[OpenJDK 2D-Dev] [9] Review Request: JDK-8165212 VolatileImage should not be compatible with GraphicsConfiguration which transform is changed

[Prahalad Kumar Narayanan]

Hello Everyone on Java2D Group

This is a follow-up on the bug fix for JDK-8165212.
      Link: https://bugs.openjdk.java.net/browse/JDK-8165212
      Title: VolatileImage should not be compatible with GraphicsConfiguration which transform is changed

First, Thanks to Alexandr for his review suggestions on webrev.00

Root Cause: 
Upon any change to display's state (Eg: DPI) the callback method- displayChanged() is invoked on VolatileSurfaceManager. The callback method updates the volatile image's surface only if the acceleration is enabled. For non-accelerated volatile images, the surface isn't updated. This caused the bug on OSs where user can change screen's DPI on the fly without having to restart/re-login.

Updates to the Fix:
In the previous fix version (webrev.00), the software surface was re-created for non-accelerated volatile images as well. This fixed the problem. The suggestion from Alexandr was to re-create the software surface only when the affine transformation of GraphicsConfiguration changes. This is incorporated in the current fix.

It is important to note that, the affine transformation of GraphicsConfiguration is actually derived from the screen device. When end-user modifies screen's DPI, the affine transformation is updated on the screen device first; followed by a call to displayChanged() callback on the listeners. Henceforth, a copy of the transformation is kept in the volatile surface manager, to aid in comparing changes to affine transformation (before & after screen's DPI change)

Kindly review the changes and provide your suggestions at your convenience.
Review link: http://cr.openjdk.java.net/~pnarayanan/8165212/webrev.01/

Thank you for your time in review
Have a good day

Prahalad N.
---

From: Alexandr Scherbatiy 
Sent: Friday, October 28, 2016 4:57 PM
To: Prahalad Kumar Narayanan; 2d-dev at openjdk.java.net
Subject: Re: [OpenJDK 2D-Dev] [9] Review Request: JDK-8165212 VolatileImage should not be compatible with GraphicsConfiguration which transform is changed

 350         if (!isAccelerationEnabled()) {
 351             // Ideally there is no need to re-create a software surface. But
 352             // some OSs allow changes to display state at runtime. Such a
 353             // provision would cause mismatch in graphics configuration of the
 354             // display and the surface. Hence we re-create the software surface
 355             // as well.
 356             sdBackup = null;
 357             sdCurrent = getBackupSurface();
 358         }
 359     }

It seems that the surface is always recreated when the acceleration is not enabled. May be it should be only done when the graphics configuration transform scales are differ from the ones from vImg graphics configuration?

Thanks,
Alexandr.
 
On 10/14/2016 1:38 PM, Prahalad Kumar Narayanan wrote:

Hello Everyone
 
Good day to you.
 
Request your time in reviewing the fix for-
      Bug : JDK-8165212
      Title : VolatileImage should not be compatible with GraphicsConfiguration which transform is changed
 
Description on the bug-
       . As per the bug, Volatile Image's graphics configuration is not updated when the host machine display's DPI is changed at runtime (while still running the java app). In addition, the method contentsLost() does not return true when display's DPI is modified.
       . It is important to note that, the issue is not reproducible with D3D/OpenGL backend. It is reproducible with non-accelerated Volatile Image.
 
Root Cause
       . A callback method- displayChanged() in VolatileSurfaceManager.java is invoked when display's settings (DPI) is modified.
       . The callback method, currently, updates the graphics configuration only for Accelerated volatile image. Graphics configuration is not updated for non-accelerated system memory based VolatileImage.
       . Until recently, there wasn't any need for updating graphics configuration for non-accelerated volatileImage. However, Win 8.1 and above provide feature to dynamically update the DPI setting (without requiring for log-off/ log-in), which causes the current bug.
 
Bug Fix
      . First, the callback method is modified to update graphics configuration for non-accelerated volatile image also.
      . An update to graphics configuration might require re-creation of the surface. Especially, when the scale factor is increased. Hence the system memory based backupSurface is re-created here.
      . The above change is followed by change to Validate() API, so that the backup surface re-creation in displayChanged() method, correctly returns IMAGE_RESTORED from validate() API. This way, the code flow for non-accelerated Volatile Images behaves just the same way as accelerated volatile images.
       . Approximately 81 Jtreg test cases (that contained VolatileImage) were run on win7, linux, and osx. No new regressions have been found after the modification.
       . In addition, a manual test case has been provided to ensure the proper functioning of the fix
 
Kindly review the changes and provide your suggestions
Review link: http://cr.openjdk.java.net/~pnarayanan/8165212/webrev.00/
 
Thank you for your time in review
Have a good day
 
Prahalad N.