win32: Add GdkWin32MessageSource

The source does nothing but run PeekMessage() + DispatchMessage().
But we need it in every thread where we want to use a main loop.

No users yet.

gdk/win32/gdkwin32messagesource.c

@@ -0,0 +1,123 @@
+#include "config.h"
+
+#include "gdkwin32messagesourceprivate.h"
+
+#include "gdkevents.h"
+
+#include <windows.h>
+
+typedef struct _GdkWin32MessageSource GdkWin32MessageSource;
+
+struct _GdkWin32MessageSource
+{
+  GSource source;
+
+  GPollFD poll_fd;
+} ;
+
+static gboolean
+gdk_win32_message_source_prepare (GSource *source,
+		                          int     *timeout)
+{
+  GdkWin32MessageSource *self = (GdkWin32MessageSource *) source;
+  gboolean retval;
+
+  *timeout = -1;
+
+  return GetQueueStatus (QS_ALLINPUT) != 0;
+}
+
+static gboolean
+gdk_win32_message_source_check (GSource *source)
+{
+  GdkWin32MessageSource *self = (GdkWin32MessageSource *) source;
+
+  self->poll_fd.revents = 0;
+
+  return GetQueueStatus (QS_ALLINPUT) != 0;
+}
+
+static gboolean
+gdk_win32_message_source_dispatch (GSource     *source,
+                                   GSourceFunc  callback,
+                                   gpointer     user_data)
+{
+  MSG msg;
+
+  while (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))
+    {
+      TranslateMessage (&msg);
+      DispatchMessage (&msg);
+    }
+  
+  return G_SOURCE_CONTINUE;
+}
+
+static void
+gdk_win32_message_source_finalize (GSource *source)
+{
+#ifdef G_WITH_CYGWIN
+  close (self->poll_fd.fd);
+#endif
+}
+
+static GSourceFuncs gdk_win32_message_source_funcs = {
+  gdk_win32_message_source_prepare,
+  gdk_win32_message_source_check,
+  gdk_win32_message_source_dispatch,
+  gdk_win32_message_source_finalize,
+};
+
+/*
+ * gdk_win32_message_source_new:
+ *
+ * Creates a new source for processing events of the Windows main loop.
+ * 
+ * Returns: The new source
+ */
+GSource *
+gdk_win32_message_source_new (void)
+{
+  GdkWin32MessageSource *self;
+  GSource *source;
+
+  source = g_source_new (&gdk_win32_message_source_funcs, sizeof (GdkWin32MessageSource));
+  g_source_set_static_name (source, "GDK Win32 message source");
+  g_source_set_priority (source, GDK_PRIORITY_EVENTS);
+  
+  self = (GdkWin32MessageSource *) source;
+#ifdef G_WITH_CYGWIN
+  self->poll_fd.fd = open ("/dev/windows", O_RDONLY);
+  if (self->poll_fd.fd == -1)
+    g_error ("can't open \"/dev/windows\": %s", g_strerror (errno));
+#else
+  self->poll_fd.fd = G_WIN32_MSG_HANDLE;
+#endif
+  self->poll_fd.events = G_IO_IN;
+
+  g_source_add_poll (source, &self->poll_fd);
+  g_source_set_can_recurse (source, TRUE);
+
+  return source;
+}
+
+/*
+ * gdk_win32_message_source_add:
+ * @context: (nullable): The context to add the source to
+ *
+ * Adds a message source to the default main context.
+ * 
+ * Returns: the ID (greater than 0) of the event source.
+ */
+guint
+gdk_win32_message_source_add (GMainContext *context)
+{
+  GSource *source;
+  guint id;
+
+  source = gdk_win32_message_source_new ();
+  id = g_source_attach (source, context);
+  g_source_unref (source);
+
+  return id;
+}

gdk/win32/gdkwin32messagesourceprivate.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <glib.h>
+
+GSource *               gdk_win32_message_source_new            (void);
+
+guint                   gdk_win32_message_source_add            (GMainContext   *context);

gdk/win32/meson.build

@@ -33,6 +33,7 @@ gdk_win32_sources = gdk_win32_public_sources + files([
   'gdkvulkancontext-win32.c',
   'gdkwin32cursor.h',
   'gdkwin32display.h',
+  'gdkwin32messagesource.c',
   'gdkwin32keys.h',
 ])