Unfortunately, the previous commit for keeping the main window active does not function as desires on Linux.  It appears (on Linux) that the active window is always the top most window.  The functionality remains for Mac so that the Identification window is over the main window after an ID but the main window retains mouse focus.  A difference between the main window on Linux is that if the main window is not active, clicking any control (slice spin box), makes the window active.  On Mac it is different as the user must click the titlebar to make the window active (clicking a control such as slice spin box does not activate the window).

Previous commit for keeping main window active after identification operation was obscuring the identification window if it was behind the main window.  This fix (at least on Mac) keeps the main window as the active window (mouse focus) but keeps identification window visible over the main window.

When an identification operation was performed, the identification window became the top window and the keyboard focus was moved to the identification window.  This has been changed so that the keyboard focus no longer is transferred to the identification window and the keyboard focus remains with the main window.

Code that processed mouse wheel (track pad is reported as mouse wheel event) was using an obsolete function, QWheelEvent::delete(), and it was replaced with QWheelEvent::pixelDelta() and QWheelEvent::angleDelta() as a fallback.  This seems to have fixed the sort oscillation that was noticed when trying to use the track pad on Macs.

For the experimental texture volume drawing, changed the texture 'magnification filter' to GL_NEAREST.  When zoomed in on a slice, the drawing is much like the current cubic interpolation drawing.  The different is when the volume slice is rotated.  The interpolated drawing draws voxels whose edges horizontal and vertical (aligned with screen axes).  Whereas, in texture drawing the voxel edges are aligned with the stereotaxic axes and thus the voxels edges rotate with the slice rotations.

WB-858 Do not yoke the volume slice plane (Axial, Coronal, Parasagittal, or All): Fixed change of slice plane caused by a change in tab yoking.

Fixed crash in experimental volume slice drawing using a texture when a volume dimension greater than 256.  Also fix compilation warnings on a couple of systems.

Modified LockAspectWarning dialog so that it also used, under some conditions, when the user clicks the ToolBar's Lock Aspect button.

For warning when Lock Aspect button is clicked, add an additional test so that the warning is not displayed when there is only one tab in the window.

When user clicks the Lock Aspect button and it is not selected and Tile Tabs is not enabled, warn user that it is important to adjust the window size and enable tile tabs prior to locking the aspect ratio.

On Enter Annotations Mode dialog, emphasize that tile tabs should be enabled prior to entering Annotations mode.

Removed the developer flag for "tile tabs centering correction".  An "Options" group has been added to the Tile Tabs Configuration dialog that contains a "Centering Correction" checkbox.  Use of this option corrects the layout of tabs from an older scene file, particularly when the height of tab is limited by the aspect ratio and this height is less than the height of the row containing the tab.

For testing purposes only, made updates to oblique slice drawing that uses a 3D Texture and offers better performance than the current oblique implementation.  It must be enabled using an item in the Develop Menu.

Add horizontal centering and correction and change Develop Menu item to Tile Tabs Centering Correction.

Added a developer flag for a tile tabs layout modification as Develop Menu --> Tile Tabs Vertical Centering.  When this is enabled, each row in Tile Tabs is set to the minimum needed and the positions of the rows is adjusted so that any extra space is above all rows and below all rows; NOT between the rows.

A scene created in an older version of wb_view (September 2018) did not display correctly with extra space between the two rows of tabs.  The available height for each tab was greater than the height needed by aspect locking so tabs were taller than needed.  It is possible that the user locked aspect before entering tile tabs as this has been found to cause a similar layout problem.  Using the item in the Develop Menu, fixes this scene and others in the same scene file.

For testing purposes only, added an partial implementation of oblique slice drawing that uses a 3D Texture and offers better performance than the current oblique implementation.  It must be enabled using an item in the Develop Menu.

WB-855 Change All Slice Plane Default to Row: Fix for older scenes prior to the addition of the All Slice Planes value.  Theses older scenes need to restore to GRID and ignore the user's preference for the layout.

WB-855 Change All Slice Plane Default to Row: Slice order in ROW is not Parasagittal, Coronal, and Axial (consistent with other layouts).  Preference default is now ROW.

Resolve WB-853 Converting annotation labels from one mesh to another: Old parameters (-source-surface and -target-surface) were removed.  Users must use "-surface-pair" for source and target surfaces.

Resolve WB-855: Change All Slice Plane Default to Row: The slice planes layout for new tabs is now set in Preferences --> New Tabs.  The default layout remains GRID as it has always been.  Users desiring ROW or COLUMN just need to change the Preference one time.  Note that the All Slice Planes Layout is a 'per tab' property and affected by yoking.  Thus, if new tabs are "Yoked to Group A", the All Slice Planes Layout will be that associated with  "Tab A" and may be different than the Preference for All Slice Planes Layout.

Improved usage of new CaretPreferenceDataValue for the crosshair gap preference so that user just sets/gets gap value from CaretPreferences.

WB-851 Cross-hair improvement: Default crosshair gap in preferences to 0.0 so that crosshairs do not have a gap by default.

Fixing compilation errors on Linux systems from use of std::array initialization with another std::array.

WB-857: Absolute paths were also found for surfaces used for volume surface outline.  This has been corrected to use ScenePathName so that the file names are absolute in memory and relative in the scene file.

More on WB-857: Removed code that was replaced by new relative path for writing scene.  Older code for restoring remains and is used with scene files created prior to this bug fix.

WB-857: Older code fixed a problem with identical file names by saving the full path into the scene file and then performing a 'right-most characters" match to restore the data. While it works, we should not have absolute paths in the scene file.  It was probably done this way since the file was the name of a scene XML element and the scene path absolute/relative mechanism only works on 'ScenePathName' elements.

Now the name of the element is just the name of the file (no path).  A new child element, using a ScenePathName element has been added that is the absolute path in memory and a relative path in the scene file is now used to properly restore the data file's scene data.

Partial implementation of WB-851 Crosshair improvement: Adjustable gap is functioning for orthogonal mode and saved/restored from scenes and in preferences.  Next is adding gap to crosshairs in oblique mode.

For wb_command -annotation-resample; Added '-surface-pair <source-surface> <target-surface>' option.  It replaces the '-source-surface' and '-target-surface' options that are still available but produce a depreciated warning.  The old options will be removed in about a week.

Correct compilation error in OperationShowScene caused by a failure of my build system properly detecting MesaGL libraries (without mesa, some code is not compiled that contained a function with changed parameters).

Added ON and OFF buttons to the Annotation controls in the Features Toolbox.  This allows the user to select groups of annotations while using the shift/ctrl keys and change the display status of a large numbers of annotations.  Prior to this change the user had to turn on/off each annotation individually by clicking its checkbox.  In addition, the user may also select annotations in the Features Toolbox while NOT in Annotation Mode so that groups of then can be turned on/off (note that the "sizing handles" that are drawn around each of the selected annotations are only displayed in Annotation Mode).

In Features ToolBox --> Annotations, add On and Off buttons so that user can select more than one (often many) annotations in the list of annotations and turn their display status checkboxes on and off.