cgtk3cairo
I need to know the simplest way to draw a shape in gtk with cairo
Can someone tell me the SIMPLEST way to draw like a rectangle in a window in gtk? Please? Simple. Here is a challenge. Write a file to draw ANY cairo shape in a few lines of code possible. I found working drawing code online, but it is super complicated and not all of it is necessary. Can someone write me the code to draw any cairo shape in a few lines of code possible so I can use it as reference for my game?
Here is some working code, but is much to complicated. I don't need to draw rectangles were the mouse clicks, just draw one rectangle from four numbers. Someone, please reduce this to what is ABSOLUTELY necessary to draw one rectangle. Preferably I wanna draw a rectangle without any other functions other than the main function (Once the main function returns zero, everything ends)
The code:
#include <gtk/gtk.h>
/* Surface to store current scribbles */
static cairo_surface_t *surface = NULL;
static void
clear_surface (void)
{
cairo_t *cr;
cr = cairo_create (surface);
cairo_set_source_rgb (cr, 1, 1, 1);
cairo_paint (cr);
cairo_destroy (cr);
}
/* Create a new surface of the appropriate size to store our scribbles */
static gboolean
configure_event_cb (GtkWidget *widget,
GdkEventConfigure *event,
gpointer data)
{
if (surface)
cairo_surface_destroy (surface);
surface = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
CAIRO_CONTENT_COLOR,
gtk_widget_get_allocated_width (widget),
gtk_widget_get_allocated_height (widget));
/* Initialize the surface to white */
clear_surface ();
/* We've handled the configure event, no need for further processing. */
return TRUE;
}
/* Redraw the screen from the surface. Note that the ::draw
* signal receives a ready-to-be-used cairo_t that is already
* clipped to only draw the exposed areas of the widget
*/
static gboolean
draw_cb (GtkWidget *widget,
cairo_t *cr,
gpointer data)
{
cairo_set_source_surface (cr, surface, 0, 0);
cairo_paint (cr);
return FALSE;
}
/* Draw a rectangle on the surface at the given position */
static void
draw_brush (GtkWidget *widget,
gdouble x,
gdouble y)
{
cairo_t *cr;
/* Paint to the surface, where we store our state */
cr = cairo_create (surface);
cairo_rectangle (cr, x - 3, y - 3, 6, 6);
cairo_fill (cr);
cairo_destroy (cr);
/* Now invalidate the affected region of the drawing area. */
gtk_widget_queue_draw_area (widget, x - 3, y - 3, 6, 6);
}
/* Handle button press events by either drawing a rectangle
* or clearing the surface, depending on which button was pressed.
* The ::button-press signal handler receives a GdkEventButton
* struct which contains this information.
*/
static gboolean
button_press_event_cb (GtkWidget *widget,
GdkEventButton *event,
gpointer data)
{
/* paranoia check, in case we haven't gotten a configure event */
if (surface == NULL)
return FALSE;
if (event->button == GDK_BUTTON_PRIMARY)
{
draw_brush (widget, event->x, event->y);
}
else if (event->button == GDK_BUTTON_SECONDARY)
{
clear_surface ();
gtk_widget_queue_draw (widget);
}
/* We've handled the event, stop processing */
return TRUE;
}
/* Handle motion events by continuing to draw if button 1 is
* still held down. The ::motion-notify signal handler receives
* a GdkEventMotion struct which contains this information.
*/
static gboolean
motion_notify_event_cb (GtkWidget *widget,
GdkEventMotion *event,
gpointer data)
{
/* paranoia check, in case we haven't gotten a configure event */
if (surface == NULL)
return FALSE;
if (event->state & GDK_BUTTON1_MASK)
draw_brush (widget, event->x, event->y);
/* We've handled it, stop processing */
return TRUE;
}
static void
close_window (void)
{
if (surface)
cairo_surface_destroy (surface);
}
static void
activate (GtkApplication *app,
gpointer user_data)
{
GtkWidget *window;
GtkWidget *frame;
GtkWidget *drawing_area;
window = gtk_application_window_new (app);
gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");
g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
gtk_container_set_border_width (GTK_CONTAINER (window), 8);
frame = gtk_frame_new (NULL);
gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
gtk_container_add (GTK_CONTAINER (window), frame);
drawing_area = gtk_drawing_area_new ();
/* set a minimum size */
gtk_widget_set_size_request (drawing_area, 100, 100);
gtk_container_add (GTK_CONTAINER (frame), drawing_area);
/* Signals used to handle the backing surface */
g_signal_connect (drawing_area, "draw",
G_CALLBACK (draw_cb), NULL);
g_signal_connect (drawing_area,"configure-event",
G_CALLBACK (configure_event_cb), NULL);
/* Event signals */
g_signal_connect (drawing_area, "motion-notify-event",
G_CALLBACK (motion_notify_event_cb), NULL);
g_signal_connect (drawing_area, "button-press-event",
G_CALLBACK (button_press_event_cb), NULL);
/* Ask to receive events the drawing area doesn't normally
* subscribe to. In particular, we need to ask for the
* button press and motion notify events that want to handle.
*/
gtk_widget_set_events (drawing_area, gtk_widget_get_events (drawing_area)
| GDK_BUTTON_PRESS_MASK
| GDK_POINTER_MOTION_MASK);
gtk_widget_show_all (window);
}
int
main (int argc,
char **argv)
{
GtkApplication *app;
int status;
app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
status = g_application_run (G_APPLICATION (app), argc, argv);
g_object_unref (app);
return status;
}
Solution
Can someone tell me the SIMPLEST way to draw like a rectangle in a window in gtk?
Yes, but you will just get a default Gtk window with a cairo_rectangle filling the default 200x200 window with a 10-pixel border around the rectangle. There isn't much to drawing a rectangle, (you don't even have to fill it with a separate color - though that makes it indistinguishable from the normal window background).
Simply create the gtk window and add the cairo drawing area using the gtk window as a container (you won't be able to add anything else to the window unless you use a layout container like vbox, etc..)
About the minimal would be:
#include <cairo.h>
#include <gtk/gtk.h>
static void draw_rect (cairo_t *cr)
{
cairo_rectangle (cr, 10, 10, 180, 180); /* set rectangle */
cairo_set_source_rgb (cr, 0.3, 0.4, 0.6); /* set fill color */
cairo_fill (cr); /* fill rectangle */
}
static gboolean on_draw_event (GtkWidget *widget, cairo_t *cr,
gpointer user_data)
{
draw_rect (cr); /* draw rectangle in window */
return FALSE;
(void)user_data, (void)widget; /* suppress -Wunused warning */
}
int main (int argc, char *argv[])
{
GtkWidget *window; /* gtk windows */
GtkWidget *darea; /* cairo drawing area */
gtk_init (&argc, &argv); /* required with every gtk app */
window = gtk_window_new (GTK_WINDOW_TOPLEVEL); /* create window */
darea = gtk_drawing_area_new(); /* create cairo area */
gtk_container_add (GTK_CONTAINER(window), darea); /* add to window */
/* connect callbacks to draw rectangle and close window/quit app */
g_signal_connect (G_OBJECT(darea), "draw",
G_CALLBACK(on_draw_event), NULL);
g_signal_connect (G_OBJECT(window), "destroy",
G_CALLBACK(gtk_main_quit), NULL);
gtk_widget_show_all (window); /* show all windows */
gtk_main(); /* pass control to gtk event-loop */
}
(note: you can remove the (void)user_data, (void)widget; line which just suppresses an unused parameter warning)
Compile
gcc -Wall -Wextra -pedantic -std=c11 -O3 `pkg-config --cflags --libs gtk+-3.0`
Example Use/Output
$ ./bin/cairo_rectangle_min
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