Further improve the reliability of UI element transfer.

A protocol has been implemented between the server and client to acknowledge
each UI_INITIAL_GUI and UI_EXTEND_GUI from the client javascript. This
prevents the internal websocket buffers from becoming flooded when the
number of controls gets too high.

data/js/controls.js

@@ -252,6 +252,13 @@ function start() {
           };
           handleEvent(fauxEvent);
         });
+
+        //If there are more elements in the complete UI, then request them
+        //Note: we subtract 1 from data.controls.length because the controls always
+        //includes the title element
+        if(data.totalcontrols > (data.controls.length - 1)) {
+          websock.send("uiok:" + (data.controls.length - 1));
+        }
         break;
 
       case UI_EXTEND_GUI:
@@ -261,6 +268,11 @@ function start() {
           };
           handleEvent(fauxEvent);
         });
+
+        //Do we need to keep requesting more UI elements?
+        if(data.totalcontrols > data.startindex + (data.controls.length - 1)) {
+          websock.send("uiok:" + (data.startindex + (data.controls.length - 1)));
+        }
         break;
       
       case UI_RELOAD:

data/js/controls.min.js

@@ -8,7 +8,9 @@ function conStatusError(){websockConnected=false;$("#conStatus").removeClass("co
 function handleVisibilityChange(){if(!websockConnected&&!document.hidden){restart();}}
 function start(){document.addEventListener("visibilitychange",handleVisibilityChange,false);if(window.location.port!=""||window.location.port!=80||window.location.port!=443){websock=new WebSocket("ws://"+window.location.hostname+":"+window.location.port+"/ws");}else{websock=new WebSocket("ws://"+window.location.hostname+"/ws");}
 websock.onopen=function(evt){console.log("websock open");$("#conStatus").addClass("color-green");$("#conStatus").text("Connected");websockConnected=true;};websock.onclose=function(evt){console.log("websock close");conStatusError();};websock.onerror=function(evt){console.log(evt);conStatusError();};var handleEvent=function(evt){console.log(evt);var data=JSON.parse(evt.data);var e=document.body;var center="";switch(data.type){case UI_INITIAL_GUI:$("#row").html("");$("#tabsnav").html("");$("#tabscontent").html("");if(data.sliderContinuous){sliderContinuous=data.sliderContinuous;}
-data.controls.forEach(element=>{var fauxEvent={data:JSON.stringify(element),};handleEvent(fauxEvent);});break;case UI_EXTEND_GUI:data.controls.forEach(element=>{var fauxEvent={data:JSON.stringify(element),};handleEvent(fauxEvent);});break;case UI_RELOAD:window.location.reload();break;case UI_TITEL:document.title=data.label;$("#mainHeader").html(data.label);break;case UI_LABEL:case UI_NUMBER:case UI_TEXT_INPUT:case UI_SELECT:case UI_GAUGE:case UI_SEPARATOR:if(data.visible)addToHTML(data);break;case UI_BUTTON:if(data.visible){addToHTML(data);$("#btn"+data.id).on({touchstart:function(e){e.preventDefault();buttonclick(data.id,true);},touchend:function(e){e.preventDefault();buttonclick(data.id,false);},});}
+data.controls.forEach(element=>{var fauxEvent={data:JSON.stringify(element),};handleEvent(fauxEvent);});if(data.totalcontrols>(data.controls.length-1)){websock.send("uiok:"+(data.controls.length-1));}
+break;case UI_EXTEND_GUI:data.controls.forEach(element=>{var fauxEvent={data:JSON.stringify(element),};handleEvent(fauxEvent);});if(data.totalcontrols>data.startindex+(data.controls.length-1)){websock.send("uiok:"+(data.startindex+(data.controls.length-1)));}
+break;case UI_RELOAD:window.location.reload();break;case UI_TITEL:document.title=data.label;$("#mainHeader").html(data.label);break;case UI_LABEL:case UI_NUMBER:case UI_TEXT_INPUT:case UI_SELECT:case UI_GAUGE:case UI_SEPARATOR:if(data.visible)addToHTML(data);break;case UI_BUTTON:if(data.visible){addToHTML(data);$("#btn"+data.id).on({touchstart:function(e){e.preventDefault();buttonclick(data.id,true);},touchend:function(e){e.preventDefault();buttonclick(data.id,false);},});}
 break;case UI_SWITCHER:if(data.visible){addToHTML(data);switcher(data.id,data.value);}
 break;case UI_CPAD:case UI_PAD:if(data.visible){addToHTML(data);$("#pf"+data.id).on({touchstart:function(e){e.preventDefault();padclick(UP,data.id,true);},touchend:function(e){e.preventDefault();padclick(UP,data.id,false);},});$("#pl"+data.id).on({touchstart:function(e){e.preventDefault();padclick(LEFT,data.id,true);},touchend:function(e){e.preventDefault();padclick(LEFT,data.id,false);},});$("#pr"+data.id).on({touchstart:function(e){e.preventDefault();padclick(RIGHT,data.id,true);},touchend:function(e){e.preventDefault();padclick(RIGHT,data.id,false);},});$("#pb"+data.id).on({touchstart:function(e){e.preventDefault();padclick(DOWN,data.id,true);},touchend:function(e){e.preventDefault();padclick(DOWN,data.id,false);},});$("#pc"+data.id).on({touchstart:function(e){e.preventDefault();padclick(CENTER,data.id,true);},touchend:function(e){e.preventDefault();padclick(CENTER,data.id,false);},});}
 break;case UI_SLIDER:if(data.visible){addToHTML(data);rangeSlider(!sliderContinuous);}

src/ESPUI.cpp

@@ -422,7 +422,7 @@ void onWsEvent(
         }
 #endif
 
-        ESPUI.jsonDom(client);
+        ESPUI.jsonDom(0, client);
 
 #if defined(DEBUG_ESPUI)
         if (ESPUI.verbosity)
@@ -442,9 +442,15 @@ void onWsEvent(
             msg += (char)data[i];
         }
 
+        if (msg.startsWith(F("uiok:")))
+        {
+            int idx = msg.substring(msg.indexOf(':') + 1).toInt();
+            ESPUI.jsonDom(idx);
+        } else 
+        {
             uint16_t id = msg.substring(msg.lastIndexOf(':') + 1).toInt();
 
-#if defined(DEBUG_ESPUI)
+    #if defined(DEBUG_ESPUI)
             if (ESPUI.verbosity >= Verbosity::VerboseJSON)
             {
                 Serial.print(F("WS rec: "));
@@ -452,32 +458,32 @@ void onWsEvent(
                 Serial.print(F("WS recognised ID: "));
                 Serial.println(id);
             }
-#endif
+    #endif
 
             Control* c = ESPUI.getControl(id);
 
             if (c == nullptr)
             {
-#if defined(DEBUG_ESPUI)
+    #if defined(DEBUG_ESPUI)
                 if (ESPUI.verbosity)
                 {
                     Serial.print(F("No control found for ID "));
                     Serial.println(id);
                 }
-#endif
+    #endif
 
                 return;
             }
 
             if (c->callback == nullptr)
             {
-#if defined(DEBUG_ESPUI)
+    #if defined(DEBUG_ESPUI)
                 if (ESPUI.verbosity)
                 {
                     Serial.print(F("No callback found for ID "));
                     Serial.println(id);
                 }
-#endif
+    #endif
 
                 return;
             }
@@ -572,12 +578,13 @@ void onWsEvent(
             }
             else
             {
-#if defined(DEBUG_ESPUI)
+    #if defined(DEBUG_ESPUI)
                 if (ESPUI.verbosity)
                 {
                     Serial.println(F("Malformated message from the websocket"));
                 }
-#endif
+    #endif
+            }
         }
     }
     break;
@@ -608,6 +615,8 @@ uint16_t ESPUIClass::addControl(ControlType type, const char* label, const Strin
         iterator->next = control;
     }
 
+    this->controlCount++;
+
     return control->id;
 }
 
@@ -622,13 +631,14 @@ bool ESPUIClass::removeControl(uint16_t id, bool force_reload_ui)
     {
         this->controls = it->next;
         delete it;
+        this->controlCount--;
         if (force_reload_ui)
         {
             jsonReload();
         }
         else
         {
-            jsonDom();
+            jsonDom(0);
         }
         return true;
     }
@@ -644,13 +654,14 @@ bool ESPUIClass::removeControl(uint16_t id, bool force_reload_ui)
     {
         it->next = it_next->next;
         delete it_next;
+        this->controlCount--;
         if (force_reload_ui)
         {
             jsonReload();
         }
         else
         {
-            jsonDom(); // resends to all
+            jsonDom(0); // resends to all
         }
         return true;
     }
@@ -977,29 +988,44 @@ void ESPUIClass::addGraphPoint(uint16_t id, int nValue, int clientId)
         tryId++;
     }
 }
+
 /*
-Convert & Transfer Arduino elements to JSON elements
-Initially this function used to send the control element data individually.
-Due to a change in the ESPAsyncWebserver library this had top be changed to be
-sent as one blob at the beginning. Therefore a new type is used as well
+Convert & Transfer Arduino elements to JSON elements. This function sends a chunk of 
+JSON describing the controls of the UI, starting from the control at index startidx.
+If startidx is 0 then a UI_INITIAL_GUI message will be sent, else a UI_EXTEND_GUI.
+Both message types contain a list of serialised UI elements. Only a portion of the UI
+will be sent in order to avoid websocket buffer overflows. The client will acknowledge 
+receipt of a partial message by requesting the next chunk of UI.
+
+The protocol is:
+SERVER: jsonDom(0): 
+    "UI_INITIAL_GUI: n serialised UI elements"
+CLIENT: controls.js:handleEvent()
+    "uiok:n"
+SERVER: jsonDom(n):
+    "UI_EXTEND_GUI: n serialised UI elements"
+CLIENT: controls.js:handleEvent()
+    "uiok:2*n"
+etc. 
 */
-void ESPUIClass::jsonDom(AsyncWebSocketClient* client)
+void ESPUIClass::jsonDom(uint16_t startidx, AsyncWebSocketClient* client)
 {
+    if(startidx >= this->controlCount)
+    {
+        return;
+    }
 
     DynamicJsonDocument document(jsonInitialDocumentSize);
-    document["type"] = (int)UI_INITIAL_GUI;
+    document["type"] = startidx ? (int)UI_EXTEND_GUI : (int)UI_INITIAL_GUI;
     document["sliderContinuous"] = sliderContinuous;
+    document["startindex"] = startidx;
+    document["totalcontrols"] = this->controlCount;
     JsonArray items = document.createNestedArray("controls");
-
-    Control* control = this->controls;
-
     JsonObject titleItem = items.createNestedObject();
     titleItem["type"] = (int)UI_TITLE;
     titleItem["label"] = ui_title;
 
-    while (1)
-    {
-        control = prepareJSONChunk(client, control, &items);
+    prepareJSONChunk(client, startidx, &items);
 
     String json;
     serializeJson(document, json);
@@ -1014,24 +1040,27 @@ void ESPUIClass::jsonDom(AsyncWebSocketClient* client)
         client->text(json);
     else
         this->ws->textAll(json);
-
-        if (control == nullptr)
-            break;
-
-        document.clear();
-        items.clear();
-        document["type"] = (int)UI_EXTEND_GUI;
-        items = document.createNestedArray("controls");
-    }
 }
 
 /* Prepare a chunk of elements as a single JSON string. If the allowed number of elements is greater than the total
-number this will represent the entire UI and this function will return null. If a control pointer is returned then the
-limit was reached, the currently serialised must be sent, and then processing resumed to send the next chunk. */
-Control* ESPUIClass::prepareJSONChunk(AsyncWebSocketClient* client, Control* control, JsonArray* items)
+number this will represent the entire UI. More likely, it will represent a small section of the UI to be sent. The client
+will acknoledge receipt by requesting the next chunk. */
+void ESPUIClass::prepareJSONChunk(AsyncWebSocketClient* client, uint16_t startindex, JsonArray* items)
 {
-    int elementcount = 0;
+    //First check that there will be sufficient nodes in the list
+    if(startindex >= this->controlCount) 
+    {
+        return;
+    }
 
+    //Follow the list until control points to the startindex'th node
+    Control* control = this->controls;
+    for(auto i = 0; i < startindex; i++) {
+        control = control->next;
+    }
+
+    //To prevent overflow, keep track of the number of elements we have serialised into this message
+    int elementcount = 0;
     while (control != nullptr && elementcount < 10)
     {
         JsonObject item = items->createNestedObject();
@@ -1071,7 +1100,7 @@ Control* ESPUIClass::prepareJSONChunk(AsyncWebSocketClient* client, Control* con
         control = control->next;
         elementcount++;
     }
-    return control;
+    return;
 }
 
 void ESPUIClass::jsonReload()

src/ESPUI.h

@@ -298,7 +298,7 @@ public:
     const char* ui_title = "ESPUI"; // Store UI Title and Header Name
     Control* controls = nullptr;
     void jsonReload();
-    void jsonDom(AsyncWebSocketClient* client = nullptr);
+    void jsonDom(uint16_t startidx, AsyncWebSocketClient* client = nullptr);
 
     Verbosity verbosity;
 
@@ -310,7 +310,9 @@ private:
     const char* basicAuthPassword = nullptr;
     bool basicAuth = true;
 
-    Control* prepareJSONChunk(AsyncWebSocketClient* client, Control* control, JsonArray* items);
+    uint16_t controlCount = 0;
+
+    void prepareJSONChunk(AsyncWebSocketClient* client, uint16_t startindex, JsonArray* items);
 };
 
 extern ESPUIClass ESPUI;