[gparted] Create unallocated space within new extended partition after aligning boundaries (#757671)

[Curtis Gedak <gedakc src gnome org>]

commit c86b25847511ff1f85c8d8c5f228881e5bf7437f
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Tue Sep 22 12:13:25 2015 +0100

    Create unallocated space within new extended partition after aligning boundaries (#757671)
    
    When creating a new extended partition, the unallocated space within it
    was being created before adjusting the partition boundaries for
    alignment reasons.  This must be wrong.  Move creation of the
    unallocated space to after adjusting the partition boundaries for
    alignment reasons.  First introduced by this commit:
    
        a30f991ca57453f29e2c3ad85c05be8e436fe860
        Fix size reduced by 1 MiB when created after cylinder aligned partition
    
    Also added a big FIXME comment explaining how further adjustments are
    still made by snap_to_alignment() to the partition boundaries including
    a test case where this too late adjustment causes overlapping boundaries
    and apply to fail.
    
    Bug 757671 - Rework Dialog_Partition_New::Get_New_Partition() a bit

 src/Dialog_Partition_New.cc |   46 ++++++++++++++++++++++++++++++------------
 1 files changed, 33 insertions(+), 13 deletions(-)
---
diff --git a/src/Dialog_Partition_New.cc b/src/Dialog_Partition_New.cc
index b3ee247..927f9c2 100644
--- a/src/Dialog_Partition_New.cc
+++ b/src/Dialog_Partition_New.cc
@@ -224,19 +224,6 @@ Partition Dialog_Partition_New::Get_New_Partition( Byte_Value sector_size )
                part_temp.sector_start = new_partition.sector_start;
        if ( (new_partition.sector_end - part_temp.sector_end) < (MEBIBYTE / sector_size) )
                part_temp.sector_end = new_partition.sector_end;
-       
-       //if new is extended...
-       if ( part_temp .type == GParted::TYPE_EXTENDED )
-       {
-               Partition UNALLOCATED ;
-               UNALLOCATED.Set_Unallocated( part_temp.device_path,
-                                            part_temp.whole_device,
-                                            part_temp.sector_start,
-                                            part_temp.sector_end,
-                                            sector_size,
-                                            true );
-               part_temp .logicals .push_back( UNALLOCATED ) ;
-       }
 
        //set alignment
        switch ( optionmenu_alignment .get_history() )
@@ -260,6 +247,39 @@ Partition Dialog_Partition_New::Get_New_Partition( Byte_Value sector_size )
 
        part_temp .free_space_before = Sector(spinbutton_before .get_value_as_int()) * (MEBIBYTE / 
sector_size) ;
 
+       // Create unallocated space within this new extended partition
+       //
+       // FIXME:
+       // Even after moving creation of the unallocated space within this new extended
+       // partition to here after the above alignment adjustment, the boundaries of the
+       // extended partition may be further adjusted by snap_to_alignment().  However the
+       // UI when creating logical partitions within this extended partition will use the
+       // boundaries as defined now by this unallocated space.  Hence boundaries of
+       // logical partitions may be wrong or overlapping.
+       //
+       // Test case:
+       // On an empty MSDOS formatted disk, create a cylinder aligned extended partition.
+       // Then create a default MiB aligned logical partition filling the extended
+       // partition.  Apply the operations.  Creation of logical partition fails with
+       // libparted message "Can't have overlapping partitions."
+       //
+       // To fix this properly all the alignment constraints need to be applied here in
+       // the dialogs which create and modify partition boundaries.  The logic in
+       // snap_to_alignment() needs including in it.  It will need abstracting into a set
+       // of methods so that it can be used in each dialog which creates and modified
+       // partition boundaries.
+       if ( part_temp.type == TYPE_EXTENDED )
+       {
+               Partition unallocated;
+               unallocated.Set_Unallocated( part_temp.device_path,
+                                            part_temp.whole_device,
+                                            part_temp.sector_start,
+                                            part_temp.sector_end,
+                                            sector_size,
+                                            true );
+               part_temp.logicals.push_back( unallocated );
+       }
+
        return part_temp;
 }