sway-patched-tray-menu/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](http://webchat.freenode.net/?channels=sway&uio=d4) upfront and discuss
your plans.

## Coding Style

Sway is written in C. The style guidelines is [kernel
style](https://www.kernel.org/doc/Documentation/CodingStyle), but all braces go
on the same line (*"but K&R!" is silly*). 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

```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;
}
```