[PATCH v2] hw/display/artist: Fix bug in coordinate extraction in artist_vram_read() and artist_vram_write()

[Helge Deller <deller@gmx.de>]

The CDE desktop on HP-UX 10 shows wrongly rendered pixels when the local screen
menu is closed. This bug was introduced by commit c7050f3f167b
("hw/display/artist: Refactor x/y coordination extraction") which converted the
coordinate extraction in artist_vram_read() and artist_vram_write() to use the
ADDR_TO_X and ADDR_TO_Y macros, but forgot to right-shift the address by 2 as
it was done before.

Signed-off-by: Helge Deller <deller@gmx.de>
Fixes: c7050f3f167b ("hw/display/artist: Refactor x/y coordination extraction")
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Sven Schnelle <svens@stackframe.org>

---
v2: Fix artist_vram_write() too, noticed by Philippe Mathieu-Daudé

diff --git a/hw/display/artist.c b/hw/display/artist.c
index ed0e637f25..8758c77bbf 100644
--- a/hw/display/artist.c
+++ b/hw/display/artist.c
@@ -1171,8 +1171,8 @@ static void artist_vram_write(void *opaque, hwaddr addr, uint64_t val,
     }

     buf = vram_write_buffer(s);
-    posy = ADDR_TO_Y(addr);
-    posx = ADDR_TO_X(addr);
+    posy = ADDR_TO_Y(addr >> 2);
+    posx = ADDR_TO_X(addr >> 2);

     if (!buf->size) {
         return;
@@ -1233,8 +1233,8 @@ static uint64_t artist_vram_read(void *opaque, hwaddr addr, unsigned size)
         return 0;
     }

-    posy = ADDR_TO_Y(addr);
-    posx = ADDR_TO_X(addr);
+    posy = ADDR_TO_Y(addr >> 2);
+    posx = ADDR_TO_X(addr >> 2);

     if (posy > buf->height || posx > buf->width) {
         return 0;