Merge pull request #62 from tsoding/54

(#54) Make all deceleration animations depend on the current speed of the animation

src/boomer.nim

@@ -84,12 +84,13 @@ type Flashlight = object
 
 const
   INITIAL_FL_DELTA_RADIUS = 100.0
-  FL_DELTA_RADIUS_DECELERATION = 400.0
+  FL_DELTA_RADIUS_DECELERATION = 5.0
 
 proc update(flashlight: var Flashlight, dt: float32) =
   flashlight.radius = max(0.0, flashlight.radius + flashlight.deltaRadius * dt)
+
   if abs(flashlight.deltaRadius) > 0.5:
-    flashlight.deltaRadius -= sgn(flashlight.deltaRadius).float32 * FL_DELTA_RADIUS_DECELERATION * dt
+    flashlight.deltaRadius -= flashlight.deltaRadius * FL_DELTA_RADIUS_DECELERATION * dt
 
   if flashlight.isEnabled:
     flashlight.shadow = min(flashlight.shadow + 6.0 * dt, 0.8)
@@ -347,6 +348,7 @@ proc main() =
         of Button1:
           mouse.prev = mouse.curr
           mouse.drag = true
+          camera.velocity = vec2(0.0, 0.0)
 
         of Button4:             # Scroll up
           if (xev.xkey.state and ControlMask) > 0.uint32 and flashlight.isEnabled:

src/config.nim

@@ -10,9 +10,8 @@ type Config* = object
 const defaultConfig* = Config(
   scrollSpeed: 1.0,
   dragVelocityFactor: 10.0,
-  # TODO(#54): For a natual feel dragFriction probably should depend on velocity
-  dragFriction: 600.0,
-  scaleFriction: 10.0,
+  dragFriction: 2.0,
+  scaleFriction: 4.0,
   fps: 60
 )
 

src/navigation.nim

@@ -27,8 +27,8 @@ proc update*(camera: var Camera, config: Config, dt: float, mouse: Mouse, image:
     let p1 = (mouse.curr - (windowSize * 0.5)) / camera.scale
     camera.position += p0 - p1
 
-    camera.delta_scale -= sgn(camera.delta_scale).float * config.scale_friction * dt
+    camera.delta_scale -= camera.delta_scale * dt * config.scale_friction
 
   if not mouse.drag and (camera.velocity.length > VELOCITY_THRESHOLD):
     camera.position += camera.velocity * dt
-    camera.velocity -= camera.velocity.normalize * (config.dragFriction * dt)
+    camera.velocity -= camera.velocity * dt * config.dragFriction