From f472dc1158bb29392fdb28fe3d4a2a1b14a5d06c Mon Sep 17 00:00:00 2001
From: MartinMueller2003 <MartinMueller2003@yahoo.com>
Date: Thu, 29 Feb 2024 16:32:04 -0500
Subject: [PATCH] Added mechanism to estimate the marshaled size of a control.

---
 src/ESPUIcontrol.cpp | 12 ++++++++++--
 src/ESPUIcontrol.h   | 12 ++++++++++--
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/ESPUIcontrol.cpp b/src/ESPUIcontrol.cpp
index 44002ac..554e7d5 100644
--- a/src/ESPUIcontrol.cpp
+++ b/src/ESPUIcontrol.cpp
@@ -19,6 +19,7 @@ Control::Control(ControlType type, const char* label, std::function<void(Control
 {
     id = ++idCounter;
     ControlChangeID = 1;
+    EstimateMarshaledSize();
 }
 
 Control::Control(const Control& Control)
@@ -31,7 +32,8 @@ Control::Control(const Control& Control)
         visible(Control.visible),
         parentControl(Control.parentControl),
         next(Control.next),
-        ControlChangeID(Control.ControlChangeID)
+        ControlChangeID(Control.ControlChangeID),
+        EstimatedMarshaledSize(Control.EstimatedMarshaledSize)
 { }
 
 void Control::SendCallback(int type)
@@ -97,7 +99,7 @@ void Control::MarshalControl(JsonObject & _item, bool refresh, uint32_t Starting
     }
 
     item[F("label")]   = label;
-    item[F ("value")]   = (ControlType::Password == type) ? F ("--------") : value.substring(StartingOffset, length + StartingOffset);
+    item[F ("value")]  = (ControlType::Password == type) ? F ("--------") : value.substring(StartingOffset, length + StartingOffset);
     item[F("visible")] = visible;
     item[F("color")]   = (int)color;
     item[F("enabled")] = enabled;
@@ -281,3 +283,9 @@ void Control::onWsEvent(String & cmd, String& data)
     } while (false);
 }
 
+void Control::EstimateMarshaledSize()
+{
+    EstimatedMarshaledSize = MarshalingOverhead + (JsonMarshalingRatio * (strlen(label) + value.length()));
+
+} // EstimateSerializedSize
+
diff --git a/src/ESPUIcontrol.h b/src/ESPUIcontrol.h
index d075353..a84d094 100644
--- a/src/ESPUIcontrol.h
+++ b/src/ESPUIcontrol.h
@@ -89,12 +89,20 @@ public:
     void onWsEvent(String& cmd, String& data);
     inline bool ToBeDeleted() { return _ToBeDeleted; }
     inline bool NeedsSync(uint32_t lastControlChangeID) {return (false == _ToBeDeleted) && (lastControlChangeID < ControlChangeID);}
-    void    SetControlChangedId(uint32_t value) {ControlChangeID = value;}
-    
+    void    SetControlChangedId(uint32_t value) {ControlChangeID = value; EstimateMarshaledSize();}
+    uint32_t GetEstimatedMarshaledSize() {return EstimatedMarshaledSize;}
+
 private:
     bool _ToBeDeleted = false;
     uint32_t ControlChangeID = 0;
+    uint32_t EstimatedMarshaledSize = 0;
     String OldValue = emptyString;
+
+    // multiplier for converting a typical controller label and value to a Json object
+    #define JsonMarshalingRatio 6
+    // estimated number of bytes for the fixed portion of a control rendered as Json
+    #define MarshalingOverhead 90
+    void EstimateMarshaledSize();
 };
 
 #define UI_TITLE            ControlType::Title