The LCL in various platforms

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Many LCL properties, methods and other functionality represent a concept, which is then mapped to a specific native behavior in each platform. This sections aims at clarifying LCL behavior which changes across platforms by clarifying what is to be expected in each platform so that more reliable software can be built.

Linker options

The LCL passes various linker options depending on platform. Here is the conditionals script from the LCL:

// linker options
if TargetOS='darwin' then begin
  if LCLWidgetType='gtk' then
    UsageLibraryPath := '/usr/X11R6/lib;/sw/lib'
  else if LCLWidgetType='gtk2' then
    UsageLibraryPath := '/usr/X11R6/lib;/sw/lib;/sw/lib/pango-ft219/lib'
  else if LCLWidgetType='carbon' then begin
    UsageLinkerOptions := '-framework Carbon'
      +' -framework OpenGL'
      +' ''-dylib_file'' ''/System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib:/System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib''';
  end else if LCLWidgetType='cocoa' then
    UsageLinkerOptions := '-framework Cocoa';
end else if TargetOS='solaris' then begin


The BorderStyle of a Form represents a kind of form, and different platforms have different standards about how should the border of each kind of form be, and the LCL respects that. For example, message dialogs are usually not resizable under Windows, but resizable under X11-based Unixes. By using bsDialog it is possible to create a form which will have the adequate dialog appearance in every platform. Bellow is a full list of expected behaviors:


BorderStyle Has Border? Resizable? Decoration
bsNone No No None
bsDialog Yes No Only X (Close)
bsSingle Yes No All
bsSizable Yes Yes All
bsSizeToolWin Yes Yes Only X and small title
bsToolWin Yes No Only X and small title

Windows CE

For Windows CE see here: Windows_CE_Development_Notes#Positioning_and_size_of_Dialogs_and_Forms


Under Gtk on X11 the best one can do is ask the window manager to set a certain style, and it may ignore our request, so nothing, except sizable border vs. no border at all is guaranteed. i.e. only bsSizable and bsNone have a guaranteed behavior and the other ones will be either somewhere in between or equal to bsSizable.

Gtk 1 Gtk 2
BorderStyle Has Border? Resizable? Decoration Has Border? Resizable? Decoration
bsNone No No None No No None
bsDialog Yes Yes* All* Yes Yes* All*
bsSingle Yes No (WM) All Yes No (WM) All
bsSizable Yes Yes All Yes Yes All
bsSizeToolWin Yes Yes All* Yes Yes All*
bsToolWin Yes No (WM) All* Yes No (WM) All*

Values with * differ from the Windows Implementation.

Values with (WM) indicate that the feature is Window Manager specific.

Associated bug track items: [1]


Shortcut Keys

Some Key sequences cannot be used by the Application in some platforms because the Operating System or Windows Manager is already using them. Bellow is a list for each platform.

Mac OS X

You should refer to Apple Human Interface Guidelines for system reserved shortcuts:

Key Sequence Alternative Description
F12 / Shift+F12 ? F12 Brings the Dashboard
F11 / Shift+F11 ? F11 Shows the Desktop

Popup Menus

Normally the popup menus are the items in the TPopupMenu assigned to the PopupMenu property.

GTK (1+2)

The GTK automatically adds to the TNoteBook and TPageControl headers for each page a menu item to quick jump to the page.


The GTK2 automatically adds to all edit controls like TEdit and TComboBox unicode and accessibility items.

Command line parameters

Some widgetsets parse the command line parameters and react to some parameters.


  • --gtk-module
  • --g-fatal-warnings
  • --gtk-debug
  • --gtk-no-debug
  • --gdk-debug
  • --gdk-no-debug
  • --display
  • --sync
  • --no-xshm
  • --name
  • --class