From 4197ad064f87e8262ea281736d7e3bb6d4797e0a Mon Sep 17 00:00:00 2001
From: Mikko Juola <mikko.juola@kolumbus.fi>
Date: Mon, 16 Aug 2010 16:35:58 +0300
Subject: [PATCH] Add a dirty hack to stop flickering on non-synchronizing DF
 processes.

---
 library/modules/Position.cpp | 48 ++++++++++++++++++++++++++++++++----
 1 file changed, 43 insertions(+), 5 deletions(-)

diff --git a/library/modules/Position.cpp b/library/modules/Position.cpp
index 694db6838..4499b6089 100644
--- a/library/modules/Position.cpp
+++ b/library/modules/Position.cpp
@@ -43,6 +43,11 @@ struct Position::Private
     uint32_t hotkey_size;
     
     uint32_t screen_tiles_ptr_offset;
+    uint32_t last_screen_offset;
+
+    uint8_t* tiles;
+    uint32_t tiles_size;
+    bool first_read; // used in getScreenTiles
 
     DFContextShared *d;
     Process * owner;
@@ -57,6 +62,11 @@ Position::Position(DFContextShared * d_)
     d = new Private;
     d->d = d_;
     d->owner = d_->p;
+    d->last_screen_offset = (uint32_t) 0;
+    d->tiles = (uint8_t*) 0;
+    d->first_read = true;
+    d->tiles_size = 0;
+
     d->Inited = true;
     d->StartedHotkeys = d->Started = d->StartedScreen = false;
     memory_info * mem;
@@ -90,6 +100,7 @@ Position::Position(DFContextShared * d_)
 
 Position::~Position()
 {
+    if (d->tiles) delete[] d->tiles;
     delete d;
 }
 
@@ -176,13 +187,42 @@ bool Position::getScreenTiles (int32_t width, int32_t height, t_screen screen[])
     if(!d->Inited) return false;
     if(!d->StartedScreen) return false;
 
+    /*
+      To work around flickering without synchronization,
+      we take advantage of double buffering in DF.
+
+      We don't return the buffer currently in use,
+      but the buffer that was last used. This has much less
+      chance of being empty or flicker.
+    */
+
     uint32_t screen_addr;
+    
     d->owner->read (d->screen_tiles_ptr_offset, sizeof(uint32_t), (uint8_t *) &screen_addr);
+    if (d->first_read)
+        d->last_screen_offset = screen_addr;
+    
+    if (d->tiles && width * height * 4 != d->tiles_size)
+    {
+        delete[] d->tiles;
+        d->tiles = (uint8_t*) 0;
+    }
 
-    uint8_t* tiles = new uint8_t[width*height*4/* + 80 + width*height*4*/];
-
-    d->owner->read (screen_addr, (width*height*4/* + 80 + width*height*4*/), (uint8_t *) tiles);
+    if (!d->tiles)
+    {
+        d->tiles = new uint8_t[width * height * 4];
+        d->tiles_size = width * height * 4;
+    }
+    
+    if (d->last_screen_offset != screen_addr || d->first_read)
+    {
+        d->owner->read (d->last_screen_offset, width*height*4, (uint8_t*) d->tiles);
+        d->last_screen_offset = screen_addr;
+    }
 
+    d->first_read = false;
+    const uint8_t* tiles = d->tiles;
+    
     for(int32_t iy=0; iy<height; iy++)
     {
         for(int32_t ix=0; ix<width; ix++)
@@ -196,7 +236,5 @@ bool Position::getScreenTiles (int32_t width, int32_t height, t_screen screen[])
         }
     }
 
-    delete [] tiles;
-
     return true;
 }
\ No newline at end of file