How to do batch display using NSTextView - appkit

Question

I'd like to be able to show a view that resembles something like a console log, with multiple lines of text that are scrollable and selectable.
The fundamental procedure I have in mind is maintaining an array of strings (call it lines) and appending these to the textStorage of the NSTextView using a new line character as delimiter.
However there are a few factors to consider, such as:
Updating the textStorage on scroll so that it appears seamless to the user
Updating the textStorage on resizing the view height
Maintaining scroll position after the textStorage gets updated
Handling an out of memory possibility
Can someone please provide some guidance or a sample to get me started?

Answer 1

Add a string from your array to the NSTextStorage and animate the NSClipView bounds origin.
- (void)appendText:(NSString*)string {
// Add a newline, if you need to
string = [NSString stringWithFormat:#"%#\n", string];
// Find range
[self.textView.textStorage replaceCharactersInRange:NSMakeRange(self.textView.textStorage.string.length, 0) withString:string];
// Get clip view
NSClipView *clipView = self.textView.enclosingScrollView.contentView;
// Calculate the y position by subtracting
// clip view height from total document height
CGFloat scrollTo = self.textView.frame.size.height - clipView.frame.size.height;
// Animate bounds
[[clipView animator] setBoundsOrigin:NSMakePoint(0, scrollTo)];
}
If you have elasticity set in your NSTextView you need to monitor for its frame changes to get exact results. Add frameDidChange listener to your text view and animate in the handler:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
// Text view setup
[_textView setPostsFrameChangedNotifications:YES];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(scrollToBottom) name:NSViewFrameDidChangeNotification object:_textView];
}
- (void)appendText:(NSString*)string {
// Add a newline, if you need to
string = [NSString stringWithFormat:#"%#\n", string];
// Find range
[self.textView.textStorage replaceCharactersInRange:NSMakeRange(self.textView.textStorage.string.length, 0) withString:string];
}
- (void)scrollToBottom {
// Get the clip view and calculate y position
NSClipView *clipView = self.textView.enclosingScrollView.contentView;
// Y position for bottom is document's height - viewport height
CGFloat scrollTo = self.textView.frame.size.height - clipView.frame.size.height;
[[clipView animator] setBoundsOrigin:NSMakePoint(0, scrollTo)];
}
In real-life application you would probably need to set some sort of threshold to see if the user has scrolled away from the end more than the height of a line.