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@@ -0,0 +1,2 @@
+test: test.c
+	gcc -o test test.c -lxcb -lxcb-util -lxcb-present -lcairo -pthread

test.c

@@ -0,0 +1,346 @@
+#include <pthread.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <cairo/cairo.h>
+#include <cairo/cairo-xcb.h>
+#include <xcb/xcb.h>
+#include <xcb/present.h>
+
+/************************************************************************************************************/
+/************************************************************************************************************/
+/************************************************************************************************************/
+
+#define WIN_W 600
+#define WIN_H 400
+
+#define RECT_W     100
+#define RECT_SPEED 5  /* 300 px/s at 60 Hz */
+
+/************************************************************************************************************/
+/************************************************************************************************************/
+/************************************************************************************************************/
+
+static void _draw          (void);
+static void _init_graphics (void);
+static void _init_threads  (void);
+static void _reset         (void);
+
+static void * _thread_event  (void *p);
+static void * _thread_render (void *p);
+
+/************************************************************************************************************/
+/************************************************************************************************************/
+/************************************************************************************************************/
+
+static xcb_connection_t    *_x_con = NULL;
+static xcb_screen_t        *_x_scr = NULL;
+static xcb_visualtype_t    *_x_vis = NULL;
+static xcb_window_t         _x_win = 0;
+static xcb_pixmap_t         _x_pix = 0;
+static xcb_gcontext_t       _x_ctx = 0;
+
+static uint8_t _x_opcode = 0;
+
+static cairo_surface_t *_c_srf = NULL;
+static cairo_t         *_c_ctx = NULL;
+
+static pthread_t       _t_id_ev;
+static pthread_t       _t_id_rd;
+static pthread_cond_t  _t_cond_rd_1;
+static pthread_cond_t  _t_cond_rd_2;
+static pthread_mutex_t _t_mutex_rd_1;
+static pthread_mutex_t _t_mutex_rd_2;
+
+static int _rect_pos = WIN_W;
+static int _update = 1;
+static int _serial = 0;
+
+/************************************************************************************************************/
+/************************************************************************************************************/
+/************************************************************************************************************/
+
+int
+main(int argc, char **argv)
+{
+	/* initialisation */
+
+	_init_graphics();
+	_init_threads();
+	
+	/* initial render for first expose event */
+
+	_draw(); 
+
+	/* start the threads                */
+	/* the event thread leads the tempo */
+
+	pthread_create(&_t_id_ev, NULL, _thread_event,  NULL);
+	pthread_create(&_t_id_rd, NULL, _thread_render, NULL);
+
+	pthread_join(_t_id_ev, NULL);
+
+	pthread_cancel(_t_id_rd);
+	pthread_join(_t_id_rd, NULL);
+
+	/* end */
+
+	_reset();
+}
+
+/************************************************************************************************************/
+/************************************************************************************************************/
+/************************************************************************************************************/
+
+static void
+_draw(void)
+{
+	/* update position */
+
+	_rect_pos += RECT_SPEED;
+	if (_rect_pos >= WIN_W) {
+		_rect_pos = -RECT_W;
+	}
+
+	/* update pixmap */
+
+	cairo_set_source_rgb(_c_ctx, 0.3, 0.3, 0.3);
+	cairo_paint(_c_ctx);
+
+	cairo_set_source_rgb(_c_ctx, 0.7, 0.7, 0.7);
+	cairo_rectangle(_c_ctx, _rect_pos, 0, RECT_W, WIN_H);
+	cairo_fill(_c_ctx);
+
+	cairo_surface_flush(_c_srf);
+}
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/
+
+static void
+_init_graphics(void)
+{
+	/* setup xcb */
+
+	_x_con = xcb_connect(NULL, NULL);
+	_x_scr = xcb_setup_roots_iterator(xcb_get_setup(_x_con)).data;
+
+	xcb_visualtype_iterator_t x_vi;
+	xcb_depth_iterator_t      x_di;
+
+	x_di = xcb_screen_allowed_depths_iterator(_x_scr);
+	for (; x_di.rem; xcb_depth_next(&x_di)) {
+		x_vi = xcb_depth_visuals_iterator(x_di.data);
+		for (; x_vi.rem; xcb_visualtype_next(&x_vi)) {
+			if (_x_scr->root_visual == x_vi.data->visual_id) {
+				_x_vis = x_vi.data;
+				break;
+			}
+		}
+	}
+
+	/* setup generic xcb graphical context for copying the pixmap */
+
+	_x_ctx = xcb_generate_id(_x_con);
+	xcb_create_gc(
+		_x_con,
+		_x_ctx,
+		_x_scr->root,
+		XCB_GC_FOREGROUND | XCB_GC_GRAPHICS_EXPOSURES,
+		&(uint32_t[2]){_x_scr->black_pixel, 0});
+
+	/* setup xcb window */
+
+	uint32_t mask_vals[2];
+	mask_vals[0] = _x_scr->black_pixel;
+	mask_vals[1] = XCB_EVENT_MASK_EXPOSURE |
+	               XCB_EVENT_MASK_STRUCTURE_NOTIFY |
+				   XCB_EVENT_MASK_KEY_PRESS |
+				   XCB_EVENT_MASK_BUTTON_PRESS;
+
+	_x_win = xcb_generate_id(_x_con);
+	xcb_create_window(
+		_x_con,
+		XCB_COPY_FROM_PARENT,
+		_x_win,
+		_x_scr->root,
+		0, 0,
+		WIN_W, WIN_H,
+		0,
+		XCB_WINDOW_CLASS_INPUT_OUTPUT,
+		_x_scr->root_visual,
+		XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK,
+		mask_vals);
+
+	xcb_map_window(_x_con, _x_win);
+
+	/* setup xcb pixmap */
+
+	_x_pix = xcb_generate_id(_x_con);
+	xcb_create_pixmap(_x_con, _x_scr->root_depth, _x_pix, _x_win, WIN_W, WIN_H);
+
+	/* setup xcb present extension */
+
+	xcb_present_select_input(
+		_x_con,
+		xcb_generate_id(_x_con),
+		_x_win,
+		XCB_PRESENT_EVENT_MASK_COMPLETE_NOTIFY);
+
+	/* dynamicaly get the present extention opcode for event identification */
+
+	xcb_query_extension_reply_t *r =
+		xcb_query_extension_reply(_x_con, xcb_query_extension(_x_con, 7, "Present"), NULL);
+
+	_x_opcode = r->major_opcode;
+	free(r);
+
+	/* setup cairo drawable */
+
+	_c_srf = cairo_xcb_surface_create(_x_con, _x_pix, _x_vis, WIN_W, WIN_H);
+	_c_ctx = cairo_create(_c_srf);
+
+	/* end */
+
+	cairo_surface_flush(_c_srf);
+	xcb_flush(_x_con);
+}
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/
+
+static void
+_init_threads(void)
+{
+	pthread_mutex_init(&_t_mutex_rd_1, NULL);
+	pthread_mutex_init(&_t_mutex_rd_2, NULL);
+
+	pthread_cond_init(&_t_cond_rd_1, NULL);
+	pthread_cond_init(&_t_cond_rd_2, NULL);
+}
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/
+
+void
+_reset(void)
+{
+	pthread_mutex_destroy(&_t_mutex_rd_1);
+	pthread_mutex_destroy(&_t_mutex_rd_2);
+
+	pthread_cond_destroy(&_t_cond_rd_1);
+	pthread_cond_destroy(&_t_cond_rd_2);
+
+	cairo_destroy(_c_ctx);
+	cairo_surface_destroy(_c_srf);
+
+	xcb_free_gc(_x_con, _x_ctx);
+	xcb_free_pixmap(_x_con, _x_pix);
+	xcb_destroy_window(_x_con, _x_win);
+	xcb_disconnect(_x_con);
+}
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/
+
+static void *
+_thread_event(void *p)
+{
+	int run = 1;
+	int x_pev_serial;
+
+	xcb_generic_event_t                 *x_ev;
+	xcb_ge_generic_event_t              *x_gev;
+	xcb_present_complete_notify_event_t *x_pev;
+
+	while (run && (x_ev = xcb_wait_for_event(_x_con))) {
+		switch (x_ev->response_type & ~0x80) {
+			
+			case XCB_EXPOSE:
+				/* immediate update without syncing to the refresh rate          */
+				/* without it there are visual glitches when resizing the window */
+				xcb_copy_area(_x_con, _x_pix, _x_win, _x_ctx, 0, 0, 0, 0, WIN_W, WIN_H);
+				break;
+
+			case XCB_BUTTON_PRESS:
+				pthread_mutex_lock(&_t_mutex_rd_2);
+				_update = !_update;
+				pthread_mutex_unlock(&_t_mutex_rd_2);
+				pthread_cond_signal(&_t_cond_rd_2);
+				break;
+
+			case XCB_KEY_PRESS:
+				run = 0;
+				break;
+
+			case XCB_GE_GENERIC:
+				/* most of this is just checking that we got the right event */
+				/* unecessary in simple cases                                */
+				x_gev = (xcb_ge_generic_event_t*)x_ev;
+				if (x_gev->extension == _x_opcode && x_gev->event_type == XCB_PRESENT_EVENT_COMPLETE_NOTIFY) {
+					x_pev = (xcb_present_complete_notify_event_t*)x_ev;	
+					pthread_mutex_lock(&_t_mutex_rd_2);
+					x_pev_serial = _serial;
+					pthread_mutex_unlock(&_t_mutex_rd_2);
+					if (x_pev->kind == XCB_PRESENT_COMPLETE_KIND_PIXMAP && x_pev->serial == x_pev_serial) {
+						pthread_cond_signal(&_t_cond_rd_1);
+					}
+				}
+				break;
+		}
+		xcb_flush(_x_con);
+		free(x_ev);
+	}
+
+	pthread_exit(NULL);
+}
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/
+
+static void *
+_thread_render(void *p)
+{
+	pthread_mutex_lock(&_t_mutex_rd_1);
+
+	while (1) {
+
+		/* check if an update is needed, if not, wait */
+
+		pthread_mutex_lock(&_t_mutex_rd_2);
+		if (!_update) {
+			pthread_cond_wait(&_t_cond_rd_2, &_t_mutex_rd_2);
+		}
+		pthread_mutex_unlock(&_t_mutex_rd_2);
+
+		/* update pixmap */
+
+		_draw();
+
+		/* update window with pixmap */
+
+		_serial++;
+
+		xcb_present_pixmap(
+			_x_con,
+			_x_win,
+			_x_pix,
+			_serial,
+			XCB_XFIXES_REGION_NONE,
+			XCB_XFIXES_REGION_NONE,
+			0, 0,
+			0,
+			0,
+			0,
+			XCB_PRESENT_OPTION_NONE,
+			0, 0, 0,
+			0,
+			NULL);
+		
+		/* important af, don't forget it */
+
+		xcb_flush(_x_con); 
+
+		/* wait for present event notification in the event thread */
+
+		pthread_cond_wait(&_t_cond_rd_1, &_t_mutex_rd_1);
+	}
+
+	pthread_mutex_unlock(&_t_mutex_rd_1);
+	pthread_exit(NULL);
+}