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POMultithreading, gtk3 and cairo: drawing in a cairo surface
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  1. POMultithreading, gtk3 and cairo: drawing in a cairo surface
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    copied!<p>I'm trying to draw into a cairo image surface from a thread and I'm getting an assertion error:</p> <blockquote> <p>gtk_mt: /build/buildd/cairo-1.10.2/src/cairo-surface.c:385: _cairo_surface_begin_modification: Assertion `! surface->finished' failed. Aborted (core dumped)</p> </blockquote> <p>This is my program:</p> <pre><code>#include &lt;stdlib.h&gt; #include &lt;gtk/gtk.h&gt; #include &lt;gdk/gdk.h&gt; #include &lt;cairo.h&gt; #define IMAGE_WIDTH 320 #define IMAGE_HEIGHT 200 gpointer thread_func(gpointer data) { int x, y; unsigned char rgb_r, rgb_g, rgb_b; GtkWidget *widget = (GtkWidget*)data; GdkWindow *window; cairo_t *cr; cairo_format_t format = CAIRO_FORMAT_ARGB32; cairo_surface_t *surface; unsigned char *image_data, *rgbptr; int width = IMAGE_WIDTH; int height = IMAGE_HEIGHT; int stride; gdk_threads_enter(); stride = cairo_format_stride_for_width(format, width); image_data = malloc(stride * height); surface = cairo_image_surface_create_for_data(image_data, format, width, height, stride); window = gtk_widget_get_window(widget); cr = gdk_cairo_create(window); gdk_threads_leave(); while(1) { rgb_r = random() &amp; 0xff; rgb_g = random() &amp; 0xff; rgb_b = random() &amp; 0xff; for(y = 0; y &lt; height; ++y) { rgbptr = &amp;image_data[y * stride]; if(!(random() &amp; 0x3f)) { rgb_r = random() &amp; 0xff; rgb_g = random() &amp; 0xff; rgb_b = random() &amp; 0xff; } for(x = 0; x &lt; width; ++x) { *rgbptr++ = rgb_r; *rgbptr++ = rgb_g; *rgbptr++ = rgb_b; *rgbptr = 0xff; } } gdk_threads_enter(); cairo_set_source_surface(cr, surface, 0, 0); cairo_paint(cr); gdk_threads_leave(); sleep(2); } return( NULL ); } int main(int argc, char **argv) { GtkWidget *window; GtkWidget *darea; GThread *thread; GError *error = NULL; if(! g_thread_supported()) g_thread_init(NULL); gdk_threads_init(); gdk_threads_enter(); gtk_init(&amp;argc, &amp;argv); window = gtk_window_new(GTK_WINDOW_TOPLEVEL); darea = gtk_drawing_area_new(); gtk_widget_set_size_request(darea, IMAGE_WIDTH, IMAGE_HEIGHT); gtk_container_add(GTK_CONTAINER (window), darea); gtk_widget_show_all (window); thread = g_thread_create(thread_func, (gpointer)darea, FALSE, &amp;error); if(!thread) { g_print("Error: %s\n", error-&gt;message); return(-1); } gtk_main(); gdk_threads_leave(); return( 0 ); } </code></pre> <p>Any help appreciated!</p>
 

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