Implemented a screen shake effect system in the viewport class.

The screen can either be "nudged" in a random direction with a specific
intensity or you can define an exact x and y intensity, decay factor and
duration. On a tmwAthena server an effect is triggered when the player
character dies. A method for stopping all shake effects is also
implemented, but not used yet. I added a netcode message for Manaserv to
trigger an effect server-sided. Because our protocol has currently no way
to transport floating point values, the decay is transported as a fixed
point value with 4 decimals which is entirely sufficient for this purpose.

2 files changed, 65 insertions, 1 deletions

diff --git a/src/gui/viewport.cpp b/src/gui/viewport.cpp
index ac910d5f..9d03cab5 100644
--- a/src/gui/viewport.cpp
+++ b/src/gui/viewport.cpp
@@ -42,6 +42,8 @@
 
 #include "utils/stringutils.h"
 
+#include <cmath>
+
 extern volatile int tick_time;
 
 Viewport::Viewport():
@@ -121,9 +123,9 @@ void Viewport::draw(gcn::Graphics *gcnGraphics)
     if (mScrollLaziness < 1)
         mScrollLaziness = 1; // Avoids division by zero
 
-    // Apply lazy scrolling
     while (lastTick < tick_time)
     {
+        // Apply lazy scrolling
         if (player_x > mPixelViewX + mScrollRadius)
         {
             mPixelViewX += (player_x - mPixelViewX - mScrollRadius) /
@@ -144,6 +146,22 @@ void Viewport::draw(gcn::Graphics *gcnGraphics)
             mPixelViewY += (player_y - mPixelViewY + mScrollRadius) /
                             mScrollLaziness;
         }
+
+        // manage shake effect
+        for (ShakeEffects::iterator i = mShakeEffects.begin();
+             i != mShakeEffects.end();
+             i++)
+        {
+            // apply the effect to viewport
+            mPixelViewX += i->x *= -i->decay;
+            mPixelViewY += i->y *= -i->decay;
+            // check death conditions
+            if (abs(i->x) + abs(i->y) < 1.0f ||
+                (i->duration > 0 && --i->duration == 0))
+            {
+                i = mShakeEffects.erase(i);
+            }
+        }
         lastTick++;
     }
 
@@ -222,6 +240,24 @@ void Viewport::draw(gcn::Graphics *gcnGraphics)
     WindowContainer::draw(gcnGraphics);
 }
 
+void Viewport::shakeScreen(int intensity)
+{
+    float direction = rand()%628 / 100.0f; // random value between 0 and 2PI
+    float x = std::sin(direction) * intensity;
+    float y = std::cos(direction) * intensity;
+    shakeScreen(x, y);
+}
+
+void Viewport::shakeScreen(float x, float y, float decay, unsigned duration)
+{
+    ShakeEffect effect;
+    effect.x = x;
+    effect.y = y;
+    effect.decay = decay;
+    effect.duration = duration;
+    mShakeEffects.push_back(effect);
+}
+
 void Viewport::logic()
 {
     WindowContainer::logic();
diff --git a/src/gui/viewport.h b/src/gui/viewport.h
index 93e36b5b..f4db806b 100644
--- a/src/gui/viewport.h
+++ b/src/gui/viewport.h
@@ -29,6 +29,8 @@
 
 #include <guichan/mouselistener.hpp>
 
+#include <list>
+
 class ActorSprite;
 class Being;
 class BeingPopup;
@@ -153,6 +155,22 @@ class Viewport : public WindowContainer, public gcn::MouseListener,
          */
         void hideBeingPopup();
 
+        /**
+         * Makes the screen shake in a random direction
+         */
+        void shakeScreen(int intensity);
+
+        /**
+         * Makes the screen shake in a specific direction
+         */
+        void shakeScreen(float x, float y, float decay = 0.95f, unsigned duration = 0);
+
+        /**
+         * Stops all active screen shake effects
+         */
+        void shakeScreenStop()
+        { mShakeEffects.clear(); }
+
         void event(Channels channel, const Mana::Event &event);
 
     private:
@@ -190,6 +208,16 @@ class Viewport : public WindowContainer, public gcn::MouseListener,
         float mPixelViewY;           /**< Current viewpoint in pixels. */
         int mShowDebugPath;         /**< Show a path from player to pointer. */
 
+        struct ShakeEffect
+        {
+            float x;
+            float y;
+            float decay;
+            unsigned duration;
+        };
+        typedef std::list<ShakeEffect> ShakeEffects;
+        ShakeEffects mShakeEffects;
+
         bool mPlayerFollowMouse;
 
         int mLocalWalkTime; /**< Timestamp before the next walk can be sent. */