View-based NSTableView with rows that have dynamic heights

I have an application with a view-based NSTableView in it. Inside this table view, I have rows that have cells that have content consisting of a multi-row NSTextField with word-wrap enabled. Depending on the textual content of the NSTextField, the size of the rows needed to display the cell will vary.

I know that I can implement the NSTableViewDelegate method -tableView:heightOfRow: to return the height, but the height will be determined based on the word wrapping used on the NSTextField. The word wrapping of the NSTextField is similarly based on how wide the NSTextField is… which is determined by the width of the NSTableView.

Soooo… I guess my question is… what is a good design pattern for this? It seems like everything I try winds up being a convoluted mess. Since the TableView requires knowledge of the height of the cells to lay them out... and the NSTextField needs knowledge of it's layout to determine the word wrap… and the cell needs knowledge of the word wrap to determine it's height… it's a circular mess… and it's driving me insane.

Suggestions?

If it matters, the end result will also have editable NSTextFields that will resize to adjust to the text within them. I already have this working on the view level, but the tableview does not yet adjust the heights of the cells. I figure once I get the height issue worked out, I'll use the -noteHeightOfRowsWithIndexesChanged method to inform the table view the height changed… but it's still then going to ask the delegate for the height… hence, my quandry.

Thanks in advance!

This is a chicken and the egg problem. The table needs to know the row height because that determines where a given view will lie. But you want a view to already be around so you can use it to figure out the row height. So, which comes first?

The answer is to keep an extra NSTableCellView (or whatever view you are using as your "cell view") around just for measuring the height of the view. In the tableView:heightOfRow: delegate method, access your model for 'row' and set the objectValue on NSTableCellView. Then set the view's width to be your table's width, and (however you want to do it) figure out the required height for that view. Return that value.

Don't call noteHeightOfRowsWithIndexesChanged: from in the delegate method tableView:heightOfRow: or viewForTableColumn:row: ! That is bad, and will cause mega-trouble.

To dynamically update the height, then what you should do is respond to the text changing (via the target/action) and recalculate your computed height of that view. Now, don't dynamically change the NSTableCellView's height (or whatever view you are using as your "cell view"). The table must control that view's frame, and you will be fighting the tableview if you try to set it. Instead, in your target/action for the text field where you computed the height, call noteHeightOfRowsWithIndexesChanged:, which will let the table resize that individual row. Assuming you have your autoresizing mask setup right on subviews (i.e.: subviews of the NSTableCellView), things should resize fine! If not, first work on the resizing mask of the subviews to get things right with variable row heights.

Don't forget that noteHeightOfRowsWithIndexesChanged: animates by default. To make it not animate:

[NSAnimationContext beginGrouping];
[[NSAnimationContext currentContext] setDuration:0];
[tableView noteHeightOfRowsWithIndexesChanged:indexSet];
[NSAnimationContext endGrouping];

PS: I respond more to questions posted on the Apple Dev Forums than stack overflow.

PSS: I wrote the view based NSTableView

This got a lot easier in macOS 10.13 with .usesAutomaticRowHeights. The details are here: https://developer.apple.com/library/content/releasenotes/AppKit/RN-AppKit/#10_13 (In the section titled "NSTableView Automatic Row Heights").

Basically you just select your NSTableView or NSOutlineView in the storyboard editor and select this option in the Size Inspector:

Then you set the stuff in your NSTableCellView to have top and bottom constraints to the cell and your cell will resize to fit automatically. No code required!

Your app will ignore any heights specified in heightOfRow (NSTableView) and heightOfRowByItem (NSOutlineView). You can see what heights are getting calculated for your auto layout rows with this method:

func outlineView(_ outlineView: NSOutlineView, didAdd rowView: NSTableRowView, forRow row: Int) {
  print(rowView.fittingSize.height)
}

Based on Corbin's answer (btw thanks shedding some light on this):

Swift 3, View-Based NSTableView with Auto-Layout for macOS 10.11 (and above)

My setup: I have a NSTableCellView that is laid out using Auto-Layout. It contains (besides other elements) a multi-line NSTextField that can have up to 2 rows. Therefore, the height of the whole cell view depends on the height of this text field.

I update tell the table view to update the height on two occasions:

1) When the table view resizes:

func tableViewColumnDidResize(_ notification: Notification) {
        let allIndexes = IndexSet(integersIn: 0..<tableView.numberOfRows)
        tableView.noteHeightOfRows(withIndexesChanged: allIndexes)
}

2) When the data model object changes:

tableView.noteHeightOfRows(withIndexesChanged: changedIndexes)

This will cause the table view to ask it's delegate for the new row height.

func tableView(_ tableView: NSTableView, heightOfRow row: Int) -> CGFloat {

    // Get data object for this row
    let entity = dataChangesController.entities[row]

    // Receive the appropriate cell identifier for your model object
    let cellViewIdentifier = tableCellViewIdentifier(for: entity)

    // We use an implicitly unwrapped optional to crash if we can't create a new cell view
    var cellView: NSTableCellView!

    // Check if we already have a cell view for this identifier
    if let savedView = savedTableCellViews[cellViewIdentifier] {
        cellView = savedView
    }
    // If not, create and cache one
    else if let view = tableView.make(withIdentifier: cellViewIdentifier, owner: nil) as? NSTableCellView {
        savedTableCellViews[cellViewIdentifier] = view
        cellView = view
    }

    // Set data object
    if let entityHandler = cellView as? DataEntityHandler {
        entityHandler.update(with: entity)
    }

    // Layout
    cellView.bounds.size.width = tableView.bounds.size.width
    cellView.needsLayout = true
    cellView.layoutSubtreeIfNeeded()

    let height = cellView.fittingSize.height

    // Make sure we return at least the table view height
    return height > tableView.rowHeight ? height : tableView.rowHeight
}

First, we need to get our model object for the row (entity) and the appropriate cell view identifier. We then check if we have already created a view for this identifier. To do that we have to maintain a list with cell views for each identifier:

// We need to keep one cell view (per identifier) around
fileprivate var savedTableCellViews = [String : NSTableCellView]()

If none is saved, we need to created (and cache) a new one. We update the cell view with our model object and tell it to re-layout everything based on the current table view width. The fittingSize height can then be used as the new height.

For anyone wanting more code, here is the full solution I used. Thanks corbin dunn for pointing me in the right direction.

I needed to set the height mostly in relation to how high a NSTextView in my NSTableViewCell was.

In my subclass of NSViewController I temporary create a new cell by calling outlineView:viewForTableColumn:item:

- (CGFloat)outlineView:(NSOutlineView *)outlineView heightOfRowByItem:(id)item
{
    NSTableColumn *tabCol = [[outlineView tableColumns] objectAtIndex:0];
    IBAnnotationTableViewCell *tableViewCell = (IBAnnotationTableViewCell*)[self outlineView:outlineView viewForTableColumn:tabCol item:item];
    float height = [tableViewCell getHeightOfCell];
    return height;
}

- (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item
{
    IBAnnotationTableViewCell *tableViewCell = [outlineView makeViewWithIdentifier:@"AnnotationTableViewCell" owner:self];
    PDFAnnotation *annotation = (PDFAnnotation *)item;
    [tableViewCell setupWithPDFAnnotation:annotation];
    return tableViewCell;
}

In my IBAnnotationTableViewCell which is the controller for my cell (subclass of NSTableCellView) I have a setup method

-(void)setupWithPDFAnnotation:(PDFAnnotation*)annotation;

which sets up all outlets and sets the text from my PDFAnnotations. Now I can "easily" calcutate the height using:

-(float)getHeightOfCell
{
    return [self getHeightOfContentTextView] + 60;
}

-(float)getHeightOfContentTextView
{
    NSDictionary *attributes = [NSDictionary dictionaryWithObjectsAndKeys:[self.contentTextView font],NSFontAttributeName,nil];
    NSAttributedString *attributedString = [[NSAttributedString alloc] initWithString:[self.contentTextView string] attributes:attributes];
    CGFloat height = [self heightForWidth: [self.contentTextView frame].size.width forString:attributedString];
    return height;
}

.

- (NSSize)sizeForWidth:(float)width height:(float)height forString:(NSAttributedString*)string
{
    NSInteger gNSStringGeometricsTypesetterBehavior = NSTypesetterLatestBehavior ;
    NSSize answer = NSZeroSize ;
    if ([string length] > 0) {
        // Checking for empty string is necessary since Layout Manager will give the nominal
        // height of one line if length is 0.  Our API specifies 0.0 for an empty string.
        NSSize size = NSMakeSize(width, height) ;
        NSTextContainer *textContainer = [[NSTextContainer alloc] initWithContainerSize:size] ;
        NSTextStorage *textStorage = [[NSTextStorage alloc] initWithAttributedString:string] ;
        NSLayoutManager *layoutManager = [[NSLayoutManager alloc] init] ;
        [layoutManager addTextContainer:textContainer] ;
        [textStorage addLayoutManager:layoutManager] ;
        [layoutManager setHyphenationFactor:0.0] ;
        if (gNSStringGeometricsTypesetterBehavior != NSTypesetterLatestBehavior) {
            [layoutManager setTypesetterBehavior:gNSStringGeometricsTypesetterBehavior] ;
        }
        // NSLayoutManager is lazy, so we need the following kludge to force layout:
        [layoutManager glyphRangeForTextContainer:textContainer] ;

        answer = [layoutManager usedRectForTextContainer:textContainer].size ;

        // Adjust if there is extra height for the cursor
        NSSize extraLineSize = [layoutManager extraLineFragmentRect].size ;
        if (extraLineSize.height > 0) {
            answer.height -= extraLineSize.height ;
        }

        // In case we changed it above, set typesetterBehavior back
        // to the default value.
        gNSStringGeometricsTypesetterBehavior = NSTypesetterLatestBehavior ;
    }

    return answer ;
}

.

- (float)heightForWidth:(float)width forString:(NSAttributedString*)string
{
    return [self sizeForWidth:width height:FLT_MAX forString:string].height ;
}

I was looking for a solution for quite some time and came up with the following one, which works great in my case:

- (double)tableView:(NSTableView *)tableView heightOfRow:(long)row
{
    if (tableView == self.tableViewTodo)
    {
        CKRecord *record = [self.arrayTodoItemsFiltered objectAtIndex:row];
        NSString *text = record[@"title"];

        double someWidth = self.tableViewTodo.frame.size.width;
        NSFont *font = [NSFont fontWithName:@"Palatino-Roman" size:13.0];
        NSDictionary *attrsDictionary =
        [NSDictionary dictionaryWithObject:font
                                    forKey:NSFontAttributeName];
        NSAttributedString *attrString =
        [[NSAttributedString alloc] initWithString:text
                                        attributes:attrsDictionary];

        NSRect frame = NSMakeRect(0, 0, someWidth, MAXFLOAT);
        NSTextView *tv = [[NSTextView alloc] initWithFrame:frame];
        [[tv textStorage] setAttributedString:attrString];
        [tv setHorizontallyResizable:NO];
        [tv sizeToFit];

        double height = tv.frame.size.height + 20;

        return height;
    }

    else
    {
        return 18;
    }
}