XdgPopup: send configure after initial commit

Currently we send the first configure for xdg popups before the popup
has made its initial commit. This is incorrect according to the protocol
and may confuse clients.

 river/XdgPopup.zig | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/river/XdgPopup.zig b/river/XdgPopup.zig
index 5198e9b..fd82fbe 100644
--- a/river/XdgPopup.zig
+++ b/river/XdgPopup.zig
@@ -35,6 +35,7 @@ root: *wlr.SceneTree,
 tree: *wlr.SceneTree,
 
 destroy: wl.Listener(void) = wl.Listener(void).init(handleDestroy),
+commit: wl.Listener(*wlr.Surface) = wl.Listener(*wlr.Surface).init(handleCommit),
 new_popup: wl.Listener(*wlr.XdgPopup) = wl.Listener(*wlr.XdgPopup).init(handleNewPopup),
 reposition: wl.Listener(void) = wl.Listener(void).init(handleReposition),
 
@@ -54,22 +55,30 @@ pub fn create(
     };
 
     wlr_xdg_popup.base.events.destroy.add(&xdg_popup.destroy);
+    wlr_xdg_popup.base.surface.events.commit.add(&xdg_popup.commit);
     wlr_xdg_popup.base.events.new_popup.add(&xdg_popup.new_popup);
     wlr_xdg_popup.events.reposition.add(&xdg_popup.reposition);
-
-    handleReposition(&xdg_popup.reposition);
 }
 
 fn handleDestroy(listener: *wl.Listener(void)) void {
     const xdg_popup: *XdgPopup = @fieldParentPtr("destroy", listener);
 
     xdg_popup.destroy.link.remove();
+    xdg_popup.commit.link.remove();
     xdg_popup.new_popup.link.remove();
     xdg_popup.reposition.link.remove();
 
     util.gpa.destroy(xdg_popup);
 }
 
+fn handleCommit(listener: *wl.Listener(*wlr.Surface), _: *wlr.Surface) void {
+    const xdg_popup: *XdgPopup = @fieldParentPtr("commit", listener);
+
+    if (xdg_popup.wlr_xdg_popup.base.initial_commit) {
+        handleReposition(&xdg_popup.reposition);
+    }
+}
+
 fn handleNewPopup(listener: *wl.Listener(*wlr.XdgPopup), wlr_xdg_popup: *wlr.XdgPopup) void {
     const xdg_popup: *XdgPopup = @fieldParentPtr("new_popup", listener);