If new line is shorter than previous, clear part of buffer used by previous line

diff --git a/drawing.cpp b/drawing.cpp
index b7ca249dbd6374e6e0395a8ecef8d2ff14ff72bf..ca6564b3418aa70582495edcf86558a8a45f7e37 100644 (file)
--- a/drawing.cpp
+++ b/drawing.cpp
@@ -313,6 +313,7 @@ static int sprite_offs[256];
 /* OCS/ECS color lookup table. */
 xcolnr xcolors[4096];
 
+static int chunky_out_prev_len;
 static uae_u32 chunky_out[4096], dpf_chunky_out[4096];
 
 #ifdef AGA
@@ -6863,7 +6864,6 @@ static void pfield_doline_8(int planecnt, int wordcount, uae_u8 *datap, struct l
        uae_u32 *data = (uae_u32 *)datap;
        switch (planecnt) {
                default: break;
-               case 0: memset(data, 0, wordcount * 32); break;
                case 1: pfield_doline32_n1_8(data, wordcount, real_bplpt); break;
                case 2: pfield_doline32_n2_8(data, wordcount, real_bplpt); break;
                case 3: pfield_doline32_n3_8(data, wordcount, real_bplpt); break;
@@ -7182,8 +7182,17 @@ void draw_denise_bitplane_line_fast(int gfx_ypos, enum nln_how how, struct lines
        }
 
        uae_u32 *cstart = chunky_out + 1024;
-       int len = (ls->bpllen + 3) / 4;
-       pfield_doline_8(planecnt, len, (uae_u8*)cstart, ls);
+       int len = 0;
+       if (planecnt > 0) {
+               len = (ls->bpllen + 3) / 4;
+               pfield_doline_8(planecnt, len, (uae_u8*)cstart, ls);
+       }
+       int byteoutlen = len * 8 * 4;
+       // if previous line was longer: clear the unused part
+       if (chunky_out_prev_len > byteoutlen) {
+               memset((uae_u8*)cstart + byteoutlen, 0, chunky_out_prev_len - byteoutlen);
+       }
+       chunky_out_prev_len = byteoutlen;
 
        bool ecsena = ecs_denise && (ls->bplcon0 & 1) != 0;
        bool brdblank = (ls->bplcon3 & 0x20) && ecsena;