Difference between revisions of "Cocoa Interface"

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[[Roadmap|Roadmap: Status of Features in each Widget set]]
[[Roadmap|Roadmap: Status of Features in each Widget set]]

Revision as of 17:56, 16 December 2019

English (en)


This article applies to macOS only.

See also: Multiplatform Programming Guide

Other Interfaces

Platform specific Tips

Interface Development Articles

Cocoa bindings

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


Use FPC 3.0.4a

For macOS 10.14 Mojave and later you should be installing FPC 3.0.4a available at the official site.

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/Project Options
  • 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 the error:

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

when compiling a project for macOS using FPC 3.0.4, you either:

  • set the CPU target explicitly to i386. (FPC 3.0.4 compiles to x86_64 for the Darwin target by default. This is done due Apple having dropped support for 32-bit target in macOS 10.15 Catalina released in October 2019.)
  • by setting the target in Project options (switching it from default to i386)
  • by setting the CPU_TARGET=i386 parameter for the make command if compiling from the command line.
  • or set the LCL target (widgetset) to "Cocoa".

Cocoa Debugging

See the Cocoa Debugging article.

Cocoa FAQ

TButton looks too small!

If you design a button in another widgetset with Autosize=False it might happen that the button looks too small in Cocoa, and a number of people have complained about this, such as in this bug report.

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 want 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 see this bug report.


Roadmap: Status of Features in each Widget set