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. Thanks and regards, Shashi From: Semyon Sadetsky Sent: Saturday, February 24, 2018 2:12 AM To: Shashidhara Veerabhadraiah <shashidhara.veerabhadra...@oracle.com>; awt-dev@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 HYPERLINK "mailto:shashidhara.veerabhadra...@oracle.com";<shashidhara.veerabhadra...@oracle.com>; HYPERLINK "mailto:awt-dev@openjdk.java.net"awt-dev@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 HYPERLINK "https://docs.oracle.com/javase/9/docs/api/java/awt/ScrollPane.html#SCROLLBARS_ALWAYS"SCROLLBARS_ALWAYS Specifies that horizontal/vertical scrollbars should always be shown regardless of the respective sizes of the scrollpane and child. static int HYPERLINK "https://docs.oracle.com/javase/9/docs/api/java/awt/ScrollPane.html#SCROLLBARS_AS_NEEDED"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 HYPERLINK "https://docs.oracle.com/javase/9/docs/api/java/awt/ScrollPane.html#SCROLLBARS_NEVER"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 HYPERLINK "mailto:shashidhara.veerabhadra...@oracle.com";<shashidhara.veerabhadra...@oracle.com>; HYPERLINK "mailto:awt-dev@openjdk.java.net"awt-dev@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: HYPERLINK "http://cr.openjdk.java.net/%7Esveerabhadra/8195738/webrev.00/"http://cr.openjdk.java.net/~sveerabhadra/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
