Add JavaScript panic catcher to doodads

* Add example mischievous doodad script that alters the logger date
  format and animates its canvas's mask color.

dev-assets/doodads/mischievous.js

@@ -0,0 +1,43 @@
+function main() {
+	console.log("%s initialized!", Self.Doodad.Title);
+
+	console.log(Object.keys(console));
+	console.log(Object.keys(log));
+	console.log(Object.keys(log.Config));
+	console.log(Object.keys(Self.Canvas.Palette));
+	console.log(Object.keys(Self.Canvas.Palette.Swatches[0]));
+
+	Self.Canvas.Palette.Swatches[0].Color = RGBA(255, 0, 255, 255);
+	Self.Canvas.Palette.Swatches[1].Color = RGBA(0, 255, 255, 255);
+	console.log(Self.Canvas.Palette.Swatches);
+	log.Config.TimeFormat = "haha";
+
+	var colors = [
+		RGBA(255, 0, 0, 255),
+		RGBA(255, 153, 0, 255),
+		RGBA(255, 255, 0, 255),
+		RGBA(0, 255, 0, 255),
+		RGBA(0, 153, 255, 255),
+		RGBA(0, 0, 255, 255),
+		RGBA(255, 0, 255, 255)
+	];
+	var colorIndex = 0;
+	setInterval(function() {
+		console.log("sticky tick");
+		Self.Canvas.MaskColor = colors[colorIndex];
+		colorIndex++;
+		if (colorIndex == colors.length) {
+			colorIndex = 0;
+		}
+	}, 100);
+
+	// log.Config.Colors = 0; // panics, can't set a golog.Color
+
+	Events.OnCollide( function() {
+
+		Self.ShowLayer(1);
+		setTimeout(function() {
+			Self.ShowLayer(0);
+		}, 200);
+	})
+}

pkg/balance/numbers.go

@@ -10,7 +10,7 @@ var (
 	CanvasScrollSpeed int32 = 8
 
 	// Window scrolling behavior in Play Mode.
-	ScrollboxHoz      = 64 // horizontal px from window border to start scrol
+	ScrollboxHoz      = 256 // horizontal px from window border to start scrol
 	ScrollboxVert     = 128
 	ScrollMaxVelocity = 8 // 24
 

pkg/level/chunk.go

@@ -34,6 +34,7 @@ type Chunk struct {
 	uuid               uuid.UUID
 	texture            render.Texturer
 	textureMasked      render.Texturer
+	textureMaskedColor render.Color
 	dirty              bool
 }
 
@@ -87,7 +88,7 @@ func (c *Chunk) Texture(e render.Engine) render.Texturer {
 
 // TextureMasked returns a cached texture with the ColorMask applied.
 func (c *Chunk) TextureMasked(e render.Engine, mask render.Color) render.Texturer {
-	if c.textureMasked == nil {
+	if c.textureMasked == nil || c.textureMaskedColor != mask {
 		// Generate the normal bitmap and one with a color mask if applicable.
 		bitmap := c.toBitmap(mask)
 		defer os.Remove(bitmap)
@@ -97,6 +98,7 @@ func (c *Chunk) TextureMasked(e render.Engine, mask render.Color) render.Texture
 		}
 
 		c.textureMasked = tex
+		c.textureMaskedColor = mask
 	}
 	return c.textureMasked
 }

pkg/scripting/vm.go

@@ -92,6 +92,13 @@ func (vm *VM) Main() error {
 		return nil
 	}
 
+	// Catch panics.
+	defer func() {
+		if err := recover(); err != nil {
+			log.Error("Panic caught in JavaScript VM: %s", err)
+		}
+	}()
+
 	_, err = function.Call(otto.Value{})
 	return err
 }

pkg/uix/canvas_actors.go

@@ -53,7 +53,10 @@ func (w *Canvas) InstallScripts() error {
 		vm := w.scripting.To(actor.ID())
 		vm.Self = actor
 		vm.Set("Self", vm.Self)
-		vm.Run(actor.Drawing.Doodad.Script)
+
+		if _, err := vm.Run(actor.Doodad.Script); err != nil {
+			log.Error("Run script for actor %s failed: %s", actor.ID(), err)
+		}
 
 		// Call the main() function.
 		log.Debug("Calling Main() for %s", actor.ID())

pkg/uix/canvas_scrolling.go

@@ -159,6 +159,9 @@ func (w *Canvas) loopFollowActor(ev *events.State) error {
 				delta = int32(balance.ScrollMaxVelocity)
 			}
 
+			// TODO: add gravity to counteract jitters on scrolling vertically
+			scrollBy.Y -= int32(balance.Gravity)
+
 			if delta < 0 {
 				delta = -delta
 			}
@@ -172,6 +175,9 @@ func (w *Canvas) loopFollowActor(ev *events.State) error {
 				delta = int32(balance.ScrollMaxVelocity)
 			}
 			scrollBy.Y = -delta
+
+			// TODO: add gravity to counteract jitters on scrolling vertically
+			scrollBy.Y += int32(balance.Gravity * 3)
 		}
 
 		if scrollBy != render.Origin {