randr: Add "RANDR Emulation" property

When RANDR is emulated as with Xwayland, the actual output configuration
does not change as RANDR is emulated using viewports.

As a result, changes to the CRTC may be skipped, resulting in the
configuration being (wrongly) assumed to be unchanged.

Add a new output property "RANDR Emulation" that the DDX can set to
force RRCrtcSet() to reconfigure the CRTC regardless of the change.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>

randr/rrcrtc.c

@@ -709,6 +709,25 @@ rrCheckPixmapBounding(ScreenPtr pScreen,
     return TRUE;
 }
 
+#define XRANDR_EMULATION_PROP "RANDR Emulation"
+static Bool
+rrCheckEmulated(RROutputPtr output)
+{
+    const char *emulStr = XRANDR_EMULATION_PROP;
+    Atom emulProp;
+    RRPropertyValuePtr val;
+
+    emulProp = MakeAtom(emulStr, strlen(emulStr), FALSE);
+    if (emulProp == None)
+        return FALSE;
+
+    val = RRGetOutputProperty(output, emulProp, TRUE);
+    if (val && val->data)
+        return !!val->data;
+
+    return FALSE;
+}
+
 /*
  * Request that the Crtc be reconfigured
  */
@@ -728,11 +747,13 @@ RRCrtcSet(RRCrtcPtr crtc,
 
     crtcChanged = FALSE;
     for (o = 0; o < numOutputs; o++) {
-        if (outputs[o] && outputs[o]->crtc != crtc) {
+        if (outputs[o]) {
+            if (rrCheckEmulated(outputs[o]) || (outputs[o]->crtc != crtc)) {
                 crtcChanged = TRUE;
                 break;
             }
         }
+    }
 
     /* See if nothing changed */
     if (crtc->mode == mode &&