core: implement flush and poll

src/core/linux/Wayland.zig

@@ -49,6 +49,7 @@ state: *Core,
 core: *Core,
 title: [:0]const u8,
 size: *Core.Size,
+pending_size: ?Core.Size = null,
 surface_descriptor: *gpu.Surface.DescriptorFromWaylandSurface,
 configured: bool = false,
 
@@ -178,6 +179,27 @@ pub fn deinit(
 }
 
 pub fn update(wl: *Wayland) !void {
+    while (wl.libwaylandclient.wl_display_flush(wl.display) == -1) {
+        if (std.posix.errno(-1) == std.posix.E.AGAIN) {
+            log.err("flush error", .{});
+            return error.FlushError;
+        }
+        var pollfd = [_]std.posix.pollfd{
+            std.posix.pollfd{
+                .fd = wl.libwaylandclient.wl_display_get_fd(wl.display),
+                .events = std.posix.POLL.OUT,
+                .revents = 0,
+            },
+        };
+        while (try std.posix.poll(&pollfd, 1) == -1) {
+            const errno = std.posix.errno(-1);
+            if (errno == std.posix.E.INTR or errno == std.posix.E.AGAIN) {
+                log.err("poll error", .{});
+                return error.PollError;
+            }
+        }
+    }
+
     _ = wl.libwaylandclient.wl_display_roundtrip(wl.display);
 
     wl.core.input.tick();
@@ -716,6 +738,10 @@ const xdg_surface_listener = struct {
             wl.configured = true;
         }
 
+        if (wl.pending_size) |pending_size| {
+            wl.size.* = pending_size;
+            wl.pending_size = null;
+        }
         setContentAreaOpaque(wl, wl.size.*);
     }
 
@@ -733,7 +759,7 @@ const xdg_toplevel_listener = struct {
         _ = states;
 
         if (width > 0 and height > 0) {
-            wl.size.* = .{ .width = @intCast(width), .height = @intCast(height) };
+            wl.pending_size = .{ .width = @intCast(width), .height = @intCast(height) };
         }
     }