[gparted] Allow creation of partition at sector 2048 when following another (#172)

[Curtis Gedak <gedakc src gnome org>]

commit 0bfbac4f65f0ba082e8a8abf30599ea2bcc33f34
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Tue Oct 19 19:06:20 2021 +0100

    Allow creation of partition at sector 2048 when following another (#172)
    
    [This commit message and test case is written assuming a drive with a
    (logical) sector size of 512 bytes.  GParted equally well works with
    other sector sizes because the limit is expressed as 1 MiB / sector
    size.  Adjust the test case sector counts as needed when testing with
    different sector sized drives.]
    
    Prepare an MSDOS or GPT partitioned disk with the first partition within
    the first 1 MiB.
    
    For MSDOS use:
        dd if=/dev/zero bs=1M of=/dev/sdb
        echo 1,2047 | sfdisk -uS --force /dev/sdb
    
    For GPT use:
        sgdisk --zap-all /dev/sdb
        sgdisk --set-alignment=1 --new 1:34:2047 /dev/sdb
    
    In GParted create a new partition on /dev/sdb as near to the start of
    the drive as possible.  GParted insists on added an extra 1 MiB of space
    before the new partition, making it start at sector 4096, even though
    sector 2048 is free and aligns to whole megabytes.
    
    Delete the preceding partition.  Now GParted allows the new partition
    to be created starting at sector 2048.
    
    GParted only needs to add padding of 1 MiB to account for the partition
    table at the start of the drive when the possible start is within the
    first MiB, not already at the first MiB.  Fix this off by one error in
    the sector comparison.
    
    The reason this has bug has never occurred before is because it is very
    unusual to have the first partition entirely within the first 1 MiB.
    Normally either the (start of) the drive is free so GParted creates an
    unallocated partition object starting at sector 0, so adding 1 MiB of
    padding to preserve the partition table is correct; or the first
    partition starts at 1 MiB so the possible start for a second partition
    is much later in the drive.
    
    Closes #172 - GParted doesn't allow creation of a partition starting at
                  sector 2048 if there is a partition before it

 src/Dialog_Base_Partition.cc | 2 +-
 src/Win_GParted.cc           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/Dialog_Base_Partition.cc b/src/Dialog_Base_Partition.cc
index 943ef816..a025ac49 100644
--- a/src/Dialog_Base_Partition.cc
+++ b/src/Dialog_Base_Partition.cc
@@ -510,7 +510,7 @@ int Dialog_Base_Partition::MB_Needed_for_Boot_Record( const Partition & partitio
               )
            || ( partition .type == TYPE_LOGICAL )
                                             /* Beginning of disk device */
-           || ( partition .sector_start <= (MEBIBYTE / partition .sector_size) )
+           || (partition.sector_start < (MEBIBYTE / partition.sector_size))
           )
                return 1 ;
        else
diff --git a/src/Win_GParted.cc b/src/Win_GParted.cc
index 9e07a801..3bf5054d 100644
--- a/src/Win_GParted.cc
+++ b/src/Win_GParted.cc
@@ -1363,7 +1363,7 @@ void Win_GParted::set_valid_operations()
                               )
                            || ( selected_partition_ptr->type == TYPE_LOGICAL )
                                                             /* Beginning of disk device */
-                           || ( selected_partition_ptr->sector_start <= (MEBIBYTE / 
selected_partition_ptr->sector_size) )
+                           || (selected_partition_ptr->sector_start < (MEBIBYTE / 
selected_partition_ptr->sector_size))
                           )
                                required_size += MEBIBYTE;