Windows Platform Guide

The Windows backend uses the native Win32 API and GDI/GDI+ for all drawing. It is written in C++ and compiled with MSVC or BCC. This is the most mature and feature-complete backend in HarbourBuilder.

Architecture Overview

Native Window Creation

Every HarbourBuilder window and control is a native Win32 window created via CreateWindowEx(). The backend registers custom window classes at startup:

// win32_backend.cpp - Window class registration
void RegisterClasses( HINSTANCE hInstance )
{
   WNDCLASSEX wc = { sizeof( WNDCLASSEX ) };
   wc.hInstance     = hInstance;
   wc.lpfnWndProc   = WndProc;
   wc.hCursor       = LoadCursor( NULL, IDC_ARROW );
   wc.hbrBackground = (HBRUSH)( COLOR_WINDOW + 1 );

   wc.lpszClassName = "HBBUILDER_FORM";
   RegisterClassEx( &wc );

   wc.lpszClassName = "HBBUILDER_BUTTON";
   RegisterClassEx( &wc );

   // ... additional classes for EDIT, STATIC, etc.
}

Controls are standard Win32 common controls: BUTTON, EDIT, STATIC, COMBOBOX, LISTBOX, msctls_progress32, msctls_trackbar32, SysTreeView32, SysListView32, and RichEdit.

Event Handling (WndProc)

The Windows backend uses a central WndProc (window procedure) that receives all messages from the OS. It dispatches them to Harbour event handlers:

// win32_backend.cpp - Message dispatch
LRESULT CALLBACK WndProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
   switch( msg )
   {
      case WM_COMMAND:
         FireEvent( hWnd, EVENT_CLICK, CT_BUTTON );
         break;

      case WM_LBUTTONDOWN:
         FireEvent( hWnd, EVENT_MOUSEDOWN, (int) LOWORD( lParam ), (int) HIWORD( lParam ) );
         break;

      case WM_KEYDOWN:
         FireEvent( hWnd, EVENT_KEYDOWN, (int) wParam );
         break;

      case WM_PAINT:
         FireEvent( hWnd, EVENT_PAINT );
         break;

      case WM_CLOSE:
         if( !FireCloseQuery( hWnd ) )
            return 0;  // Cancel close
         break;

      // ... additional message handling
   }
   return DefWindowProc( hWnd, msg, wParam, lParam );
}

Dark Mode Support

HarbourBuilder on Windows follows the system theme. Dark mode is implemented using:

• DwmSetWindowAttribute() — Enables dark title bars on Windows 10/11 by setting DWMWA_USE_IMMERSIVE_DARK_MODE.
• Dark window class styles — When the system is in dark mode, the backend registers window classes with dark background brushes.
• GDI dark colors — Control colors use dark palette values (near-black backgrounds, light text).
• Scintilla dark theme — The code editor uses a dark lexer style matching the IDE theme.

// win32_backend.cpp - Dark title bar
void EnableDarkTitleBar( HWND hWnd )
{
   BOOL dark = TRUE;
   DwmSetWindowAttribute(
      hWnd,
      DWMWA_USE_IMMERSIVE_DARK_MODE,
      &dark,
      sizeof( dark )
   );
}

Scintilla Integration

The Windows backend uses Scintilla 5.6.1 as a dynamic library:

Scintilla is loaded at runtime via LoadLibrary() and GetProcAddress(). The backend creates a Scintilla window as a child of the code editor tab and communicates with it via SendMessage().

// Loading Scintilla at runtime
HMODULE hSci = LoadLibrary( "Scintilla.dll" );
SCI_CREATE fnCreate = (SCI_CREATE) GetProcAddress( hSci, "Scintilla_DirectFunction" );

// Creating the editor window
HWND hEditor = CreateWindowEx(
   0, "Scintilla", "",
   WS_CHILD | WS_VISIBLE | WS_VSCROLL | WS_HSCROLL | ES_MULTILINE,
   0, 0, 800, 600,
   hParent, NULL, hInstance, NULL
);

Compiler Options

Supported Compilers

Build Script

The build_win.bat script handles the entire build process:

1. Compiler detection — Scans for MSVC installations (2019, 2022, Community, BuildTools) and BCC.
2. Environment setup — Calls vcvarsall.bat to set up the compiler environment.
3. Harbour compilation — Builds Harbour from source if not already present.
4. Scintilla build — Compiles Scintilla and Lexilla DLLs.
5. IDE compilation — Compiles the HarbourBuilder IDE source.
6. Linking — Links against user32.lib, gdi32.lib, comctl32.lib, dwmapi.lib, and the Harbour runtime.

:: build_win.bat - Build process
set HBDIR=C:\harbour
call "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvarsall.bat" x64

harbour hbbuilder.prg /n /q /gc1
cl /O2 /c hbbuilder.c win32_backend.cpp /I%HBDIR%\include /I.\include
link hbbuilder.obj win32_backend.obj /SUBSYSTEM:WINDOWS ^
     user32.lib gdi32.lib comctl32.lib dwmapi.lib ^
     %HBDIR%\lib\win\msvc64\harbour.lib

Platform-Specific Features

Known Limitations

• Manifest requirement — Windows applications need an embedded manifest for visual styles (ComCtl32 v6) and DPI awareness. HarbourBuilder includes this in the build.
• DPI scaling — The backend is DPI-aware but control positioning uses pixel coordinates. High-DPI displays may require manual size adjustments.
• RichEdit version — The RichEdit control depends on msftedit.dll which may not be available on very old Windows versions (pre-Windows 8).
• Windows XP/Vista/7/8 — Not officially supported. The backend targets Windows 10+ APIs. Some features (dark title bars via DWM) require Windows 10 build 18985+.

Dependencies