Difference between revisions of "Cocoa Internals"
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** Any control that has scroll bars (i.e. TCustomWSList) the it its the embedding NSScrollView (TCocoaScrollView) | ** Any control that has scroll bars (i.e. TCustomWSList) the it its the embedding NSScrollView (TCocoaScrollView) | ||
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! LCL Control | ! LCL Control | ||
! Cocoa class | ! Cocoa class |
Revision as of 18:39, 23 December 2017
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 | |
TGroupBox | TCocoaGroupBox (NSBox) | There's also a content view created to hold all the child controls within the box |
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 Interface
- Cocoa Internals/Buttons - provides the information about internal implementation of Button controls.