devel-docs: Update content according to 'gimp-web-devel'

- Drops HACKING file (it is outdated and we have the "same thing",
  updated, in the devel site), but moved PDB content to the README
* Update various links now to the devel site
+ Added 'TODOs' to avoid confusion from titles with empty content
  and removed some that are already implemented

devel-docs/HACKING.md

@@ -1,155 +0,0 @@
-# Building from git and contributing
-
-While packagers are expected to compile GIMP from tarballs (same for
-personal usage), developers who wish to contribute patches should
-compile from the git repository.
-
-The procedure is basically the same (such as described in the `INSTALL`
-file, which you will notice doesn't exist in the repository; you can
-find [INSTALL.in](/INSTALL.in) instead, whose base text is the same
-before substitution by the build configuration step). Yet it has a few
-extra steps.
-
-## Git
-
-GIMP is available from GNOME Git. You can use the following commands
-to get GIMP from the the git server:
-
-    $ git clone https://gitlab.gnome.org/GNOME/gimp.git
-
-You can read more on using GNOME's git service at these URLs:
-
-    https://wiki.gnome.org/Git
-    https://www.kernel.org/pub/software/scm/git/docs/
-
-
-The development branches of GIMP closely follow the development branches
-of `babl` and `GEGL` which are considered part of the project. Therefore
-you will also have to clone and build these repositories:
-
-    $ git clone https://gitlab.gnome.org/GNOME/babl.git
-    $ git clone https://gitlab.gnome.org/GNOME/gegl.git
-
-
-As for other requirements as listed in the `INSTALL` file, if you use
-a development-oriented Linux distribution (Debian Testing or Fedora for
-instance), you will often be able to install all of them from your
-package manager. On Windows, the MSYS2 project is great for keeping up
-with libraries too. On macOS, it is unfortunately much more of a hurdle
-and you should probably look at instructions in our [gimp-macos-build
-repository](https://gitlab.gnome.org/Infrastructure/gimp-macos-build)
-which is how we build GIMP for macOS.
-
-We also know that GIMP is built on various \*BSD, proprietary Unixes,
-even on GNU-Hurd and less known systems such as Haiku OS but we don't
-have much details to help you there. Yet we still welcome patches to
-improve situation on any platform.
-
-In any case, if you use a system providing too old packages, you might
-be forced to build from source (tarballs or repositories) the various
-dependencies list in `INSTALL`.
-
-## Additional Requirements
-
-Our autotools build system requires the following packages (or newer
-versions) installed when building from git (unlike building from
-tarball):
-
-    * GNU autoconf 2.54 or over
-        - ftp://ftp.gnu.org/gnu/autoconf/
-    * GNU automake 1.13 or over
-        - ftp://ftp.gnu.org/gnu/automake/
-    * GNU libtool 1.5 or over
-        - ftp://ftp.gnu.org/gnu/libtool/
-
-Alternatively a build with meson 0.53.0 or over is possible but it is
-not complete yet, hence not usable for packaging (yet usable for
-development).
-
-For some specific build rules, you will also need:
-
-    * xsltproc
-        - ftp://ftp.gnome.org/pub/GNOME/sources/libxslt/1.1/
-
-In any cases, you will require this tool for dependency retrieval:
-
-    * pkg-config 0.16.0 (or preferably a newer version)
-        - https://www.freedesktop.org/software/pkgconfig/
-
-These are only the additional requirements if you want to compile from
-the git repository. The file `INSTALL` lists the various libraries we
-depend on.
-
-
-## Additional Compilation Steps
-
-If you are accessing GIMP via git, then you will need to take more
-steps to get it to compile.  You can do all these steps at once by
-running:
-
-    gimp/trunk$ ./autogen.sh
-
-Basically this does the following for you:
-
-    gimp/trunk$ aclocal-1.9; libtoolize; automake-1.9 -a;
-    gimp/trunk$ autoconf;
-
-The above commands create the "configure" script.  Now you can run the
-configure script in gimp/trunk to create all the Makefiles.
-
-Before running autogen.sh or configure, make sure you have libtool in
-your path. Also make sure glib-2.0.m4 glib-gettext.m4, gtk-3.0.m4 and
-pkg.m4 are either installed in the same $prefix/share/aclocal relative to your
-automake/aclocal installation or call autogen.sh as follows:
-
-    $ ACLOCAL_FLAGS="-I $prefix/share/aclocal" ./autogen.sh
-
-Note that autogen.sh runs configure for you.  If you wish to pass
-options like --prefix=/usr to configure you can give those options to
-autogen.sh and they will be passed on to configure.
-
-If AUTOGEN_CONFIGURE_ARGS is set, these options will also be passed to
-the configure script. If for example you want to enable the build of
-the GIMP API reference manuals, you can set AUTOGEN_CONFIGURE_ARGS to
-"--enable-gi-docgen".
-
-If you want to use libraries from a non-standard prefix, you should set
-PKG_CONFIG_PATH appropriately. Some libraries do not use pkgconfig, see
-the output of ./configure --help for information on what environment
-variables to set to point the compiler and linker to the correct path.
-Note that you need to do this even if you are installing GIMP itself
-into the same prefix as the library.
-
-
-## Patches
-
-The best way to submit patches is to provide files created with
-git-format-patch. The recommended command for a patch against the
-`master` branch is:
-
-  $ git format-patch origin/master
-
-It is recommended that you file a bug report in our
-[tracker](https://gitlab.gnome.org/GNOME/gimp) and either create a merge
-request or attach your patch to the report as a plain text file, not
-compressed.
-
-Please follow the guidelines for coding style and other requirements
-listed in [CODING_STYLE.md](https://developer.gimp.org/core/coding_style/). When
-you will contribute your first patches, you will notice that we care very much
-about clean and tidy code, which helps for understanding. Hence we care about
-coding style and consistency!
-
-
-## Auto-generated Files
-
-Please notice that some files in the source are generated from other
-sources. All those files have a short notice about being generated
-somewhere at the top. Among them are the files ending in `pdb.[ch]` in
-the `libgimp/` directory and the files ending in `cmds.c` in the
-`app/pdb/` subdirectory. Those are generated from the respective `.pdb`
-files in `pdb/groups`.
-
-Other files are:
-
-* `AUTHORS` from `authors.xml`

devel-docs/README.md

@@ -72,7 +72,7 @@ The whole C reference documentation for both these libraries can be
 generated in the main GIMP build with the `-Dgi-docgen=enabled` meson
 option (you need to have the `gi-docgen` tools installed).
 
-TODO: add online links when it is up for the new APIs.
+See the [API documentation](https://developer.gimp.org/api/3.0/)
 
 ### Programming Languages
 
@@ -101,7 +101,7 @@ full-featured since they don't require manual tweaking. Therefore any
 function in the C library should have an equivalent in any of the
 bindings.
 
-TODO: binding reference documentation.
+**TODO**: binding reference documentation.
 
 **Note**: several GObject-Introspection's Scheme bindings exist though
 we haven't tested them. Nevertheless, GIMP also provides historically
@@ -112,17 +112,18 @@ development](#script-fu-development) section.
 
 ### Tutorials
 
-TODO: at least in C and in one of the officially supported binding
+**TODO**: at least in C and in one of the officially supported binding
 (ideally even in all of them).
 
 ### Porting from GIMP 2 plug-ins
 
+Take a look at our [porting guide](GIMP3-plug-in-porting-guide/README.md).
+
 ### Debugging
 
 GIMP provides an infrastructure to help debugging plug-ins.
 
-You are invited to read the [dedicated
+You are invited to read the [dedicated documentation](https://developer.gimp.org/resource/debug-plug-ins/).
-documentation](debug-plug-ins.txt).
 
 ## Script-fu development
 
@@ -132,11 +133,13 @@ Scheme mini-interpreter and therefore `Script-fu` scripts do not use
 `libgimp` or `libgimpui`. They interface with the PDB through the
 `Script-fu` plug-in.
 
-### Tutorials
+### TODO: Tutorials
 
 ### Porting from GIMP 2 scripts
 
-## GEGL operation development
+Take a look at our [ScriptFu porting guide](GIMP3-plug-in-porting-guide/script-fu-author-guide.md)
+
+## TODO: GEGL operation development
 
 ## Custom data
 
@@ -176,8 +179,8 @@ recent versions.
 
 If you are interested in brushes from a developer perspective, you are
 welcome to read specifications of GIMP formats:
-[GBR](specifications/gbr.txt), [GIH](specifications/gih.txt),
+[GBR](https://developer.gimp.org/core/standards/gbr/), [GIH](https://developer.gimp.org/core/standards/gih/),
-[VBR](specifications/vbr.txt) or the obsolete [GPB](specifications/gpb.txt).
+[VBR](https://developer.gimp.org/core/standards/vbr/) or the obsolete [GPB](https://developer.gimp.org/core/standards/gpb/).
 
 If you want to contribute brushes to the official GIMP, be aware we
 would only accept brushes in non-obsolete GIMP formats. All these
@@ -199,11 +202,11 @@ within GIMP.
 ### Patterns
 
 GIMP supports the GIMP Pattern format (PAT, whose
-[specification](specifications/pat.txt) is available for developers).
+[specification](https://developer.gimp.org/core/standards/pat/) is available for developers).
 
 This format can be exported by GIMP itself.
 
-Alternatively GIMP supports patterns from `GdkPixbuf` (TODO: get more
+Alternatively GIMP supports patterns from `GdkPixbuf` (**TODO**: get more
 information?).
 
 ### Palettes
@@ -214,7 +217,7 @@ GIMP.
 ### Gradients
 
 GIMP supports the GIMP Gradient format (GGR, whose
-[specification](specifications/ggr.txt) is available for developers)
+[specification](https://developer.gimp.org/core/standards/ggr/) is available for developers)
 which can be generated from within GIMP.
 
 Alternatively GIMP supports the SVG Gradient format.
@@ -239,14 +242,7 @@ Finally you can look at our existing themes, like the [System
 theme](https://gitlab.gnome.org/GNOME/gimp/-/blob/master/themes/System/gimp.css).
 Note though that this `System` theme is pretty bare, and that's its goal
 (try to theme as few as possible over whatever is the current real
-system theme).
+GTK system theme).
-
-TODO: for any theme maker reading this, what we want for GIMP 3.0 are at
-least the following additional themes:
-
-- a full custom theme using neutral grayscale colors with a dark and
-  light variant;
-- a mid-gray neutral theme.
 
 As a last trick for theme makers, we recommend to work with the
 GtkInspector tool, which allows you to test CSS rules live in the `CSS`
@@ -294,10 +290,10 @@ styling.
 See the dedicated [icons documentation](icons.md) for more technical
 information.
 
-### Tool presets
+### TODO: Tool presets
 
 
-## GIMP extensions (*.gex*)
+## TODO: GIMP extensions (*.gex*)
 
 ## Continuous Integration
 
@@ -385,35 +381,20 @@ When writing code, any core developer is expected to follow:
 - the [directory structure](#directory-structure-of-gimp-source-tree)
 - our [header file inclusion policy](includes.txt)
 
-[GIMP's developer wiki](https://wiki.gimp.org/index.php/Main_Page) can
+[GIMP's developer site](https://developer.gimp.org/) contain various valuable resources.
-also contain various valuable resources.
 
-Finally the [debugging-tips](debugging-tips.md) file contain many very
+Finally the [debugging-tips](https://developer.gimp.org/core/debug/debugging-tips/) file contain many very
 useful tricks to help you debugging in various common cases.
 
 ### Newcomers
 
 If this is your first time contributing to GIMP, you might be interested
-by build instructions. The previously mentioned wiki in particular has a
+by [build instructions](https://developer.gimp.org/core/setup/).
-[Hacking:Building](https://wiki.gimp.org/wiki/Hacking:Building) page
-with various per-platform subpages. The [HACKING](HACKING.md) docs will
-also be of interest.
 
-You might also like to read these [instructions on submitting
+You might also like to read these instructions on the process of
-patches](https://gimp.org/bugs/howtos/submit-patch.html).
+[submitting patches](https://developer.gimp.org/core/submit-patch/).
 
-If you are unsure what to work on, this [list of bugs for
+### TODO: Core Contributors
-newcomers](https://gitlab.gnome.org/GNOME/gimp/-/issues?scope=all&state=opened&label_name[]=4.%20Newcomers)
-might be a good start. It doesn't necessarily contain only bugs for
-beginner developers. Some of them might be for experienced developers
-who just don't know yet enough the codebase.
-
-Nevertheless we often recommend to rather work on topics which you
-appreciate, or even better: fixes for bugs you encounter or features you
-want. These are the most self-rewarding contributions which will really
-make you feel like developing on GIMP means developing for yourself.
-
-### Core Contributors
 
 ### Directory structure of GIMP source tree
 
@@ -484,6 +465,19 @@ The source code of the main GIMP application is found in the `app/` directory:
 | app/widgets/    | Collection of widgets used in the application GUI                                |
 | app/xcf/        | XCF file handling in **core**                                                    |
 
+#### Auto-generated Files
+
+Please notice that some files in the source are generated from other
+sources. All those files have a short notice about being generated
+somewhere at the top. Among them are the files ending in `pdb.[ch]` in
+the `libgimp/` directory and the files ending in `cmds.c` in the
+`app/pdb/` subdirectory. Those are generated from the respective `.pdb`
+files in `pdb/groups`.
+
+Other files are:
+
+* `AUTHORS` from `authors.xml`
+
 You should also check out [gimp-module-dependencies.svg](gimp-module-dependencies.svg).
 **TODO**: this SVG file is interesting yet very outdated. It should not
 be considered as some kind dependency rule and should be updated.
@@ -497,7 +491,7 @@ features made available in GIMP. More than an image format, you may
 consider it as a work or project format, as it is not made for finale
 presentation of an artwork but for the work-in-progress processus.
 
-Developers are welcome to read the [specifications of XCF](specifications/xcf.txt).
+Developers are welcome to read the [specifications of XCF](https://developer.gimp.org/core/standards/xcf/).
 
 #### Locks
 
@@ -510,8 +504,8 @@ This is further explained in [the specifications of locks](https://developer.gim
 
 GIMP has an evolved GUI framework, with a toolbox, dockables, menus…
 
-This [document describing how the GIMP UI framework functions and how it
+This document describing how the GIMP UI framework functions and how it
-is implemented](ui-framework.txt) might be of interest.
+is [implemented](ui-framework.txt) might be of interest.
 
 #### Contexts