Cocoa Interface

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Revision as of 21:12, 15 February 2019 by McSquirrel (talk | contribs) (Compiling: added instructions for compiling Cocoa 64bit apps)

This article applies to macOS only.

See also: Multiplatform Programming Guide

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This article applies to iOS only.

See also: Multiplatform Programming Guide

Other Interfaces

Platform specific Tips

Interface Development Articles

Cocoa bindings

This interface uses the native support in Free Pascal for direct communication with Objective-C was added through the Objective Pascal dialect.


Prepare your Lazarus project for using Cocoa

You may need to set the Target to the 64bit processor and select the Cocoa Widget set:

  • Open your project with Lazarus and click Project/ProjectOptions
  • In the "Config and Target" panel set the "Target CPU family" to be "x86_64"
  • In the "Additions and Overrides" panel click on "Set LCLWidgetType" pulldown and set the value to "Cocoa"
  • In the past, for some reason Lazarus kept setting the compiler to "/usr/local/bin/ppc386" - which results in 32 bit apps. Make sure under Tools->Options that "Compiler Executable" is set to "/usr/local/bin/fpc" to get 64 bit apps.
  • Now compile your project - with any luck it will work OK.

Error ATSUFindFontFromName

if you're getting an error

carbonproc.pp(563,13) Error: Identifier not found "ATSUFindFontFromName"

when compiling a project for macOS using FPC 3.0.4 you need:

  • either set CPU target explicitly to i386. (FPC 3.0.4 compiles to x86_64 for darwin target by default. This is done due Apple stopping support for 32-bit target)
  • You either set the target in Project options (by switching it from default to i386)
  • or if you compiling from command-line (i.e building an IDE) set up the following parameter to make command
  • either set LCL target (widgetset) to "Cocoa"

Cocoa FAQ

TButton looks too small!

If you design a button in another widgetset with Autosize=Off it might happen that the button looks too small in Cocoa, and a number of people complained about this, such as in these BTS reports: [1].

If you don't care about the button size, just set AutoSize=True. If you want to have a custom width for the button, but wants to allow the LCL to choose the right Height so that the button will look good in Cocoa, then the solution in this case is to set the following properties in the Object Inspector:

  • AutoSize=True
  • Constrains.MinWidth = Constrains.MaxWidth = your desired width.

Overlapping Widgets

Lazarus allows you to set the depth of different widgets, such that when two widgets overlap, the "closer" object blocks the view of the more "distant" object. You can do this at design time (right-click on object and click "Z-order") or at run time with functions like "BringToFront" and "SendToBack". Be aware that this may not always work with Cocoa. This is a 'feature' of Cocoa, as clipping is optimized for performance. Therefore, if you plan to compile your projects for Cocoa it is a good strategy to avoid overlapping widgets or to place them on different panels to provide explicit control of Z-order. For more details [2].


Located here: Roadmap#Status_of_features_on_each_widgetset