Difference between revisions of "Cocoa Interface"

From Free Pascal wiki
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m (macOS 10.10 and earlier)
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===macOS 10.10 and earlier===
===macOS 10.10 and earlier===
The precompiled CocoaAll header
The precompiled CocoaAll header comes with the instruction to link CoreImage framework. The framework was introduced in macOS10.11 and later.
  make rtl
  make rtl
  make pacakges
  make pacakges

Revision as of 05:33, 21 June 2020

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.

FPC 3.2.0 for older macOS

It's likely you will not encounter ANY problems using FPC 3.2.0 on macOS 10.11 and later.

macOS 10.10 and earlier

The precompiled CocoaAll header comes with the instruction to link CoreImage framework. The framework was introduced in macOS10.11 and later.

make rtl
make pacakges

for version prior to 10.8 (see the note below

make rtl OPT="-Aas-darwin -WM10.4"
make packages OPT="-Aas-darwin -WM10.4"

macOS 10.7 and earlier

If after updating to FPC 3.2. update, you're getting following error during compilation:

Error: Assembler clang not found, switching to external assembling

You need to add the following options to the compilation

-Aas-darwin -MW10.4

(where -MW10.x can match your hosting system. It doesn't have to be 10.4)

However, if you don't want to each of your project compilation settings, you can simply update /etc/fpc.cfg file, by adding the following lines to the beginning of the configuration file

## this is new for FPC 3.2.0
## it's default target changed to macOS 10.8
## thus clang is used by default and some extra CRT is used
## the actual -WM version might vary


  • editing /etc/fpc.cfg requires admin privileges.
  • if you're not using default /etc/fpc.cfg you might want to edit the configuration file your compiler relies on

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

DPI and scaling issues

See the Cocoa DPI article.

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