我正在从事一个已经使用xcb的项目,需要获取单个输出的分辨率而不是合并屏幕的分辨率。我可以使用RandR扩展来实现这一点吗?如果可以,那么我该如何使用我的xcb_connection_t
对象来实现呢。
client : "I'd like to order a beer."
bartender: "OK, I'll get you a beer."
*bartender handles a ticket with an ID of the beer order to the client*
*client waits and waits and then he approaches bartender*
client : "Dude, give me my beer finally, here's your damn ticket"
*client handles the ticket to bartender, who looks for the order from the
ticket in his order book and when he finds it he replies*
bartender: "Here's your beer, enjoy."
好的,那么为什么XCB不直接发送请求并一次性获得答案呢?这正是Xlib的工作方式,但事实证明,在某些条件下,XCB的速度可以快117倍。如果您想了解更多,请阅读XCB教程中的基本XCB概念。
回到问题——如何获取输出(或者更确切地说是CRTCs)的分辨率?以下是我使用的简化版本:
#include <cstdio>
#include <xcb/xcb.h>
#include <xcb/randr.h>
int main()
{
//Open connection to X server
xcb_connection_t* XConnection = xcb_connect(0, 0);
//Get the first X screen
xcb_screen_t* XFirstScreen = xcb_setup_roots_iterator(
xcb_get_setup(XConnection)).data;
//Generate ID for the X window
xcb_window_t XWindowDummy = xcb_generate_id(XConnection);
//Create dummy X window
xcb_create_window(XConnection, 0, XWindowDummy, XFirstScreen->root,
0, 0, 1, 1, 0, 0, 0, 0, 0);
//Flush pending requests to the X server
xcb_flush(XConnection);
//Send a request for screen resources to the X server
xcb_randr_get_screen_resources_cookie_t screenResCookie = {};
screenResCookie = xcb_randr_get_screen_resources(XConnection,
XWindowDummy);
//Receive reply from X server
xcb_randr_get_screen_resources_reply_t* screenResReply = {};
screenResReply = xcb_randr_get_screen_resources_reply(XConnection,
screenResCookie, 0);
int crtcs_num = 0;
xcb_randr_crtc_t* firstCRTC;
//Get a pointer to the first CRTC and number of CRTCs
//It is crucial to notice that you are in fact getting
//an array with firstCRTC being the first element of
//this array and crtcs_length - length of this array
if(screenResReply)
{
crtcs_num = xcb_randr_get_screen_resources_crtcs_length(screenResReply);
firstCRTC = xcb_randr_get_screen_resources_crtcs(screenResReply);
}
else
return -1;
//Array of requests to the X server for CRTC info
xcb_randr_get_crtc_info_cookie_t* crtcResCookie = new
xcb_randr_get_crtc_info_cookie_t[crtcs_num];
for(int i = 0; i < crtcs_num; i++)
crtcResCookie[i] = xcb_randr_get_crtc_info(XConnection,
*(firstCRTC+i), 0);
//Array of pointers to replies from X server
xcb_randr_get_crtc_info_reply_t** crtcResReply = new
xcb_randr_get_crtc_info_reply_t*[crtcs_num];
for(int i = 0; i < crtcs_num; i++)
crtcResReply[i] = xcb_randr_get_crtc_info_reply(XConnection,
crtcResCookie[i], 0);
//Self-explanatory
for(int i = 0; i < crtcs_num; i++)
{
if(crtcResReply[i])
{
printf("CRTC[%i] INFO:\n", i);
printf("x-off\t: %i\n", crtcResReply[i]->x);
printf("y-off\t: %i\n", crtcResReply[i]->y);
printf("width\t: %i\n", crtcResReply[i]->width);
printf("height\t: %i\n\n", crtcResReply[i]->height);
}
}
xcb_disconnect(XConnection);
return 0;
}
示例输出:
CRTC[0] INFO:
x-off : 1920
y-off : 0
width : 1920
height : 1200
CRTC[1] INFO:
x-off : 0
y-off : 0
width : 1920
height : 1200
CRTC[2] INFO:
x-off : 0
y-off : 0
width : 0
height : 0
CRTC[3] INFO:
x-off : 0
y-off : 0
width : 0
height : 0