This is SimpleGraphicsChange.m in view mode; [Download] [Up]
#import "drawundo.h"
/*
* Please refer to external documentation about Draw
* with Undo for information about what SimpleGraphicsChange
* is and where it fits in.
*/
@interface SimpleGraphicsChange(PrivateMethods)
- undoDetails;
- redoDetails;
- (BOOL)subsumeIdenticalChange:change;
@end
@implementation SimpleGraphicsChange
- saveBeforeChange
{
[super saveBeforeChange];
[changeDetails makeObjectsPerform:@selector(recordDetail)];
return self;
}
- (BOOL)subsumeChange:change
/*
* ChangeManager will call subsumeChange: when we are the last
* completed change and a new change has just begun. We override
* the subsumeChange: to offer our subclasses a chance to
* consolidate multiple changes into a single change.
* First we check to make sure that the new change is of the
* same class as the last. If it is then we check to make sure
* that it's operating on the same selection. If not we simply
* return NO, declining to subsume it. If it does operate on
* the same change then we offer our subclass a change to
* subsume it by sending [self subsumeIdenticalChange:change].
*
* For example, if the user presses the up arrow key to move
* a graphic up one pixel, that immediately becomes a complete,
* undoable change, as it should. If she continues to press
* use the arrow keys we don't want to end up making hundreds
* of independent move changes that would each have to be
* undone seperately. So instead we have the first move
* subsume all subsequent MoveGraphicsChanges that operate
* on the same selection.
*/
{
BOOL identicalChanges = NO;
List *selectedGraphics;
int count, i;
if ([change isKindOf:[self class]]) {
identicalChanges = YES;
selectedGraphics = [graphicView selectedGraphics];
count = [selectedGraphics count];
for (i = 0; (i < count) && (identicalChanges); i++) {
if ([graphics objectAt:i] != [selectedGraphics objectAt:i])
identicalChanges = NO;
}
}
if (identicalChanges)
return [self subsumeIdenticalChange:change];
else
return NO;
}
- undoDetails
{
[changeDetails makeObjectsPerform:@selector(undoDetail)];
return self;
}
- redoDetails
{
[changeDetails makeObjectsPerform:@selector(redoDetail)];
return self;
}
- (BOOL)subsumeIdenticalChange:change
{
return NO;
}
@end
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.