Fixed 2 bugs in sprite drawing

- A bug with sprite priority (sprites with lower priority
  didn't draw under overlapping sprites with higher
  priority)

- A memory corruption bug when a sprite went over the right
  edge of the screen :$

diff --git a/core/GBVideo.cc b/core/GBVideo.cc
index 55dd82ba199cf2b9c2362be313e0c8d7cc3450b8..2981fe93380d5952d8ea8628c36ea4aecc7c793e 100644 (file)
--- a/core/GBVideo.cc
+++ b/core/GBVideo.cc
@@ -371,11 +371,11 @@ void GBVideo::draw()
 
                        //logger.trace("LY=",LY," sprites=",v.size());
                        // draw sprites
-                       int cur_x = 0;
                        for (u32 i=0; i<v.size() && i<10 ; i++)
                        {
-                               int screen_x = std::max(cur_x, v[i].x-8);
+                               int screen_x = std::max(0, v[i].x-8);
                                int sprite_x = screen_x - (v[i].x-8);
+                               int max_sprite_x = std::min(8, 168-v[i].x);
                                int sprite_y = LY - (v[i].y - 16);
                                bool mirror_x = check_bit(v[i].flags, 5);
                                bool mirror_y = check_bit(v[i].flags, 6);
@@ -404,7 +404,7 @@ void GBVideo::draw()
                                u16 current_tile_addr = 16*current_tile_index;
                                u8 current_row_low  = VRAM[current_tile_addr+2*sprite_y];
                                u8 current_row_high = VRAM[current_tile_addr+2*sprite_y+1];
-                               for (int x=sprite_x; x < 8; x++)
+                               for (int x=sprite_x; x < max_sprite_x; x++)
                                {
                                        int mx = mirror_x? x : 7-x;
                                        u8 color = ((current_row_high >> mx)&1) << 1 | 
@@ -412,8 +412,9 @@ void GBVideo::draw()
 
                                        if (color != 0)
                                        {
-                                               if (newscreen[line_base+screen_x+x]==0 ||
-                                                               check_bit(v[i].flags,7)==false)
+                                               if (newscreen[line_base+screen_x+x] >> 4 == 0 &&
+                                                               (newscreen[line_base+screen_x+x]==0 ||
+                                                               check_bit(v[i].flags,7)==false))
                                                {
                                                        newscreen[line_base+screen_x+x] = color | ((pal_num + 1) << 4);
                                                }
@@ -421,7 +422,6 @@ void GBVideo::draw()
                                        //logger.trace((pal_num + 1) << 4);
                                }
 
-                               cur_x = v[i].x;
                        }
                }       
                // Apply pallettes to the line