<AWT Dev> [11] JDK-8195738: scroll poistion in ScrollPane is reset after calling validate()
Semyon Sadetsky
semyon.sadetsky at oracle.com
Wed Feb 28 19:08:31 UTC 2018
Hi Sashi,
The parent with and height shouldn't be decreased by the size of the
scrollbars in case of SCROLLBARS_NEVER.
--Semyon
On 2/27/2018 12:45 AM, Shashidhara Veerabhadraiah wrote:
>
> Hi Semyon, Thanks for your help. I did some debugging from that
> perspective and could find the problem and the solution. Here is the
> new webrev, please review it:
>
> http://cr.openjdk.java.net/~sveerabhadra/8195738/webrev.01/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8195738/webrev.01/>
>
> The problem was that in the case of SCROLLBARS_NEVER, scroll bar info
> was set using setScrollInfo() with SIF_RANGE with ranges being (0, 0).
> This forced the windows to pick a default value and hence reset it to
> that value every time. Now the logic is modified in a very similar
> fashion as the other scroll bar display modes but without displaying
> it using the new win api ShowScrollBar(). The scroll bar info is
> supplied with a proper range per the corresponding base component but
> without the scroll bar pane size(as we don’t display it). This should
> suffice a good range for the scroll bars to operate and correct itself
> if there is any out of range value is supplied.
>
> Thanks and regards,
> Shashi
>
> *From:*Semyon Sadetsky
> *Sent:* Tuesday, February 27, 2018 1:22 AM
> *To:* shashidhara veerabhadraiah <shashidhara.veerabhadraiah at oracle.com>
> *Cc:* awt-dev at openjdk.java.net
> *Subject:* Re: <AWT Dev> [11] JDK-8195738: scroll poistion in
> ScrollPane is reset after calling validate()
>
> The bug was failed against Windows platform. So, I'd try to find the
> root cause why when the scroll is notified with the scrolled component
> size the scroll position is set to the wrong value.
>
> --Semyon
>
> On 02/26/2018 09:51 AM, shashidhara veerabhadraiah wrote:
>
> I think I agree Semyon. Thanks for your detailed explanation.
>
> So how do we approach on this? I see a different behaviour on
> other platforms. Shouldn’t we have a common behaviour across
> platforms? I agree with your analysis and hence should we change
> the behaviour on other platforms so that all of them will have the
> same behaviour?
>
> Thanks and regards,
>
> Shashi
>
> On 26-Feb-2018, at 10:17 PM, Semyon Sadetsky
> <semyon.sadetsky at oracle.com
> <mailto:semyon.sadetsky at oracle.com>> wrote:
>
> On 02/24/2018 05:27 AM, Shashidhara Veerabhadraiah wrote:
>
> Hi Semyon, Thanks for your review and these questions help
> us to reach the right requirements.
>
> Without this change, there is different behavior on
> windows compared to Mac/Linux platforms. Hence this change
> is required to make the behavior same across the
> platforms. Since the scroll pane control is not displayed
> for the SCROLLBARS_NEVER case and if not in the
> setScrollPosition() then how can the user can move to a
> different position? Since we used to update/recalculate
> the scroll pane geometry caused changes to move to a
> different position other than the setScrollPosition()!!
> This causes SCROLLBARS_NEVER mode as unusable as the user
> is unable to control the scrolling movement because
> neither he can set one setScrollPosition() nor the control
> is displayed to explicitly set the movement. Hope this
> answers your question.
>
> You need to think once again about two facts I brought in my
> previous message.
>
> 1. User still may scroll using mouse wheel even when
> scrollbars are not visible.
>
> 2. Visibility of scrollbars doesn't affect the requirement to
> notify the scroll about the scrolled component size changes.
> If the scrolled component was 500x500 in size and its position
> in the 200x200 viewport was (300,300) after the size of the
> component is changed to 300x300 it may not be shown at the
> same position because the previously visible component area
> doesn't exist anymore and the scroll should be moved to
> (100,100). This should work in the same way regardless the
> selected scrlollbar visibility policy.
>
> --Semyon
>
>
> Thanks and regards,
> Shashi
>
> *From:*Semyon Sadetsky
> *Sent:*Saturday, February 24, 2018 2:12 AM
> *To:*Shashidhara
> Veerabhadraiah<shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>;awt-dev at openjdk.java.net
> <mailto:awt-dev at openjdk.java.net>
> *Subject:*Re: <AWT Dev> [11] JDK-8195738: scroll poistion
> in ScrollPane is reset after calling validate()
>
> On 2/23/18 10:57 AM, Shashidhara Veerabhadraiah wrote:
>
> Hi Semyon, Whenever the container is resized we used
> to update the scroll pane sizes/geometry regardless of
> the scroll bar display policies. This resizing make
> sense for the non SCROLLBARS_NEVER cases as the scroll
> pane is displayed or needed an update. This additional
> update posed issues for the SCROLLBARS_NEVER case
> where we are not supposed to display the scroll pane
> per the java doc, then why update?
>
> Scroll pane geometry gets updated in 2 ways, one thro’
> setScrollPosition() and childResized(). So I derived
> the conclusion based on the javadoc information that
> since we don’t display the scroll pane there is no
> need to update the scroll pane geometry based on the
> childResized() as it was altering the position already
> set by the setScrollPosition(). This behavior is same
> as the other non SCROLLBARS_NEVER mode and setting the
> scroll bar display to SCROLLBARS_NEVER didn’t made any
> difference.
>
> The only difference of SCROLLBARS_NEVER from others I got
> from javadoc is that the scroll bar controls are hidden.
> So the scrolling itself happens in the same way as in the
> case of visible scroll bars but it can be only controlled
> by mouse wheel or programmatically. In my understanding
> this means that the notification about the scrolled
> component size changes should happen in the same way as
> for all other cases. I see no reason for the
> differentiation that your fix introduces. What will happen
> if to remove this notification for visible scroll bars modes?
>
> --Semyon
>
>
> Thanks and regards,
> Shashi
>
> *From:*Semyon Sadetsky
> *Sent:*Friday, February 23, 2018 10:17 PM
> *To:*Shashidhara
> Veerabhadraiah<shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>;awt-dev at openjdk.java.net
> <mailto:awt-dev at openjdk.java.net>
> *Subject:*Re: <AWT Dev> [11] JDK-8195738: scroll
> poistion in ScrollPane is reset after calling validate()
>
> On 2/22/18 8:23 PM, Shashidhara Veerabhadraiah wrote:
>
> Hi Semyon, Thanks for your review comments.
>
> Here are those different scroll bar pane modes and
> their description:
>
> *Modifier and Type*
>
>
>
> *Field*
>
>
>
> *Description*
>
> |static int|
>
>
>
> *SCROLLBARS_ALWAYS
> <https://docs.oracle.com/javase/9/docs/api/java/awt/ScrollPane.html#SCROLLBARS_ALWAYS>*
>
>
>
> Specifies that horizontal/vertical scrollbars
> should always be shown regardless of the
> respective sizes of the scrollpane and child.
>
> |static int|
>
>
>
> *SCROLLBARS_AS_NEEDED
> <https://docs.oracle.com/javase/9/docs/api/java/awt/ScrollPane.html#SCROLLBARS_AS_NEEDED>*
>
>
>
> Specifies that horizontal/vertical scrollbar
> should be shown only when the size of the child
> exceeds the size of the scrollpane in the
> horizontal/vertical dimension.
>
> |static int|
>
>
>
> *SCROLLBARS_NEVER
> <https://docs.oracle.com/javase/9/docs/api/java/awt/ScrollPane.html#SCROLLBARS_NEVER>*
>
>
>
> Specifies that horizontal/vertical scrollbars
> should never be shown regardless of the respective
> sizes of the scrollpane and child.
>
> This javadoc, you've copy-pasted here, doesn't explain
> why in your fix the notification about changed child
> size is disabled for SCROLLBARS_NEVER case.
>
> Thanks and regards,
> Shashi
>
> *From:*Semyon Sadetsky
> *Sent:*Thursday, February 22, 2018 11:58 PM
> *To:*Shashidhara
> Veerabhadraiah<shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>;awt-dev at openjdk.java.net
> <mailto:awt-dev at openjdk.java.net>
> *Subject:*Re: <AWT Dev> [11] JDK-8195738: scroll
> poistion in ScrollPane is reset after calling
> validate()
>
> Hi Shashi,
>
> Can you clarify what is the principal difference
> between SCROLLBARS_NEVER and other scroll policies
> that requires to avoid updating the scroll
> geometry according to the inner component size?
>
> --Semyon
>
> On 02/19/2018 11:08 PM, Shashidhara Veerabhadraiah
> wrote:
>
> Hi All, Please review a code fix for the below
> bug.
>
> Bug:https://bugs.openjdk.java.net/browse/JDK-8195738
>
> Webrev:http://cr.openjdk.java.net/~sveerabhadra/8195738/webrev.00/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8195738/webrev.00/>
>
> Problematic platform: Windows only.
>
> Summary: This bug occurs only on windows
> platform and whereas the behavior is different
> on Mac/Linux platforms. Now after this fix
> there is common behavior across the platforms.
>
> The main problem was with resetting the state
> of the scroll bars even though the scroll bar
> panes are spawned with SCROLLBARS_NEVER as the
> scroll bar display policy. This resetting
> should not occur as the scroll bar display
> policy makes the
>
> scroll bar panes invisible. Hence except the
> setScrollPosition() calls, we don’t need to
> resize/update the scroll bars state upon
> calling the scroll bars validation if
> SCROLLBARS_NEVER policy is used as the scroll
> bars are not displayed.
>
> Thanks and regards,
> Shashi
>
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