Cocoa Internals

The page is about Cocoa Widgetset internal implementation. The page should be useful for Cocoa widgetset developers (maintainers and/or constributors) as well as any developers who need to use Cocoa specific API.

LCL specific ObjC classes

In order to control and handle an NSView's behavior LCL uses decedent classes from standard Cocoa controls. I.e. for NSWindow TCocoaWindow is introduced. The decedent are used for the purpose of "overriding" default class implementation, where it is needed. In some cases using delegate classes is not enough.

Handles

• Window handle (HWND) is always NSView.
  • TCustomWSForm it is content NSView.
  • Any control that has scroll bars (i.e. TCustomWSList) the it its the embedding NSScrollView (TCocoaScrollView)

LCL Control	Cocoa class	Notes
TMemo	NSTextView inside a NSScrollView	-

Code Style

The following requirement applies for Cocoa widgetset. Other widgetset my be following some other rules (historically), but in general LCL follows the same requirements.

• Operators Keep the operator separated by spaces between operands

 A := B; 
 A := B * C;

• Blocks The main rule is to make 2 character spacing from the code block start. Begin / Else should start on a new line.

procedure B;
begin
  if A then // 2 character spacing from begin
  begin
    Start Here // 2 character spacing from begin
    Next Line
  end
  else
  begin
    Another Line
  end;
end;

• Standard Function Name please keep naming in ProperCase. Reserved words should be lower case. Name of (global/local) variables and fields should match declaration. (local variables should start with lower case)

 if not Assigned(A) then
 begin
   Result := nil;
 end;

Themed Drawing / Custom Controls

HITheme API is deprecated by Apple together with Carbon. It's still available in OSX, but for i386 only. Presumably will be completely removed on 64-bit only OSX.

However, some LCL controls cannot be mapped to existing Cocoa provided controls and thus might require some "custom drawing". The drawing should look system native though. In order to achieve that NSCell family could be used. NSCell allows to draw (hit-test and as well as handle user input) for OSX native elements. If Apple to change appears of controls (cells), the LCL application would "pick-up" the look automatically.

In order to be drawn NSCells requires a present of NSView, thus it's hard to use them forthe implementation of LCL TTheme APIs

Example of NSCell usage is CocoaStatusBar drawing

Fonts

NSFont class provides a number of class methods to get proper system font without selecting the font by name. The same of getting system-native font size.

Writing a Cocoa app without the LCL

This is useful for testing hard to debug bugs in the LCL. Here is an example program written in Pascal-Cocoa which creates a window with 2 buttons and a simple set of menus:

program cocoa_without_lcl;

{$mode objfpc}{$H+}
{$modeswitch objectivec1}

uses
  CocoaAll, classes, sysutils;

type
  { TMyDelegate }
  TMyDelegate = objcclass(NSObject)
  public
    procedure HandleButtonClick_A(sender: id); message 'HandleButtonClick_A:';
    procedure HandleButtonClick_B(sender: id); message 'HandleButtonClick_B:';
    procedure HandleMenuClick_A(sender: id); message 'HandleMenuClick_A:';
    procedure HandleMenuClick_B(sender: id); message 'HandleMenuClick_B:';
  end;

var
  appName: NSString;
  window: NSWindow;
  pool: NSAutoreleasePool;
  lText: NSTextField;
  lButton: NSButton;
  lDelegate: TMyDelegate;
  //
  MainMenu_A: NSMenu;
  TopItem_A: NSMenuItem;
  TopMenu_A: NSMenu;
  MenuItem_A: NSMenuItem;
  //
  MainMenu_B: NSMenu;
  TopItem_B: NSMenuItem;
  TopMenu_B: NSMenu;
  MenuItem_B: NSMenuItem;

procedure TMyDelegate.HandleButtonClick_A(sender: id);
begin
  NSApp.setMainMenu(MainMenu_A);
end;

procedure TMyDelegate.HandleButtonClick_B(sender: id);
begin
  NSApp.setMainMenu(MainMenu_B);
end;

procedure TMyDelegate.HandleMenuClick_A(sender: id);
var
  Str: string;
begin
  Str := 'A '+inttostr(random(888));
  window.setTitle(NSSTR(@Str[1]));
end;

procedure TMyDelegate.HandleMenuClick_B(sender: id);
var
  Str: string;
begin
  Str := 'B '+inttostr(random(888));
  window.setTitle(NSSTR(@Str[1]));
end;

procedure CreateMenus;
var
  nsTitle: NSString;
  nsKey  : NSString;

  function CreateMenuItem(AName, AShortcut: string; ASelector: SEL): NSMenuItem;
  begin
    nsKey := NSSTR(PChar(AShortcut));
    nsTitle := NSSTR(PChar(AName));
    Result := NSMenuItem.alloc.initWithTitle_action_keyEquivalent(nsTitle, ASelector, nsKey);
    Result.setKeyEquivalentModifierMask(NSCommandKeyMask);
    nsTitle.release;
    nsKey.release;
    Result.setKeyEquivalentModifierMask(NSCommandKeyMask);
    Result.setTarget(lDelegate);
  end;

begin
  MainMenu_A := NSMenu.alloc.initWithTitle(NSSTR('Menu A'));
  TopItem_A := CreateMenuItem('TopItem A', '', nil);
  MainMenu_A.insertItem_atIndex(TopItem_A, 0);
  TopMenu_A := NSMenu.alloc.initWithTitle(NSSTR('TopMenu A'));
  TopItem_A.setSubmenu(TopMenu_A);
  MenuItem_A := CreateMenuItem('MenuItem A', 'A', objcselector('HandleMenuClick_A:'));
  MenuItem_A.setTarget(lDelegate);
  TopMenu_A.insertItem_atIndex(MenuItem_A, 0);

  MainMenu_B := NSMenu.alloc.initWithTitle(NSSTR('Menu B'));
  TopItem_B := CreateMenuItem('TopItem B', '', nil);
  MainMenu_B.insertItem_atIndex(TopItem_B, 0);
  TopMenu_B := NSMenu.alloc.initWithTitle(NSSTR('TopMenu B'));
  TopItem_B.setSubmenu(TopMenu_B);
  MenuItem_B := CreateMenuItem('MenuItem B', 'B', objcselector('HandleMenuClick_B:'));
  MenuItem_B.setTarget(lDelegate);
  TopMenu_B.insertItem_atIndex(MenuItem_B, 0);
end;


begin
  // Autorelease pool, app and window creation
  pool := NSAutoreleasePool.new;
  NSApp := NSApplication.sharedApplication;
  NSApp.setActivationPolicy(NSApplicationActivationPolicyRegular);
  appName := NSProcessInfo.processInfo.processName;
  window := NSWindow.alloc.initWithContentRect_styleMask_backing_defer(NSMakeRect(0, 0, 200, 200),
    NSTitledWindowMask or NSClosableWindowMask or NSMiniaturizableWindowMask,
    NSBackingStoreBuffered, False).autorelease;
  lDelegate := TMyDelegate.alloc.init;

  // text label
  lText := NSTextField.alloc.initWithFrame(NSMakeRect(50, 50, 120, 50)).autorelease;
  lText.setBezeled(False);
  lText.setDrawsBackground(False);
  lText.setEditable(False);
  lText.setSelectable(False);
  lText.setStringValue(NSSTR('NSTextField'));
  window.contentView.addSubview(lText);

  // button
  lButton := NSButton.alloc.initWithFrame(NSMakeRect(50, 100, 120, 50)).autorelease;
  window.contentView.addSubview(lButton);
  lButton.setTitle(NSSTR('Button A!'));
  lButton.setButtonType(NSMomentaryLightButton);
  lButton.setBezelStyle(NSRoundedBezelStyle);
  // button event handler setting
  lButton.setTarget(lDelegate);
  lButton.setAction(ObjCSelector(lDelegate.HandleButtonClick_A));

  // button B
  lButton := NSButton.alloc.initWithFrame(NSMakeRect(50, 150, 120, 50)).autorelease;
  window.contentView.addSubview(lButton);
  lButton.setTitle(NSSTR('Button B!'));
  lButton.setButtonType(NSMomentaryLightButton);
  lButton.setBezelStyle(NSRoundedBezelStyle);
  // button event handler setting
  lButton.setTarget(lDelegate);
  lButton.setAction(ObjCSelector(lDelegate.HandleButtonClick_B));

  // Menus
  CreateMenus();
  NSApp.setMainMenu(MainMenu_A);

  // Window showing and app running
  window.center;
  window.setTitle(appName);
  window.makeKeyAndOrderFront(nil);
  NSApp.activateIgnoringOtherApps(true);
  NSApp.run;
end.

See Also

• Cocoa Interfaces