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使用XCB编写X Window程序（四） 在窗口中绘制文字2015-05-13在前面的几节中，我展示了使用XCB创建窗口、在窗口中画图以及捕获并处理事件。在这一篇中，我将展示在窗口中绘制文字。绘制文字当然离不开字体，所以我还会简单地探讨一下X Server的核心字体系统。老规矩，先上代码和运行效果图，代码如下：

1 #include <stdlib.h>
 2 #include <stdio.h>
 3 #include <string.h>
 4 #include <inttypes.h>
 5 #include <xcb/xcb.h>
 6 
 7 
 8 #defineWIDTH 600
 9 #defineHEIGHT 400
10 #define TEST_COOKIE（fn,errMessage） 
11 cookie=fn; 
12 error=xcb_request_check（connection,cookie）; 
13 if（error）{ 
14 fprintf（stderr, "Error: %s : %"PRIu8"
", errMessage, error->error_code）; 
15 } 
16 
17 static void drawText（xcb_connection_t *connection, xcb_screen_t *screen, xcb_window_t window,
18 int16_t x, int16_t y, const char *font_name, const char *string）{
19 /*cookie and error, for TEST_COOKIE */
20 xcb_void_cookie_t cookie;
21 xcb_generic_error_t *error;
22 
23 xcb_font_t font = xcb_generate_id（connection）;
24 TEST_COOKIE（xcb_open_font_checked（connection, font, strlen（font_name）, font_name）, "Can"t open font"）;
25 xcb_gcontext_t gc = xcb_generate_id（connection）;
26 uint32_t mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
27 uint32_t values[3] = {screen->black_pixel, screen->white_pixel, font};
28 TEST_COOKIE（xcb_create_gc_checked（connection, gc, window, mask, values）, "Can"t create GC"）
29 /*draw the text*/
30 TEST_COOKIE（xcb_image_text_8_checked（connection, strlen（string）, window, gc, x, y, string）, "Can"t draw text"）;
31 /*close the font*/
32 xcb_close_font（connection, font）;
33 xcb_free_gc（connection, gc）;
34 }
35 
36 int main（）
37 {
38 xcb_connection_t *connection = xcb_connect（NULL, NULL）;
39 xcb_screen_t *screen = xcb_setup_roots_iterator（ xcb_get_setup（connection））.data;
40 
41 /*Create the window*/
42 xcb_window_t window = xcb_generate_id（connection）;
43 uint32_t mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
44 uint32_t values[2];
45 values[0] = screen->white_pixel;
46 values[1] = XCB_EVENT_MASK_KEY_RELEASE | XCB_EVENT_MASK_BUTTON_PRESS |
47 XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_POINTER_MOTION;
48 xcb_create_window（connection, screen->root_depth,
49 window, screen->root, 20, 200,
50 WIDTH, HEIGHT,
51 0, XCB_WINDOW_CLASS_INPUT_OUTPUT,
52 screen->root_visual,
53 mask, values）;
54 xcb_map_window（connection, window）;
55 xcb_flush（connection）;
56 
57 /*event loop*/
58 xcb_generic_event_t *event;
59 while（（event = xcb_wait_for_event（connection）））{
60 switch（event->response_type & ~0x80）{
61 case XCB_EXPOSE:
62 {
63 drawText（connection, screen, window, 10, 20,"fixed", "Press ESC key to exit."）;
64 drawText（connection, screen, window, 10, 40, "Dejavu Sans Mono", "Press ESC key to exit."）;
65 drawText（connection, screen, window, 10, 60, "文泉驿正黑", "按ESC键退出。"）;
66 break;
67 }
68 case XCB_KEY_RELEASE:
69 {
70 xcb_key_release_event_t *kr = （xcb_key_release_event_t*）event;
71 switch（kr->detail）{
72 case 9: /* ESC */
73 {
74 free（event）;
75 xcb_disconnect（connection）;
76 return 0;
77 }
78 }
79 }
80 }
81 free（event）;
82 }
83 return 0;
84 }