new features

actor.animation.go

@@ -1,10 +1,93 @@
 package pncdsl
 
-// AnimationClip is a placeholder for sprite-sheet animation data. Not used
-// for rendering yet — characters draw as flat colored rectangles in this
-// milestone — but the field exists so domain code can reference it.
+import "image"
+
+// AnimationClip describes one named sprite-sheet animation. Frames are
+// source rectangles into the character's Sprite asset; the renderer
+// projects them onto the character's screen-space W×H footprint.
+//
+// FrameTime is the time (seconds) each frame is shown; Loop=true rewinds
+// to the first frame after the last, Loop=false freezes on the final
+// frame. A clip with zero frames or zero FrameTime is treated as static
+// and the renderer falls back to the whole-sprite draw path.
 type AnimationClip struct {
-	Frames     []Rectangle // source rects on the sprite sheet
-	FrameTime  float64
-	Loop       bool
+	Frames    []Rectangle
+	FrameTime float64
+	Loop      bool
+}
+
+// Reserved clip names the engine picks automatically:
+//
+//	"idle"  — selected when the character is not moving.
+//	"walk"  — selected while the character has an active path.
+//
+// A character with neither name falls back to the static whole-sprite
+// (or placeholder) draw.
+const (
+	clipIdle = "idle"
+	clipWalk = "walk"
+)
+
+// tickAnimation advances a character's current animation clip and
+// switches between idle/walk based on the moving flag.
+func (g *Game) tickAnimation(c *runtimeChar, dt float64) {
+	desired := clipIdle
+	if c.moving {
+		desired = clipWalk
+	}
+	clip, has := c.def.Animations[desired]
+	if !has {
+		// Fall back to the other clip if the desired one is missing —
+		// a character with only "idle" defined keeps idling during walks.
+		other := clipIdle
+		if desired == clipIdle {
+			other = clipWalk
+		}
+		if cl, ok := c.def.Animations[other]; ok {
+			desired = other
+			clip = cl
+			has = true
+		}
+	}
+	if !has || len(clip.Frames) == 0 || clip.FrameTime <= 0 {
+		c.currentClip = ""
+		c.clipElapsed = 0
+		c.clipFrame = 0
+		return
+	}
+	if c.currentClip != desired {
+		c.currentClip = desired
+		c.clipElapsed = 0
+		c.clipFrame = 0
+	}
+	c.clipElapsed += dt
+	for c.clipElapsed >= clip.FrameTime {
+		c.clipElapsed -= clip.FrameTime
+		c.clipFrame++
+		if c.clipFrame >= len(clip.Frames) {
+			if clip.Loop {
+				c.clipFrame = 0
+			} else {
+				c.clipFrame = len(clip.Frames) - 1
+				c.clipElapsed = 0
+				break
+			}
+		}
+	}
+}
+
+// currentFrameRect returns the source rectangle of the character's
+// current animation frame, in image.Rectangle form so it can feed
+// ebiten.Image.SubImage directly. ok=false when the character should be
+// drawn without animation (no clip / empty clip / out-of-range frame).
+func (c *runtimeChar) currentFrameRect() (image.Rectangle, bool) {
+	if c.currentClip == "" {
+		return image.Rectangle{}, false
+	}
+	clip, ok := c.def.Animations[c.currentClip]
+	if !ok || c.clipFrame < 0 || c.clipFrame >= len(clip.Frames) {
+		return image.Rectangle{}, false
+	}
+	r := clip.Frames[c.clipFrame]
+	return image.Rect(int(r.X), int(r.Y), int(r.X+r.W), int(r.Y+r.H)), true
 }