24 Oct 2024

Crash fix part 5: crash report tool

In previous blog posts about crashes in LibreOffice, I have discussed how to debug and fix some of crashes. Now I discuss a nice tool to keep track of the crash reports from volunteers: Crash report tool.

Crash Report Statistics

Crash report is available via this LibreOffice website:

You can see that different versions of LibreOffice listed there, and for each and every tracked version, number of crashes during the previous 1, 3, 7, 14 and 28 days can be seen. This is possible using the appropriate buttons on the top.

This data is gathered from those to volunteer to submit reports to make LibreOffice better.

This statistic is very helpful to understand the robustness of the builds in different versions.

Crash Signatures

If you choose a specific version, you may see signatures of the crashes. This is helpful when trying to fix crashes. For example, this is one of the crash signatures found in LibreOffice 24.8.0.3:

This shows that the crash happens in GetCharFormat() function. One may use this information to track and fix the problem.

Looking into one of the crashes, one may see the details of the crash, including the stack trace in the crashing thread, and link to the exact place of the source code that leads to the crash.

As an example, you can see this crash report.

Sometimes, experienced developers may be able to reproduce the bug using crash signatures while knowing some background. Otherwise, in most cases, filing a bug with documents and instructions to reproduce the bug is essential. Adding a link to the crash report can be helpful.

17 Oct 2024

WSL for building LibreOffice

Windows Subsystem for Linux (WSL) is a mechanism to use complete Linux distributions on Windows. Here I discuss how to use it to build LibreOffice for both Linux and Windows binaries.

What is WSL?

WSL is the relatively new mechanism in Windows that lets you use a complete Linux distribution alongside your Windows. Interoperability between WSL and Windows lets you to share files and utilities between Windows and Linux. That is where it becomes helpful for LibreOffice, as LibreOffice make depends heavily on GNU tools, which are available in Linux.

Linux or Windows?

You can use WSL for 2 different scenarios:

1. Building for Linux: this is the full Linux build, in which Linux compilers, libraries and utilities will be used to create a Linux binary. You can then run or package the Linux build. You can find more information here:

Using WSL2 is recommended, as it is supposed to be faster, and also you can simply use the graphical interface of LibreOffice.

LibreOffice build on WSL with Linux binaries, displayed on Windows

LibreOffice build on WSL with Linux binaries, displayed on Windows

When you run the resulting binary, the graphical interface is usable, and it will use GTK fronted by default.

2. Building for Windows: this is the WSL as helper mode, where it uses only a few Linux utilities like pkg-config, make, automake and a few other utilities to configure the project.  Then, GNU Make for Windows will be the tool to build the project. More information is available here:

The results are Windows .exe files, and you can simply run them on Windows as native programs.

Build Options on Windows

You can build LibreOffice on different platforms. On Windows, it is possible to use Cygwin, but using WSL can be faster, and considering some issues with recent Cygwin versions, WSL is an alternative.

One can imagine of other ways to build LibreOffice on Windows, including MinGW. But, at the moment, MinGW, both as a helper to use Visual Studio, and also as an independent distribution to build LibreOffice, is not usable due to various reasons.

And last note: if you do not have prior experience with LibreOffice development but you are interested, you can start from our video tutorial for getting started with LibreOffice development.

3 Oct 2024

Setting dialogs that are available via UNO Commands

LibreOffice options page provides rich set of settings for everyone who wants to tune LibreOffice to match their needs. But, what if you as a developer, need setting dialogs that are needed elsewhere in the LibreOffice application? Here I discuss some of such use cases, which are handled by defining UNO commands.

Options Page

The code for providing “Tools > Options” is not in a single module, but main part resides in cui module, which contains code which is used across different modules. Looking into cui/source/options/ folder from LibreOffice core source code, you can see various different source files related to the options. The biggest file there is cui/source/options/treeopt.cxx, which is the actual implementation of the tree-based dialog that you see when you open Tools > Options dialog. There are other C++ files that handle .ui files related to options. You can find those UI files in cui/uiconfig/ui/ folder with a name like opt*.ui:

$ ls cui/uiconfig/ui/opt*.ui

These files can be edited and they are used as described in the LibreOffice design blog:

UNO Dispatch Commands

Only some of the dialogs can be opened available via UNO dispatch commands. As an example, you may see “.uno:AdditionsDialog” is used both in cui/source/options/optgdlg.cxx for creating a dialog in Tools > Options (when you click for “more icons”), and also in sfx2/source/appl/appserv.cxx.

You can try running this UNO command in LibreOffice BASIC editor with this code snippet:

Sub Main()
    Set oDispatch = CreateUnoService("com.sun.star.frame.DispatchHelper")
    Dim args(0) As New com.sun.star.beans.PropertyValue
    Set oFrame = StarDesktop.Frames.getByIndex(0)
    oDispatch.executeDispatch(oFrame, ".uno:AdditionsDialog", "", 0, args)
End Sub

The above command is defined specifically to help developers use the “Extensions” dialog, anywhere in LibreOffice UI, from top menus to context menus and toolbars and also in code, in a simple way.

"Extensions

There is another dialog titled “Security Options and Warnings”, which is opened through .uno:OptionsSecurityDialog UNO command. In this way, it can be used easily in other modules of LibreOffice.

SecurityOptionsDialog

SecurityOptionsDialog

Implementing UNO Command

Adding a new UNO command was discussed before, in a separate blog post:

Adding a new UNO command

Adding a new UNO command for an options dialog is basically the same. There can be differences regarding the configurations and the data that is passed between the dialog and the caller.

When you create a dialog box directly like the code snippet below, you have access to the member functions defined for that specific dialog:

IMPL_LINK_NOARG( SwGlossaryDlg, PathHdl, weld::Button&, void )
{
    SvxAbstractDialogFactory* pFact = SvxAbstractDialogFactory::Create();
    ScopedVclPtr<AbstractSvxMultiPathDialog> pDlg(pFact->CreateSvxPathSelectDialog(m_xDialog.get()));
    SvtPathOptions aPathOpt;
    const OUString sGlosPath( aPathOpt.GetAutoTextPath() );
    pDlg->SetPath(sGlosPath);
    if(RET_OK == pDlg->Execute())
    {
        const OUString sTmp(pDlg->GetPath());
        if(sTmp != sGlosPath)
        {
            aPathOpt.SetAutoTextPath( sTmp );
            ::GetGlossaries()->UpdateGlosPath( true );
            Init();
        }
    }
}

As you can see, pDlg->GetPath() is accessible here, and you can use it to pass data. But when you are using UNO commands, those functions will not be available directly. Instead, you may pass values that denote the data that will be read from somewhere else, like the configuration.

For example, consider there are multiple paths that you may want to edit using this UNO command with the same dialog. In this case, you can pass a value that shows the associated path that you are changing. It can be passed as an enumeration, and then you set and/or get the value directly from the configuration.

In this way, the callers in the C++ code will have much easier task to do, as it is only calling the UNO command, and the rest is done in the implementation of the UNO command.

For AdditionsDialog, the calling code is as simple as this in cui/source/options/optgdlg.cxx:

IMPL_STATIC_LINK_NOARG(OfaViewTabPage, OnMoreIconsClick, weld::Button&, void)
{
    css::uno::Sequence<css::beans::PropertyValue> aArgs{ comphelper::makePropertyValue(
u"AdditionsTag"_ustr, u"Icons"_ustr) };
    comphelper::dispatchCommand(u".uno:AdditionsDialog"_ustr, aArgs);
}

Passing Parameters to UNO Commands

UNO dispatch commands can take parameters. As an example, take a look at .uno:NewDoc defined in sfx2/sdi/sfx.sdi:

SfxStringItem NewDoc SID_NEWDOC
(SfxStringItem Region SID_TEMPLATE_REGIONNAME,SfxStringItem Name SID_TEMPLATE_NAME)
[
...
]

As you can see, there are two parameters:

SfxStringItem Region SID_TEMPLATE_REGIONNAME SfxStringItem Name SID_TEMPLATE_NAME

The SfxStringItem is the type, Region and Name are the names of the parameters, SID_TEMPLATE_REGIONNAME and SID_TEMPLATE_NAME are the constants used for passing parameters. The parameter type is not limited to numbers and strings, and it can be any defined class.

To set and get data for this parameters, you may use appropriate Set and Put functions. For example, this gets the parameter if set:

const SfxStringItem *pItem = rSet.GetItemIfSet( SID_TEMPLATE_REGIONNAME, false)

Or, this sets the data:

OUString sVal = u"test"_ustr;

rSet.Put( SfxStringItem( SID_TEMPLATE_REGIONNAME, sVal ) );

Final Notes

To get to know better how to implement more complex UNO dispatch commands, you can refer to the implementation of the existing UNO commands to get idea about how they are implemented. You can see a comprehensive list of UNO commands here:

15 Aug 2024

Extending the UNO API

Various functionalities of the LibreOffice are available through its programming interface, the UNO API. Here I discuss how to extend it. (more…)

29 Jul 2024

Fuzz testing to maintain LibreOffice code quality

Here I discuss what fuzz testing is, and how LibreOffice developers use it incrementally to maintain LibreOffice code quality. (more…)

25 Jul 2024

LibreOfficeKit for document conversion

In the previous blog post, I provided a brief introduction to LibreOfficeKit API which one can use for accessing LibreOffice functionalities in an external application. Here I discuss in detail how to use LibreOfficeKit for converting an ODT to PDF, or from/to virtually any other format that LibreOffice supports. (more…)

27 Jun 2024

LibreOfficeKit API in action

If you want to use LibreOffice functionality in your applications, LibreOfficeKit API is one of the good ways to do that. Here I describe how, with some examples. If you want to add the capability of loading, displaying, editing, saving and/or converting LibreOffice/MS Office files to your application, you have come to a good place. (more…)

30 May 2024

Porting Java tests to C++

In this blog post, I discuss porting Java tests from Java to C++. We have many Java tests, and porting them to C++ is beneficial for LibreOffice. Here I discuss why, and how. (more…)

14 May 2024

Crash fixes, part 4: assertion failure

In the previous parts of the blog posts series on fixing software crashes, I have written about some crash fixes in LibreOffice around segfaults, aborts, and I discussed how test them. Here I write about fixing assertion failure. (more…)

18 Apr 2024

Crash fixes part 3 – Testing crashes

I have previously discussed fixing crashes in 2 parts (segfaults, aborts). Here I discuss testing crashes to avoid creating re-creating regressions. (more…)