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doc/developer: add examples to clarify code style

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Given the frequency that new developers, myself included, get the
code style wrong, it is useful to add some examples to clarify how
things should be done.
This commit is contained in:
Marvin Scholz 2024-05-18 19:00:50 +02:00
parent 83c1c622a5
commit 9cdd3cbe9b
1 changed files with 100 additions and 1 deletions
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doc/developer.texi
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@ -115,7 +115,7 @@ Objective-C where required for interacting with macOS-specific interfaces.
@section Code formatting conventions
There are the following guidelines regarding the indentation in files:
There are the following guidelines regarding the code style in files:
@itemize @bullet
@item
@ -135,6 +135,105 @@ K&R coding style is used.
@end itemize
The presentation is one inspired by 'indent -i4 -kr -nut'.
@subsection Examples
Some notable examples to illustrate common code style in FFmpeg:
@itemize @bullet
@item
Space around assignments and after
@code{if}/@code{do}/@code{while}/@code{for} keywords:
@example c, good
// Good
if (condition)
av_foo();
@end example
@example c, good
// Good
for (size_t i = 0; i < len; i++)
av_bar(i);
@end example
@example c, good
// Good
size_t size = 0;
@end example
However no spaces between the parentheses and condition, unless it helps
readability of complex conditions, so the following should not be done:
@example c, bad
// Bad style
if ( condition )
av_foo();
@end example
@item
No unnecessary parentheses, unless it helps readability:
@example c, good
// Good
int fields = ilace ? 2 : 1;
@end example
@item
No braces around single-line blocks:
@example c, good
// Good
if (bits_pixel == 24)
avctx->pix_fmt = AV_PIX_FMT_BGR24;
else if (bits_pixel == 8)
avctx->pix_fmt = AV_PIX_FMT_GRAY8;
else @{
av_log(avctx, AV_LOG_ERROR, "Invalid pixel format.\n");
return AVERROR_INVALIDDATA;
@}
@end example
@item
Avoid assignments in conditions where it makes sense:
@example c, good
// Good
video_enc->chroma_intra_matrix = av_mallocz(sizeof(*video_enc->chroma_intra_matrix) * 64)
if (!video_enc->chroma_intra_matrix)
return AVERROR(ENOMEM);
@end example
@example c, bad
// Bad style
if (!(video_enc->chroma_intra_matrix = av_mallocz(sizeof(*video_enc->chroma_intra_matrix) * 64)))
return AVERROR(ENOMEM);
@end example
@example c, good
// Ok
while ((entry = av_dict_iterate(options, entry)))
av_log(ctx, AV_LOG_INFO, "Item '%s': '%s'\n", entry->key, entry->value);
@end example
@item
When declaring a pointer variable, the @code{*} goes with the variable not the type:
@example c, good
// Good
AVStream *stream;
@end example
@example c, bad
// Bad style
AVStream* stream;
@end example
@end itemize
If you work on a file that does not follow these guidelines consistently,
change the parts that you are editing to follow these guidelines but do
not make unrelated changes in the file to make it conform to these.
@subsection Vim configuration
In order to configure Vim to follow FFmpeg formatting conventions, paste
the following snippet into your @file{.vimrc}: