Render characters immediately during parsing, not in deferred pass

WriteDeferredBuf now acquires a screen DC and renders each character
run via ExtTextOut as it arrives, eliminating the per-row deferred
dirty scan.  FlushPendingScrolls coalesces scroll-ups into a single
ScrollDC call.  FlipToScreen becomes a lightweight blink/fallback pass.

Removed 50ms render throttle from TESTMAIN -- no longer needed since
characters appear on screen as they are parsed.

Simplified: removed ClearLine (duplicate of AllocLine), DirtyAll,
DirtyRow, GetCursorCol/Row (dead code), FTextBlinkOn (always equal
to FBlinkOn), ParseData (inlined), ETO_CLIPPED (unused), redundant
zero-initializations in constructor.  Write and WriteDeferred now
delegate to WriteDeferredBuf.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

delphi/KPANSI.PAS

@@ -7,11 +7,11 @@ unit KPAnsi;
 { Renders incoming data using standard ANSI/VT100 escape sequences for      }
 { cursor positioning, color attributes, and screen manipulation.            }
 {                                                                           }
-{ Rendering uses ExtTextOut with color-run batching directly to the screen  }
+{ Immediate-mode rendering: each character run is rendered via ExtTextOut   }
-{ DC (CS_OWNDC retains the selected OEM font across GetDC calls).  No      }
+{ directly to the screen DC as it arrives during parsing.  WriteDeferredBuf }
-{ intermediate bitmap -- the display driver renders text directly into the  }
+{ acquires a DC, parses data (rendering inline), and releases.  No         }
-{ framebuffer via its optimized raster font path.  Smart blink tracking     }
+{ deferred dirty-row pass needed for normal data flow.  FlipToScreen only   }
-{ dirties only cursor and blink rows instead of the entire screen.          }
+{ handles blink toggle and fallback paths (scrollback view, WM_PAINT).     }
 {                                                                           }
 { Installs to the "KP" palette tab alongside TKPComm.                      }
 
@@ -101,29 +101,24 @@ type
     FDirtyRow:       array[0..255] of Boolean; { True = row needs re-render }
     FAllDirty:       Boolean;    { True = all rows need re-render }
     FScrollbarDirty: Boolean;    { True = scrollbar range/position needs update }
-    FTextBlinkOn:    Boolean;    { Text blink phase: True=visible, False=hidden }
+    FLiveDC:         HDC;       { Non-zero during immediate rendering }
 
     procedure AllocLine(Line: PTermLine);
-    procedure ClearLine(Line: PTermLine);
     procedure CMFontChanged(var Msg: TMessage); message cm_FontChanged;
     procedure CreatePaintFont;
     procedure DeleteChars(N: Integer);
     procedure DeleteLines(N: Integer);
-    procedure DirtyAll;
     procedure DirtyBlinkRows;
-    procedure DirtyRow(Row: Integer);
     procedure DoScrollDown;
     procedure DoScrollUp;
     procedure EraseDisplay(Mode: Integer);
     procedure EraseLine(Mode: Integer);
     procedure ExecuteCSI(FinalCh: Char);
     procedure ExecuteMusic;
+    procedure FlushPendingScrolls;
     procedure FreeLineList(List: TList);
-    function  GetCursorCol: Integer;
-    function  GetCursorRow: Integer;
     procedure InsertChars(N: Integer);
     procedure InsertLines(N: Integer);
-    procedure ParseData(const S: string);
     procedure ParseDataBuf(Buf: PChar; Len: Integer);
     procedure ParseSGR;
     procedure ProcessChar(Ch: Char);
@@ -154,8 +149,8 @@ type
     procedure Write(const S: string);
     procedure WriteDeferred(const S: string);
     procedure WriteDeferredBuf(Buf: PChar; Len: Integer);
-    property CursorCol: Integer read GetCursorCol;
+    property CursorCol: Integer read FCursorCol;
-    property CursorRow: Integer read GetCursorRow;
+    property CursorRow: Integer read FCursorRow;
   published
     property Cols: Integer read FCols write SetCols default 80;
     property Rows: Integer read FRows write SetRows default 25;
@@ -199,9 +194,8 @@ const
   { OUT_RASTER_PRECIS may not be defined in Delphi 1.0 WinTypes }
   OutRasterPrecis = 6;
 
-  { ExtTextOut option flags (may not be in Delphi 1.0 WinTypes) }
+  { ExtTextOut option flag (may not be in Delphi 1.0 WinTypes) }
   ETO_OPAQUE = $0002;
-  ETO_CLIPPED = $0004;
 
   { ANSI music note frequencies (octave 0, multiply by 2^octave) }
   { C, C#, D, D#, E, F, F#, G, G#, A, A#, B }
@@ -308,21 +302,6 @@ begin
 end;
 
 
-procedure TKPAnsi.ClearLine(Line: PTermLine);
-var
-  I: Integer;
-begin
-  for I := 0 to FCols - 1 do
-  begin
-    Line^.Cells[I].Ch    := ' ';
-    Line^.Cells[I].FG    := 7;
-    Line^.Cells[I].BG    := 0;
-    Line^.Cells[I].Bold  := False;
-    Line^.Cells[I].Blink := False;
-  end;
-end;
-
-
 procedure TKPAnsi.CMFontChanged(var Msg: TMessage);
 begin
   inherited;
@@ -346,34 +325,13 @@ begin
   FCursorVisible   := True;
   FScreen          := TList.Create;
   FScrollback      := TList.Create;
-  FCursorRow       := 0;
-  FCursorCol       := 0;
-  FLastCursorRow   := 0;
-  FSaveCurRow      := 0;
-  FSaveCurCol      := 0;
   FAttrFG          := 7;
-  FAttrBG          := 0;
-  FAttrBold        := False;
-  FAttrBlink       := False;
-  FAttrReverse     := False;
-  FParseState      := psNormal;
-  FParamLen        := 0;
-  FCSIParam1       := 0;
-  FCSIParam2       := 0;
-  FCSIParamIdx     := 0;
-  FMusicStr        := '';
   FCellWidth       := 8;
   FCellHeight      := 16;
   FBlinkOn         := True;
   FLastBlinkTick   := GetTickCount;
-  FScrollPos       := 0;
-  FPendingScrolls  := 0;
   FWrapMode        := True;
-  FPaintFont       := 0;
-  FStockFont       := False;
   FAllDirty        := True;
-  FScrollbarDirty  := False;
-  FTextBlinkOn     := True;
   { Set a monospace font -- OEM charset selected in CreatePaintFont }
   Font.Name  := 'Terminal';
   Font.Size  := 9;
@@ -466,6 +424,12 @@ begin
       Line^.Cells[I].Blink := False;
     end;
   end;
+  if FLiveDC <> 0 then
+  begin
+    FlushPendingScrolls;
+    RenderRow(FLiveDC, FCursorRow);
+  end
+  else
     FDirtyRow[FCursorRow] := True;
 end;
 
@@ -490,9 +454,18 @@ begin
       FScreen.Add(Line);
     end;
   end;
+  if FLiveDC <> 0 then
+  begin
+    FlushPendingScrolls;
+    for J := FCursorRow to FRows - 1 do
+      RenderRow(FLiveDC, J);
+  end
+  else
+  begin
     for J := FCursorRow to FRows - 1 do
       FDirtyRow[J] := True;
   end;
+end;
 
 
 destructor TKPAnsi.Destroy;
@@ -510,12 +483,6 @@ begin
 end;
 
 
-procedure TKPAnsi.DirtyAll;
-begin
-  FAllDirty := True;
-end;
-
-
 procedure TKPAnsi.DirtyBlinkRows;
 { Targeted dirty marking for blink toggle.  Instead of DirtyAll (which    }
 { forces a full 25-row re-render), only dirty the                         }
@@ -554,16 +521,12 @@ begin
 end;
 
 
-procedure TKPAnsi.DirtyRow(Row: Integer);
-begin
-  if (Row >= 0) and (Row <= 255) then
-    FDirtyRow[Row] := True;
-end;
-
-
 procedure TKPAnsi.DoScrollDown;
 var
   Line:    PTermLine;
+  ScrollR: TRect;
+  ClipR:   TRect;
+  UpdateR: TRect;
 begin
   if FScreen.Count < FRows then
     Exit;
@@ -575,7 +538,18 @@ begin
   GetMem(Line, SizeOf(TTermLineRec));
   AllocLine(Line);
   FScreen.Insert(0, Line);
-  { Scroll down is rare; just repaint everything }
+  if FLiveDC <> 0 then
+  begin
+    FlushPendingScrolls;
+    ScrollR.Left   := 0;
+    ScrollR.Top    := 0;
+    ScrollR.Right  := FCols * FCellWidth;
+    ScrollR.Bottom := FRows * FCellHeight;
+    ClipR := ScrollR;
+    ScrollDC(FLiveDC, 0, FCellHeight, ScrollR, ClipR, 0, @UpdateR);
+    RenderRow(FLiveDC, 0);
+  end
+  else
     FAllDirty := True;
 end;
 
@@ -604,8 +578,6 @@ begin
 end;
 
 
-
-
 procedure TKPAnsi.EraseDisplay(Mode: Integer);
 var
   I:    Integer;
@@ -628,7 +600,7 @@ begin
         { Erase all lines below }
         for I := FCursorRow + 1 to FScreen.Count - 1 do
         begin
-          ClearLine(FScreen[I]);
+          AllocLine(FScreen[I]);
         end;
       end;
     1: { Erase above: start of screen to current position }
@@ -636,7 +608,7 @@ begin
         { Erase all lines above }
         for I := 0 to FCursorRow - 1 do
         begin
-          ClearLine(FScreen[I]);
+          AllocLine(FScreen[I]);
         end;
         { Erase current line up to and including cursor }
         Line := FScreen[FCursorRow];
@@ -666,7 +638,24 @@ begin
         UpdateScrollbar;
       end;
   end;
-  { Mark affected rows dirty for deferred batch rendering }
+  { Immediate render or deferred dirty }
+  if FLiveDC <> 0 then
+  begin
+    FlushPendingScrolls;
+    case Mode of
+      0:
+        for I := FCursorRow to FRows - 1 do
+          RenderRow(FLiveDC, I);
+      1:
+        for I := 0 to FCursorRow do
+          RenderRow(FLiveDC, I);
+      2:
+        for I := 0 to FRows - 1 do
+          RenderRow(FLiveDC, I);
+    end;
+  end
+  else
+  begin
     case Mode of
       0:
         for I := FCursorRow to FRows - 1 do
@@ -678,11 +667,13 @@ begin
         FAllDirty := True;
     end;
   end;
+end;
 
 
 procedure TKPAnsi.EraseLine(Mode: Integer);
 var
   J:    Integer;
+  R:    TRect;
   Line: PTermLine;
 begin
   Line := FScreen[FCursorRow];
@@ -710,8 +701,38 @@ begin
         end;
       end;
     2: { Erase entire line }
-      ClearLine(Line);
+      AllocLine(Line);
   end;
+  if FLiveDC <> 0 then
+  begin
+    FlushPendingScrolls;
+    SetBkColor(FLiveDC, AnsiColors[0]);
+    case Mode of
+      0:
+        begin
+          R.Left   := FCursorCol * FCellWidth;
+          R.Top    := FCursorRow * FCellHeight;
+          R.Right  := FCols * FCellWidth;
+          R.Bottom := R.Top + FCellHeight;
+        end;
+      1:
+        begin
+          R.Left   := 0;
+          R.Top    := FCursorRow * FCellHeight;
+          R.Right  := (FCursorCol + 1) * FCellWidth;
+          R.Bottom := R.Top + FCellHeight;
+        end;
+      2:
+        begin
+          R.Left   := 0;
+          R.Top    := FCursorRow * FCellHeight;
+          R.Right  := FCols * FCellWidth;
+          R.Bottom := R.Top + FCellHeight;
+        end;
+    end;
+    ExtTextOut(FLiveDC, R.Left, R.Top, ETO_OPAQUE, @R, nil, 0, nil);
+  end
+  else
     FDirtyRow[FCursorRow] := True;
 end;
 
@@ -1044,6 +1065,35 @@ begin
 end;
 
 
+procedure TKPAnsi.FlushPendingScrolls;
+var
+  ScrollR: TRect;
+  ClipR:   TRect;
+  UpdateR: TRect;
+  Row:     Integer;
+begin
+  if (FPendingScrolls = 0) or (FLiveDC = 0) then
+    Exit;
+  if FPendingScrolls >= FRows then
+  begin
+    for Row := 0 to FRows - 1 do
+      RenderRow(FLiveDC, Row);
+    FPendingScrolls := 0;
+    Exit;
+  end;
+  ScrollR.Left   := 0;
+  ScrollR.Top    := 0;
+  ScrollR.Right  := FCols * FCellWidth;
+  ScrollR.Bottom := FRows * FCellHeight;
+  ClipR := ScrollR;
+  ScrollDC(FLiveDC, 0, -(FPendingScrolls * FCellHeight),
+    ScrollR, ClipR, 0, @UpdateR);
+  for Row := FRows - FPendingScrolls to FRows - 1 do
+    RenderRow(FLiveDC, Row);
+  FPendingScrolls := 0;
+end;
+
+
 procedure TKPAnsi.FlipToScreen;
 { Render dirty rows via ExtTextOut directly to the screen DC.  CS_OWNDC    }
 { retains the selected font across GetDC calls, so no per-frame font       }
@@ -1170,18 +1220,6 @@ begin
 end;
 
 
-function TKPAnsi.GetCursorCol: Integer;
-begin
-  Result := FCursorCol;
-end;
-
-
-function TKPAnsi.GetCursorRow: Integer;
-begin
-  Result := FCursorRow;
-end;
-
-
 procedure TKPAnsi.InsertChars(N: Integer);
 var
   Line: PTermLine;
@@ -1203,6 +1241,12 @@ begin
       Line^.Cells[I].Blink := False;
     end;
   end;
+  if FLiveDC <> 0 then
+  begin
+    FlushPendingScrolls;
+    RenderRow(FLiveDC, FCursorRow);
+  end
+  else
     FDirtyRow[FCursorRow] := True;
 end;
 
@@ -1227,9 +1271,18 @@ begin
     AllocLine(Line);
     FScreen.Insert(FCursorRow, Line);
   end;
+  if FLiveDC <> 0 then
+  begin
+    FlushPendingScrolls;
+    for J := FCursorRow to FRows - 1 do
+      RenderRow(FLiveDC, J);
+  end
+  else
+  begin
     for J := FCursorRow to FRows - 1 do
       FDirtyRow[J] := True;
   end;
+end;
 
 
 procedure TKPAnsi.KeyDown(var Key: Word; Shift: TShiftState);
@@ -1314,7 +1367,6 @@ end;
 
 procedure TKPAnsi.Paint;
 var
-  DC:  HDC;
   Row: Integer;
 begin
   if FPaintFont = 0 then
@@ -1337,14 +1389,6 @@ begin
 end;
 
 
-procedure TKPAnsi.ParseData(const S: string);
-{ String wrapper -- delegates to ParseDataBuf for actual processing. }
-begin
-  if Length(S) > 0 then
-    ParseDataBuf(@S[1], Length(S));
-end;
-
-
 procedure TKPAnsi.ParseDataBuf(Buf: PChar; Len: Integer);
 { Process incoming data from a PChar buffer (no string allocation needed).  }
 {                                                                           }
@@ -1365,6 +1409,9 @@ var
   BGIdx:       Byte;
   RunEnd:      Integer;
   Remaining:   Integer;
+  RunStartI:   Integer;
+  RunStartCol: Integer;
+  R:           TRect;
 begin
   Line := nil;
   I    := 0;
@@ -1411,6 +1458,10 @@ begin
                   (RunEnd - I < Remaining) do
               Inc(RunEnd);
 
+            { Save run start for immediate rendering }
+            RunStartI   := I;
+            RunStartCol := FCursorCol;
+
             { Fill cells in tight loop }
             if FAttrReverse then
             begin
@@ -1438,6 +1489,29 @@ begin
                 Inc(I);
               end;
             end;
+
+            { Immediate render or deferred dirty }
+            if FLiveDC <> 0 then
+            begin
+              FlushPendingScrolls;
+              if FAttrReverse then
+              begin
+                SetTextColor(FLiveDC, AnsiColors[BGIdx]);
+                SetBkColor(FLiveDC, AnsiColors[FGIdx]);
+              end
+              else
+              begin
+                SetTextColor(FLiveDC, AnsiColors[FGIdx]);
+                SetBkColor(FLiveDC, AnsiColors[BGIdx]);
+              end;
+              R.Left   := RunStartCol * FCellWidth;
+              R.Top    := FCursorRow * FCellHeight;
+              R.Right  := FCursorCol * FCellWidth;
+              R.Bottom := R.Top + FCellHeight;
+              ExtTextOut(FLiveDC, R.Left, R.Top, ETO_OPAQUE, @R,
+                @Buf[RunStartI], I - RunStartI, nil);
+            end
+            else
               FDirtyRow[FCursorRow] := True;
           end
           else if Buf[I] = #27 then
@@ -1941,7 +2015,7 @@ begin
   for Col := 0 to FCols - 1 do
   begin
     { Determine effective colors }
-    if Line^.Cells[Col].Blink and not FTextBlinkOn then
+    if Line^.Cells[Col].Blink and not FBlinkOn then
       FGIdx := Line^.Cells[Col].BG
     else
       FGIdx := Line^.Cells[Col].FG;
@@ -2151,7 +2225,6 @@ begin
   begin
     FLastBlinkTick := Now;
     FBlinkOn       := not FBlinkOn;
-    FTextBlinkOn   := not FTextBlinkOn;
     DirtyBlinkRows;
   end;
 end;
@@ -2202,7 +2275,7 @@ procedure TKPAnsi.Write(const S: string);
 begin
   if Length(S) > 0 then
   begin
-    ParseData(S);
+    WriteDeferredBuf(@S[1], Length(S));
     FlipToScreen;
   end;
 end;
@@ -2211,14 +2284,28 @@ end;
 procedure TKPAnsi.WriteDeferred(const S: string);
 begin
   if Length(S) > 0 then
-    ParseData(S);
+    WriteDeferredBuf(@S[1], Length(S));
 end;
 
 
 procedure TKPAnsi.WriteDeferredBuf(Buf: PChar; Len: Integer);
 begin
   if Len > 0 then
+  begin
+    if HandleAllocated and (FPaintFont <> 0) and (FScrollPos = 0) then
+    begin
+      FLiveDC := GetDC(Handle);
+      SelectObject(FLiveDC, FPaintFont);
+      SetBkMode(FLiveDC, OPAQUE);
+    end;
     ParseDataBuf(Buf, Len);
+    if FLiveDC <> 0 then
+    begin
+      FlushPendingScrolls;
+      ReleaseDC(Handle, FLiveDC);
+      FLiveDC := 0;
+    end;
+  end;
 end;
 
 

delphi/TESTMAIN.PAS

@@ -166,19 +166,15 @@ end;
 
 procedure TMainForm.Run;
 const
-  RenderMs = 50;   { Minimum ms between renders during bulk flow (20 fps) }
   BufSize = 2048; { Read buffer -- 8x larger than 255-byte string limit  }
 var
   Msg:     TMsg;
   Buf:     array[0..BufSize - 1] of Char;
   Len:     Integer;
   HasData: Boolean;
-  Now:            Longint;
-  LastRenderTick: Longint;
 begin
   Show;
   FDone := False;
-  LastRenderTick := GetTickCount;
   while not FDone do
   begin
     { Process all pending Windows messages (keyboard, paint, scrollbar) }
@@ -196,8 +192,8 @@ begin
     if FDone then
       Break;
 
-    { Drain all available serial data before rendering.  Reads up to    }
+    { Drain all available serial data.  WriteDeferredBuf renders each   }
-    { 2048 bytes per call, bypassing the 255-byte short string limit.   }
+    { character run immediately via ExtTextOut -- no deferred pass.      }
     { Messages are checked between chunks so keyboard stays responsive. }
     HasData := False;
     if FComm.PortOpen then
@@ -225,16 +221,11 @@ begin
     if FDone then
       Break;
 
-    { Render throttle: during bulk data flow, only render every RenderMs }
+    { Blink + dirty-row pass.  During normal data flow, WriteDeferredBuf }
-    { to decouple parse throughput from GDI overhead.  When idle, render  }
+    { already rendered inline so FlipToScreen is a no-op.  Only blink    }
-    { immediately for interactive responsiveness.                         }
+    { toggle (every 500ms) or scrollbar updates produce dirty rows here. }
-    Now := GetTickCount;
-    if (not HasData) or (Now - LastRenderTick >= RenderMs) then
-    begin
     FAnsi.TickBlink;
     FAnsi.FlipToScreen;
-      LastRenderTick := Now;
-    end;
 
     { Yield CPU to other apps when no serial data is flowing.          }
     { PM_NOYIELD keeps message draining fast; Yield here gives other   }