randr: Use XRRGetScreenResourcesCurrent (rhbz#888821)

Using XRRGetScreenResources, causes the X-server to actively check for
new monitors, which generates Xrandr events even if nothing is changed, which
causes gnome-setting-manager to muck with the settings, racing with the
agent doing the same.

XRRGetScreenResourcesCurrent OTOH simply returns the last known settings
without any polling of the hardware and matching events being involved.

So use XRRGetScreenResourcesCurrent instead of XRRGetScreenResources, with
one exception. When the number of monitors is changed, so some outputs are
enabled or disabled, then the hardware polling is necessary to properly
reflect the connected / disconnected state in xrandr.

This requires Xrandr >= 1.3, note that since 0.12.0 we already depended
on >= 1.2 anyways, this patch raises the requirement to 1.3 and makes
it explict.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

1 files changed, 16 insertions, 9 deletions

diff --git a/src/vdagent-x11-randr.c b/src/vdagent-x11-randr.c
index 6a9a4ed..d9bf741 100644
--- a/src/vdagent-x11-randr.c
+++ b/src/vdagent-x11-randr.c
@@ -109,13 +109,15 @@ static void free_randr_resources(struct vdagent_x11 *x11)
     x11->randr.num_monitors = 0;
 }
 
-static void update_randr_res(struct vdagent_x11 *x11)
+static void update_randr_res(struct vdagent_x11 *x11, int poll)
 {
     int i;
 
     free_randr_resources(x11);
-    /* Note: we don't need XRRGetScreenResourcesCurrent since we cache the changes */
-    x11->randr.res = XRRGetScreenResources(x11->display, x11->root_window);
+    if (poll)
+        x11->randr.res = XRRGetScreenResources(x11->display, x11->root_window);
+    else
+        x11->randr.res = XRRGetScreenResourcesCurrent(x11->display, x11->root_window);
     x11->randr.outputs = malloc(x11->randr.res->noutput * sizeof(*x11->randr.outputs));
     x11->randr.crtcs = malloc(x11->randr.res->ncrtc * sizeof(*x11->randr.crtcs));
     for (i = 0 ; i < x11->randr.res->noutput; ++i) {
@@ -143,9 +145,13 @@ void vdagent_x11_randr_init(struct vdagent_x11 *x11)
     int i;
 
     if (XRRQueryExtension(x11->display, &i, &i)) {
-        x11->has_xrandr = 1;
-        update_randr_res(x11);
         XRRQueryVersion(x11->display, &x11->xrandr_major, &x11->xrandr_minor);
+        if (x11->xrandr_major == 1 && x11->xrandr_minor >= 3)
+            x11->has_xrandr = 1;
+    }
+
+    if (x11->has_xrandr) {
+        update_randr_res(x11, 0);
     } else {
         x11->randr.res = NULL;
     }
@@ -238,7 +244,7 @@ static void delete_mode(struct vdagent_x11 *x11, int output_index, const char* n
     }
 
     /* silly to update everytime for more then one monitor */
-    update_randr_res(x11);
+    update_randr_res(x11, 0);
 }
 
 static void set_reduced_cvt_mode(XRRModeInfo *mode, int width, int height)
@@ -335,7 +341,7 @@ static XRRModeInfo *create_new_mode(struct vdagent_x11 *x11, int output_index,
     check_error_handler(x11);
 
     /* silly to update everytime for more then one monitor */
-    update_randr_res(x11);
+    update_randr_res(x11, 0);
 
     return find_mode_by_name(x11, modename);
 }
@@ -586,7 +592,7 @@ static int same_monitor_configs(struct vdagent_x11 *x11,
     VDAgentMonConfig *client_mode;
     XRRScreenResources *res;
 
-    update_randr_res(x11);
+    update_randr_res(x11, 0);
     res = x11->randr.res;
 
     if (res->noutput > res->ncrtc) {
@@ -734,7 +740,8 @@ void vdagent_x11_set_monitor_config(struct vdagent_x11 *x11,
     }
 
 update:
-    update_randr_res(x11);
+    update_randr_res(x11,
+        x11->randr.num_monitors != mon_config->num_of_monitors);
     x11->width = primary_w;
     x11->height = primary_h;