ea5641baee
Previously, all of the README files have been renamed to README.md and now, the contents of these files were changed to use Markdown format. Other than format inconsistency, some README.md files lacked information about modules, or were out of date. By using LibreOffice / OpenOffice wiki and other documentation websites, these files were updated. Now every README.md file has a title, and some description. The top-level README.md file is changed to add links to the modules. The result of processing the Markdown format README.md files can be seen at: https://docs.libreoffice.org/ Change-Id: Ic3b0c3c064a2498d6a435253b041df010cd7797a Reviewed-on: https://gerrit.libreoffice.org/c/core/+/113424 Tested-by: Jenkins Reviewed-by: Michael Stahl <michael.stahl@allotropia.de> Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
39 lines
2.3 KiB
Markdown
39 lines
2.3 KiB
Markdown
# Registries, Reflection, Introspection Implementation for UNO
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The UNO types and services bootstrapping code is very old, and concepts
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are tightly knit together. Whenever you want to change something you risk
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backwards incompatibility. The code causes mental pain, and whenever
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you need to touch it you want to run away screaming. One typically ends
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up doing minimally invasive changes. That way, you have a chance of
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surviving the process. But you also pile up guilt.
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At the heart of the matter there is the old binary "store" file structure
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and the `XRegistry` interface on top of it. At runtime, both all the UNO
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type information (scattered across a number of binary `.rdb` files) and
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all the UNO service information (scattered across a number of `.rdb` files
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that used to be binary but have been mostly changed to XML now) are
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represented by a single `XRegistry` instance each.
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The way the respective information is represented in the `XRegistry`
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interface simply corresponds to the way the information is stored in the
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binary `.rdb` files. Those files are designed for storage of hierarchically
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nested small blobs of information. Hence, for example information about
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a UNO interface type `com.sun.star.foo.XBar` is stored in a nested "folder"
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with path `com - sun - star - foo - XBar`, containing little blobs of
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information about the type's ancestors, its methods, etc. Similarly
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for information about instantiable services like `com.sun.star.baz.Boz`.
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As there are typically multiple `.rdb` files containing types resp.
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services (URE specific, LO specific, from extensions, ...), but they need
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to be represented by a single `XRegistry` instance, so "nested registries"
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were invented. They effectively form a linear list of chaining `XRegistry`
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instances together. Whenever a path needs to be looked up in the top-level
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registry, it effectively searches through the linear list of nested
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registries. All with the cumbersome UNO `XRegistry` interface between
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the individual parts. Horror.
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When the XML service `.rdb`s were introduced, we chickened out (see above
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for rationale) and put them behind an `XRegistry` facade, so that they
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would seamlessly integrate with the existing mess. We postponed
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systematic clean-up to the pie-in-the-sky days of LibreOffice 4 (or, "once we'll
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become incompatible with OpenOffice.org," as the phrase used to be back then)
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