Refactoring resizing into state machine.

- Fixes MSTSC resizing (with RFX as well).
- Queue system so that resizes are processed when XRDP and the X server
are ready, not immediately.
- Deletes and recreates the encoder (RFX fix)
- Introduces a dynamic_monitor_description struct that is used for the
queue system.
- Fix some lines previously introduced by the original resizing code to
be 80 chars long, as is the standard for XRDP.

5 files changed, 466 insertions, 195 deletions

diff --git a/xrdp/xrdp.h b/xrdp/xrdp.h
index 88ec8814..d1ae20fb 100644
--- a/xrdp/xrdp.h
+++ b/xrdp/xrdp.h
@@ -147,8 +147,12 @@ xrdp_wm_get_wait_objs(struct xrdp_wm *self, tbus *robjs, int *rc,
                       tbus *wobjs, int *wc, int *timeout);
 int
 xrdp_wm_check_wait_objs(struct xrdp_wm *self);
+const char *
+xrdp_wm_login_state_to_str(enum wm_login_state login_state);
 int
 xrdp_wm_set_login_state(struct xrdp_wm *self, enum wm_login_state login_state);
+int
+xrdp_wm_can_resize(struct xrdp_wm *self);
 void
 xrdp_wm_mod_connect_done(struct xrdp_wm *self, int status);
 
@@ -397,18 +401,12 @@ xrdp_bitmap_compress(char *in_data, int width, int height,
 
 /* xrdp_mm.c */
 
-struct dynamic_monitor_layout
+struct display_control_monitor_layout_data
 {
-    int flags;
-    int left;
-    int top;
-    int width;
-    int height;
-    int physical_width;
-    int physical_height;
-    int orientation;
-    int desktop_scale_factor;
-    int device_scale_factor;
+    struct display_size_description description;
+    enum display_resize_state state;
+    int last_state_update_timestamp;
+    int start_time;
 };
 
 int
diff --git a/xrdp/xrdp_mm.c b/xrdp/xrdp_mm.c
index 3d65675a..89aa108c 100644
--- a/xrdp/xrdp_mm.c
+++ b/xrdp/xrdp_mm.c
@@ -43,6 +43,7 @@
 
 #include "xrdp_encoder.h"
 #include "xrdp_sockets.h"
+#include <limits.h>
 
 
 /* Forward declarations */
@@ -65,6 +66,8 @@ struct xrdp_mm *
 xrdp_mm_create(struct xrdp_wm *owner)
 {
     struct xrdp_mm *self;
+    char buf[1024];
+    int pid;
 
     self = (struct xrdp_mm *)g_malloc(sizeof(struct xrdp_mm), 1);
     self->wm = owner;
@@ -72,6 +75,14 @@ xrdp_mm_create(struct xrdp_wm *owner)
     self->login_names->auto_free = 1;
     self->login_values = list_create();
     self->login_values->auto_free = 1;
+    self->resize_queue = list_create();
+    self->resize_queue->auto_free = 1;
+
+    pid = g_getpid();
+    /* setup wait objects for signalling */
+    g_snprintf(buf, sizeof(buf), "xrdp_%8.8x_resize_ready", pid);
+    self->resize_ready = g_create_wait_obj(buf);
+    self->resize_data = NULL;
 
     LOG_DEVEL(LOG_LEVEL_INFO, "xrdp_mm_create: bpp %d mcs_connection_type %d "
               "jpeg_codec_id %d v3_codec_id %d rfx_codec_id %d "
@@ -165,6 +176,9 @@ xrdp_mm_delete(struct xrdp_mm *self)
     self->sesman_trans = 0;
     list_delete(self->login_names);
     list_delete(self->login_values);
+    list_delete(self->resize_queue);
+    g_free(self->resize_data);
+    g_delete_wait_obj(self->resize_ready);
     g_free(self);
 }
 
@@ -969,7 +983,8 @@ dynamic_monitor_open_response(intptr_t id, int chan_id, int creation_status)
     struct stream *s;
     int bytes;
 
-    LOG_DEVEL(LOG_LEVEL_TRACE, "dynamic_monitor_open_response: chan_id %d creation_status 0x%8.8x", chan_id, creation_status);
+    LOG_DEVEL(LOG_LEVEL_TRACE, "dynamic_monitor_open_response: chan_id %d "
+              "creation_status 0x%8.8x", chan_id, creation_status);
     if (creation_status != 0)
     {
         LOG(LOG_LEVEL_ERROR, "dynamic_monitor_open_response: error");
@@ -1031,207 +1046,386 @@ sync_dynamic_monitor_data(struct xrdp_wm *wm,
              MAXIMUM_MONITOR_SIZE);
 }
 
+int
+advance_resize_state_machine(struct xrdp_mm *mm,
+                             enum display_resize_state new_state)
+{
+    struct display_control_monitor_layout_data *description = mm->resize_data;
+    LOG_DEVEL(LOG_LEVEL_INFO,
+              "advance_resize_state_machine:"
+              " Processing resize to: %d x %d."
+              " Advancing state from %s to %s."
+              " Previous state took %d MS.",
+              description->description.session_width,
+              description->description.session_height,
+              XRDP_DISPLAY_RESIZE_STATE_TO_STR(description->state),
+              XRDP_DISPLAY_RESIZE_STATE_TO_STR(new_state),
+              g_time3() - description->last_state_update_timestamp);
+    description->state = new_state;
+    description->last_state_update_timestamp = g_time3();
+    g_set_wait_obj(mm->resize_ready);
+    return 0;
+}
+
 /******************************************************************************/
 static int
-process_dynamic_monitor_description(struct xrdp_wm *wm,
-                                    struct display_size_description *description)
+dynamic_monitor_data(intptr_t id, int chan_id, char *data, int bytes)
 {
     int error = 0;
-    struct xrdp_mm *mm = wm->mm;
-    struct xrdp_mod *module = mm->mod;
+    struct stream ls;
+    struct stream *s;
+    int msg_type;
+    int msg_length;
+    struct xrdp_process *pro;
+    struct xrdp_wm *wm;
+    int monitor_layout_size;
+    struct display_size_description *display_size_data;
 
-    LOG_DEVEL(LOG_LEVEL_TRACE, "process_dynamic_monitor_description:");
+    LOG_DEVEL(LOG_LEVEL_TRACE, "dynamic_monitor_data:");
+    pro = (struct xrdp_process *) id;
+    wm = pro->wm;
 
     if (wm->client_info->suppress_output == 1)
     {
-        LOG(LOG_LEVEL_ERROR,
-            "process_dynamic_monitor_description:"
-            " Not allowing resize. Suppress output is active.");
-        return 0;
-    }
-    if (description == NULL)
-    {
-        LOG_DEVEL(LOG_LEVEL_ERROR,
-                  "process_dynamic_monitor_description:"
-                  " description is null.");
-        return 0;
+        LOG(LOG_LEVEL_INFO, "dynamic_monitor_data: Not allowing resize."
+            " Suppress output is active.");
+        return error;
     }
-    if (description->session_width <= 0 || description->session_height <= 0)
+
+    g_memset(&ls, 0, sizeof(ls));
+    ls.data = data;
+    ls.p = ls.data;
+    ls.size = bytes;
+    ls.end = ls.data + bytes;
+    s = &ls;
+    in_uint32_le(s, msg_type);
+    in_uint32_le(s, msg_length);
+    LOG_DEVEL(LOG_LEVEL_DEBUG,
+              "dynamic_monitor_data: msg_type %d msg_length %d",
+              msg_type, msg_length);
+
+    if (msg_type != DISPLAYCONTROL_PDU_TYPE_MONITOR_LAYOUT
+            && msg_length >= 0)
     {
-        LOG(LOG_LEVEL_ERROR,
-            "process_dynamic_monitor_description: Not allowing resize due to"
-            " invalid dimensions (w: %d x h: %d)",
-            description->session_width, description->session_height);
+        // Unsupported message types
+        switch (msg_type)
+        {
+            case DISPLAYCONTROL_PDU_TYPE_CAPS:
+                LOG(LOG_LEVEL_ERROR, "dynamic_monitor_data: Received"
+                    " DISPLAYCONTROL_PDU_TYPE_CAPS. Per MS-RDPEDISP 2.2.2.1,"
+                    " this is a server-to-client message, client should never"
+                    " send this. Ignoring message");
+                break;
+            default:
+                LOG(LOG_LEVEL_ERROR, "dynamic_monitor_data: Received neither"
+                    " nor DISPLAYCONTROL_PDU_TYPE_CAPS. Ignoring message.");
+                break;
+        }
         return 0;
     }
-    if (description->session_width
-            == wm->client_info->display_sizes.session_width
-            && description->session_height
-            == wm->client_info->display_sizes.session_height)
+    in_uint32_le(s, monitor_layout_size);
+    if (monitor_layout_size != 40)
     {
-        LOG(LOG_LEVEL_WARNING, "process_dynamic_monitor_description:"
-            " Not resizing. Already this size. (w: %d x h: %d)",
-            description->session_width,
-            description->session_height);
-        sync_dynamic_monitor_data(wm, description);
-        return 0;
+        /* 2.2.2.2 DISPLAYCONTROL_MONITOR_LAYOUT_PDU */
+        LOG(LOG_LEVEL_ERROR, "dynamic_monitor_data: monitor_layout_size"
+            " is %d. Per spec ([MS-RDPEDISP] 2.2.2.2"
+            " DISPLAYCONTROL_MONITOR_LAYOUT_PDU) it must be 40.",
+            monitor_layout_size);
+        return 1;
     }
 
-    // TODO: Unify this logic with server_reset
-    error = libxrdp_reset(wm->session,
-                          description->session_width,
-                          description->session_height,
-                          wm->screen->bpp);
-    if (error != 0)
-    {
-        LOG_DEVEL(LOG_LEVEL_ERROR,
-                  "process_dynamic_monitor_description:"
-                  " libxrdp_reset failed %d", error);
-        return error;
-    }
-    /* reset cache */
-    error = xrdp_cache_reset(wm->cache, wm->client_info);
-    if (error != 0)
+    display_size_data = (struct display_size_description *)
+                        g_malloc(sizeof(struct display_size_description), 1);
+    if (!display_size_data)
     {
-        LOG_DEVEL(LOG_LEVEL_ERROR,
-                  "process_dynamic_monitor_description: xrdp_cache_reset"
-                  " failed %d", error);
-        return error;
+        return 1;
     }
-    /* load some stuff */
-    error = xrdp_wm_load_static_colors_plus(wm, 0);
-    if (error != 0)
+    error = libxrdp_process_monitor_stream(s, display_size_data, 1);
+    if (error)
     {
-        LOG_DEVEL(LOG_LEVEL_ERROR, "process_dynamic_monitor_description:"
-                  " xrdp_wm_load_static_colors_plus failed %d", error);
+        LOG(LOG_LEVEL_ERROR, "dynamic_monitor_data:"
+            " libxrdp_process_monitor_stream"
+            " failed with error %d.", error);
+        g_free(display_size_data);
         return error;
     }
+    list_add_item(wm->mm->resize_queue, (tintptr)display_size_data);
+    g_set_wait_obj(wm->mm->resize_ready);
+    LOG(LOG_LEVEL_DEBUG, "dynamic_monitor_data:"
+        " received width %d, received height %d.", display_size_data->session_width, display_size_data->session_height);
+    return 0;
+}
 
-    error = xrdp_wm_load_static_pointers(wm);
-    if (error != 0)
+/******************************************************************************/
+static int
+advance_error(int error,
+              struct xrdp_mm *mm)
+{
+    advance_resize_state_machine(mm, WMRZ_ERROR);
+    return error;
+}
+
+/******************************************************************************/
+static int
+process_display_control_monitor_layout_data(struct xrdp_wm *wm)
+{
+    int error = 0;
+    struct xrdp_mm *mm;
+    struct xrdp_mod *module;
+
+    LOG_DEVEL(LOG_LEVEL_TRACE, "process_display_control_monitor_layout_data:");
+
+    if (wm == NULL)
     {
-        LOG_DEVEL(LOG_LEVEL_ERROR, "process_dynamic_monitor_description:"
-                  " xrdp_wm_load_static_pointers failed %d", error);
-        return error;
+        return 1;
     }
-    /* resize the main window */
-    error = xrdp_bitmap_resize(wm->screen,
-                               description->session_width,
-                               description->session_height);
-    if (error != 0)
+    mm = wm->mm;
+    if (mm == NULL)
     {
-        LOG_DEVEL(LOG_LEVEL_ERROR, "process_dynamic_monitor_description:"
-                  " xrdp_bitmap_resize failed %d", error);
-        return error;
+        return 1;
     }
-    /* redraw */
-    error = xrdp_bitmap_invalidate(wm->screen, 0);
-    if (error != 0)
+    module = mm->mod;
+    if (module == NULL)
     {
-        LOG_DEVEL(LOG_LEVEL_ERROR,
-                  "process_dynamic_monitor_description:"
-                  " xrdp_bitmap_invalidate failed %d", error);
-        return error;
+        return 1;
     }
 
-    if (module != 0)
+    if (!xrdp_wm_can_resize(wm))
     {
-        error = module->mod_server_version_message(module);
-        if (error != 0)
-        {
-            LOG_DEVEL(LOG_LEVEL_ERROR, "process_dynamic_monitor_description:"
-                      " mod_server_version_message failed %d", error);
-            return error;
-        }
-        error = module->mod_server_monitor_resize(
-                    module,
-                    description->session_width,
-                    description->session_height);
-        if (error != 0)
-        {
-            LOG_DEVEL(LOG_LEVEL_ERROR, "process_dynamic_monitor_description:"
-                      "mod_server_monitor_resize failed %d", error);
-            return error;
-        }
-        error = module->mod_server_monitor_full_invalidate(
-                    module,
-                    description->session_width,
-                    description->session_height);
-        if (error != 0)
-        {
-            LOG_DEVEL(LOG_LEVEL_ERROR, "process_dynamic_monitor_description:"
-                      "mod_server_monitor_full_invalidate failed %d", error);
-            return error;
-        }
+        return 0;
     }
 
-    // Need to recreate the encoder for connections that use it.
-    if (mm->encoder != NULL)
-    {
-        xrdp_encoder_delete(mm->encoder);
-        mm->encoder = NULL;
-    }
-    if (mm->encoder == NULL)
+    struct display_control_monitor_layout_data *description
+            = mm->resize_data;
+    const unsigned int desc_width = description->description.session_width;
+    const unsigned int desc_height = description->description.session_height;
+
+    switch (description->state)
     {
-        mm->encoder = xrdp_encoder_create(mm);
-    }
+        case WMRZ_ENCODER_DELETE:
+            // Disable the encoder until the resize is complete.
+            if (mm->encoder != NULL)
+            {
+                xrdp_encoder_delete(mm->encoder);
+                mm->encoder = NULL;
+            }
+            advance_resize_state_machine(mm, WMRZ_SERVER_MONITOR_RESIZE);
+            break;
+        case WMRZ_SERVER_MONITOR_RESIZE:
+            error = module->mod_server_monitor_resize(
+                        module, desc_width, desc_height);
+            if (error != 0)
+            {
+                LOG_DEVEL(LOG_LEVEL_INFO,
+                          "process_display_control_monitor_layout_data:"
+                          " mod_server_monitor_resize failed %d", error);
+                return advance_error(error, mm);
+            }
+            advance_resize_state_machine(mm, WMRZ_SERVER_VERSION_MESSAGE);
+            break;
+        case WMRZ_SERVER_VERSION_MESSAGE:
+            error = module->mod_server_version_message(module);
+            if (error != 0)
+            {
+                LOG_DEVEL(LOG_LEVEL_INFO,
+                          "process_display_control_monitor_layout_data:"
+                          " mod_server_version_message failed %d", error);
+                return advance_error(error, mm);
+            }
+            advance_resize_state_machine(mm, WMRZ_XRDP_CORE_RESIZE);
+            break;
+        case WMRZ_XRDP_CORE_RESIZE:
+            // TODO: Unify this logic with server_reset
+            error = libxrdp_reset(
+                        wm->session, desc_width, desc_height, wm->screen->bpp);
+            if (error != 0)
+            {
+                LOG_DEVEL(LOG_LEVEL_INFO,
+                          "process_display_control_monitor_layout_data:"
+                          " libxrdp_reset failed %d", error);
+                return advance_error(error, mm);
+            }
+            /* reset cache */
+            error = xrdp_cache_reset(wm->cache, wm->client_info);
+            if (error != 0)
+            {
+                LOG_DEVEL(LOG_LEVEL_INFO,
+                          "process_display_control_monitor_layout_data:"
+                          " xrdp_cache_reset failed %d", error);
+                return advance_error(error, mm);
+            }
+            /* load some stuff */
+            error = xrdp_wm_load_static_colors_plus(wm, 0);
+            if (error != 0)
+            {
+                LOG_DEVEL(LOG_LEVEL_INFO,
+                          "process_display_control_monitor_layout_data:"
+                          " xrdp_wm_load_static_colors_plus failed %d", error);
+                return advance_error(error, mm);
+            }
 
-    sync_dynamic_monitor_data(wm, description);
+            error = xrdp_wm_load_static_pointers(wm);
+            if (error != 0)
+            {
+                LOG_DEVEL(LOG_LEVEL_INFO,
+                          "process_display_control_monitor_layout_data:"
+                          " xrdp_wm_load_static_pointers failed %d", error);
+                return advance_error(error, mm);
+            }
+            /* resize the main window */
+            error = xrdp_bitmap_resize(
+                        wm->screen, desc_width, desc_height);
+            if (error != 0)
+            {
+                LOG_DEVEL(LOG_LEVEL_INFO,
+                          "process_display_control_monitor_layout_data:"
+                          " xrdp_bitmap_resize failed %d", error);
+                return advance_error(error, mm);
+            }
+            sync_dynamic_monitor_data(wm, &(description->description));
+            advance_resize_state_machine(mm, WMRZ_ENCODER_CREATE);
+            break;
+        case WMRZ_ENCODER_CREATE:
+            if (mm->encoder == NULL)
+            {
+                mm->encoder = xrdp_encoder_create(mm);
+            }
+            advance_resize_state_machine(mm, WMRZ_SERVER_INVALIDATE);
+            break;
+        case WMRZ_SERVER_INVALIDATE:
+            /* redraw */
+            error = xrdp_bitmap_invalidate(wm->screen, 0);
+            if (error != 0)
+            {
+                LOG_DEVEL(LOG_LEVEL_INFO,
+                          "process_display_control_monitor_layout_data:"
+                          " xrdp_bitmap_invalidate failed %d", error);
+                return advance_error(error, mm);
+            }
+            if (module != 0)
+            {
+                // Ack all frames to speed up resize.
+                module->mod_frame_ack(module, 0, INT_MAX);
+            }
+            advance_resize_state_machine(mm, WMRZ_COMPLETE);
+            break;
+        default:
+            break;
+    }
     return 0;
 }
 
 /******************************************************************************/
 static int
-dynamic_monitor_data(intptr_t id, int chan_id, char *data, int bytes)
+dynamic_monitor_process_queue(struct xrdp_mm *self)
 {
-    int error = 0;
-    struct stream ls;
-    struct stream *s;
-    int msg_type;
-    int msg_length;
-    struct xrdp_process *pro;
-    struct xrdp_wm *wm;
-    int monitor_layout_size;
+    LOG_DEVEL(LOG_LEVEL_TRACE, "dynamic_monitor_process_queue:");
 
-    LOG_DEVEL(LOG_LEVEL_TRACE, "dynamic_monitor_data:");
-    pro = (struct xrdp_process *) id;
-    wm = pro->wm;
-    g_memset(&ls, 0, sizeof(ls));
-    ls.data = data;
-    ls.p = ls.data;
-    ls.size = bytes;
-    ls.end = ls.data + bytes;
-    s = &ls;
-    in_uint32_le(s, msg_type);
-    in_uint32_le(s, msg_length);
-    LOG(LOG_LEVEL_DEBUG, "dynamic_monitor_data: msg_type %d msg_length %d",
-        msg_type, msg_length);
-
-    if (msg_type != DISPLAYCONTROL_PDU_TYPE_MONITOR_LAYOUT)
+    if (self == 0)
     {
         return 0;
     }
-    in_uint32_le(s, monitor_layout_size);
-    if (monitor_layout_size != 40)
+
+    struct xrdp_wm *wm = self->wm;
+
+    if (!xrdp_wm_can_resize(wm))
     {
-        LOG(LOG_LEVEL_ERROR, "dynamic_monitor_data: monitor_layout_size"
-            " is %d. Per spec ([MS-RDPEDISP] 2.2.2.2"
-            " DISPLAYCONTROL_MONITOR_LAYOUT_PDU) it must be 40.",
-            monitor_layout_size);
-        return 1;
+        return 0;
     }
 
-    struct display_size_description *description =
-        (struct display_size_description *)
-        g_malloc(sizeof(struct display_size_description), 1);
+    if (self->resize_data == NULL)
+    {
+        if  (self->resize_queue->count <= 0)
+        {
+            LOG_DEVEL(LOG_LEVEL_DEBUG, "Resize queue is empty.");
+            return 0;
+        }
+        LOG_DEVEL(LOG_LEVEL_DEBUG, "dynamic_monitor_process_queue: Queue is"
+                  " not empty. Filling out description.");
+        const struct display_size_description *queue_head =
+            (struct display_size_description *)
+            list_get_item(self->resize_queue, 0);
+
+        const int invalid_dimensions = queue_head->session_width <= 0
+                                       || queue_head->session_height <= 0;
+
+        if (invalid_dimensions)
+        {
+            LOG(LOG_LEVEL_DEBUG,
+                "dynamic_monitor_process_queue: Not allowing"
+                " resize due to invalid dimensions (w: %d x h: %d)",
+                queue_head->session_width,
+                queue_head->session_height);
+        }
+
+        const struct display_size_description *current_size
+                = &wm->client_info->display_sizes;
+
+        const int already_this_size = queue_head->session_width
+                                      == current_size->session_width
+                                      && queue_head->session_height
+                                      == current_size->session_height;
+
+        if (already_this_size)
+        {
+            LOG(LOG_LEVEL_DEBUG,
+                "dynamic_monitor_process_queue: Not resizing."
+                " Already this size. (w: %d x h: %d)",
+                queue_head->session_width,
+                queue_head->session_height);
+        }
+
+        if (!invalid_dimensions && !already_this_size)
+        {
+            const int LAYOUT_DATA_SIZE =
+                sizeof(struct display_control_monitor_layout_data);
+            self->resize_data = (struct display_control_monitor_layout_data *)
+                                g_malloc(LAYOUT_DATA_SIZE, 1);
+            g_memcpy(&(self->resize_data->description), queue_head,
+                     sizeof(struct display_size_description));
+            const int time = g_time3();
+            self->resize_data->start_time = time;
+            self->resize_data->last_state_update_timestamp = time;
+            advance_resize_state_machine(self, WMRZ_ENCODER_DELETE);
+        }
+        else
+        {
+            g_set_wait_obj(self->resize_ready);
+        }
+        list_remove_item(self->resize_queue, 0);
+        return 0;
+    }
+    else
+    {
+        LOG_DEVEL(LOG_LEVEL_DEBUG, "dynamic_monitor_process_queue:"
+                  " Resize data is not null.");
+    }
 
-    error = libxrdp_process_monitor_stream(s, description, 1);
-    if (error == 0)
+    if (self->resize_data->state == WMRZ_COMPLETE)
     {
-        error = process_dynamic_monitor_description(wm, description);
+        LOG(LOG_LEVEL_INFO, "dynamic_monitor_process_queue: Clearing"
+            " completed resize (w: %d x h: %d). It took %d milliseconds.",
+            self->resize_data->description.session_width,
+            self->resize_data->description.session_height,
+            g_time3() - self->resize_data->start_time);
+        g_set_wait_obj(self->resize_ready);
     }
-    g_free(description);
-    return error;
+    else if (self->resize_data->state == WMRZ_ERROR)
+    {
+        LOG(LOG_LEVEL_INFO, "dynamic_monitor_process_queue: Clearing"
+            " failed request to resize to: (w: %d x h: %d)",
+            self->resize_data->description.session_width,
+            self->resize_data->description.session_height);
+        g_set_wait_obj(self->resize_ready);
+    }
+    else
+    {
+        // No errors, process it!
+        return process_display_control_monitor_layout_data(self->wm);
+    }
+    g_free(self->resize_data);
+    self->resize_data = NULL;
+    return 0;
 }
 
 /******************************************************************************/
@@ -1266,6 +1460,7 @@ dynamic_monitor_initialize(struct xrdp_mm *self)
 int
 xrdp_mm_drdynvc_up(struct xrdp_mm *self)
 {
+    struct display_control_monitor_layout_data *ignore_marker;
     const char *enable_dynamic_resize;
     int error = 0;
 
@@ -1279,11 +1474,12 @@ xrdp_mm_drdynvc_up(struct xrdp_mm *self)
             !g_text2bool(enable_dynamic_resize))
     {
         LOG(LOG_LEVEL_INFO, "User has disabled dynamic resizing.");
+        return error;
     }
-    else
-    {
-        error = dynamic_monitor_initialize(self);
-    }
+    ignore_marker = (struct display_control_monitor_layout_data *)
+                    g_malloc(sizeof(struct display_control_monitor_layout_data), 1);
+    list_add_item(self->resize_queue, (tintptr)ignore_marker);
+    error = dynamic_monitor_initialize(self);
     return error;
 }
 
@@ -1317,7 +1513,8 @@ xrdp_mm_drdynvc_open_response(intptr_t id, int chan_id, int creation_status)
     struct xrdp_process *pro;
     int chansrv_chan_id;
 
-    LOG_DEVEL(LOG_LEVEL_DEBUG, "xrdp_mm_drdynvc_open_response: chan_id %d creation_status %d",
+    LOG_DEVEL(LOG_LEVEL_DEBUG, "xrdp_mm_drdynvc_open_response: "
+              " chan_id %d creation_status %d",
               chan_id, creation_status);
     pro = (struct xrdp_process *) id;
     wm = pro->wm;
@@ -2684,6 +2881,11 @@ xrdp_mm_get_wait_objs(struct xrdp_mm *self,
         read_objs[(*rcount)++] = self->encoder->xrdp_encoder_event_processed;
     }
 
+    if (self->resize_queue != 0)
+    {
+        read_objs[(*rcount)++] = self->resize_ready;
+    }
+
     return rv;
 }
 
@@ -2908,6 +3110,12 @@ xrdp_mm_check_wait_objs(struct xrdp_mm *self)
         }
     }
 
+    if (g_is_wait_obj_set(self->resize_ready))
+    {
+        g_reset_wait_obj(self->resize_ready);
+        dynamic_monitor_process_queue(self);
+    }
+
     if (self->encoder != NULL)
     {
         if (g_is_wait_obj_set(self->encoder->xrdp_encoder_event_processed))
@@ -3557,7 +3765,8 @@ server_reset(struct xrdp_mod *mod, int width, int height, int bpp)
     if (wm->client_info->display_sizes.session_width == (uint32_t)width &&
             wm->client_info->display_sizes.session_height == (uint32_t)height &&
             wm->client_info->bpp == bpp &&
-            (wm->client_info->display_sizes.monitorCount == 0 || wm->client_info->multimon == 0))
+            (wm->client_info->display_sizes.monitorCount == 0 ||
+             wm->client_info->multimon == 0))
     {
         return 0;
     }
diff --git a/xrdp/xrdp_types.h b/xrdp/xrdp_types.h
index d800370c..41d109a0 100644
--- a/xrdp/xrdp_types.h
+++ b/xrdp/xrdp_types.h
@@ -311,6 +311,30 @@ enum mm_connect_state
     MMCS_DONE
 };
 
+enum display_resize_state
+{
+    WMRZ_ENCODER_DELETE = 0,
+    WMRZ_SERVER_MONITOR_RESIZE,
+    WMRZ_SERVER_VERSION_MESSAGE,
+    WMRZ_XRDP_CORE_RESIZE,
+    WMRZ_ENCODER_CREATE,
+    WMRZ_SERVER_INVALIDATE,
+    WMRZ_COMPLETE,
+    WMRZ_ERROR
+};
+
+#define XRDP_DISPLAY_RESIZE_STATE_TO_STR(status) \
+    ((status) == WMRZ_ENCODER_DELETE ? "WMRZ_ENCODER_DELETE" : \
+     (status) == WMRZ_SERVER_MONITOR_RESIZE ? "WMRZ_SERVER_MONITOR_RESIZE" : \
+     (status) == WMRZ_SERVER_VERSION_MESSAGE ? "WMRZ_SERVER_VERSION_MESSAGE" : \
+     (status) == WMRZ_XRDP_CORE_RESIZE ? "WMRZ_XRDP_CORE_RESIZE" : \
+     (status) == WMRZ_ENCODER_CREATE ? "WMRZ_ENCODER_CREATE" : \
+     (status) == WMRZ_SERVER_INVALIDATE ? "WMRZ_SERVER_INVALIDATE" : \
+     (status) == WMRZ_COMPLETE ? "WMRZ_COMPLETE" : \
+     (status) == WMRZ_ERROR ? "WMRZ_ERROR" : \
+     "unknown" \
+    )
+
 struct xrdp_mm
 {
     struct xrdp_wm *wm; /* owner */
@@ -344,6 +368,11 @@ struct xrdp_mm
     int cs2xr_cid_map[256];
     int xr2cr_cid_map[256];
     int dynamic_monitor_chanid;
+
+    /* Resize on-the-fly control */
+    struct display_control_monitor_layout_data *resize_data;
+    struct list *resize_queue;
+    tbus resize_ready;
 };
 
 struct xrdp_key_info
diff --git a/xrdp/xrdp_wm.c b/xrdp/xrdp_wm.c
index 6d5f1b89..ff37deb7 100644
--- a/xrdp/xrdp_wm.c
+++ b/xrdp/xrdp_wm.c
@@ -2230,9 +2230,8 @@ xrdp_wm_check_wait_objs(struct xrdp_wm *self)
 }
 
 /*****************************************************************************/
-
-static const char *
-wm_login_state_to_str(enum wm_login_state login_state)
+const char *
+xrdp_wm_login_state_to_str(enum wm_login_state login_state)
 {
     const char *result = "unknown";
     /* Use a switch for this, as some compilers will warn about missing states
@@ -2266,10 +2265,24 @@ int
 xrdp_wm_set_login_state(struct xrdp_wm *self, enum wm_login_state login_state)
 {
     LOG(LOG_LEVEL_DEBUG, "Login state change request %s -> %s",
-        wm_login_state_to_str(self->login_state),
-        wm_login_state_to_str(login_state));
+        xrdp_wm_login_state_to_str(self->login_state),
+        xrdp_wm_login_state_to_str(login_state));
 
     self->login_state = login_state;
     g_set_wait_obj(self->login_state_event);
     return 0;
 }
+
+int
+xrdp_wm_can_resize(struct xrdp_wm *self)
+{
+    if (self->login_state != WMLS_CLEANUP
+            && self->login_state != WMLS_INACTIVE)
+    {
+        LOG(LOG_LEVEL_INFO, "Not allowing resize. Login in progress.");
+        LOG_DEVEL(LOG_LEVEL_INFO,
+                  "State is %s", xrdp_wm_login_state_to_str(self->login_state));
+        return 0;
+    }
+    return 1;
+}
diff --git a/xup/xup.c b/xup/xup.c
index cae29100..fcb65d75 100644
--- a/xup/xup.c
+++ b/xup/xup.c
@@ -28,10 +28,12 @@
 #include "string_calls.h"
 
 static int
-send_server_monitor_resize(struct mod *mod, struct stream *s, int width, int height, int bpp);
+send_server_monitor_resize(
+    struct mod *mod, struct stream *s, int width, int height, int bpp);
 
 static int
-send_server_monitor_full_invalidate(struct mod *mod, struct stream *s, int width, int height);
+send_server_monitor_full_invalidate(
+    struct mod *mod, struct stream *s, int width, int height);
 
 static int
 send_server_version_message(struct mod *v, struct stream *s);
@@ -154,10 +156,15 @@ lib_mod_connect(struct mod *mod)
     mod->server_msg(mod, "started connecting", 0);
 
     /* only support 8, 15, 16, 24, and 32 bpp connections from rdp client */
-    if (mod->bpp != 8 && mod->bpp != 15 && mod->bpp != 16 && mod->bpp != 24 && mod->bpp != 32)
+    if (mod->bpp != 8
+            && mod->bpp != 15
+            && mod->bpp != 16
+            && mod->bpp != 24
+            && mod->bpp != 32)
     {
         mod->server_msg(mod,
-                        "error - only supporting 8, 15, 16, 24, and 32 bpp rdp connections", 0);
+                        "error - only supporting 8, 15, 16, 24, and 32"
+                        " bpp rdp connections", 0);
         return 1;
     }
 
@@ -220,12 +227,14 @@ lib_mod_connect(struct mod *mod)
     if (error == 0)
     {
         /* send screen size message */
-        error = send_server_monitor_resize(mod, s, mod->width, mod->height, mod->bpp);
+        error = send_server_monitor_resize(
+                    mod, s, mod->width, mod->height, mod->bpp);
     }
 
     if (error == 0)
     {
-        error = send_server_monitor_full_invalidate(mod, s, mod->width, mod->height);
+        error = send_server_monitor_full_invalidate(
+                    mod, s, mod->width, mod->height);
     }
 
     free_stream(s);
@@ -1261,7 +1270,8 @@ send_server_version_message(struct mod *mod, struct stream *s)
 /******************************************************************************/
 /* return error */
 static int
-send_server_monitor_resize(struct mod *mod, struct stream *s, int width, int height, int bpp)
+send_server_monitor_resize(
+    struct mod *mod, struct stream *s, int width, int height, int bpp)
 {
     /* send screen size message */
     init_stream(s, 8192);
@@ -1271,8 +1281,9 @@ send_server_monitor_resize(struct mod *mod, struct stream *s, int width, int hei
     out_uint32_le(s, width);
     out_uint32_le(s, height);
     /*
-        TODO: The bpp here is only necessary for initial creation. We should modify XUP to require this
-        only on server initialization, but not on resize. Microsoft's RDP protocol does not support changing
+        TODO: The bpp here is only necessary for initial creation. We should
+        modify XUP to require this only on server initialization, but not on
+        resize. Microsoft's RDP protocol does not support changing
         the bpp on resize.
     */
     out_uint32_le(s, bpp);
@@ -1282,14 +1293,16 @@ send_server_monitor_resize(struct mod *mod, struct stream *s, int width, int hei
     s_pop_layer(s, iso_hdr);
     out_uint32_le(s, len);
     int rv = lib_send_copy(mod, s);
-    LOG_DEVEL(LOG_LEVEL_DEBUG, "send_server_monitor_resize: sent resize message with following properties to xorgxrdp backend "
-              "width=%d, height=%d, bpp=%d, return value=%d",
+    LOG_DEVEL(LOG_LEVEL_DEBUG, "send_server_monitor_resize:"
+              " sent resize message with following properties to"
+              " xorgxrdp backend width=%d, height=%d, bpp=%d, return value=%d",
               width, height, bpp, rv);
     return rv;
 }
 
 static int
-send_server_monitor_full_invalidate(struct mod *mod, struct stream *s, int width, int height)
+send_server_monitor_full_invalidate(
+    struct mod *mod, struct stream *s, int width, int height)
 {
     /* send invalidate message */
     init_stream(s, 8192);
@@ -1309,8 +1322,10 @@ send_server_monitor_full_invalidate(struct mod *mod, struct stream *s, int width
     s_pop_layer(s, iso_hdr);
     out_uint32_le(s, len);
     int rv = lib_send_copy(mod, s);
-    LOG_DEVEL(LOG_LEVEL_DEBUG, "send_server_monitor_full_invalidate: sent invalidate message with following properties to xorgxrdp backend "
-              "width=%d, height=%d, return value=%d",
+    LOG_DEVEL(LOG_LEVEL_DEBUG, "send_server_monitor_full_invalidate:"
+              " sent invalidate message with following"
+              " properties to xorgxrdp backend"
+              " width=%d, height=%d, return value=%d",
               width, height, rv);
     return rv;
 }
@@ -1456,7 +1471,8 @@ lib_mod_process_orders(struct mod *mod, int type, struct stream *s)
             rv = process_server_paint_rect_shmem_ex(mod, s);
             break;
         default:
-            LOG_DEVEL(LOG_LEVEL_WARNING, "lib_mod_process_orders: unknown order type %d", type);
+            LOG_DEVEL(LOG_LEVEL_WARNING,
+                      "lib_mod_process_orders: unknown order type %d", type);
             rv = 0;
             break;
     }
@@ -1523,7 +1539,8 @@ lib_mod_process_message(struct mod *mod, struct stream *s)
         }
         else if (type == 2) /* caps */
         {
-            LOG_DEVEL(LOG_LEVEL_TRACE, "lib_mod_process_message: type 2 len %d", len);
+            LOG_DEVEL(LOG_LEVEL_TRACE,
+                      "lib_mod_process_message: type 2 len %d", len);
             for (index = 0; index < num_orders; index++)
             {
                 phold = s->p;
@@ -1533,7 +1550,9 @@ lib_mod_process_message(struct mod *mod, struct stream *s)
                 switch (type)
                 {
                     default:
-                        LOG_DEVEL(LOG_LEVEL_TRACE, "lib_mod_process_message: unknown cap type %d len %d",
+                        LOG_DEVEL(LOG_LEVEL_TRACE,
+                                  "lib_mod_process_message: unknown"
+                                  " cap type %d len %d",
                                   type, len);
                         break;
                 }
@@ -1661,7 +1680,8 @@ lib_mod_check_wait_objs(struct mod *mod)
 int
 lib_mod_frame_ack(struct mod *amod, int flags, int frame_id)
 {
-    LOG_DEVEL(LOG_LEVEL_TRACE, "lib_mod_frame_ack: flags 0x%8.8x frame_id %d", flags, frame_id);
+    LOG_DEVEL(LOG_LEVEL_TRACE,
+              "lib_mod_frame_ack: flags 0x%8.8x frame_id %d", flags, frame_id);
     send_paint_rect_ex_ack(amod, flags, frame_id);
     return 0;
 }
@@ -1672,7 +1692,8 @@ int
 lib_mod_suppress_output(struct mod *amod, int suppress,
                         int left, int top, int right, int bottom)
 {
-    LOG_DEVEL(LOG_LEVEL_TRACE, "lib_mod_suppress_output: suppress 0x%8.8x left %d top %d "
+    LOG_DEVEL(LOG_LEVEL_TRACE,
+              "lib_mod_suppress_output: suppress 0x%8.8x left %d top %d "
               "right %d bottom %d", suppress, left, top, right, bottom);
     send_suppress_output(amod, suppress, left, top, right, bottom);
     return 0;
@@ -1699,7 +1720,8 @@ mod_init(void)
     mod->mod_frame_ack = lib_mod_frame_ack;
     mod->mod_suppress_output = lib_mod_suppress_output;
     mod->mod_server_monitor_resize = lib_send_server_monitor_resize;
-    mod->mod_server_monitor_full_invalidate = lib_send_server_monitor_full_invalidate;
+    mod->mod_server_monitor_full_invalidate
+        = lib_send_server_monitor_full_invalidate;
     mod->mod_server_version_message = lib_send_server_version_message;
     return (tintptr) mod;
 }