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@luser-dr00g
Created August 30, 2014 09:35
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xcb+cairo hello world window
//xcr.c
//cc -o xcr $(pkg-config --cflags --libs cairo xcb xcb-icccm) xcr.c -lcairo -lxcb -lxcb-icccm
#include <stdlib.h>
#include <string.h>
#include <cairo.h>
#include <cairo-xcb.h>
#include <xcb/xcb.h>
#include <xcb/xcb_image.h>
#include <xcb/xcb_aux.h>
#include <xcb/xcb_icccm.h>
typedef struct {
int width, height;
int scrno;
xcb_screen_t *scr;
xcb_connection_t *connection;
xcb_drawable_t win;
unsigned int white;
xcb_visualtype_t *visual_type;
cairo_surface_t *surface;
cairo_t *cr;
} Window;
Window window;
int makewindow()
{
xcb_screen_iterator_t iter;
xcb_depth_iterator_t depth_iter;
window.width = 300;
window.height = 200;
window.connection = xcb_connect(NULL,&window.scrno);
iter = xcb_setup_roots_iterator(xcb_get_setup(window.connection));
for (; iter.rem; --window.scrno, xcb_screen_next(&iter))
if (window.scrno == 0)
{
window.scr = iter.data;
break;
}
window.win = xcb_generate_id(window.connection);
window.white = window.scr->white_pixel;
xcb_create_window(window.connection, XCB_COPY_FROM_PARENT,
window.win, window.scr->root,
0, 0,
window.width, window.height,
5,
XCB_WINDOW_CLASS_INPUT_OUTPUT,
window.scr->root_visual,
XCB_CW_BACK_PIXEL,
&window.white);
xcb_icccm_set_wm_name(window.connection, window.win, XCB_ATOM_STRING, 8, strlen("xcr"), "xcr");
xcb_map_window(window.connection, window.win);
xcb_flush(window.connection);
depth_iter = xcb_screen_allowed_depths_iterator(window.scr);
for (; depth_iter.rem; xcb_depth_next(&depth_iter)) {
xcb_visualtype_iterator_t visual_iter;
visual_iter = xcb_depth_visuals_iterator(depth_iter.data);
for (; visual_iter.rem; xcb_visualtype_next(&visual_iter)) {
if (window.scr->root_visual == visual_iter.data->visual_id) {
window.visual_type = visual_iter.data;
goto visual_found;
}
}
}
visual_found: ;
{
window.surface = cairo_xcb_surface_create (window.connection, window.win, window.visual_type, window.width, window.height);
window.cr = cairo_create (window.surface);
cairo_select_font_face (window.cr, "serif", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_BOLD);
cairo_set_font_size (window.cr, 32.0);
cairo_set_source_rgb (window.cr, 0.0, 0.0, 1.0);
cairo_move_to (window.cr, 10.0, 50.0);
cairo_show_text (window.cr, "Hello, world");
cairo_surface_flush(window.surface);
xcb_flush(window.connection);
}
return 0;
}
int destroywindow() {
cairo_destroy (window.cr);
cairo_surface_destroy (window.surface);
xcb_disconnect(window.connection);
return 0;
}
int main(int argc, char **argv)
{
makewindow();
sleep(100);
destroywindow();
return 0;
}
@sorenvonsarvort
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Thank You for publishing this example. It does work, but there are some things I want to notice.

In order to compile You also should add #include <unistd.h> (for sleep() function).

It is unnecessary to pass -l... flags, pkg-config already does it.

After resizing window gets filled in white. I am not familiar with XCB and I cannot suggest how to fix it. If this example don't tries to handle resize event - please, make it clear, write this information in a comment.

@etale-cohomology
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etale-cohomology commented May 16, 2018

The image gets filled with white after resizing because the code is setting the XCB_CW_BACK_PIXEL of the xcb_window_t to white. Instead of a single color as background for windows, you can also set an X pixmap, using XCB_CW_BACK_PIXMAP instead of XCB_CW_BACK_PIXEL. In general, xcb is poorly documented, but for the most part it's a thin wrapper around the X protocol to help you send requests (using the X protocol) to the X server. Once you begin understanding the X protocol itself, you will find that most xcb calls correspond very nicely to X protocol requests, replies, events, and errors (these are the 4 types of packets that the X server understands).

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