Okular: another improvement to annotation

Continuing with the addition of line terminating style for the Straight Line annotation tool, I have added the ability to select the line start style also. The required code changes are committed today.

Line annotation with circled start and closed arrow ending.

Currently it is supported only for PDF documents (and poppler version ≥ 0.72), but that will change soon — thanks to another change by Tobias Deiminger under review to extend the functionality for other documents supported by Okular.

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Okular: improved PDF annotation tool

Okular, KDE’s document viewer has very good support for annotating/reviewing/commenting documents. Okular supports a wide variety of annotation tools out-of-the-box (enable the ‘Review’ tool [F6] and see for yourself) and even more can be configured (such as the ‘Strikeout’ tool) — right click on the annotation tool bar and click ‘Configure Annotations’.

One of the annotation tools me and my colleagues frequently wanted to use is a line with arrow to mark an indent. Many PDF annotating software have this tool, but Okular was lacking it.

So a couple of weeks ago I started looking into the source code of okular and poppler (which is the PDF library used by Okular) and noticed that both of them already has support for the ‘Line Ending Style’ for the ‘Straight Line’ annotation tool (internally called the TermStyle). Skimming through the source code for a few hours and adding a few hooks in the code, I could add an option to configure the line ending style for ‘Straight Line’ annotation tool. Many line end styles are provided out of the box, such as open and closed arrows, circle, diamond etc.

An option to the ‘Straight Line’ tool configuration is added to choose the line ending style:

New ‘Line Ending Style’ for the ‘Straight Line’ annotation tool.

Here’s the review tool with ‘Open Arrow’ ending in action:

‘Arrow’ annotation tool in action.

Once happy with the outcome, I’ve created a review request to upstream the improvement. A number of helpful people reviewed and commented. One of the suggestions was to add icon/shape of the line ending style in the configuration options so that users can quickly preview what the shape will look like without having to try each one. The first attempt to implement this feature was by adding Unicode symbols (instead of a SVG or internally drawn graphics) and it looked okay. Here’s a screen shot:

‘Line End’ with symbols preview.

But it had various issues — some symbols are not available in Unicode and the localization of these strings without some context would be difficult. So, for now it is decided to drop the symbols.

For now, this feature works only on PDF documents. The patch is committed today and will be available in the next version of Okular.

New package in Fedora: python-xslxwriter

XlsxWriter is a Python module for creating files in xlsx (MS Excel 2007+) format. It is used by certain python modules some of our customers needed (such as OCA report_xlsx module).

This module is available in pypi but it was not packaged for Fedora. I’ve decided to maintain it in Fedora and created a package review request which is helpfully reviewed by Robert-André Mauchin.

The package, providing python3 compatible module, is available for Fedora 28 onwards.

Smarter tabular editing with Vim

I happen to edit tabular data in LaTeX format quite a bit. Being scientific documents, the table columns are (almost) always left-aligned, even for numbers. That warrants carefully crafted decimal and digit alignment on such columns containing only numbers.

I also happen to edit the text (almost) always in Vim, and just selecting/changing a certain column only is not easily doable (like in a spreadsheet). If there are tens of rows that needs manual digit/decimal align adjustment, it gets even more tedious. There must be another way!

Thankfully, smarter people already figured out better ways (h/t MasteringVim).

With that neat trick, it is much more palatable to look at the tabular data and edit it. Even then, though, it is not possible to search & replace only within a column using Visual Block selection. The Visual Block (^v) sets mark on the column of first row till the column on last row, so any :<','>s/.../.../g would replace any matching text in-between (including any other columns).

To solve that, I’ve figured out another way. It is possible to copy the Visual Block alone and pasting any other content over (though cutting it and pasting would not work as you think). Thus, the plan is:

  • Copy the required column using Visual Block (^v + y)
  • Open a new buffer and paste the copied column there
  • Edit/search & replace to your need in that buffer, so nothing else would be unintentionally changed
  • Select the modified content as Visual Block again, copy/cut it and come back to the main buffer/file
  • Re-select the required column using Visual Block again and paste over
  • Profit!

Here’s a short video of how to do so. I’d love to hear if there are better ways.

Column editing in Vim
Demo of column editing in Vim

Powerline git dirty status without powerline_gitstatus

With git-prompt it is possible to display the dirty state (when a tracked file is modified) by setting the env variable GIT_PS1_SHOWDIRTYSTATE=true. Powerline can display the status of a git repository, such as number of commits ahead/behind, number of modified files etc. using the powerline_gitstatus module. Unfortunately, Fedora doesn’t have it packaged. I did some digging in, and found that there’s colour highlighting for branch_dirty and powerline.segments.common.vcs.branch function (which displays the current branch name) takes 2 parameters  to modify its behaviour. Modify the shell theme /etc/xdg/powerline/themes/shell/default.json under the left segment (because only left works in shell) then as follows:
...
    {   "function": "powerline.segments.common.vcs.branch",
        "args": {"ignore_statuses": ["U"], "status_colors": true},
        "priority": 20
    }
...
The branch will now be highlighted if a tracked file is modified (ignore_statuses = ["U"] causes untracked files to be ignored). Clean repository:
Clean repo
Once a tracked file is modified:
Dirty repo

Adventures in upgrading to Fedora 27/28 using ‘dnf system-upgrade’

[This post was drafted on the day Fedora 27 released, about half a year ago, but was not published. The issue bit me again with Fedora 28, so documenting it for referring next time.]

UPDATE: The issue occurred in Fedora 28 because I had exclude=grub2-tools in /etc/dnf/dnf.conf which is the reason error “nothing provides grub2-tools” was coming up. Removing that previously added and then forgotten line fixes the issue with updating grub2 packages.

With fedup and subsequently dnf improving the upgrade experience of Fedora for power users, last few system upgrades have been smooth, quiet, even unnoticeable. That actually speaks volumes of the maturity and user friendliness achieved by these tools.

Upgrading from Fedora 25 to 26 was so event-less and smooth (btw: I have installed and used every version of Fedora from its inception and the default wallpaper of Fedora 26 was the most elegant of them all!).

With that, on the release day I set out to upgrade the main workstation from Fedora 26 to 27 using dnf system-upgrade as documented. Before downloading the packages, dnf warned that upgrade cannot be done because of package dependency issues with grub2-efi-modules and grub2-tools.

Things go wrong!

I simply removed both the offending packages and their dependencies (assuming were probably installed for the grub2-breeze-theme dependency, but grub2-tools actually provides grub2-mkconfig) and proceeded with dnf upgrade --refresh and dnf system-upgrade download --refresh --releasever=27. If you are attempting this, don’t remove the grub2 packages yet, but read on!

Once the download and check is completed, running dnf system-upgrade reboot will cause the system reboot to upgrade target and actual upgrade happen.

Except, I was greeted with EFI MOK (Machine Owner Key) screen on reboot. Now that the grub2 bootloader is broken thanks to the removal of grub2-efi-modules and other related packages, a recovery must be attempted.

Rescue

It is important to have a (possibly EUFI enabled) live media where you can boot from. Boot into the live media and try to reinstall grub. Once booted in, mount the root filesystem under /mnt/sysimage, and EFI boot partition at /mnt/sysimage/boot/efi. Then chroot /mnt/sysimage and try to reinstall grub2-efi-x64 and shim packages. If there’s no network connectivity, don’t despair, nmcli is to your rescue. Connect to wifi using nmcli device wifi connect <ssid> password <wifi_password>. Generate the boot configuration using grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg followed by actual install grub2-install --target=x86_64-efi /dev/sdX (the –target option ensures correct host installation even if the live media is booted via legacy BIOS). You may now reboot and proceed with the upgrade.

But this again failed at the upgrade stage because of grub package clash that dnf warned earlier about.

Solution

Once booted into old installation, take a backup of the /boot/ directory, remove the conflicting grub related packages, and copy over the backed up /boot/ directory contents, especially /boot/efi/EFI/fedora/grubx64.efi. Now rebooting (using dnf system-upgrade reboot) had  the grub contents intact and the upgrade worked smoothly.

For more details on the package conflict issue, follow this bug.

Switching Raspbian to Pixel desktop

Official Raspbian images based on Debian Stretch by default has the Pixel desktop environment and will login new users to it. But if you have had a Raspbian installation with another DE (such as LXDE), here are the steps to install and login to the Pixel desktop.

apt-get install raspberrypi-ui-mods
sed -i 's/^autologin-user=pi/#autologin-user=pi/' /etc/lightdm/lightdm.conf
update-alternatives --set x-session-manager /usr/bin/startlxde-pi
sed -i 's/^Session=.*/Session=lightdm-xsession/' ${USER}/.dmrc

Make sure the user’s ‘.dmrc’ file is updated with the new startlxde-pi session as that is where lightdm login manager looks to decide which desktop should be launched.