According to Apple Technical Note HW26: "Macintosh Quadra Built-In Video" the
in-built framebuffer encodes each 24-bit pixel into 4 bytes. Adjust the 24-bit
RGB pixel encoding accordingly which agrees with the encoding expected by MacOS
when changing into 24-bit colour mode.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/display/macfb.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/hw/display/macfb.c b/hw/display/macfb.c
index 0c9e181b9b..29f6ad8eba 100644
--- a/hw/display/macfb.c
+++ b/hw/display/macfb.c
@@ -224,10 +224,10 @@ static void macfb_draw_line24(MacfbState *s, uint8_t *d, uint32_t addr,
     int x;
 
     for (x = 0; x < width; x++) {
-        r = macfb_read_byte(s, addr);
-        g = macfb_read_byte(s, addr + 1);
-        b = macfb_read_byte(s, addr + 2);
-        addr += 3;
+        r = macfb_read_byte(s, addr + 1);
+        g = macfb_read_byte(s, addr + 2);
+        b = macfb_read_byte(s, addr + 3);
+        addr += 4;
 
         *(uint32_t *)d = rgb_to_pixel32(r, g, b);
         d += 4;
-- 
2.20.1

On 02/10/2021 13:00, Mark Cave-Ayland wrote:
> According to Apple Technical Note HW26: "Macintosh Quadra Built-In Video" the
> in-built framebuffer encodes each 24-bit pixel into 4 bytes. Adjust the 24-bit
> RGB pixel encoding accordingly which agrees with the encoding expected by MacOS
> when changing into 24-bit colour mode.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>   hw/display/macfb.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/display/macfb.c b/hw/display/macfb.c
> index 0c9e181b9b..29f6ad8eba 100644
> --- a/hw/display/macfb.c
> +++ b/hw/display/macfb.c
> @@ -224,10 +224,10 @@ static void macfb_draw_line24(MacfbState *s, uint8_t *d, uint32_t addr,
>       int x;
>   
>       for (x = 0; x < width; x++) {
> -        r = macfb_read_byte(s, addr);
> -        g = macfb_read_byte(s, addr + 1);
> -        b = macfb_read_byte(s, addr + 2);
> -        addr += 3;
> +        r = macfb_read_byte(s, addr + 1);
> +        g = macfb_read_byte(s, addr + 2);
> +        b = macfb_read_byte(s, addr + 3);
> +        addr += 4;
>   
>           *(uint32_t *)d = rgb_to_pixel32(r, g, b);
>           d += 4;
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>