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.

6 files changed, 106 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. */
diff --git a/src/net/manaserv/effecthandler.cpp b/src/net/manaserv/effecthandler.cpp
index 2df3fe0b..7051bedd 100644
--- a/src/net/manaserv/effecthandler.cpp
+++ b/src/net/manaserv/effecthandler.cpp
@@ -25,6 +25,8 @@
 #include "effectmanager.h"
 #include "log.h"
 
+#include "gui/viewport.h"
+
 #include "net/messagein.h"
 
 #include "net/manaserv/manaserv_protocol.h"
@@ -36,6 +38,7 @@ EffectHandler::EffectHandler()
     static const Uint16 _messages[] = {
         GPMSG_CREATE_EFFECT_POS,
         GPMSG_CREATE_EFFECT_BEING,
+        GPMSG_SHAKE,
         0
     };
     handledMessages = _messages;
@@ -51,6 +54,9 @@ void EffectHandler::handleMessage(Net::MessageIn &msg)
         case GPMSG_CREATE_EFFECT_BEING:
             handleCreateEffectBeing(msg);
             break;
+        case GPMSG_SHAKE:
+            handleShake(msg);
+            break;
         default:
             break;
     }
@@ -75,4 +81,36 @@ void EffectHandler::handleCreateEffectBeing(Net::MessageIn &msg)
         logger->log("Warning: CreateEffect called for unknown being #%d", bid);
 }
 
+void EffectHandler::handleShake(Net::MessageIn &msg)
+{
+    int16_t intensityX = 0;
+    int16_t intensityY = 0;
+    float decay;
+    int duration;
+
+    switch (msg.getUnreadLength())
+    {
+        case 4:
+            intensityX =  msg.readInt16();
+            intensityY =  msg.readInt16();
+            viewport->shakeScreen(intensityX, intensityY);
+            break;
+        case 6:
+            intensityX =  msg.readInt16();
+            intensityY =  msg.readInt16();
+            decay =  msg.readInt16() / 10000.0f;
+            viewport->shakeScreen(intensityX, intensityY, decay);
+            break;
+        case 8:
+            intensityX =  msg.readInt16();
+            intensityY =  msg.readInt16();
+            decay =  msg.readInt16() / 10000.0f;
+            duration =  msg.readInt16();
+            viewport->shakeScreen(intensityX, intensityY, decay, duration);
+            break;
+        default:
+            logger->log("Warning: Received GPMSG_SHAKE message with unexpected length of %d bytes", msg.getUnreadLength());
+    }
+}
+
 } // namespace ManaServ
diff --git a/src/net/manaserv/effecthandler.h b/src/net/manaserv/effecthandler.h
index a0445aad..d31c3421 100644
--- a/src/net/manaserv/effecthandler.h
+++ b/src/net/manaserv/effecthandler.h
@@ -36,6 +36,7 @@ class EffectHandler : public MessageHandler
     private:
         void handleCreateEffectPos(Net::MessageIn &msg);
         void handleCreateEffectBeing(Net::MessageIn &msg);
+        void handleShake(Net::MessageIn &msg);
 };
 
 } // namespace ManaServ
diff --git a/src/net/manaserv/manaserv_protocol.h b/src/net/manaserv/manaserv_protocol.h
index 84f1c1a5..16e56183 100644
--- a/src/net/manaserv/manaserv_protocol.h
+++ b/src/net/manaserv/manaserv_protocol.h
@@ -163,6 +163,7 @@ enum {
     GPMSG_BEINGS_DAMAGE            = 0x0310, // { W being id, W amount }*
     GPMSG_CREATE_EFFECT_POS        = 0x0320, // W effect id, W*2 position
     GPMSG_CREATE_EFFECT_BEING      = 0x0321, // W effect id, W BeingID
+    GPMSG_SHAKE                    = 0x0330, // W intensityX, W intensityY, [W decay_times_10000, [W duration]]
 
     // Guild
     PCMSG_GUILD_CREATE                  = 0x0350, // S name
diff --git a/src/net/tmwa/playerhandler.cpp b/src/net/tmwa/playerhandler.cpp
index b82968a3..725a00cc 100644
--- a/src/net/tmwa/playerhandler.cpp
+++ b/src/net/tmwa/playerhandler.cpp
@@ -282,6 +282,7 @@ void PlayerHandler::handleMessage(Net::MessageIn &msg)
 
                 if (PlayerInfo::getAttribute(HP) == 0 && !deathNotice)
                 {
+                    viewport->shakeScreen(100);
                     deathNotice = new OkDialog(_("Message"),
                                                randomDeathMessage(),
                                                false);