From 3e3dd1b8405c9271dc790c4cc757eb108fd856c0 Mon Sep 17 00:00:00 2001
From: Ray Greenwell <ray@threerings.net>
Date: Tue, 17 May 2005 20:16:31 +0000
Subject: [PATCH] Allow the start or end alpha levels to be outside the normal
 range so that useful delays can be built into the beginning or end of the
 animation. Detect bogus parameters in the constructor and throw an exception
 to save developer head-scratching time when the animation doesn't actually do
 any fading.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3560 542714f4-19e9-0310-aa3c-eee0fc999fb1
---
 .../threerings/media/effects/FadeEffect.java  | 24 +++++++++++++++----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/java/com/threerings/media/effects/FadeEffect.java b/src/java/com/threerings/media/effects/FadeEffect.java
index dec37687e..e475b4ef7 100644
--- a/src/java/com/threerings/media/effects/FadeEffect.java
+++ b/src/java/com/threerings/media/effects/FadeEffect.java
@@ -32,24 +32,32 @@ public class FadeEffect
 {
     public FadeEffect (float alpha, float step, float target)
     {
+        if ((step == 0f) || (alpha > target && step > 0f) ||
+                (alpha < target && step < 0f)) {
+            throw new IllegalArgumentException("Step specified is illegal: " +
+                "Fade would never finish (start=" + alpha + ", step=" + step +
+                ", target=" + target + ")");
+        }
+
         // save things off
-        _startAlpha = _alpha = Math.max(alpha, 0.0f);
+        _startAlpha = alpha; 
         _step = step;
-        _target = Math.min(target, 1.0f);
+        _target = target;
 
         // create the initial composite
+        _alpha = Math.max(0f, Math.min(1f, _startAlpha));
         _comp = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, _alpha);
     }
 
     public void init (long tickStamp)
     {
+        _finished = false;
         _initStamp = tickStamp;
     }
 
     public boolean finished ()
     {
-        return (_startAlpha < _target) ?
-            (_alpha >= _target) : (_alpha <= _target);
+        return _finished;
     }
 
     public float getAlpha ()
@@ -62,6 +70,8 @@ public class FadeEffect
         // figure out the current alpha
         long msecs = tickStamp - _initStamp;
         float alpha = _startAlpha + (msecs * _step);
+        _finished = (_startAlpha < _target) ? (alpha >= _target)
+                                            : (alpha <= _target);
         if (alpha < 0.0f) {
             alpha = 0.0f;
         } else if (alpha > 1.0f) {
@@ -74,7 +84,8 @@ public class FadeEffect
             return true;
         }
 
-        return false;
+        // return false, unless we're finished
+        return _finished;
     }
 
     public void beforePaint (Graphics2D gfx)
@@ -108,4 +119,7 @@ public class FadeEffect
 
     /** Time zero. */
     protected long _initStamp;
+
+    /** True when we're finished. */
+    protected boolean _finished;
 }