patch 8.0.0299: a window resize is sometimes not taking effect

Problem:    When the GUI window is resized Vim does not always take over the
            new size. (Luchr)
Solution:   Reset new_p_guifont in gui_resize_shell().  Call
            gui_may_resize_shell() in the main loop.
diff --git a/src/gui.c b/src/gui.c
index 87b0839..203035f 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -1459,6 +1459,8 @@
     }
 
 again:
+    new_pixel_width = 0;
+    new_pixel_height = 0;
     busy = TRUE;
 
     /* Flush pending output before redrawing */
@@ -1468,8 +1470,8 @@
     gui.num_rows = (pixel_height - gui_get_base_height()) / gui.char_height;
 
     gui_position_components(pixel_width);
-
     gui_reset_scroll_region();
+
     /*
      * At the "more" and ":confirm" prompt there is no redraw, put the cursor
      * at the last line here (why does it have to be one row too low?).
@@ -1491,17 +1493,22 @@
 
     busy = FALSE;
 
-    /*
-     * We could have been called again while redrawing the screen.
-     * Need to do it all again with the latest size then.
-     */
+    /* We may have been called again while redrawing the screen.
+     * Need to do it all again with the latest size then.  But only if the size
+     * actually changed. */
     if (new_pixel_height)
     {
-	pixel_width = new_pixel_width;
-	pixel_height = new_pixel_height;
-	new_pixel_width = 0;
-	new_pixel_height = 0;
-	goto again;
+	if (pixel_width == new_pixel_width && pixel_height == new_pixel_height)
+	{
+	    new_pixel_width = 0;
+	    new_pixel_height = 0;
+	}
+	else
+	{
+	    pixel_width = new_pixel_width;
+	    pixel_height = new_pixel_height;
+	    goto again;
+	}
     }
 }
 
@@ -1511,18 +1518,10 @@
     void
 gui_may_resize_shell(void)
 {
-    int		h, w;
-
     if (new_pixel_height)
-    {
 	/* careful: gui_resize_shell() may postpone the resize again if we
 	 * were called indirectly by it */
-	w = new_pixel_width;
-	h = new_pixel_height;
-	new_pixel_width = 0;
-	new_pixel_height = 0;
-	gui_resize_shell(w, h);
-    }
+	gui_resize_shell(new_pixel_width, new_pixel_height);
 }
 
     int