Cocoa

Fun With PyObjc: Growl Notification Hell

Most of the time PyObjc is wonderful to work in, I love the python libraries and language.

Other times it just makes me angry.

It seems, at least initially, that PyObjc (2.2b3, the default installation with 10.6 snow leopard) does not work with the Growl framework. You can register your application with growl fine, but if you try to push notifications to growl nothing happens.

Here is what I tried initially to post a growl notification in pyobjc:

[code lang=”python”] GrowlApplicationBridge.notifyWithTitle_description_notificationName_iconData_priority_isSticky_clickContext_(u”Notification”, “A description.”, u”Notification”, objc.nil, 0, objc.NO, objc.nil) [/code]

This does not work, and for a minute I thought I was the only one experiencing this problem (all open source pyobjc projects using growl had almost identical growl notification code) until I found this commit message on github. I found an associated discussion on the growl discussion group and was disheartened that the developer resorted using a command line version of growl to post notifications. However I decided to try one last thing, and checked the className of python objects passed through the objc bridge.

Here is a table of the objc className of different string creation methods in python:

Interestingly enough a python string (unicode, str, raw) is not ‘toll free’ bridged like CFString & NSString are. I guess this is to be expected and shouldn’t cause any problems since both OC_PythonString and OC_PythonUnicode are subclasses of NSString, the documentation even states “A Python unicode may be used anywhere a NSString is expected”. It seems that this is not always the case though. I tried one last thing before resorting to rewriting the code in objc:

[code lang=”python”] GrowlApplicationBridge.notifyWithTitle_description_notificationName_iconData_priority_isSticky_clickContext_(NSString.stringWithString_(“Notification”), NSString.stringWithString_(“A description.”), NSString.stringWithString_(“Notification”), objc.nil, 0, objc.NO, objc.nil) [/code]

And it worked. Note that the created NSString’s don’t get converted by the bridge into a OC_PythonString object, they pass through as regular NSString’s. Note that you also write the above as the more python native:

[code lang=”python”] GrowlApplicationBridge.notifyWithTitle_description_notificationName_iconData_priority_isSticky_clickContext_(NSString.stringWithString_(“Notification”), NSString.stringWithString_(“A description.”), NSString.stringWithString_(“Notification”), False, 0, False, None) [/code]

One other interesting that I found is that bridge throws a memory leak warning when running NSString.alloc().initWithString_("Notification"):

[code] UninitializedDeallocWarning: leaking an uninitialized object of type NSPlaceholderString [/code]

My only guess is that because initWithString is called instead of init the bridge sees it as a uninitialized object (so I would guess that this warning is falsely thown). Unfortunately the PyObjc documentation is too sparse for me to able to determine what the real cause of the error is.

Jump To A HTML Anchor in a WebView

This isn’t something that is as straightfoward as you would think. There is no real ‘cocoa native’ way to acomplish this, and there seemed to be no information anywhere on how to acomplish this until I found this post. So it seems the only way to scroll to an anchor is to resort to evaluating javascript code: [code lang=”javascript”] – (void) jumpToAnchor:(NSString *)anchor { [oWebView stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@”var anchor = document.anchors[“%@”];window.scrollTo(anchor.offsetLeft, anchor.offsetTop);”, anchor]]; } [/code]

mach_override on Intel Macs

I was disappointed last month when after a hour or two of hacking I couldn’t get mach_override (evil, I know) to work on my new MacBook Pro even though it had been ported to intel macs. I added myself to the procmod group and tried everything that google could come up with, but I could only get it to succesfully override local functions, it wouldn’t override any library/system functions no-matter what i did.

Today I’ve found the solution on the ExtendAMac mailing list hosted on sourceforge: this simple post contains a small patch that seems to fix all the issues I’ve been having. There doesn’t seem to be any replies to the post on the mailing list, and the post wont come up on any google searched related to mach_override on intel macs – pretty frusterating when you don’t know about the ExtendAMac mailing list. The solution is very simple, replace this block of code: [code lang=”c”] static AsmInstructionMatch possibleInstructions[] = { { 0x1, {0xFF}, {0x90} }, // nop { 0x1, {0xFF}, {0x55} }, // push %esp { 0x2, {0xFF, 0xFF}, {0x89, 0xE5} }, // mov %esp,%ebp { 0x1, {0xFF}, {0x53} }, // push %ebx { 0x3, {0xFF, 0xFF, 0x00}, {0x83, 0xEC, 0x00} }, // sub 0x??, %esp { 0x0 } }; [/code]

with this:

[code lang=”c”] static AsmInstructionMatch possibleInstructions[] = { { 0x1, {0xFF}, {0x90} }, // nop { 0x1, {0xF8}, {0x50} }, // push %eax | %ebx | %ecx | %edx | %ebp | %esp | %esi | %edi { 0x2, {0xFF, 0xFF}, {0x89, 0xE5} }, // mov %esp,%ebp { 0x3, {0xFF, 0xFF, 0x00}, {0x83, 0xEC, 0x00} }, // sub 0x??, %esp { 0x0 } }; [/code]

Hopefully this helps someone who was banging their head against the wall trying to figure this out like I was!

Add To Login/Startup Items Functionality

Such a simple piece of functionality, you would assume it would be trivial to implement. As you might have guessed – it’s not. There has been a few hack-ishy ways outlined here but none are complete and easy to integrate into your app.

I’ve created MABLoginItems, an easy way to add the ‘add to startup items’ functionality into your application. With one line of code you can add your application to the users login items (you can also remove from login items, and check if the application already exists in the login items). MABLoginItems is released under a BSD license, you can download it here.