On 03/10/2024, 14:05, "Daniel P. Berrangé" <berra...@redhat.com> wrote:
> The QEMU VNC code has logic which rounds up display sizes to a multiple
> of 16:
>
> static int vnc_width(VncDisplay *vd)
> {
> return MIN(VNC_MAX_WIDTH, ROUND_UP(surface_width(vd->ds),
> VNC_DIRTY_PIXELS_PER_BIT));
> }
>
> Separately, it also tracks the "true" width, but untangling which it
> uses where & the implications is hard to do. ie i'm not going to try
> to explain it further, as I don't know what's going on without spending
> some hours to trace through it all :-)
On a hunch I revisited Frediano's patch (mentioned in the original post). I had
focused on the change to the VNC functions but he also had a small change to
the masking of the display width in the VGA code. I've applied a similar change
and … I now get a proper display!
Patch is simply
diff --git a/hw/display/vga.c b/hw/display/vga.c
index 892fedc8dc..ea659e2812 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -581,14 +581,14 @@ static void vbe_fixup_regs(VGACommonState *s)
}
/* check width */
- r[VBE_DISPI_INDEX_XRES] &= ~7u;
+ r[VBE_DISPI_INDEX_XRES] &= ~1u;
if (r[VBE_DISPI_INDEX_XRES] == 0) {
r[VBE_DISPI_INDEX_XRES] = 8;
}
if (r[VBE_DISPI_INDEX_XRES] > VBE_DISPI_MAX_XRES) {
r[VBE_DISPI_INDEX_XRES] = VBE_DISPI_MAX_XRES;
}
- r[VBE_DISPI_INDEX_VIRT_WIDTH] &= ~7u;
+ r[VBE_DISPI_INDEX_VIRT_WIDTH] &= ~1u;
if (r[VBE_DISPI_INDEX_VIRT_WIDTH] > VBE_DISPI_MAX_XRES) {
r[VBE_DISPI_INDEX_VIRT_WIDTH] = VBE_DISPI_MAX_XRES;
}
I don't know how functional correct this is.
Regards
Simon
