Google Summer of Code 2021 Work Product Submission

Introduction

Hello, my name is Panos Korovesis and during 2021 I was accepted in the Google Summer of Code program. I chose a project from LibreOffice and I work under the mentorship of Tomaž Vajngerl and Miklos Vajna. The objective of the project was to complete the missing import/export tests of the SVM format and then separate the writing/reading functionality of the VCL Metafile to its own classes, in order to allow further refactoring of the VCL.

Technical Overview

This project can be broken down in five distinct phases.

  • Phase One - Missing SVM Tests: This part included the completion of the commented out methods in svmtest.cxx. In some cases additions were required in mtfxmldump.cxx in order for the svm file to be produced.
  • Phase Two - SvmReader: This part included the creation of a new class SvmReader.hxx in order to handle the reading functionality of the VCL. Reading is done with SvmReader::Read method, which works as follows:
    • Sets up the stream, as was previously done in ReadGDIMetaFile
    • For each MetaAction call the created MetaActionHandler
    • The MetaActionHandler calls the appropriate read handler - which performs the reading - (e.g PixelHandler) for each MetaAction depending on the MetaActionType. The handlers are modified versions of the MetaAction::Read methods. Note: In order for the read handlers to work, Set methods had to be created for each MetaAct’s protected members (one can be seen here).
  • Phase Three - SvmWriter: This part included the creation of a new class SvmWriter.hxx in order to handle the writing functionality of the VCL. Writing is done with SvmWriter::Write method, which works as follows:
    • Sets up the stream, as was previously done in GDIMetaFile::Write
    • For each MetaAction in the MetaFile, call the created MetaActionHandler
    • The MetaActionHandler calls the appropriate write handler - which performs the writing - (e.g PointHandler) for each MetaAction depending on the MetaActionType. The handlers are modified versions of the MetaAction::Write methods.
  • Phase Four - Replacing: The reading/writing was performed by four methods. Those are: GDIMetaFile::Read, GDIMetaFile::Write, ReadGDIMetaFile, WriteGDIMetaFile. Whereas the new functionality is performed by SvmWriter::Write and SvmReader::Read. This part included the replacement of the method calls of the methods mentioned above with the new ones (SvmWriter::Write, SvmReader::Read) Note: GDIMetaFile::GetChecksum had to be moved in SvmWriter because it was using the MetaAction::Write method.
  • Phase Five - Cleanup: This part included the deletion of methods that were no longer in use. Those were:
    • GDIMetaFile::Write
    • GDIMetaFile::Read
    • WriteGDIMetaFile
    • ReadGDIMetaFile
    • MetaAction::Write
    • MetaAction::Read
    • GDIMetaFile::GetChecksum

Commits

A list with all the commits can be found at the bottom of this post

Some important commits for each phase are listed below:

Phase One The commits regarding this phase start from Add RefPoint cppunit test to vcl and end at Add FloatTransparent cppunit test to vcl.

Example: Add Comment cppunit test to vcl

  • Fill the TestComment method with the required elements to be tested. They are then written in a .svm file in xml format
  • Create a CheckComment method, which checks if the Comment attributes declared in the method above are the expected in the xml
  • Modify mtfxmldump.cxx to format the xml output in the format we need

Phase Two The commits regarding this phase start from Create Separate SvmReader class and end at Add Handler for MetaAction Read.

Example: Create Separate SvmReader class

  • Create the required files for a new class and update the appropriate makefile
  • Create a constructor
  • Create the Read method. It sets up the stream and calls the MetaActionHandler. At this stage the MetaActionHandler uses the original read functionality (MetaAction::Read). The next commits start replacing it with the new one.
  • Update svmtest.cxx in order to use SvmReader::Read instead of GDIMetaFile::Read

Example: Add Handler for MetaPoint Read

  • Create the PointHandler
  • Create Set methods for MetaPointAction private members, as they are required by the PointHandler
  • Adjust the MetaActionHandler to call the PointHandler where needed. Thus, the new read functionality is used instead of the MetaPointAction::Read

Phase Three The commits regarding this phase start from Create SvmWriter class and end at Add Handler for TextLineColor Write

Example: Create SvmWriter class

  • Create the required files for a new class and update the appropriate makefile
  • Create a constructor
  • Create the MetaActionHandler and the ActionHandler which replaces MetaAction::Write.
  • Create the Write method. It sets up the stream and calls the MetaActionHandler. At this stage the MetaActionHandler uses the original read functionality (MetaAction::Write) for all actions except MetaAction. The next commits continue replacing with the new one.
  • Update svmtest.cxx in order to use SvmWriter::Write instead of GDIMetaFile::Write

Example: Add Handler for Ellipse Write

  • Create the EllipseHandler
  • Adjust the MetaActionHandler to call the EllipseHandler where needed. Thus, the new read functionality is used instead of the MetaPointAction::Write

Phase Four The commits regarding this phase start with “Replace”

Example: Replace ReadGDIMetaFile with Svmreader::Read

  • Removes the old method call

  • Creates a SvmReader object and calls SvmReader::Read, thus replacing the old Read with the new

    Note: These steps are repeated for each file that needs replacing

Phase Five The commits regarding this phase start with “Remove”. It also includes the commit Move GDIMetaFile::GetChecksum to SvmWriter::GetChecksum

Example: Remove unused methods from gdimtf.hxx

  • Removes GDIMetaFile::Read

  • Removes GDIMetaFile::Write

  • Removes ReadGDIMetaFile

  • Removes WriteGDIMetaFile

    Note: This can be done, as the functionality of the removed methods is covered by SvmReader, SvmWriter.

Example: Move GDIMetaFile::GetChecksum to SvmWriter::GetChecksum

  • Moves the method to SvmWriter while applying any changes needed in order to be compatible

  • Removes the method from it’s initial location

    Note: This change was required as the method was using MetaAction::Write, which is replaced by the SvmWriter.

Next Steps

The remaining steps for the completion of the project are

  • Go through the tests of the svm format trying to find edge cases and if so, write tests for them

Those steps do not need to be implemented by someone else however as I am determined to see this project to the end, even if it it goes beyond the GSoC Coding period.

Conclusion

Working at LibreOffice was a beautiful experience. Getting in touch with people all over the world while aiming at the same goal was something new for me, but definitely something I will seek in the future! I would also like to thank the dev community for it’s constant support on all my questions (silly or not) and especially my mentors Tomaž Vajngerl, Miklos Vajna for their continuous support as without them I would not be able to progress. Lastly, as I had a great experience, I plan to continue contributing to LibreOffice in the feature! Sere you all around!

Commit List

All the commits regarding the project and thus listed below, have been successfully merged.

The commits are:

  1. https://gerrit.libreoffice.org/c/core/+/116780
  2. https://gerrit.libreoffice.org/c/core/+/116819
  3. https://gerrit.libreoffice.org/c/core/+/116967
  4. https://gerrit.libreoffice.org/c/core/+/116959
  5. https://gerrit.libreoffice.org/c/core/+/117153
  6. https://gerrit.libreoffice.org/c/core/+/117232
  7. https://gerrit.libreoffice.org/c/core/+/117245
  8. https://gerrit.libreoffice.org/c/core/+/117155
  9. https://gerrit.libreoffice.org/c/core/+/117368
  10. https://gerrit.libreoffice.org/c/core/+/117575
  11. https://gerrit.libreoffice.org/c/core/+/117702
  12. https://gerrit.libreoffice.org/c/core/+/117694
  13. https://gerrit.libreoffice.org/c/core/+/118143
  14. https://gerrit.libreoffice.org/c/core/+/118275
  15. https://gerrit.libreoffice.org/c/core/+/118217
  16. https://gerrit.libreoffice.org/c/core/+/118396
  17. https://gerrit.libreoffice.org/c/core/+/118398
  18. https://gerrit.libreoffice.org/c/core/+/118399
  19. https://gerrit.libreoffice.org/c/core/+/118403
  20. https://gerrit.libreoffice.org/c/core/+/118433
  21. https://gerrit.libreoffice.org/c/core/+/118473
  22. https://gerrit.libreoffice.org/c/core/+/118545
  23. https://gerrit.libreoffice.org/c/core/+/118550
  24. https://gerrit.libreoffice.org/c/core/+/118565
  25. https://gerrit.libreoffice.org/c/core/+/118566
  26. https://gerrit.libreoffice.org/c/core/+/118598
  27. https://gerrit.libreoffice.org/c/core/+/118608
  28. https://gerrit.libreoffice.org/c/core/+/118610
  29. https://gerrit.libreoffice.org/c/core/+/118633
  30. https://gerrit.libreoffice.org/c/core/+/118636
  31. https://gerrit.libreoffice.org/c/core/+/118637
  32. https://gerrit.libreoffice.org/c/core/+/118653
  33. https://gerrit.libreoffice.org/c/core/+/118665
  34. https://gerrit.libreoffice.org/c/core/+/118667
  35. https://gerrit.libreoffice.org/c/core/+/118672
  36. https://gerrit.libreoffice.org/c/core/+/118673
  37. https://gerrit.libreoffice.org/c/core/+/118674
  38. https://gerrit.libreoffice.org/c/core/+/118677
  39. https://gerrit.libreoffice.org/c/core/+/118698
  40. https://gerrit.libreoffice.org/c/core/+/118829
  41. https://gerrit.libreoffice.org/c/core/+/118833
  42. https://gerrit.libreoffice.org/c/core/+/118834
  43. https://gerrit.libreoffice.org/c/core/+/118836
  44. https://gerrit.libreoffice.org/c/core/+/118830
  45. https://gerrit.libreoffice.org/c/core/+/118837
  46. https://gerrit.libreoffice.org/c/core/+/118845
  47. https://gerrit.libreoffice.org/c/core/+/118892
  48. https://gerrit.libreoffice.org/c/core/+/118894
  49. https://gerrit.libreoffice.org/c/core/+/118895
  50. https://gerrit.libreoffice.org/c/core/+/118896
  51. https://gerrit.libreoffice.org/c/core/+/118955
  52. https://gerrit.libreoffice.org/c/core/+/118956
  53. https://gerrit.libreoffice.org/c/core/+/118957
  54. https://gerrit.libreoffice.org/c/core/+/118967
  55. https://gerrit.libreoffice.org/c/core/+/118968
  56. https://gerrit.libreoffice.org/c/core/+/118979
  57. https://gerrit.libreoffice.org/c/core/+/118980
  58. https://gerrit.libreoffice.org/c/core/+/118981
  59. https://gerrit.libreoffice.org/c/core/+/119092
  60. https://gerrit.libreoffice.org/c/core/+/119170
  61. https://gerrit.libreoffice.org/c/core/+/119171
  62. https://gerrit.libreoffice.org/c/core/+/119192
  63. https://gerrit.libreoffice.org/c/core/+/119193
  64. https://gerrit.libreoffice.org/c/core/+/119194
  65. https://gerrit.libreoffice.org/c/core/+/119537
  66. https://gerrit.libreoffice.org/c/core/+/119538
  67. https://gerrit.libreoffice.org/c/core/+/119539
  68. https://gerrit.libreoffice.org/c/core/+/119541
  69. https://gerrit.libreoffice.org/c/core/+/119580
  70. https://gerrit.libreoffice.org/c/core/+/119591
  71. https://gerrit.libreoffice.org/c/core/+/119592
  72. https://gerrit.libreoffice.org/c/core/+/119593
  73. https://gerrit.libreoffice.org/c/core/+/119594
  74. https://gerrit.libreoffice.org/c/core/+/119733
  75. https://gerrit.libreoffice.org/c/core/+/119734
  76. https://gerrit.libreoffice.org/c/core/+/119735
  77. https://gerrit.libreoffice.org/c/core/+/119736
  78. https://gerrit.libreoffice.org/c/core/+/119737
  79. https://gerrit.libreoffice.org/c/core/+/119738
  80. https://gerrit.libreoffice.org/c/core/+/119846
  81. https://gerrit.libreoffice.org/c/core/+/119898
  82. https://gerrit.libreoffice.org/c/core/+/119899
  83. https://gerrit.libreoffice.org/c/core/+/119900
  84. https://gerrit.libreoffice.org/c/core/+/119901
  85. https://gerrit.libreoffice.org/c/core/+/119902
  86. https://gerrit.libreoffice.org/c/core/+/119903
  87. https://gerrit.libreoffice.org/c/core/+/119920
  88. https://gerrit.libreoffice.org/c/core/+/119921
  89. https://gerrit.libreoffice.org/c/core/+/119922
  90. https://gerrit.libreoffice.org/c/core/+/119923
  91. https://gerrit.libreoffice.org/c/core/+/119924
  92. https://gerrit.libreoffice.org/c/core/+/119925
  93. https://gerrit.libreoffice.org/c/core/+/119963
  94. https://gerrit.libreoffice.org/c/core/+/119964
  95. https://gerrit.libreoffice.org/c/core/+/119965
  96. https://gerrit.libreoffice.org/c/core/+/119966
  97. https://gerrit.libreoffice.org/c/core/+/119967
  98. https://gerrit.libreoffice.org/c/core/+/119968
  99. https://gerrit.libreoffice.org/c/core/+/120106
  100. https://gerrit.libreoffice.org/c/core/+/120107
  101. https://gerrit.libreoffice.org/c/core/+/120108
  102. https://gerrit.libreoffice.org/c/core/+/120109
  103. https://gerrit.libreoffice.org/c/core/+/120110
  104. https://gerrit.libreoffice.org/c/core/+/120111
  105. https://gerrit.libreoffice.org/c/core/+/120153
  106. https://gerrit.libreoffice.org/c/core/+/120154
  107. https://gerrit.libreoffice.org/c/core/+/120155
  108. https://gerrit.libreoffice.org/c/core/+/120156
  109. https://gerrit.libreoffice.org/c/core/+/120157
  110. https://gerrit.libreoffice.org/c/core/+/120158
  111. https://gerrit.libreoffice.org/c/core/+/120256
  112. https://gerrit.libreoffice.org/c/core/+/120257
  113. https://gerrit.libreoffice.org/c/core/+/120258
  114. https://gerrit.libreoffice.org/c/core/+/120259
  115. https://gerrit.libreoffice.org/c/core/+/120263
  116. https://gerrit.libreoffice.org/c/core/+/120264
  117. https://gerrit.libreoffice.org/c/core/+/120306
  118. https://gerrit.libreoffice.org/c/core/+/120307
  119. https://gerrit.libreoffice.org/c/core/+/120308
  120. https://gerrit.libreoffice.org/c/core/+/120309
  121. https://gerrit.libreoffice.org/c/core/+/120312
  122. https://gerrit.libreoffice.org/c/core/+/120313
  123. https://gerrit.libreoffice.org/c/core/+/120349
  124. https://gerrit.libreoffice.org/c/core/+/120350
  125. https://gerrit.libreoffice.org/c/core/+/120351
  126. https://gerrit.libreoffice.org/c/core/+/120372
  127. https://gerrit.libreoffice.org/c/core/+/120376
  128. https://gerrit.libreoffice.org/c/core/+/120408
  129. https://gerrit.libreoffice.org/c/core/+/120409
  130. https://gerrit.libreoffice.org/c/core/+/120414
  131. https://gerrit.libreoffice.org/c/core/+/120471