Q:  It seems like the scrollView ignores the frame.origin of its docView.  Also, does a ScrollView clip to its update rect(s)?

A:  A ScrollView translates the coordinate system of its contentView in response to user movement of the scrollers.  Since the frame of the docView is defined in the coordinate system of the contentView (i.e. it's a subview of the contentView), translating the coordinate system of the contentView has the effect of moving the frame, and hence the visible portion of the docView.

When you do a setDocView: the system translates the coordinate system of the contentView so that the contentView's bounds.origin is the same as the frame.origin of the docView.  For example: if the frame.origin of your docView is {100.0,100.0}, the bounds.origin of the contentView will be {100.0,100.0} as well.

So the ScrollView does pay attention to what the frame.origin of the docView is, but it doesn't really matter what it is, at least initially.

User code really shouldn't make changes to the frame of the docView as it is being managed by its superview (a ClipView). To achieve scrolling use the - rawScroll: method.

No, the drawing is not clipped to the update rects; however, you can restrict the area being redrawn yourself by using PSrectclip() or NXRectClip() in your drawSelf:: method.

QA160

Valid for 1.0, 2.0, 3.0

Q:  In my application I have subclassed the Text object and called it SubText.  I have a ScrollView which I installed using InterfaceBuilder which has a standard Text object as its docView.  I wish to replace that Text object with my own but I wish to maintain all the same behaviors--with a vertical scrollbar and text which resizes properly.  How do I do that?

A:  The following code snippet creates an instance of your new subclass of Text and inserts it into the docView of the ScrollView. The old Text object is then freed. In the code sample ``theSV'' is an outlet connected to the ScrollView. Because an existing ScrollView is used, certain setups are not required. See Chapter 9, page 35 of the Concepts volume of the 1.0 Technical Documentation for more information on setting up a brand-new ScrollView.

The key here that many people miss is to set the min size and max size on the Text object.

id stdDoc;
NXRect r;

/* Measure the old doc view. */
stdDoc = [theSV docView];
[stdDoc getFrame:&r];

[theSV setVertScrollerRequired:YES];
[theSV setHorizScrollerRequired:NO];
[theSV setDynamicScrolling:YES];

/* Instantiate the new Text object */
#ifdef 1.0
newDoc = [SubText newFrame:&r];
#else  /* 2.0 or 3.0 */
newDoc = [[SubText alloc] initFrame: &r];
#endif
[newDoc moveTo:0.0:0.0];
[newDoc notifyAncestorWhenFrameChanged: YES];
[newDoc setVertResizable:YES];
[newDoc setSelectable:YES];
[newDoc setEditable: YES];
[newDoc setAutosizing:NX_WIDTHSIZABLE];
[newDoc setMinSize:&r.size];
r.size.height = 1.0e30;
[newDoc setMaxSize:&r.size];
[theSV setDocView:newDoc];

/* Free the old Text object */
[stdDoc free];

Note that the ifdef for 1.0 is for illustration purposes only and is NOT defined in any NeXTstep include file.

QA555

Valid for 1.0, 2.0, 3.0