The Mesa 3D Graphics Library

Development Notes

Adding Extensions

To add a new GL extension to Mesa you have to do at least the following.

   If glext.h doesn't define the extension, edit include/GL/gl.h and add

   code like this:

     #ifndef GL_EXT_the_extension_name

     #define GL_EXT_the_extension_name 1

     /* declare the new enum tokens */

     /* prototype the new functions */

     /* TYPEDEFS for the new functions */

     #endif

   In the src/mapi/glapi/gen/ directory, add the new extension functions and

   enums to the gl_API.xml file.

   Then, a bunch of source files must be regenerated by executing the

   corresponding Python scripts.

   Add a new entry to the gl_extensions struct in mtypes.h

   Update the extensions.c file.

   From this point, the best way to proceed is to find another extension,

   similar to the new one, that's already implemented in Mesa and use it

   as an example.

   If the new extension adds new GL state, the functions in get.c, enable.c

   and attrib.c will most likely require new code.

   The dispatch tests check_table.cpp and dispatch_sanity.cpp

   should be updated with details about the new extensions functions. These

   tests are run using 'make check'

Coding Style

Mesa's code style has changed over the years.  Here's the latest.

Comment your code!  It's extremely important that open-source code be

well documented.  Also, strive to write clean, easily understandable code.

3-space indentation

If you use tabs, set them to 8 columns

Line width: the preferred width to fill comments and code in Mesa is 78

columns.  Exceptions are sometimes made for clarity (e.g. tabular data is

sometimes filled to a much larger width so that extraneous carriage returns

don't obscure the table).

Brace example:

	if (condition) {

	   foo;

	}

	else {

	   bar;

	}

	switch (condition) {

	case 0:

	   foo();

	   break;

	case 1: {

	   ...

	   break;

	}

	default:

	   ...

	   break;

	}

Here's the GNU indent command which will best approximate my preferred style:

(Note that it won't format switch statements in the preferred way)

	indent -br -i3 -npcs --no-tabs infile.c -o outfile.c

Local variable name example:  localVarName (no underscores)

Constants and macros are ALL_UPPERCASE, with _ between words

Global variables are not allowed.

Function name examples:

	glFooBar()       - a public GL entry point (in glapi_dispatch.c)

	_mesa_FooBar()   - the internal immediate mode function

	save_FooBar()    - retained mode (display list) function in dlist.c

	foo_bar()        - a static (private) function

	_mesa_foo_bar()  - an internal non-static Mesa function

Places that are not directly visible to the GL API should prefer the use

of bool, true, and

false over GLboolean, GL_TRUE, and

GL_FALSE.  In C code, this may mean that

#include <stdbool.h> needs to be added.  The

try_emit_* methods in src/mesa/program/ir_to_mesa.cpp and

src/mesa/state_tracker/st_glsl_to_tgsi.cpp can serve as examples.

Submitting patches

You should always run the Mesa Testsuite before submitting patches.

The Testsuite can be run using the 'make check' command. All tests

must pass before patches will be accepted, this may mean you have

to update the tests themselves.

Patches should be sent to the Mesa mailing list for review.

When submitting a patch make sure to use git send-email rather than attaching

patches to emails. Sending patches as attachments prevents people from being

able to provide in-line review comments.

When submitting follow-up patches you can use --in-reply-to to make v2, v3,

etc patches show up as replies to the originals. This usually works well

when you're sending out updates to individual patches (as opposed to

re-sending the whole series). Using --in-reply-to makes

it harder for reviewers to accidentally review old patches.

Marking a commit as a candidate for a stable branch

If you want a commit to be applied to a stable branch,

you should add an appropriate note to the commit message.

Here are some examples of such a note:

  
CC: <mesa-stable@lists.freedesktop.org>

  
CC: "9.2 10.0" <mesa-stable@lists.freedesktop.org>

  
CC: "10.0" <mesa-stable@lists.freedesktop.org>

Simply adding the CC to the mesa-stable list address is adequate to nominate

the commit for the most-recently-created stable branch. It is only necessary

to specify a specific branch name, (such as "9.2 10.0" or "10.0" in the

examples above), if you want to nominate the commit for an older stable

branch. And, as in these examples, you can nominate the commit for the older

branch in addition to the more recent branch, or nominate the commit

exclusively for the older branch.

This "CC" syntax for patch nomination will cause patches to automatically be

copied to the mesa-stable@ mailing list when you use "git send-email" to send

patches to the mesa-dev@ mailing list. Also, if you realize that a commit

should be nominated for the stable branch after it has already been committed,

you can send a note directly to the mesa-stable@lists.freedesktop.org where

the Mesa stable-branch maintainers will receive it. Be sure to mention the

commit ID of the commit of interest (as it appears in the mesa master branch).

The latest set of patches that have been nominated, accepted, or rejected for

the upcoming stable release can always be seen on the

Mesa Stable Queue

page.

Criteria for accepting patches to the stable branch

Mesa has a designated release manager for each stable branch, and the release

manager is the only developer that should be pushing changes to these

branches. Everyone else should simply nominate patches using the mechanism

described above.

The stable-release manager will work with the list of nominated patches, and

for each patch that meets the crtieria below will cherry-pick the patch with:

git cherry-pick -x <commit>. The -x option is

important so that the picked patch references the comit ID of the original

patch.

The stable-release manager may at times need to force-push changes to the

stable branches, for example, to drop a previously-picked patch that was later

identified as causing a regression). These force-pushes may cause changes to

be lost from the stable branch if developers push things directly. Consider

yourself warned.

The stable-release manager is also given broad discretion in rejecting patches

that have been nominated for the stable branch. The most basic rule is that

the stable branch is for bug fixes only, (no new features, no

regressions). Here is a non-exhaustive list of some reasons that a patch may

be rejected:

  
Patch introduces a regression. Any reported build breakage or other

  regression caused by a particular patch, (game no longer work, piglit test

  changes from PASS to FAIL), is justification for rejecting a patch.

  
Patch is too large, (say, larger than 100 lines)

  
Patch is not a fix. For example, a commit that moves code around with no

  functional change should be rejected.

  
Patch fix is not clearly described. For example, a commit message

  of only a single line, no description of the bug, no mention of bugzilla,

  etc.

  
Patch has not obviously been reviewed, For example, the commit message

  has no Reviewed-by, Signed-off-by, nor Tested-by tags from anyone but the

  author.

  
Patch has not already been merged to the master branch. As a rule, bug

  fixes should never be applied first to a stable branch. Patches should land

  first on the master branch and then be cherry-picked to a stable

  branch. (This is to avoid future releases causing regressions if the patch

  is not also applied to master.) The only things that might look like

  exceptions would be backports of patches from master that happen to look

  significantly different.

  
Patch depends on too many other patches. Ideally, all stable-branch

  patches should be self-contained. It sometimes occurs that a single, logical

  bug-fix occurs as two separate patches on master, (such as an original

  patch, then a subsequent fix-up to that patch). In such a case, these two

  patches should be squashed into a single, self-contained patch for the

  stable branch. (Of course, if the squashing makes the patch too large, then

  that could be a reason to reject the patch.)

  
Patch includes new feature development, not bug fixes. New OpenGL

  features, extensions, etc. should be applied to Mesa master and included in

  the next major release. Stable releases are intended only for bug fixes.

  Note: As an exception to this rule, the stable-release manager may accept

  hardware-enabling "features". For example, backports of new code to support

  a newly-developed hardware product can be accepted if they can be reasonably

  determined to not have effects on other hardware.

  
Patch is a performance optimization. As a rule, performance patches are

  not candidates for the stable branch. The only exception might be a case

  where an application's performance was recently severely impacted so as to

  become unusable. The fix for this performance regression could then be

  considered for a stable branch. The optimization must also be

  non-controversial and the patches still need to meet the other criteria of

  being simple and self-contained

  
Patch introduces a new failure mode (such as an assert). While the new

  assert might technically be correct, for example to make Mesa more

  conformant, this is not the kind of "bug fix" we want in a stable

  release. The potential problem here is that an OpenGL program that was

  previously working, (even if technically non-compliant with the

  specification), could stop working after this patch. So that would be a

  regression that is unaacceptable for the stable branch.

Making a New Mesa Release

These are the instructions for making a new Mesa release.

Get latest source files

Use git to get the latest Mesa files from the git repository, from whatever

branch is relevant. This document uses the convention X.Y.Z for the release

being created, which should be created from a branch named X.Y.

Perform basic testing

The release manager should, at the very least, test the code by compiling it,

installing it, and running the latest piglit to ensure that no piglit tests

have regressed since the previous release.

The release manager should do this testing with at least one hardware driver,

(say, whatever is contained in the local development machine), as well as on

both Gallium and non-Gallium software drivers. The software testing can be

performed by running piglit with the following environment-variable set:

LIBGL_ALWAYS_SOFTWARE=1

And Gallium vs. non-Gallium software drivers can be obtained by using the

following configure flags on separate builds:

--with-dri-drivers=swrast

--with-gallium-drivers=swrast

Note: If both options are given in one build, both swrast_dri.so drivers will

be compiled, but only one will be installed. The following command can be used

to ensure the correct driver is being tested:

LIBGL_ALWAYS_SOFTWARE=1 glxinfo | grep "renderer string"

If any regressions are found in this testing with piglit, stop here, and do

not perform a release until regressions are fixed.

Update version in file VERSION

Increment the version contained in the file VERSION at Mesa's top-level, then

commit this change.

Create release notes for the new release

Create a new file docs/relnotes/X.Y.Z.html, (follow the style of the previous

release notes). Note that the sha256sums section of the release notes should

be empty at this point.

Two scripts are available to help generate portions of the release notes:

	./bin/bugzilla_mesa.sh

	./bin/shortlog_mesa.sh

The first script identifies commits that reference bugzilla bugs and obtains

the descriptions of those bugs from bugzilla. The second script generates a

log of all commits. In both cases, HTML-formatted lists are printed to stdout

to be included in the release notes.

Commit these changes

Make the release archives, signatures, and the release tag

From inside the Mesa directory:

	./autogen.sh

	make -j1 tarballs

After the tarballs are created, the sha256 checksums for the files will

be computed and printed. These will be used in a step below.

It's important at this point to also verify that the constructed tar file

actually builds:

	tar xjf MesaLib-X.Y.Z.tar.bz2

	cd Mesa-X.Y.Z

	./configure --enable-gallium-llvm

	make -j6

	make install

Some touch testing should also be performed at this point, (run glxgears or

more involved OpenGL programs against the installed Mesa).

Create detached GPG signatures for each of the archive files created above:

	gpg --sign --detach MesaLib-X.Y.Z.tar.gz

	gpg --sign --detach MesaLib-X.Y.Z.tar.bz2

	gpg --sign --detach MesaLib-X.Y.Z.zip

Tag the commit used for the build:

	git tag -s mesa-X.Y.X -m "Mesa X.Y.Z release"

Note: It would be nice to investigate and fix the issue that causes the

tarballs target to fail with multiple build process, such as with "-j4". It

would also be nice to incorporate all of the above commands into a single

makefile target. And instead of a custom "tarballs" target, we should

incorporate things into the standard "make dist" and "make distcheck" targets.

Add the sha256sums to the release notes

Edit docs/relnotes/X.Y.Z.html to add the sha256sums printed as part of "make

tarballs" in the previous step. Commit this change.

Push all commits and the tag creates above

This is the first step that cannot easily be undone. The release is going

forward from this point:

	git push origin X.Y --tags

Install the release files and signatures on the distribution server

The following commands can be used to copy the release archive files and

signatures to the freedesktop.org server:

	scp MesaLib-X.Y.Z* people.freedesktop.org:

	ssh people.freedesktop.org

	cd /srv/ftp.freedesktop.org/pub/mesa

	mkdir X.Y.Z

	cd X.Y.Z

	mv ~/MesaLib-X.Y.Z* .

Back on mesa master, andd the new release notes into the tree

Something like the following steps will do the trick:

	cp docs/relnotes/X.Y.Z.html /tmp

        git checkout master

        cp /tmp/X.Y.Z.html docs/relnotes

        git add docs/relnotes/X.Y.Z.html

Also, edit docs/relnotes.html to add a link to the new release notes, and edit

docs/index.html to add a news entry. Then commit and push:

	git commit -a -m "docs: Import X.Y.Z release notes, add news item."

        git push origin

Update the mesa3d.org website

NOTE: The recent release managers have not been performing this step

themselves, but leaving this to Brian Paul, (who has access to the

sourceforge.net hosting for mesa3d.org). Brian is more than willing to grant

the permission necessary to future release managers to do this step on their

own.

Update the web site by copying the docs/ directory's files to

/home/users/b/br/brianp/mesa-www/htdocs/ with:

sftp USERNAME,mesa3d@web.sourceforge.net

Announce the release

Make an announcement on the mailing lists:

mesa-dev@lists.freedesktop.org,

and

mesa-announce@lists.freedesktop.org

Follow the template of previously-sent release announcements. The following

command can be used to generate the log of changes to be included in the

release announcement:

	git shortlog mesa-X.Y.Z-1..mesa-X.Y.Z