vdagent-x11: Add support for setups with multiple screens

Some users have a need for old-fashioned setups with multiple X11 Screens
rather then one large virtual Screen as modern X usually has. This can be
accomplished by using multiple qxl devices + a xorg.conf file assigning
one Screen per qxl device.

Limitations:
-Max one monitor per Screen / qxl device
-All monitors / Screens must have the same resolution
-No client -> guest resolution syncing

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

3 files changed, 57 insertions, 25 deletions

diff --git a/src/vdagent-x11-priv.h b/src/vdagent-x11-priv.h
index 71c26b9..c607850 100644
--- a/src/vdagent-x11-priv.h
+++ b/src/vdagent-x11-priv.h
@@ -89,6 +89,7 @@ struct vdagent_x11 {
     char *net_wm_name;
     int debug;
     int fd;
+    int screen_count;
     int width[MAX_SCREENS];
     int height[MAX_SCREENS];
     int has_xfixes;
@@ -142,7 +143,7 @@ void vdagent_x11_randr_init(struct vdagent_x11 *x11);
 void vdagent_x11_send_daemon_guest_xorg_res(struct vdagent_x11 *x11,
                                             int update);
 void vdagent_x11_randr_handle_root_size_change(struct vdagent_x11 *x11,
-                                               int width, int height);
+                                            int screen, int width, int height);
 
 void vdagent_x11_set_error_handler(struct vdagent_x11 *x11,
     int (*handler)(Display *, XErrorEvent *));
diff --git a/src/vdagent-x11-randr.c b/src/vdagent-x11-randr.c
index 1d609bd..5223f88 100644
--- a/src/vdagent-x11-randr.c
+++ b/src/vdagent-x11-randr.c
@@ -123,6 +123,12 @@ void vdagent_x11_randr_init(struct vdagent_x11 *x11)
 {
     int i;
 
+    if (x11->screen_count > 1) {
+        syslog(LOG_WARNING, "X-server has more then 1 screen, "
+               "disabling client -> guest resolution syncing");
+        return;
+    }
+
     if (XRRQueryExtension(x11->display, &i, &i)) {
         XRRQueryVersion(x11->display, &x11->xrandr_major, &x11->xrandr_minor);
         if (x11->xrandr_major == 1 && x11->xrandr_minor >= 3)
@@ -455,18 +461,18 @@ static int set_screen_to_best_size(struct vdagent_x11 *x11, int width, int heigh
 }
 
 void vdagent_x11_randr_handle_root_size_change(struct vdagent_x11 *x11,
-                                               int width, int height)
+    int screen, int width, int height)
 {
-    if (width == x11->width[0] && height == x11->height[0]) {
+    if (width == x11->width[screen] && height == x11->height[screen]) {
         return;
     }
 
     if (x11->debug)
-        syslog(LOG_DEBUG, "Root size changed to %dx%d send %d",
-               width, height, !x11->dont_send_guest_xorg_res);
+        syslog(LOG_DEBUG, "Root size of screen %d changed to %dx%d send %d",
+              screen,  width, height, !x11->dont_send_guest_xorg_res);
 
-    x11->width[0]  = width;
-    x11->height[0] = height;
+    x11->width[screen]  = width;
+    x11->height[screen] = height;
     if (!x11->dont_send_guest_xorg_res) {
         vdagent_x11_send_daemon_guest_xorg_res(x11, 1);
     }
@@ -809,7 +815,7 @@ exit:
 void vdagent_x11_send_daemon_guest_xorg_res(struct vdagent_x11 *x11, int update)
 {
     struct vdagentd_guest_xorg_resolution *res = NULL;
-    int i, screen_count = 0;
+    int i, width = 0, height = 0, screen_count = 0;
 
     if (x11->has_xrandr) {
         VDAgentMonitorsConfig *curr;
@@ -835,6 +841,8 @@ void vdagent_x11_send_daemon_guest_xorg_res(struct vdagent_x11 *x11, int update)
             res[i].y = curr->monitors[i].y;
         }
         free(curr);
+        width  = x11->width[0];
+        height = x11->height[0];
     } else if (x11->has_xinerama) {
         XineramaScreenInfo *screen_info = NULL;
 
@@ -860,16 +868,24 @@ void vdagent_x11_send_daemon_guest_xorg_res(struct vdagent_x11 *x11, int update)
             res[screen_info[i].screen_number].y = screen_info[i].y_org;
         }
         XFree(screen_info);
+        width  = x11->width[0];
+        height = x11->height[0];
     } else {
 no_info:
-        screen_count = 1;
+        screen_count = x11->screen_count;
         res = malloc(screen_count * sizeof(*res));
         if (!res)
             goto no_mem;
-        res[0].width  = x11->width[0];
-        res[0].height = x11->height[0];
-        res[0].x = 0;
-        res[0].y = 0;
+        for (i = 0; i < screen_count; i++) {
+            res[i].width  = x11->width[i];
+            res[i].height = x11->height[i];
+            /* No way to get screen coordinates, assume rtl order */
+            res[i].x = width;
+            res[i].y = 0;
+            width += x11->width[i];
+            if (x11->height[i] > height)
+                height = x11->height[i];
+        }
     }
 
     if (x11->debug) {
@@ -878,8 +894,8 @@ no_info:
                    res[i].height, res[i].x, res[i].y);
     }
 
-    udscs_write(x11->vdagentd, VDAGENTD_GUEST_XORG_RESOLUTION, x11->width[0],
-                x11->height[0], (uint8_t *)res, screen_count * sizeof(*res));
+    udscs_write(x11->vdagentd, VDAGENTD_GUEST_XORG_RESOLUTION, width, height,
+                (uint8_t *)res, screen_count * sizeof(*res));
     free(res);
     return;
 no_mem:
diff --git a/src/vdagent-x11.c b/src/vdagent-x11.c
index 51f9315..6a58532 100644
--- a/src/vdagent-x11.c
+++ b/src/vdagent-x11.c
@@ -196,12 +196,22 @@ struct vdagent_x11 *vdagent_x11_create(struct udscs_connection *vdagentd,
         return NULL;
     }
 
+    x11->screen_count = ScreenCount(x11->display);
+    if (x11->screen_count > MAX_SCREENS) {
+        syslog(LOG_ERR, "Error too much screens: %d > %d",
+               x11->screen_count, MAX_SCREENS);
+        XCloseDisplay(x11->display);
+        free(x11);
+        return NULL;
+    }
+
     if (sync) {
         XSetErrorHandler(vdagent_x11_debug_error_handler);
         XSynchronize(x11->display, True);
     }
 
-    x11->root_window[0] = RootWindow(x11->display, 0);
+    for (i = 0; i < x11->screen_count; i++)
+        x11->root_window[i] = RootWindow(x11->display, i);
     x11->fd = ConnectionNumber(x11->display);
     x11->clipboard_atom = XInternAtom(x11->display, "CLIPBOARD", False);
     x11->clipboard_primary_atom = XInternAtom(x11->display, "PRIMARY", False);
@@ -253,13 +263,15 @@ struct vdagent_x11 *vdagent_x11_create(struct udscs_connection *vdagentd,
     if (x11->max_prop_size > 262144)
         x11->max_prop_size = 262144;
 
-    /* Catch resolution changes */
-    XSelectInput(x11->display, x11->root_window[0], StructureNotifyMask);
+    for (i = 0; i < x11->screen_count; i++) {
+        /* Catch resolution changes */
+        XSelectInput(x11->display, x11->root_window[i], StructureNotifyMask);
 
-    /* Get the current resolution */
-    XGetWindowAttributes(x11->display, x11->root_window[0], &attrib);
-    x11->width[0]  = attrib.width;
-    x11->height[0] = attrib.height;
+        /* Get the current resolution */
+        XGetWindowAttributes(x11->display, x11->root_window[i], &attrib);
+        x11->width[i]  = attrib.width;
+        x11->height[i] = attrib.height;
+    }
     vdagent_x11_send_daemon_guest_xorg_res(x11, 1);
 
     /* Get net_wm_name, since we are started at the same time as the wm,
@@ -443,7 +455,7 @@ static int vdagent_x11_get_clipboard_selection(struct vdagent_x11 *x11,
 
 static void vdagent_x11_handle_event(struct vdagent_x11 *x11, XEvent event)
 {
-    int handled = 0;
+    int i, handled = 0;
     uint8_t selection;
 
     if (event.type == x11->xfixes_event_base) {
@@ -493,11 +505,14 @@ static void vdagent_x11_handle_event(struct vdagent_x11 *x11, XEvent event)
     switch (event.type) {
     case ConfigureNotify:
         // TODO: handle CrtcConfigureNotify, OutputConfigureNotify can be ignored.
-        if (event.xconfigure.window != x11->root_window[0])
+        for (i = 0; i < x11->screen_count; i++)
+            if (event.xconfigure.window == x11->root_window[i])
+                break;
+        if (i == x11->screen_count)
             break;
 
         handled = 1;
-        vdagent_x11_randr_handle_root_size_change(x11,
+        vdagent_x11_randr_handle_root_size_change(x11, i,
                 event.xconfigure.width, event.xconfigure.height);
         break;
     case MappingNotify: