font part
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TORRI Vincent
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@ -59,9 +59,10 @@
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<li><a class="section" href="#font">Handling text and fonts</a>
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<ol>
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<li><a class="subsection" href="#fontstruct">The Font structure</a>
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<li>Loading a Font
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<li>Assigning a Font to a Graphic Context
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<li>Drawing text in a window
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<li><a class="subsection" href="#openingfont">Opening a Font</a>
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<li><a class="subsection" href="#assigningfont">Assigning a Font to a Graphic Context</a>
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<li><a class="subsection" href="#drawingtext">Drawing text in a drawable</a>
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<li><a class="subsection" href="#fontcompleteexample">Complete example</a>
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</ol>
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<li>Windows hierarchy
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<ol>
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@ -977,8 +978,9 @@ main ()
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change its attributes (for example, changing the foreground
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color we use to draw a line, or changing the attributes of the
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font we use to display strings. See Subsections Drawing with a
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color and Assigning a Font to a Graphic Context). This is done
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by using this function:
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color and
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<a href="#assigningfont">Assigning a Font to a Graphic Context</a>).
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This is done by using this function:
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</p>
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<pre class="code">
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xcb_void_cookie_t xcb_change_gc (xcb_connection_t *c, /* The XCB Connection */
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@ -2046,7 +2048,7 @@ main ()
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<ol>
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<li class="subtitle"><a name="fontstruct">The Font structure</a>
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<p>
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In order to support flexible fonts, a font structure is
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In order to support flexible fonts, a font type is
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defined. You know what ? It's an Id:
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</p>
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<pre class="code">
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@ -2055,11 +2057,304 @@ typedef uint32_t xcb_font_t;
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<p>
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It is used to contain information about a font, and is passed
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to several functions that handle fonts selection and text drawing.
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We ask the X server to attribute an Id to our font with the
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function:
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</p>
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<pre class="code">
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xcb_font_t xcb_generate_id (xcb_connection_t *c);
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</pre>
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<p>
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<b>TODO:</b> example for picking a font and displaying some text.
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Even better, also demonstrate translating keypresses to text.
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<li class="subtitle"><a name="openingfont">Opening a Font</a>
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<p>
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To open a font, we use the following function:
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</p>
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<pre class="code">
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xcb_void_cookie_t xcb_open_font (xcb_connection_t *c,
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xcb_font_t fid,
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uint16_t name_len,
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const char *name);
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</pre>
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<p>
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The <span class="code">fid</span> parameter is the font Id
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defined by <span class="code">xcb_generate_id()</span> (see
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above). The <span class="code">name</span> parameter is the
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name of the font you want to open. Use the command
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<span class="code">xlsfonts</span> in a terminal to know which
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are the fonts available on your computer. The parameter
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<span class="code">name_len</span> is the length of the name
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of the font (given by <span class="code">strlen()</span>).
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</p>
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<li class="subtitle"><a name="assigningfont">Assigning a Font to a Graphic Context</a>
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<p>
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Once a font is opened, you have to create a Graphic Context
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that will contain the informations about the color of the
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foreground and the background used when you draw a text in a
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Drawable. Here is an exemple of a Graphic Context that will
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allow us to draw an opened font with a black foreground and a
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white background:
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</p>
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<pre class="code">
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/*
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* c is the connection
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* screen is the screen where the window is displayed
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* window is the window in which we will draw the text
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* font is the opened font
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*/
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uint32_t value_list[3];
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xcb_gcontext_t gc;
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uint32_t mask;
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gc = xcb_generate_id (c);
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mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
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value_list[0] = screen->black_pixel;
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value_list[1] = screen->white_pixel;
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value_list[2] = font;
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xcb_create_gc (c, gc, window, mask, value_list);
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/* The font is not needed anymore, so we close it */
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xcb_close_font (c, font);
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</pre>
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<li class="subtitle"><a name="drawingtext">Drawing text in a drawable</a>
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<p>
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To draw a text in a drawable, we use the following function:
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</p>
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<pre class="code">
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xcb_void_cookie_t xcb_image_text_8 (xcb_connection_t *c,
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uint8_t string_len,
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xcb_drawable_t drawable,
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xcb_gcontext_t gc,
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int16_t x,
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int16_t y,
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const char *string);
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</pre>
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<p>
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The <span class="code">string</span> parameter is the text to
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draw. The location of the drawing is given by the parameters
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<span class="code">x</span> and <span class="code">y</span>.
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The base line of the text is exactly the parameter
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<span class="code">y</span>.
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</p>
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<li class="subtitle"><a name="fontcompleteexample">Complete example</a>
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<p>
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This example draw a text at 10 pixels (for the base line) of
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the bottom of a window. Pressing the Esc key exits the program.
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</p>
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<pre class="code">#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <xcb/xcb.h>
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#define WIDTH 300
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#define HEIGHT 100
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static xcb_gc_t gc_font_get (xcb_connection_t *c,
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xcb_screen_t *screen,
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xcb_window_t window,
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const char *font_name);
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static void text_draw (xcb_connection_t *c,
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xcb_screen_t *screen,
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xcb_window_t window,
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int16_t x1,
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int16_t y1,
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const char *label);
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static void
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text_draw (xcb_connection_t *c,
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xcb_screen_t *screen,
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xcb_window_t window,
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int16_t x1,
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int16_t y1,
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const char *label)
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{
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xcb_void_cookie_t cookie_gc;
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xcb_void_cookie_t cookie_text;
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xcb_generic_error_t *error;
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xcb_gcontext_t gc;
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uint8_t length;
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length = strlen (label);
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gc = gc_font_get(c, screen, window, "7x13");
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cookie_text = xcb_image_text_8_checked (c, length, window, gc,
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x1,
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y1, label);
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error = xcb_request_check (c, cookie_text);
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if (error) {
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fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code);
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xcb_disconnect (c);
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exit (-1);
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}
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cookie_gc = xcb_free_gc (c, gc);
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error = xcb_request_check (c, cookie_gc);
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if (error) {
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fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code);
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xcb_disconnect (c);
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exit (-1);
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}
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}
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static xcb_gc_t
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gc_font_get (xcb_connection_t *c,
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xcb_screen_t *screen,
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xcb_window_t window,
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const char *font_name)
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{
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uint32_t value_list[3];
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xcb_void_cookie_t cookie_font;
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xcb_void_cookie_t cookie_gc;
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xcb_generic_error_t *error;
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xcb_font_t font;
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xcb_gcontext_t gc;
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uint32_t mask;
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font = xcb_generate_id (c);
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cookie_font = xcb_open_font_checked (c, font,
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strlen (font_name),
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font_name);
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error = xcb_request_check (c, cookie_font);
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if (error) {
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fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code);
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xcb_disconnect (c);
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return -1;
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}
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gc = xcb_generate_id (c);
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mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
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value_list[0] = screen->black_pixel;
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value_list[1] = screen->white_pixel;
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value_list[2] = font;
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cookie_gc = xcb_create_gc_checked (c, gc, window, mask, value_list);
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error = xcb_request_check (c, cookie_gc);
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if (error) {
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fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code);
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xcb_disconnect (c);
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exit (-1);
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}
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cookie_font = xcb_close_font_checked (c, font);
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error = xcb_request_check (c, cookie_font);
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if (error) {
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fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code);
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xcb_disconnect (c);
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exit (-1);
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}
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return gc;
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}
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int main ()
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{
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xcb_screen_iterator_t screen_iter;
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xcb_connection_t *c;
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const xcb_setup_t *setup;
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xcb_screen_t *screen;
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xcb_generic_event_t *e;
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xcb_generic_error_t *error;
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xcb_void_cookie_t cookie_window;
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xcb_void_cookie_t cookie_map;
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xcb_window_t window;
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uint32_t mask;
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uint32_t values[2];
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int screen_number;
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/* getting the connection */
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c = xcb_connect (NULL, &screen_number);
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if (!c) {
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fprintf (stderr, "ERROR: can't connect to an X server\n");
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return -1;
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}
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/* getting the current screen */
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setup = xcb_get_setup (c);
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screen = NULL;
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screen_iter = xcb_setup_roots_iterator (setup);
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for (; screen_iter.rem != 0; --screen_number, xcb_screen_next (&screen_iter))
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if (screen_number == 0)
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{
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screen = screen_iter.data;
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break;
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}
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if (!screen) {
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fprintf (stderr, "ERROR: can't get the current screen\n");
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xcb_disconnect (c);
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return -1;
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}
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/* creating the window */
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window = xcb_generate_id (c);
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mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
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values[0] = screen->white_pixel;
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values[1] =
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XCB_EVENT_MASK_KEY_RELEASE |
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XCB_EVENT_MASK_BUTTON_PRESS |
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XCB_EVENT_MASK_EXPOSURE |
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XCB_EVENT_MASK_POINTER_MOTION;
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cookie_window = xcb_create_window_checked (c,
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screen->root_depth,
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window, screen->root,
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20, 200, WIDTH, HEIGHT,
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0, XCB_WINDOW_CLASS_INPUT_OUTPUT,
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screen->root_visual,
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mask, values);
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cookie_map = xcb_map_window_checked (c, window);
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/* error managing */
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error = xcb_request_check (c, cookie_window);
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if (error) {
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fprintf (stderr, "ERROR: can't create window : %d\n", error->error_code);
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xcb_disconnect (c);
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return -1;
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}
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error = xcb_request_check (c, cookie_map);
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if (error) {
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fprintf (stderr, "ERROR: can't map window : %d\n", error->error_code);
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xcb_disconnect (c);
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return -1;
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}
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xcb_flush(c);
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while (1) {
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e = xcb_poll_for_event(c);
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if (e) {
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switch (e->response_type) {
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case XCB_EXPOSE: {
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char *text;
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text = "Press ESC key to exit...";
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text_draw (c, screen, window, 10, HEIGHT - 10, text);
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break;
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}
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case XCB_KEY_RELEASE: {
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xcb_key_release_event_t *ev;
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ev = (xcb_key_release_event_t *)e;
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switch (ev->detail) {
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/* ESC */
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case 9:
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free (e);
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xcb_disconnect (c);
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return 0;
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}
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}
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}
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free (e);
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}
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}
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return 0;
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}
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</pre>
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</ol>
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<li class="title"><a name="wm">Interacting with the window manager</a>
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<p>
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