Split parsing from rendering to avoid GDI/CPU cache thrashing

ParseDataBuf is now pure CPU work with no GDI calls -- the parsing
loop stays cache-hot in the 486 L1.  WriteDeferredBuf parses first,
then renders all dirty rows in one batch.  Removes ~105 lines of
inline FLiveDC rendering from 8 methods.  Also fixes missing DC
local variable in Paint.

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

delphi/KPANSI.PAS

@@ -7,11 +7,12 @@ unit KPAnsi;
 { Renders incoming data using standard ANSI/VT100 escape sequences for      }
 { cursor positioning, color attributes, and screen manipulation.            }
 {                                                                           }
-{ Immediate-mode rendering: each character run is rendered via ExtTextOut   }
+{ Split-phase rendering: WriteDeferredBuf first parses the entire input    }
-{ directly to the screen DC as it arrives during parsing.  WriteDeferredBuf }
+{ buffer into the cell buffer (pure CPU, no GDI calls), then renders all   }
-{ acquires a DC, parses data (rendering inline), and releases.  No         }
+{ dirty rows in one batch via RenderRow.  Scroll-ups are coalesced into    }
-{ deferred dirty-row pass needed for normal data flow.  FlipToScreen only   }
+{ a single ScrollDC call.  Separating parsing from rendering keeps the     }
-{ handles blink toggle and fallback paths (scrollback view, WM_PAINT).     }
+{ parsing loop cache-hot and avoids interleaving GDI kernel transitions    }
+{ with CPU work.  FlipToScreen handles blink and fallback paths.           }
 {                                                                           }
 { Installs to the "KP" palette tab alongside TKPComm.                      }
 
@@ -101,7 +102,7 @@ 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 }
-    FLiveDC:         HDC;       { Non-zero during immediate rendering }
+    FLiveDC:         HDC;       { Non-zero during render pass in WriteDeferredBuf }
 
     procedure AllocLine(Line: PTermLine);
     procedure CMFontChanged(var Msg: TMessage); message cm_FontChanged;
@@ -424,12 +425,6 @@ begin
       Line^.Cells[I].Blink := False;
     end;
   end;
-  if FLiveDC <> 0 then
-  begin
-    FlushPendingScrolls;
-    RenderRow(FLiveDC, FCursorRow);
-  end
-  else
   FDirtyRow[FCursorRow] := True;
 end;
 
@@ -454,18 +449,9 @@ 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;
@@ -524,9 +510,6 @@ end;
 procedure TKPAnsi.DoScrollDown;
 var
   Line: PTermLine;
-  ScrollR: TRect;
-  ClipR:   TRect;
-  UpdateR: TRect;
 begin
   if FScreen.Count < FRows then
     Exit;
@@ -538,18 +521,6 @@ begin
   GetMem(Line, SizeOf(TTermLineRec));
   AllocLine(Line);
   FScreen.Insert(0, Line);
-  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;
 
@@ -638,24 +609,6 @@ begin
         UpdateScrollbar;
       end;
   end;
-  { 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
@@ -667,13 +620,11 @@ begin
       FAllDirty := True;
   end;
 end;
-end;
 
 
 procedure TKPAnsi.EraseLine(Mode: Integer);
 var
   J:    Integer;
-  R:    TRect;
   Line: PTermLine;
 begin
   Line := FScreen[FCursorRow];
@@ -703,36 +654,6 @@ begin
     2: { Erase entire 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;
 
@@ -1071,13 +992,13 @@ var
   ClipR:    TRect;
   UpdateR:  TRect;
   Row:      Integer;
+  GhostRow: Integer;
 begin
   if (FPendingScrolls = 0) or (FLiveDC = 0) then
     Exit;
   if FPendingScrolls >= FRows then
   begin
-    for Row := 0 to FRows - 1 do
+    FAllDirty := True;
-      RenderRow(FLiveDC, Row);
     FPendingScrolls := 0;
     Exit;
   end;
@@ -1088,8 +1009,13 @@ begin
   ClipR := ScrollR;
   ScrollDC(FLiveDC, 0, -(FPendingScrolls * FCellHeight),
     ScrollR, ClipR, 0, @UpdateR);
+  { Mark exposed rows and cursor ghost row for deferred rendering }
   for Row := FRows - FPendingScrolls to FRows - 1 do
-    RenderRow(FLiveDC, Row);
+    FDirtyRow[Row] := True;
+  GhostRow := FLastCursorRow - FPendingScrolls;
+  if (GhostRow >= 0) and (GhostRow < FRows) then
+    FDirtyRow[GhostRow] := True;
+  FLastCursorRow := FCursorRow;
   FPendingScrolls := 0;
 end;
 
@@ -1241,12 +1167,6 @@ begin
       Line^.Cells[I].Blink := False;
     end;
   end;
-  if FLiveDC <> 0 then
-  begin
-    FlushPendingScrolls;
-    RenderRow(FLiveDC, FCursorRow);
-  end
-  else
   FDirtyRow[FCursorRow] := True;
 end;
 
@@ -1271,18 +1191,9 @@ 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);
@@ -1367,6 +1278,7 @@ end;
 
 procedure TKPAnsi.Paint;
 var
+  DC:  HDC;
   Row: Integer;
 begin
   if FPaintFont = 0 then
@@ -1409,9 +1321,6 @@ var
   BGIdx:       Byte;
   RunEnd:      Integer;
   Remaining:   Integer;
-  RunStartI:   Integer;
-  RunStartCol: Integer;
-  R:           TRect;
 begin
   Line := nil;
   I    := 0;
@@ -1458,10 +1367,6 @@ 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
@@ -1490,28 +1395,6 @@ begin
               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
@@ -2289,24 +2172,36 @@ end;
 
 
 procedure TKPAnsi.WriteDeferredBuf(Buf: PChar; Len: Integer);
+var
+  Row: Integer;
 begin
-  if Len > 0 then
+  if Len <= 0 then
-  begin
+    Exit;
+
+  { Parse into cell buffer -- pure CPU, no GDI calls }
+  ParseDataBuf(Buf, Len);
+
+  { Render pass: flush coalesced scrolls, then redraw dirty rows }
   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;
+    for Row := 0 to FRows - 1 do
+    begin
+      if FAllDirty or FDirtyRow[Row] then
+      begin
+        RenderRow(FLiveDC, Row);
+        FDirtyRow[Row] := False;
+      end;
+    end;
+    FAllDirty := False;
+    FLastCursorRow := FCursorRow;
     ReleaseDC(Handle, FLiveDC);
     FLiveDC := 0;
   end;
 end;
-end;
 
 
 { ----------------------------------------------------------------------- }