{"Expr":{"Expr":"0"}},"CenterX":{"Expr":{"Expr":"0"}},"CenterY":{"Expr":{"Expr":"0"}},"TrackingSettings":{"TrackByDefault":false,"NTrackingFrames":300,"Accuracy":20,"LineColor":{"R":255,"G":255,"B":255,"A":255}}},"Lines":[{"Expr":{"Expr":"x^2/3"},"GraphIf":{"Expr":"false"},"Bounce":{"Expr":"0.95"},"Colors":{"Color":{"R":0,"G":182,"B":77,"A":255},"ColorSwitch":{"R":255,"G":255,"B":255,"A":255}}},{"Expr":{"Expr":"f(x+5)-h/100"},"GraphIf":{"Expr":"x\u003c-0.01"},"Bounce":{"Expr":"0.3rand+0.8"},"Colors":{"Color":{"R":255,"G":0,"B":0,"A":255},"ColorSwitch":{"R":255,"G":0,"B":0,"A":255}}},{"Expr":{"Expr":"f(x-5)-h/100"},"GraphIf":{"Expr":"x\u003e0"},"Bounce":{"Expr":"0.3rand+0.8"},"Colors":{"Color":{"R":0,"G":0,"B":255,"A":255},"ColorSwitch":{"R":0,"G":0,"B":255,"A":255}}},{"Expr":{"Expr":"gx-bx-f(x+5)+f(x-5)"},"GraphIf":{"Expr":"false"},"Bounce":{"Expr":"0.95"},"Colors":{"Color":{"R":188,"G":174,"B":0,"A":255},"ColorSwitch":{"R":255,"G":255,"B":255,"A":255}}},{"Expr":{"Expr":"9"},"GraphIf":{"Expr":"t\u003e1\u0026\u0026cx\u003e0\u0026\u0026abs(x-cx)\u003c1"},"Bounce":{"Expr":"0.95"},"Colors":{"Color":{"R":0,"G":0,"B":255,"A":255},"ColorSwitch":{"R":255,"G":255,"B":255,"A":255}}},{"Expr":{"Expr":"9"},"GraphIf":{"Expr":"t\u003e1\u0026\u0026cx\u003c0\u0026\u0026abs(x-cx)\u003c1"},"Bounce":{"Expr":"0.95"},"Colors":{"Color":{"R":255,"G":0,"B":0,"A":255},"ColorSwitch":{"R":255,"G":255,"B":255,"A":255}}}]}
+{"Params":{"NMarbles":100,"MarbleStartX":{"Expr":"if(n%2==0, 5(rand+0.1), 5(rand-1.1))"},"MarbleStartY":{"Expr":"10-2n/nmarbles"},"StartVelocityY":{"Expr":{"Expr":"0"}},"StartVelocityX":{"Expr":{"Expr":"0"}},"UpdateRate":{"Expr":{"Expr":".02"}},"TimeStep":{"Expr":{"Expr":"0.01"}},"YForce":{"Expr":{"Expr":"-0.1"}},"XForce":{"Expr":{"Expr":"0"}},"CenterX":{"Expr":{"Expr":"0"}},"CenterY":{"Expr":{"Expr":"0"}},"TrackingSettings":{"TrackByDefault":false,"NTrackingFrames":300,"Accuracy":20,"LineColor":{"R":255,"G":255,"B":255,"A":255}}},"Lines":[{"Expr":{"Expr":"x^2/3"},"GraphIf":{"Expr":"false"},"Bounce":{"Expr":"0.95"},"Colors":{"Color":{"R":0,"G":182,"B":77,"A":255},"ColorSwitch":{"R":255,"G":255,"B":255,"A":255}}},{"Expr":{"Expr":"f(x+5)-h/100"},"GraphIf":{"Expr":"x\u003c-0.01"},"Bounce":{"Expr":"0.3rand+0.8"},"Colors":{"Color":{"R":255,"G":0,"B":0,"A":255},"ColorSwitch":{"R":255,"G":0,"B":0,"A":255}}},{"Expr":{"Expr":"f(x-5)-h/100"},"GraphIf":{"Expr":"x\u003e0"},"Bounce":{"Expr":"0.3rand+0.8"},"Colors":{"Color":{"R":0,"G":0,"B":255,"A":255},"ColorSwitch":{"R":0,"G":0,"B":255,"A":255}}},{"Expr":{"Expr":"gx-bx-f(x+5)+f(x-5)"},"GraphIf":{"Expr":"false"},"Bounce":{"Expr":"0.95"},"Colors":{"Color":{"R":188,"G":174,"B":0,"A":255},"ColorSwitch":{"R":255,"G":255,"B":255,"A":255}}},{"Expr":{"Expr":"9"},"GraphIf":{"Expr":"t\u003e1\u0026\u0026cx\u003e=0\u0026\u0026abs(x-cx)\u003c1"},"Bounce":{"Expr":"0.95"},"Colors":{"Color":{"R":0,"G":0,"B":255,"A":255},"ColorSwitch":{"R":255,"G":255,"B":255,"A":255}}},{"Expr":{"Expr":"9"},"GraphIf":{"Expr":"t\u003e1\u0026\u0026cx\u003c0\u0026\u0026abs(x-cx)\u003c1"},"Bounce":{"Expr":"0.95"},"Colors":{"Color":{"R":255,"G":0,"B":0,"A":255},"ColorSwitch":{"R":255,"G":255,"B":255,"A":255}}}]}

marbles/io.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"errors"
 	"fmt"
+	"io/fs"
 	"path/filepath"
 
 	"cogentcore.org/core/base/iox/jsonx"
@@ -31,6 +33,9 @@ func (gr *Graph) OpenJSON(filename core.Filename) error { //types:add
 // OpenAutoSave opens the last graphed graph, stays between sessions of the app
 func (gr *Graph) OpenAutoSave() error {
 	err := jsonx.Open(gr, filepath.Join(core.TheApp.AppDataDir(), "autosave.json"))
+	if errors.Is(err, fs.ErrNotExist) {
+		return nil
+	}
 	if HandleError(err) {
 		return err
 	}