fpGUI - Free Pascal GUI Toolkit

fpGUI is a cross-platform GUI toolkit written entirely in Object Pascal using the Free Pascal Compiler. It provides a custom-drawn widget set that renders consistently across all supported platforms, with no external widget toolkit dependencies. All rendering is done through the built-in AggPas hybrid canvas, which uses platform APIs (X11, GDI, Cocoa) for window management and input while delivering fully platform-independent, pixel-perfect output via software rasterisation.

Table of Contents

• 1. Features
• 2. Project Structure
• 3. Building
  • 3.1. Prerequisites
  • 3.2. Compiling the Framework
  • 3.3. Running Tests
  • 3.4. Compiling Applications
• 4. Quick Start
• 5. Licensing
• 6. Contributing
• 7. Links

1. Features

• Cross-platform: Linux (X11), Windows (GDI), macOS (Cocoa), FreeBSD, OpenSolaris

• AggPas hybrid canvas: Platform-independent rendering via 100% Object Pascal software rasteriser

• No external dependencies: No GTK, Qt, or other widget toolkit required

• Custom-drawn widgets: Consistent look and feel across all platforms

• Themeable: Multiple built-in styles including plastic and dark themes

• Layout managers: MigLayout (ported from Java), FlowLayout, and BorderLayout

• Fluent constraint API: LC, AC, and CC classes for concise layout definitions

• Rich widget set: Buttons, edits, grids, treeviews, listviews, menus, tabs, scrollbars, and more

• Visual form designer: UI Designer for rapid form creation

• PDF reporting engine: Built-in report generation with print preview

• Drag and drop: OS-independent DND support between applications and widgets

• Unicode support: Full Unicode text input and rendering

• Documentation viewer: DocView application for viewing INF/IPF help files

2. Project Structure

Directory	Description
framework/src/main/pascal/	Core fpGUI framework source
framework/src/test/pascal/	Unit tests
uidesigner/	Visual UI Designer application
docview/	Documentation viewer (INF/IPF file viewer)
examples/	Example applications and widget demos
extras/	Third-party contributed components

3. Building

3.1. Prerequisites

• Free Pascal Compiler 3.2.2 or later

• PasBuild build tool (optional but recommended)

3.1.1. Linux / FreeBSD

Install the X11 development libraries:

sudo apt-get install libx11-dev libxft-dev

3.1.2. AggPas Canvas

fpGUI uses the AggPas hybrid canvas on all platforms. Ensure the Liberation Sans font is installed on Linux/FreeBSD. On Windows, the canvas uses Arial (included with the OS) via the native Win32 TrueType font engine — no external DLL required.

3.2. Compiling the Framework

Using PasBuild from the project root:

# Linux / FreeBSD
pasbuild compile -m fpgui-framework -p unix
pasbuild compile -m fpgui-framework -p unix,debug   # with debug symbols

# Windows
pasbuild compile -m fpgui-framework -p windows
pasbuild compile -m fpgui-framework -p windows,debug  # with debug symbols

3.3. Running Tests

pasbuild test

3.4. Compiling Applications

Most applications use @extrafpc.cfg files and should be built from their respective src/ directories:

cd docview/src
fpc @extrafpc.cfg docview.lpr

4. Quick Start

program ContactForm;

{$mode objfpc}{$H+}

uses
  fpg_base, fpg_main, fpg_form, fpg_label, fpg_edit, fpg_button,
  fpg_miglayout, fpg_mig_lc, fpg_mig_cc;

type
  TMainForm = class(TfpgForm)
  public
    procedure AfterCreate; override;
  end;

procedure TMainForm.AfterCreate;
var
  mig: TfpgMigLayoutManager;
  lbl: TfpgLabel;
  edt: TfpgEdit;
  btn: TfpgButton;
begin
  inherited AfterCreate;
  WindowTitle := 'Contact Form';
  Width := 400;
  Height := 200;

  // Create a 2-column MigLayout grid
  mig := TfpgMigLayoutManager.Create;
  mig.LC.SetWrapAfter(2);
  LayoutManager := mig;

  // Row 1: Name
  lbl := TfpgLabel.Create(Self);
  lbl.Text := 'Name:';
  mig.AddLayoutComponent(lbl, TfpgMigCC.Create());

  edt := TfpgEdit.Create(Self);
  edt.PreferredSize := fpgSize(200, 24);
  mig.AddLayoutComponent(edt, TfpgMigCC.Create().GrowX());

  // Row 2: Email
  lbl := TfpgLabel.Create(Self);
  lbl.Text := 'Email:';
  mig.AddLayoutComponent(lbl, TfpgMigCC.Create());

  edt := TfpgEdit.Create(Self);
  edt.PreferredSize := fpgSize(200, 24);
  mig.AddLayoutComponent(edt, TfpgMigCC.Create().GrowX());

  // Row 3: Buttons spanning both columns
  btn := TfpgButton.Create(Self);
  btn.Text := 'OK';
  btn.PreferredSize := fpgSize(80, 24);
  mig.AddLayoutComponent(btn, TfpgMigCC.Create().SpanX.Split(2).Tag('ok'));

  btn := TfpgButton.Create(Self);
  btn.Text := 'Cancel';
  btn.PreferredSize := fpgSize(80, 24);
  mig.AddLayoutComponent(btn, TfpgMigCC.Create().Tag('cancel'));
end;

procedure MainProc;
var
  frm: TMainForm;
begin
  fpgApplication.Initialize;
  frm := TMainForm.Create(nil);
  try
    frm.Show;
    fpgApplication.Run;
  finally
    frm.Free;
  end;
end;

begin
  MainProc;
end.

5. Licensing

The fpGUI framework is distributed under the LGPL-2.1 with a static linking exception (Modified LGPL), the same license model used by the Free Pascal RTL and Lazarus LCL. This permits use in both open-source and proprietary applications without requiring the application source to be published.

See license.ModifiedLGPL.txt and license.LGPL2.txt for full details.

Component	License
Framework (framework/)	Modified LGPL
UI Designer (uidesigner/)	Modified LGPL
DocView (docview/)	GPLv2
Examples (examples/)	GPLv2
Extras (extras/)	Various (see specific directories)

6. Contributing

Contributions are welcome. Please submit pull requests against the develop branch.

7. Links

• Repository: https://github.com/graemeg/fpgui

• Free Pascal Compiler: https://www.freepascal.org