Merge pull request #116 from ascent12/contributing

Updated CONTRIBUTING.md

1 files changed, 150 insertions, 154 deletions

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 0f54749b..242c8bd4 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1,9 +1,9 @@
 # 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-devel&uio=d4) upfront and discuss
-your plans.
+successful with your contribution if you visit
+[#sway-devel](https://webchat.freenode.net/?channels=sway-devel) on
+irc.freenode.net upfront and discuss your plans.
 
 ## Pull Requests
 
@@ -11,35 +11,36 @@ 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
+1. Fork wlroots
+2. `git clone https://github.com/username/wlroots && cd wlroots`
+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
+1. `git fetch upstream`
+2. `git checkout -b add-so-and-so-feature upstream/master`
+3. Add and commit your changes
+4. `git push -u origin add-so-and-so-feature`
+5. Make a 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.
+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
+The subsequent lines should be separated 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
+it. It's also easier to review your pull requests if they're separated into
 logical commits that have good commit messages and justify themselves in the
 extended commit description.
 
@@ -47,158 +48,153 @@ 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.
 
+See [here](https://chris.beams.io/posts/git-commit/) for more details.
+
 ## Coding Style
 
-wlroots is written in C with the same style as Sway. The style guidelines is
-[kernel
+wlroots is written in C with a style similar to the [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.");
-	}
+with a few notable differences.
 
-	if (!registry->desktop_shell) {
-		sway_abort("swaybg requires the compositor to support the desktop-shell extension.");
-	}
+Try to keep your code conforming to C11 and POSIX as much as possible, and do
+not use GNU extensions.
 
-	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.");
+### Brackets
+
+Brackets always go on the same line, including in functions.  
+Always include brackets for if/while/for, even if it's a single statement.
+```c
+void function() {
+	if (condition1) {
+		do_thing1();
 	}
-	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;
+
+	if (condition2) {
+		do_thing2();
 	} else {
-		sway_abort("Unsupported scaling mode: %s", scaling_mode_str);
+		do_thing3();
 	}
+}
+```
+
+### Indentation
+
+Indentations are a single tab.
+
+For long lines that need to be broken, the continuation line should be indented
+with an additional tab.  
+If the line being broken is opening a new block (functions, if, while, etc.),
+the continuation line should be indented with two tabs, so they can't be
+misread as being part of the block.
+```c
+really_long_function(argument1, argument2, ...,
+	argument3, argument4);
+
+if (condition1 && condition2 && ...
+		condition3 && condition4) {
+	do_thing();
+}
+```
+
+Try to break the line in the place which you think is the most appropriate.
+
+
+### Line Length
+
+Try to keep your lines under 80 columns, but you can go up to 100 if it
+improves readability.
+
+### Names
+
+Function and type names should be prefixed with `wlr_submodule_` (e.g. `struct
+wlr_drm_plane`, `wlr_output_set_cursor`).  For static functions and types local
+to a file, the names chosen aren't as important.
+
+For include guards, use the header's filename relative to include.  Uppercase
+all of the characters, and replace any invalid characters with an underscore.
 
-	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);
+### Construction/Destruction Functions
+
+For functions that are responsible for constructing and destructing an object,
+they should be written as a pair of one of two forms:
+* `init`/`finish`: These initialize/deinitialize a type, but are **NOT**
+responsible for allocating it. They should accept a pointer to some
+pre-allocated memory (e.g. a member of a struct).
+* `create`/`destroy`: These also initialize/deinitialize, but will return a
+pointer to a `malloc`ed chunk of memory, and will `free` it in `destroy`.
+
+A destruction function should always be able to accept a NULL pointer or a
+zeroed value and exit cleanly; this simplifies error handling a lot.
+
+### Error Codes
+
+For functions not returning a value, they should return a (stdbool.h) bool to
+indicated if they succeeded or not.
+
+### Macros
+
+Try to keep the use of macros to a minimum, especially if a function can do the
+job.  If you do need to use them, try to keep them close to where they're being
+used and `#undef` them after.
+
+## Example
+
+```c
+struct wlr_backend *wlr_backend_autocreate(struct wl_display *display) {
+	struct wlr_backend *backend;
+	if (getenv("WAYLAND_DISPLAY") || getenv("_WAYLAND_DISPLAY")) {
+		backend = attempt_wl_backend(display);
+		if (backend) {
+			return backend;
 		}
 	}
 
-	while (wl_display_dispatch(registry->display) != -1);
+	const char *x11_display = getenv("DISPLAY");
+	if (x11_display) {
+		return wlr_x11_backend_create(display, x11_display);
+	}
+
+	// Attempt DRM+libinput
 
-	for (i = 0; i < surfaces->length; ++i) {
-		struct window *window = surfaces->items[i];
-		window_teardown(window);
+	struct wlr_session *session = wlr_session_create(display);
+	if (!session) {
+		wlr_log(L_ERROR, "Failed to start a DRM session");
+		return NULL;
 	}
-	list_free(surfaces);
-	registry_teardown(registry);
-	return 0;
+
+	int gpu = wlr_session_find_gpu(session);
+	if (gpu == -1) {
+		wlr_log(L_ERROR, "Failed to open DRM device");
+		goto error_session;
+	}
+
+	backend = wlr_multi_backend_create(session);
+	if (!backend) {
+		goto error_gpu;
+	}
+
+	struct wlr_backend *libinput = wlr_libinput_backend_create(display, session);
+	if (!libinput) {
+		goto error_multi;
+	}
+
+	struct wlr_backend *drm = wlr_drm_backend_create(display, session, gpu);
+	if (!drm) {
+		goto error_libinput;
+	}
+
+	wlr_multi_backend_add(backend, libinput);
+	wlr_multi_backend_add(backend, drm);
+	return backend;
+
+error_libinput:
+	wlr_backend_destroy(libinput);
+error_multi:
+	wlr_backend_destroy(backend);
+error_gpu:
+	wlr_session_close_file(session, gpu);
+error_session:
+	wlr_session_destroy(session);
+	return NULL;
 }
 ```