9/23/2023 0 Comments Grayscale mode in macIf you wanted to assign this functionality to a keystroke, as originally suggested, the easiest way in my opinion is to use an app like my own FastScripts. Here’s a simple C program that takes advantage of the private methods to simply toggle grayscale mode on or off, depending on the current setting. Great, so how do we call these? They’re private system functions which means you should not rely on them for production code, but for a quick hack to make toggling grayscale easier? It’s a reasonable risk in my opinion. The framework name “UniversalAccess” correlates strongly with the “UA” prefix on the pertinent function names we dug up above. System/Library/PrivateFrameworks/amework/Versions/A/UniversalAccess There’s a huge list of frameworks in the output, but the most interesting one to me is: The “otool -L” command will dump all the libraries that the preference pane “links to,” meaning the libraries it expects to load functions or data from. it expects to find these symbols, function names in this case, in another library. The capital “U” stands for “Unimplemented.” I.e. These look to me like exactly the names of functions that the preference pane is calling in order to check the current state, and to set the updated state, of the “Use grayscale” checkbox. Here’s what it spits out:Ġ000000000057210 S _OBJC_IVAR_$_UAPDisplayViewController._grayscaleCheckbox In short, that means “dump all the symbols (nm) from the VoiceOver preference pane, and search them (grep) for the word ‘gray'”. It’s a binary in /System/Library/PreferencePanes, and the following Terminal command got me on the right path:Ĭd /System/Library/PreferencePanes/UniversalAccessPref.prefPane/Contents/MacOS/ Couldn’t the option be automated via AppleScript or something? After some brief research, my conclusion was “no.”Īt this point I put on my “hacker hat” and proceeded to analyze the System Preferences code that handles the configuration. I thought there must be a way to do this in a more streamlined fashion. I could not find any easy way to do this, and searching the web for solutions revealed that most people are addressing this want by using GUI scripting to automate literally opening System Preferences and clicking the pertinent checkbox. A colleague recently asked whether it was possible to connect a custom keyboard shortcut to the system-wide “Use grayscale” setting in the macOS Voiceover system preferences:
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