TrackableOutlineView.m

/*
     File: TrackableOutlineView.m 
 Abstract: The TrackableOutlineView provides an implementation of updateTrackingAreas
 that automatically delegates to cells which implement the informal CellTrackingRect protocol.
  
  Version: 1.7 
  
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 */
 
#import "TrackableOutlineView.h"
 
#import <AppKit/NSTrackingArea.h>
#import "CellTrackingRect.h" 
 
@implementation TrackableOutlineView
 
- (id)init {
    
    self = [super init];
    if (self) {
        iMouseRow = -1;
        iMouseCol = -1;
    }
    return self;
}
 
- (id)initWithCoder:(NSCoder *)coder {
    
    self = [super initWithCoder:coder];
    if (self) {
        iMouseRow = -1;
        iMouseCol = -1;
    }
    return self;
}
 
- (void)dealloc {
    
    [iMouseCell release];
    [super dealloc];
}
 
// Tracking rect support
- (void)updateTrackingAreas {
    
    for (NSTrackingArea *area in [self trackingAreas]) {
        // We have to uniquely identify our own tracking areas
        if (([area owner] == self) && ([[area userInfo] objectForKey:@"Row"] != nil)) {
            [self removeTrackingArea:area];
        }
    }
 
     // Find the visible cells that have a non-empty tracking rect and add rects for each of them
    NSRange visibleRows = [self rowsInRect:[self visibleRect]];
    NSIndexSet *visibleColIndexes = [self columnIndexesInRect:[self visibleRect]];
 
    NSPoint mouseLocation = [self convertPoint:[[self window] convertScreenToBase:[NSEvent mouseLocation]] fromView:nil];
 
    for (NSUInteger row = visibleRows.location; row < visibleRows.location + visibleRows.length; row++ ) {
        // If it is a "full width" cell, we don't have to go through the rows
        NSCell *fullWidthCell = [self preparedCellAtColumn:-1 row:row];
        if (fullWidthCell) {
            if ([fullWidthCell respondsToSelector:@selector(addTrackingAreasForView:inRect:withUserInfo:mouseLocation:)]) {
                NSInteger col = -1;
                NSDictionary *userInfo = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInteger:col], @"Col", [NSNumber numberWithInteger:row], @"Row", nil];
                [fullWidthCell addTrackingAreasForView:self inRect:[self frameOfCellAtColumn:col row:row] withUserInfo:userInfo mouseLocation:mouseLocation];
            }
        } else {
            for (NSInteger col = [visibleColIndexes firstIndex]; col != NSNotFound; col = [visibleColIndexes indexGreaterThanIndex:col]) {
                NSCell *cell = [self preparedCellAtColumn:col row:row];
                if ([cell respondsToSelector:@selector(addTrackingAreasForView:inRect:withUserInfo:mouseLocation:)]) {
                    NSDictionary *userInfo = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInteger:col], @"Col", [NSNumber numberWithInteger:row], @"Row", nil];
                    [cell addTrackingAreasForView:self inRect:[self frameOfCellAtColumn:col row:row] withUserInfo:userInfo mouseLocation:mouseLocation];
                }
            }
        }
    }
}
 
- (void)mouseEntered:(NSEvent *)event {
    
    // Delegate this to the appropriate cell. In order to allow the cell to maintain state,
    // we copy it and use the copy until the mouse is moved outside of the cell.
    //
    NSDictionary *userInfo = [event userData];
    NSNumber *row = [userInfo valueForKey:@"Row"];
    NSNumber *col = [userInfo valueForKey:@"Col"];
    if (row && col) {
        NSInteger rowVal = [row integerValue]; 
        NSInteger colVal = [col integerValue];
        NSCell *cell = [self preparedCellAtColumn:colVal row:rowVal];
        // Only set the mouseCell properties AFTER calling preparedCellAtColumn:row:.
        if (iMouseCell != cell) {
            [iMouseCell release];
            // Store off the col/row
            iMouseCol = colVal;
            iMouseRow = rowVal;
            // Store a COPY of the cell for use when tracking in an area
            iMouseCell = [cell copy];
            [iMouseCell setControlView:self];
            [iMouseCell mouseEntered:event];
        }
    }
}
 
- (void)mouseExited:(NSEvent *)event {
    
    NSDictionary *userInfo = [event userData];
    NSNumber *row = [userInfo valueForKey:@"Row"];
    NSNumber *col = [userInfo valueForKey:@"Col"];
    if (row && col) {
        NSCell *cell = [self preparedCellAtColumn:[col integerValue] row:[row integerValue]];
        [cell setControlView:self];
        [cell mouseExited:event];
        // We are now done with the copied cell
        [iMouseCell release];
        iMouseCell = nil;
        iMouseCol = -1;
        iMouseRow = -1;
    }
}
 
/* Since NSTableView/NSOutineView uses the same cell to "stamp" out each row, we need to
    send the mouseEntered/mouseExited events each time it is drawn. The easy hook for this
    is the preparedCell method. 
*/
- (NSCell *)preparedCellAtColumn:(NSInteger)column row:(NSInteger)row {
    
    // We check if the selectedCell is nil or not -- the selectedCell is a cell that is
    // currently being edited or tracked. We don't want to return our override if we are in that state.
    //
    if ([self selectedCell] == nil && (row == iMouseRow) && (column == iMouseCol)) {
        return iMouseCell;
    } else {
        return [super preparedCellAtColumn:column row:row];
    }
}
 
/* In order for the cell to properly update itself with an "updateCell:" call,
    we must handle the "mouseCell" as a special case
*/
- (void)updateCell:(NSCell *)aCell {
    
    if (aCell == iMouseCell) {
        [self setNeedsDisplayInRect:[self frameOfCellAtColumn:iMouseCol row:iMouseRow]];
    } else {
        [super updateCell:aCell];
    }
}
 
@end