Automatically adjust height of a NSTableView

Question

I have asked this question once before, but I'm just not very satisfied with the solution.

Automatically adjust size of NSTableView

I want to display a NSTableView in a NSPopover, or in a NSWindow.
Now, the window's size should adjust with the table view.

Just like Xcode does it:

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This is fairly simple with Auto Layout, you can just pin the inner view to the super view.

My problem is, that I can't figure out the optimal height of the table view. The following code enumerates all available rows, but it doesn't return the correct value, because the table view has other elements like separators, and the table head.

- (CGFloat)heightOfAllRows:(NSTableView *)tableView {
    CGFloat __block height;
    [tableView enumerateAvailableRowViewsUsingBlock:^(NSTableRowView *rowView, NSInteger row) {
        // tried it with this one
        height += rowView.frame.size.height;

        // and this one
        // height += [self tableView:nil heightOfRow:row];
    }];

    return height;
}

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1. Question

How can I fix this? How can I correctly calculate the required height of the table view.

2. Question

Where should I run this code?
I don't want to implement this in a controller, because it's definitely something that the table view should handle itself.
And I didn't even find any helpful delegate methods.

So I figured best would be if you could subclass NSTableView.
So my question 2, where to implement it?

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Motivation

Definitely worth a bounty

Answer 1

This answer is for Swift 4, targeting macOS 10.10 and later:

1. Answer

You can use the table view's fittingSize to calculate the size of your popover.

tableView.needsLayout = true
tableView.layoutSubtreeIfNeeded()

let height = tableView.fittingSize.height

2. Answer

I understand your desire to move that code out of the view controller but since the table view itself knows nothing about the number of items (only through delegation) or model changes, I would put that in the view controller. Since macOS 10.10, you can use preferredContentSize on your NSViewController inside a popover to set the size.

func updatePreferredContentSize() {
    tableView.needsLayout = true
    tableView.layoutSubtreeIfNeeded()

    let height = tableView.fittingSize.height
    let width: CGFloat = 320

    preferredContentSize = CGSize(width: width, height: height)
}

In my example, I'm using a fixed width but you could also use the calculated one (haven't tested it yet).

You would want to call the update method whenever your data source changes and/or when you're about to display the popover.

I hope this solves your problem!

Answer 2

You can query the frame of the last row to get the table view's height:

- (CGFloat)heightOfTableView:(NSTableView *)tableView
{
    NSInteger rows = [self numberOfRowsInTableView:tableView];
    if ( rows == 0 ) {
        return 0;
    } else {
        return NSMaxY( [tableView rectOfRow:rows - 1] );
    }
}

This assumes an enclosing scroll view with no borders!

You can query the tableView.enclosingScrollView.borderType to check whether the scroll view is bordered or not. If it is, the border width needs to be added to the result (two times; bottom and top). Unfortunately, I don't know of the top of my head how to get the border width.

The advantage of querying rectOfRow: is that it works in the same runloop iteration as a [tableView reloadData];. In my experience, querying the table view's frame does not work reliably when you do a reloadData first (you'll get the previous height).

Answer 3

Interface Builder in Xcode automatically puts the NSTableView in an NSScrollView. The NSScrollView is where the headers are actually located. Create a NSScrollView as your base view in the window and add the NSTableView to it:

NSScrollView * scrollView = [[NSScrollView alloc]init];
[scrollView setHasVerticalScroller:YES];
[scrollView setHasHorizontalScroller:YES];
[scrollView setAutohidesScrollers:YES];
[scrollView setBorderType:NSBezelBorder];
[scrollView setTranslatesAutoresizingMaskIntoConstraints:NO];

NSTableView * table = [[NSTableView alloc] init];
[table setDataSource:self];
[table setColumnAutoresizingStyle:NSTableViewUniformColumnAutoresizingStyle];
[scrollView setDocumentView:table];

//SetWindow's main view to scrollView

Now you can interrogate the scrollView's contentView to find the size of the NSScrollView size

NSRect rectOfFullTable = [[scrollView contentView] documentRect];

Because the NSTableView is inside an NSScrollView, the NSTableView will have a headerView which you can use to find the size of your headers.

You could subclass NSScrollView to update it's superview when the table size changes (headers + rows) by overriding the reflectScrolledClipView: method

Answer 4

I'm not sure if my solution is any better than what you have, but thought I'd offer it anyway. I use this with a print view. I'm not using Auto Layout. It only works with bindings – would need adjustment to work with a data source.

You'll see there's an awful hack to make it work: I just add 0.5 to the value I carefully calculate.

This takes the spacing into account but not the headers, which I don't display. If you are displaying the headers you can add that in the -tableView:heightOfRow: method.

In NSTableView subclass or category:

- (void) sizeHeightToFit {
    CGFloat height = 0.f;
    if ([self.delegate respondsToSelector:@selector(tableView:heightOfRow:)]) {
        for (NSInteger i = 0; i < self.numberOfRows; ++i)
            height = height +
                     [self.delegate tableView:self heightOfRow:i] +
                     self.intercellSpacing.height;
    } else {
        height = (self.rowHeight + self.intercellSpacing.height) *
                 self.numberOfRows;
    }

    NSSize frameSize = self.frame.size;
    frameSize.height = height;
    [self setFrameSize:frameSize];
}

In table view delegate:

// Invoke bindings to get the cell contents
// FIXME If no bindings, use the datasource
- (NSString *) stringValueForRow:(NSInteger) row column:(NSTableColumn *) column {
    NSDictionary *bindingInfo = [column infoForBinding:NSValueBinding];

    id object = [bindingInfo objectForKey:NSObservedObjectKey];
    NSString *keyPath = [bindingInfo objectForKey:NSObservedKeyPathKey];

    id value = [[object valueForKeyPath:keyPath] objectAtIndex:row];

    if ([value isKindOfClass:[NSString class]])
        return value;
    else
        return @"";
}

- (CGFloat) tableView:(NSTableView *) tableView heightOfRow:(NSInteger) row {

    CGFloat result = tableView.rowHeight;

    for (NSTableColumn *column in tableView.tableColumns) {
        NSTextFieldCell *dataCell = column.dataCell;
        if (![dataCell isKindOfClass:[NSTextFieldCell class]]) continue;

        // Borrow the prototype cell, and set its text
        [dataCell setObjectValue:[self stringValueForRow:row column:column]];

        // Ask it the bounds for a rectangle as wide as the column
        NSRect cellBounds = NSZeroRect;
        cellBounds.size.width = [column width]; cellBounds.size.height = FLT_MAX;
        NSSize cellSize = [dataCell cellSizeForBounds:cellBounds];

        // This is a HACK to make this work.
        // Otherwise the rows are inexplicably too short.
        cellSize.height = cellSize.height + 0.5;

        if (cellSize.height > result)
            result = cellSize.height;
    }

    return result;
}