12825 - overflow: -moz-scrollbars-* not implemented

Status: VERIFIED FIXED

(Core :: CSS Parsing and Computation, defect, P3)

Description

[kinmoz]

The style system needs to be modified so we can independently hide the
horizontal scrollbar, the vertical scrollbar, or both, but still be able
to scroll the view.

An example of the need for this feature would be a Gfx textfield, which has no
scrollbars, but must be able to scroll as the cursor moves through the text it
contains.

Right now the only way for us to create a scrolling frame with no scrollbars is
to create one with scrollbars, then hide them by setting the scroll preference
in it's scrolling view to nsScrollPreference_kNeverScroll. Doing this makes the
scroll frame's style info and the scrolling view's scroll preference out of
sync, allowing nsScrollFrame::Reflow() to incorrectly include the scrollbar
dimensions when calculating the scrolled view's size.

I added a temporary hack to nsScrollFrame::Reflow() that gets around the
problem. The hack is currentlyl bracketed by the comments "XXX: Begin Temporary
Hack" and "XXX: End Temporary Hack".

The hack checks the scrolled view's scroll preference to see if it equals
nsScrollPreference_kNeverScroll, if it does, then we know that we have a frame
that scrolls but has it's scrollbars hidden, so it sets the scrollbar dimensions
to zero for the scrolled view size calculations.

Checking the scrolled view's scroll preference goes against the defined flow of
control between the scroll frame and it's view, so this hack should be removed
when the style system adds the support described above.

Comment 1

[kinmoz]

Accepting bug.

Comment 2

[kinmoz]

Making M13.

Comment 3

[Hixie (not reading bugmail)]

[ccing pierre as peterl was cc'ed and this probably affects pierre too]

We probably want to introduce new keywords on the 'overflow' property for this,
such as:

   overflow: -moz-no-scrollbars
   overflow: -moz-no-horizontal-scrollbars
   overflow: -moz-no-vertical-scrollbars

...in addition to the CSS2 keywords 'auto' 'hidden' 'visible' and 'scroll' (the
latter being the opposite of the suggested '-moz-no-scrollbars').

So a normal text field with both scroll bars and scrolling enabled would be:

   textarea { overflow: scroll; }

...but one with scrolling enabled and no scroll bars would be:

   input[type=text] { overflow: -moz-no-scrollbars; }

...and so on.

Comments?

Comment 4

[Hixie (not reading bugmail)]

BTW, please note that we do not need a new value for "scrolling enabled and
scroll bars only appear when required" -- that is what 'auto' does.

Comment 5

[Pierre Saslawsky]

The overflow property now supports the following values:
  -moz-scrollbars-none
  -moz-scrollbars-horizontal
  -moz-scrollbars-vertical

Comment 6

[Hixie (not reading bugmail)]

Updating summary to reflect current status.

Comment 7

[kinmoz]

I'll get the scrollbar visibility code working after I tackle some of the Linux
repaint regressions. I hope to get to this sometime this week.

Comment 8

[kinmoz]

I'm working on this right now, but I don't think I'll make tonight's M13
midnight deadline. Moving to M14 since it isn't an M13 stopper.

Comment 9

[kinmoz]

I just checked in support for the layout side of things:

    mozilla/layout/html/base/src/nsGfxScrollFrame.cpp   revision 3.29

I'll attatch a test case for this to the bug. Support should appear in the
01/27/2000 QA builds.

Comment 10

[kinmoz]

Attachment: Test case for the various overflow values.

Comment 11

[Hixie (not reading bugmail)]

It's implemented. Verified. There may be bugs in the implementation, though, in 
which case new bugs should be filed.

Comment 12

[John Morrison]

Reopening to ask a question (but it's likely a bug). Are the moz properties
-moz-scrollbars-vertical, -moz-scrollbars-horizontal, -moz-scrollbars-none
applicable to both GFX and native scrollbars? 

The curious thing I noticed is that these properties have the exact *opposite*
behaviour (20000508 mac, win32 and linux/gtk):

  i.e., GFX: -moz-scrollbars-vertical    => has VERT scrollbar
             -moz-scrollbars-horizontal  => has HORIZ scrollbar
             -moz-scrollbars-none        => has NO scrollbars

     NATIVE: -moz-scrollbars-vertical    => has HORIZ scrollbar
             -moz-scrollbars-horizontal  => has VERT scrollbar
             -moz-scrollbars-none        => has VERT && HORIZ scrollbars

Comment 13

[John Morrison]

While I'm being obnoxious ...

> Checking the scrolled view's scroll preference goes against the defined flow 
of
> control between the scroll frame and it's view, so this hack should be removed
> when the style system adds the support described above.

This code is still in the tree (nsScrollFrame.cpp). Should it be gone?

Comment 14

[kinmoz]

Changing status to FIXED.

At the time I implemented the -moz-scrollbars-* values, we were in the process 
of dropping support for native scrollbars, so I didn't think it was worth the 
effort to write code for something that was going away. Other bugs related to 
native scrollbars, especially on Linux, were being closed as WONT_FIX at the 
time for the same reason.

There is no code that supports -moz-scrollbars-* in the native implementation, 
so what you report seeing above when using -moz-scrollbars-* values and 
switching to Native Scrollbars might be due to the code using defaults because 
it doesn't recognize the -moz-scrollbars-* values.

Comment 15

[Christine Hoffman]

Verifying bug fixed.

Comment 16

[Daniel Wang]

*** Bug 107495 has been marked as a duplicate of this bug. ***