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-rw-r--r--src/blueshift_idcrtc.c67
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;
}