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The developer documentation says the addRow method adds a row to a matrix below the last one. In my app everytime I call addRow it adds a cell above the last one. This is more of an asthetic thing but does anyone know why this is happening?

OK I looked a little closer, it does add below, but it pushes the first row up. What I need to do is keep the first row where it is and have added rows add below, do i need to just move the entire matrix down every time i add a new row?? —- You’re probably running into the Cocoa Coordinate System. Since the origin (0, 0) is normally at the bottom in Cocoa, if you increase something’s size without moving its location, it will grow upwards, which is the opposite of what people coming from other systems expect. So the behavior you’re seeing makes sense, and moving it back down afterwards is perfectly reasonable.

Except that NSMatrix has a reversed coord system. ie: 0,0 is at the top left of an NSMatrix. is the matrix a part of some more complicated control or are you working with the NSMatrix class directly? (browser, tableView, etc…) the reason I am asking is that the behavior you are describing does not make sense to me and I suspect that your matrix is in a scrollView, or that perhaps there are other extenuating circumstances.

When a view is flipped, that only affects things inside it. The fact that NSMatrix uses a flipped coordinate system has no influence on what happens when you change its size, because the NSMatrix’s frame exists in its superview’s coordinate system. I maintain that the behavior being seen is normal and reasonable.

No special view just the main window. I have a button that adds a new cell (NSMatrix of combo boxes) when pressed. I have dug around a bit and it seems that combo boxes and matricies do not currently behave very well. It seems that combo boxes no longer behave as combo boxes when part of a matrix. I doubt this has anything to do with my current problem but it is still bothersome.

It may be reasonable for the matrix to “appear” to move up, but is there a simple solution to that new rows “appear” to be added at the bottom of the matrix?

You can manually reposition the matrix after you add the new cell. Assuming the matrix’s superview is NOT flipped and you want the top-left coordinate of the matrix to stay the same, that means you want the maximum Y coordinate of the matrix’s frame to stay the same. Use this code instead of just calling addRow.

// Save the current frame NSRect originalFrame = [matrix frame];

// Add the new row [matrix addRow]; [matrix sizeToCells];

// Adjust the frame’s origin so that the maximum Y coordinate // matches originalFrame, but using the new frame’s size // origin + height = maximum Y coordinate, therefore // origin = maximum Y coordinate - height NSRect newFrame = [matrix frame]; newFrame.origin.y = NSMaxY(originalFrame) - NSHeight(newFrame); [matrix setFrame:newFrame];

// The matrix and its superview need to be redrawn [matrix setNeedsDisplay:YES]; matrix superview] setNeedsDisplay:YES];

You can use simple math to ajust your matrix’s coordinates using its cell’s dimensions. Assuming your matrix’s origin is in its lower-left corner, you simply subtract the cell’s height and the intercell spacing from your matrix’s Y origin:

NSRect rect = [theMatrix frame];
rect.origin.y -= [theMatrix cellSize].height;
rect.origin.y -= [theMatrix intercellSpacing].height;
[theMatrix setFrame:rect];