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+# Contributing to wlroots
+
+Contributing just involves sending a pull request. You will probably be more
+successful with your contribution if you visit the [IRC
+channel](http://webchat.freenode.net/?channels=sway&uio=d4) upfront and discuss
+your plans.
+
+## 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 https://github.com/SirCmpwn/wlroots
+
+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](https://help.github.com/articles/closing-issues-via-commit-messages/),
+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
+
+wlroots is written in C with the same style as Sway. The style guidelines is
+[kernel
+style](https://www.kernel.org/doc/Documentation/process/coding-style.rst), 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:
+
+```C
+#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;
+}
+```