convince/CONTRIBUTING.md

Contributing to sway

Contributing just involves sending a pull request. You will probably be more successful with your contribution if you visit the IRC channel upfront and discuss your plans.

Release Cycle

The master branch of sway is always working towards becoming the next release. That release will go through each of these three stages:

In development: during this time the release lives in the master branch and is considered unstable. All pull requests merged during this time will land in the release. Only developers are encouraged to run this version.

Release candidate: at some point (usually when development is fairly quiet), SirCmpwn will announce an upcoming release candidate, often 2 weeks in advance. When the two weeks are up, a branch is cut (i.e. 0.8-rc1) and from that point only bugfixex land in this branch. Each morning, if bugfixes landed during the previous day, a new RC is cut. During the RC phase, more adventurous users are encouraged to upgrade and start looking for and reporting bugs (especially in new features).

Stable release: when no substantial changes are merged into an RC for one week, it's released as a new stable version of sway. At this point, all users are encouraged to upgrade.

Pull Requests

If you already have your own pull request habits, feel free to use them. If you don't, however, allow me to make a suggestion: feature branches pulled from upstream. Try this:

1. Fork sway
2. Clone your fork
3. git remote add upstream git://github.com/SirCmpwn/sway.git

You only need to do this once. You're never going to use your fork's master branch. Instead, when you start working on a feature, do this:

1. git fetch upstream
2. git checkout -b add-so-and-so-feature upstream/master
3. work
4. git push -u origin add-so-and-so-feature
5. Make pull request from your feature branch

Commit Messages

Please strive to write good commit messages. Here's some guidelines to follow:

The first line should be limited to 50 characters and should be a sentence that completes the thought [When applied, this commit will...] "Implement cmd_move" or "Fix #742" or "Improve performance of arrange_windows on ARM" or similar.

The subsequent lines should be seperated from the subject line by a single blank line, and include optional details. In this you can give justification for the change, reference Github issues, or explain some of the subtler details of your patch. This is important because when someone finds a line of code they don't understand later, they can use the git blame command to find out what the author was thinking when they wrote it. It's also easier to review your pull requests if they're seperated into logical commits that have good commit messages and justify themselves in the extended commit description.

As a good rule of thumb, anything you might put into the pull request description on Github is probably fair game for going into the extended commit message as well.

Coding Style

Sway is written in C. The style guidelines is kernel style, but all braces go on the same line ("but K&R says so!" is a silly way of justifying something). Some points to note:

• Do not use typedefs unless you have a good reason
• Do not use macros unless you have a really good reason
• Align case with switch
• Tabs, not spaces
• char *pointer - note position of *
• Use logging with reckless abandon
• Always include braces for if/for/while/etc, even for one-liners

An example of well formatted code:

#include <stdio.h>
#include <stdlib.h>
#include "log.h"
#include "example.h"

struct foobar {
	char *foo;
	int bar;
	long baz;
}; // Do not typedef without a good reason

int main(int argc, const char **argv) {
	if (argc != 4) {
		sway_abort("Do not run this program manually. See man 5 sway and look for output options.");
	}

	if (!registry->desktop_shell) {
		sway_abort("swaybg requires the compositor to support the desktop-shell extension.");
	}

	int desired_output = atoi(argv[1]);
	sway_log(L_INFO, "Using output %d of %d", desired_output, registry->outputs->length);
	int i;
	struct output_state *output = registry->outputs->items[desired_output];
	struct window *window = window_setup(registry, 100, 100, false);
	if (!window) {
		sway_abort("Failed to create surfaces.");
	}
	window->width = output->width;
	window->height = output->height;
	desktop_shell_set_background(registry->desktop_shell, output->output, window->surface);
	list_add(surfaces, window);

	cairo_surface_t *image = cairo_image_surface_create_from_png(argv[2]);
	double width = cairo_image_surface_get_width(image);
	double height = cairo_image_surface_get_height(image);

	const char *scaling_mode_str = argv[3];
	enum scaling_mode scaling_mode;
	if (strcmp(scaling_mode_str, "stretch") == 0) {
		scaling_mode = SCALING_MODE_STRETCH;
	} else if (strcmp(scaling_mode_str, "fill") == 0) {
		scaling_mode = SCALING_MODE_FILL;
	} else if (strcmp(scaling_mode_str, "fit") == 0) {
		scaling_mode = SCALING_MODE_FIT;
	} else if (strcmp(scaling_mode_str, "center") == 0) {
		scaling_mode = SCALING_MODE_CENTER;
	} else if (strcmp(scaling_mode_str, "tile") == 0) {
		scaling_mode = SCALING_MODE_TILE;
	} else {
		sway_abort("Unsupported scaling mode: %s", scaling_mode_str);
	}

	for (i = 0; i < surfaces->length; ++i) {
		struct window *window = surfaces->items[i];
		if (window_prerender(window) && window->cairo) {
			switch (scaling_mode) {
			case SCALING_MODE_STRETCH:
				cairo_scale(window->cairo,
						(double) window->width / width,
						(double) window->height / height);
				cairo_set_source_surface(window->cairo, image, 0, 0);
				break;
			case SCALING_MODE_FILL:
			{
				double window_ratio = (double) window->width / window->height;
				double bg_ratio = width / height;

				if (window_ratio > bg_ratio) {
					double scale = (double) window->width / width;
					cairo_scale(window->cairo, scale, scale);
					cairo_set_source_surface(window->cairo, image,
							0,
							(double) window->height/2 / scale - height/2);
				} else {
					double scale = (double) window->height / height;
					cairo_scale(window->cairo, scale, scale);
					cairo_set_source_surface(window->cairo, image,
							(double) window->width/2 / scale - width/2,
							0);
				}
				break;
			}
			case SCALING_MODE_FIT:
			{
				double window_ratio = (double) window->width / window->height;
				double bg_ratio = width / height;

				if (window_ratio > bg_ratio) {
					double scale = (double) window->height / height;
					cairo_scale(window->cairo, scale, scale);
					cairo_set_source_surface(window->cairo, image,
							(double) window->width/2 / scale - width/2,
							0);
				} else {
					double scale = (double) window->width / width;
					cairo_scale(window->cairo, scale, scale);
					cairo_set_source_surface(window->cairo, image,
							0,
							(double) window->height/2 / scale - height/2);
				}
				break;
			}
			case SCALING_MODE_CENTER:
				cairo_set_source_surface(window->cairo, image,
						(double) window->width/2 - width/2,
						(double) window->height/2 - height/2);
				break;
			case SCALING_MODE_TILE:
			{
				cairo_pattern_t *pattern = cairo_pattern_create_for_surface(image);
				cairo_pattern_set_extend(pattern, CAIRO_EXTEND_REPEAT);
				cairo_set_source(window->cairo, pattern);
				break;
			}
			default:
				sway_abort("Scaling mode '%s' not implemented yet!", scaling_mode_str);
			}

			cairo_paint(window->cairo);

			window_render(window);
		}
	}

	while (wl_display_dispatch(registry->display) != -1);

	for (i = 0; i < surfaces->length; ++i) {
		struct window *window = surfaces->items[i];
		window_teardown(window);
	}
	list_free(surfaces);
	registry_teardown(registry);
	return 0;
}