diff options
Diffstat (limited to 'src/blueshift_idcrtc.c')
| -rw-r--r-- | src/blueshift_idcrtc.c | 67 |
1 files changed, 56 insertions, 11 deletions
diff --git a/src/blueshift_idcrtc.c b/src/blueshift_idcrtc.c index 5d55a62..57064b6 100644 --- a/src/blueshift_idcrtc.c +++ b/src/blueshift_idcrtc.c @@ -60,7 +60,6 @@ int main(int argc, char** argv) { xcb_randr_query_version_cookie_t version_cookie; xcb_randr_query_version_reply_t* randr_version; - const xcb_setup_t* setup; xcb_screen_iterator_t iter; int screen_count; xcb_screen_t* screens; @@ -73,16 +72,22 @@ int main(int argc, char** argv) /* Get X connection */ + /* This acquires a connection to the + X display indicated by the DISPLAY + environ variable. */ connection = xcb_connect(NULL, NULL); /* Check RandR protocol version */ + /* Check that the version of RandR is supported. */ version_cookie = xcb_randr_query_version(connection, RANDR_VERSION_MAJOR, RANDR_VERSION_MINOR); randr_version = xcb_randr_query_version_reply(connection, version_cookie, &error); if (error || (randr_version == NULL)) { + /* If not possible, print an error message and + close the connection to the display. */ fprintf(stderr, "RandR version query returned %i", error ? error->error_code : -1); xcb_disconnect(connection); return 1; @@ -90,27 +95,35 @@ int main(int argc, char** argv) if (randr_version->major_version != RANDR_VERSION_MAJOR || randr_version->minor_version < RANDR_VERSION_MINOR) { + /* If the version did not match, print a warning, */ fprintf(stderr, "Unsupported RandR version, got %u.%u, expected %u.%u\n", randr_version->major_version, randr_version->minor_version, RANDR_VERSION_MAJOR, RANDR_VERSION_MINOR); + /* free the version information resources, */ free(randr_version); + /* and close the connection to the display. */ xcb_disconnect(connection); return 1; } + /* Free the version information resources. */ free(randr_version); /* Get screen information */ - setup = xcb_get_setup(connection); - iter = xcb_setup_roots_iterator(setup); + /* Acquire a list of all screens in the display, */ + iter = xcb_setup_roots_iterator(xcb_get_setup(connection)); + /* count the list, */ screen_count = iter.rem; + /* and start at the first screen. */ screens = iter.data; + /* Print the number available screens. */ printf("Screen count: %i\n", screen_count); for (screen_i = 0; screen_i < screen_count; screen_i++) { + /* For each screen */ xcb_screen_t* screen = screens + screen_i; xcb_randr_get_screen_resources_current_cookie_t res_cookie; xcb_randr_get_screen_resources_current_reply_t* res_reply; @@ -118,51 +131,80 @@ int main(int argc, char** argv) xcb_randr_crtc_t* crtcs; int output_i; + /* Print the screen index. */ printf("Screen: %i\n", screen_i); + /* Acquire information about the screen. */ res_cookie = xcb_randr_get_screen_resources_current(connection, screen->root); res_reply = xcb_randr_get_screen_resources_current_reply(connection, res_cookie, &error); if (error) { + /* On error print an error message and close the connection to the display. */ fprintf(stderr, "RandR screen resource query returned %i\n", error->error_code); xcb_disconnect(connection); return 1; } + /* Print the CRTC count, */ printf(" CRTC count: %i\n", res_reply->num_crtcs); + /* and the output count. */ printf(" Output count: %i\n", res_reply->num_outputs); + /* There are as many outputs as there are + connectors, that is, the number of + monitors that you could potentially + plugg into the graphics cards that + are associated with the screen, even + if that many are not supported. But + there are only as many CRTC:s as + there are monitors actually plugged + in and supported. */ /* Get output information */ + /* Extract output list. */ outputs = xcb_randr_get_screen_resources_current_outputs(res_reply); + /* Extract CRTC list. */ crtcs = xcb_randr_get_screen_resources_current_crtcs(res_reply); + /* For each output */ for (output_i = 0; output_i < res_reply->num_outputs; output_i++) { xcb_randr_get_output_info_cookie_t out_cookie; xcb_randr_get_output_info_reply_t* out_reply; - char* name; - unsigned char* name_; + char* name_; + int name_len; + /* Acquire information abou the output. */ out_cookie = xcb_randr_get_output_info(connection, outputs[output_i], res_reply->config_timestamp); out_reply = xcb_randr_get_output_info_reply(connection, out_cookie, &error); if (error) { + /* On error print an error message, release the screen resources, + and close the connection to the display. */ fprintf(stderr, "RandR output query returned %i\n", error->error_code); - xcb_disconnect(connection); free(res_reply); + xcb_disconnect(connection); return 1; } + /* Print the index, in the scope of the screen, of the output. */ printf(" Output: %i\n", output_i); - name_ = xcb_randr_get_output_info_name(out_reply); - name = alloca((out_reply->name_len + 1) * sizeof(char)); - memcpy(name, name_, out_reply->name_len * sizeof(char)); - *(name + out_reply->name_len) = 0; - printf(" Name: %s\n", name); + /* We use intention not for computer-readability, but + exclusively for human-readability, especially for + debugging. */ + + /* Extract the output name from the data structure that holds it. */ + name = xcb_randr_get_output_info_name(out_reply); + /* As well as the length of the name; it is not NUL-termianted.*/ + name_len = out_reply->name_len; + + /* Print the output name, we specified length, so that + printf does not attempt to read outside the name, + as it is not NUL-terminated. */ + printf(" Name: %.*s\n", name_len, name); switch (out_reply->connection) { @@ -287,15 +329,18 @@ int main(int argc, char** argv) break; } + /* Free the output information resources. */ free(out_reply); } + /* Free the screen information resources. */ free(res_reply); } /* Free resources **/ + /* Close the connection to the display.*/ xcb_disconnect(connection); return 0; } |