Debugger: Add Begin/EndUpdate to WatchValue

components/lazdebuggers/lazdebuggerintf/lazdebuggerintf.pas

@@ -149,6 +149,33 @@ type
   { TWatchValueIntf }
 
   TWatchValueIntf = interface(TDbgDataRequestIntf)
+    (* Begin/EndUdate
+       - shall indicate that the newly set values are now valid. Ready for display.
+         (Indicated by EndUpdate)
+       - shall protect the object from destruction.
+         A debugger backend may access the object during this time, without further checks.
+       - shall ensure changes outside the backend, will not affect calls by the
+         backend to any method setting/adding/modifing requested data.
+         ~ I.e. if the backend adds values to an array or structure, further calls
+           by the backend to add more data must be accepted without failure.
+         ~ However, further data may be discarded internally, if possible without
+           causing later failures (e.g. if the requested data is no longer needed)
+   (!) - does NOT affect, if read-only properties/functions can change their value.
+         E.g., if the requested value is no longer needed, then "Expression" and
+         other "passed in/provided values" may change (reset to default/empty)
+     * When used in the IDE (Begin/EndUpdate themself shall only be valid in the main thread),
+       shall
+       - allow the backend to read "passed in/provided values" from another thread
+       - allow the backend to set new values from another thread
+         (I.e., if the IDE (or any non-backend code) makes changes, they must
+          consider thread safety)
+       // Any "frontend" outside the IDE (commandline / dbg-server) doens not
+          need to consider thread safety, as long as it knows that this in not
+          required by any of the backends it uses.
+    *)
+    procedure BeginUpdate;
+    procedure EndUpdate;
+
     function GetDisplayFormat: TWatchDisplayFormat;
     function GetEvaluateFlags: TWatcheEvaluateFlags;
     function GetExpression: String;

ide/packages/idedebugger/debugger.pp

@@ -639,11 +639,18 @@ type
 
   { TCurrentWatchValue }
 
-  TCurrentWatchValue = class(TIdeWatchValue)
+  TCurrentWatchValue = class(TIdeWatchValue, TWatchValueIntf)
+  private
+    FCurrentExpression: String;
+    FUpdateCount: Integer;
+
+    procedure BeginUpdate;
+    procedure EndUpdate;
   private
     FSnapShot: TIdeWatchValue;
     procedure SetSnapShot(const AValue: TIdeWatchValue);
   protected
+    function GetExpression: String; override;
     procedure RequestData; override;
     procedure DoDataValidityChanged({%H-}AnOldValidity: TDebuggerDataState); override;
   public
@@ -3098,6 +3105,26 @@ end;
 
 { TCurrentWatchValue }
 
+procedure TCurrentWatchValue.BeginUpdate;
+begin
+  AddReference;
+  if FUpdateCount = 0 then
+    FCurrentExpression := Expression;
+  inc(FUpdateCount);
+end;
+
+procedure TCurrentWatchValue.EndUpdate;
+begin
+  dec(FUpdateCount);
+  if (FUpdateCount = 0) then begin
+    if Validity <> ddsValid then
+      SetValidity(ddsValid)
+    else
+      DoDataValidityChanged(ddsRequested);
+  end;
+  ReleaseReference; // Last statemnet, may call Destroy
+end;
+
 procedure TCurrentWatchValue.SetSnapShot(const AValue: TIdeWatchValue);
 begin
   assert((FSnapShot=nil) or (AValue=nil), 'TCurrentWatchValue already have snapshot');
@@ -3107,6 +3134,14 @@ begin
   then FSnapShot.Assign(self);
 end;
 
+function TCurrentWatchValue.GetExpression: String;
+begin
+  if FUpdateCount > 0 then
+    Result := FCurrentExpression
+  else
+    Result := inherited GetExpression;
+end;
+
 procedure TCurrentWatchValue.RequestData;
 begin
   TCurrentWatch(Watch).RequestData(self);
@@ -3114,6 +3149,8 @@ end;
 
 procedure TCurrentWatchValue.DoDataValidityChanged(AnOldValidity: TDebuggerDataState);
 begin
+  if FUpdateCount > 0 then
+    exit;
   if Validity = ddsRequested then exit;
   if Watch <> nil then
     TCurrentWatches(TCurrentWatch(Watch).Collection).Update(Watch);

ide/packages/idedebugger/idedebuggerbase.pas

@@ -14,13 +14,14 @@ type
 
   { TWatchValue }
 
-  TWatchValue = class(TRefCountedObject, TWatchValueIntf)
+  TWatchValue = class(TRefCountedObject)
   private
     FWatch: TWatch;
     FTypeInfo: TDBGType;
     FValue: String;
     FValidity: TDebuggerDataState;
 
+  protected
     function GetDisplayFormat: TWatchDisplayFormat;
     function GetEvaluateFlags: TWatcheEvaluateFlags;
     function GetRepeatCount: Integer;