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xwayland: Do not round non-standard modes 

Currently, Xwayland uses libxcvt to generate the mode info and then
passes that to RRModeGet() to generate a RRMode.

However, libxcvt may round down the width to match the horizontal
granularity (8), and that's a problem when the Wayland compositor is
running a non-standard size (like, e.g. running nested with a custom
size) because XRandR would report a width smaller than the actual size.

To avoid that, check whether the CVT computed size differs from the
expected size, and fallback to a simpler computation not doing any
rounding if that's the case.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Closes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1540
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
This commit is contained in:
Olivier Fourdan 2023-04-24 16:26:19 +02:00
parent 9a55c402aa
commit ad2d461dec
1 changed files with 46 additions and 16 deletions
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62
hw/xwayland/xwayland-cvt.c
View File

@ -29,30 +29,60 @@
#include "xwayland-cvt.h"
RRModePtr
xwayland_cvt(int hdisplay, int vdisplay, float vrefresh, Bool reduced,
Bool interlaced)
static void
xwayland_modinfo_from_cvt(xRRModeInfo *modeinfo,
int hdisplay, int vdisplay, float vrefresh,
Bool reduced, Bool interlaced)
{
struct libxcvt_mode_info *libxcvt_mode_info;
char name[128];
xRRModeInfo modeinfo;
libxcvt_mode_info =
libxcvt_gen_mode_info(hdisplay, vdisplay, vrefresh, reduced, interlaced);
memset(&modeinfo, 0, sizeof modeinfo);
modeinfo.width = libxcvt_mode_info->hdisplay;
modeinfo.height = libxcvt_mode_info->vdisplay;
modeinfo.dotClock = libxcvt_mode_info->dot_clock * 1000.0;
modeinfo.hSyncStart = libxcvt_mode_info->hsync_start;
modeinfo.hSyncEnd = libxcvt_mode_info->hsync_end;
modeinfo.hTotal = libxcvt_mode_info->htotal;
modeinfo.vSyncStart = libxcvt_mode_info->vsync_start;
modeinfo.vSyncEnd = libxcvt_mode_info->vsync_end;
modeinfo.vTotal = libxcvt_mode_info->vtotal;
modeinfo.modeFlags = libxcvt_mode_info->mode_flags;
modeinfo->width = libxcvt_mode_info->hdisplay;
modeinfo->height = libxcvt_mode_info->vdisplay;
modeinfo->dotClock = libxcvt_mode_info->dot_clock * 1000.0;
modeinfo->hSyncStart = libxcvt_mode_info->hsync_start;
modeinfo->hSyncEnd = libxcvt_mode_info->hsync_end;
modeinfo->hTotal = libxcvt_mode_info->htotal;
modeinfo->vSyncStart = libxcvt_mode_info->vsync_start;
modeinfo->vSyncEnd = libxcvt_mode_info->vsync_end;
modeinfo->vTotal = libxcvt_mode_info->vtotal;
modeinfo->modeFlags = libxcvt_mode_info->mode_flags;
free(libxcvt_mode_info);
}
static void
xwayland_modinfo_from_values(xRRModeInfo *modeinfo,
int hdisplay, int vdisplay, float vrefresh)
{
modeinfo->width = hdisplay;
modeinfo->height = vdisplay;
modeinfo->hTotal = hdisplay;
modeinfo->vTotal = vdisplay;
modeinfo->dotClock = hdisplay * vdisplay * vrefresh;
}
RRModePtr
xwayland_cvt(int hdisplay, int vdisplay, float vrefresh, Bool reduced,
Bool interlaced)
{
char name[128];
xRRModeInfo modeinfo = { 0, };
xwayland_modinfo_from_cvt(&modeinfo,
hdisplay, vdisplay, vrefresh, reduced, interlaced);
/* Horizontal granularity in libxcvt is 8, so if our horizontal size is not
* divisible by 8, libxcvt will round it down, and we will advertise a wrong
* size to our XRandR clients. Fallback to a simpler method in that case.
*/
if (modeinfo.width != hdisplay || modeinfo.height != vdisplay) {
memset(&modeinfo, 0, sizeof(xRRModeInfo));
xwayland_modinfo_from_values(&modeinfo,
hdisplay, vdisplay, vrefresh);
}
snprintf(name, sizeof name, "%dx%d",
modeinfo.width, modeinfo.height);