interface.c

#include <gtk/gtk.h>
#include <stdio.h>
#include <stdlib.h>

#define borderSize       4
#define fallbackCPUCount 4

#define ignore(x) (void) x

struct CPUDisplay {
  GtkWidget *box;
  GtkWidget *toggle;
  GtkWidget *usageBar;
};

static gboolean deleteEventHandler (GtkWidget *widget,
                                    GdkEvent *event,
                                    gpointer data) {
  /* ignored arguments */
  ignore(widget);
  ignore(event);
  ignore(data);

  gtk_main_quit();
  return TRUE;
}

int main (int argc, char *argv[]) {
  gtk_init(&argc, &argv);

  int CPUCount = ((argc > 1)
                  ? atoi(argv[1])
                  : fallbackCPUCount);

  GtkWidget *window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  gtk_container_set_border_width(GTK_CONTAINER (window), borderSize);

  GtkWidget *hbox = gtk_hbox_new(FALSE, borderSize);
  gtk_container_add(GTK_CONTAINER (window), hbox);

  GtkWidget *alignment = gtk_alignment_new(0, 0, 0, 0);
  gtk_box_pack_start(GTK_BOX (hbox), alignment, FALSE, FALSE, borderSize);
  gtk_widget_show(alignment);

  GtkWidget *image = gtk_image_new_from_file("placeholder.png");
  gtk_container_add(GTK_CONTAINER (alignment), image);
  gtk_image_set_pixel_size(GTK_IMAGE (image), 1);
  gtk_widget_show(image);

  GtkWidget *vbox = gtk_vbox_new(TRUE, (borderSize * 2));
  gtk_container_add(GTK_CONTAINER (hbox), vbox);

  struct CPUDisplay *CPUDisplays = malloc(sizeof (struct CPUDisplay) * CPUCount);

  for (int i = 0; i < CPUCount; i += 1) {
    char buf[15];
    sprintf(buf, "cpu%d", i);

    struct CPUDisplay *current = &CPUDisplays[i];

    current->box = gtk_hbox_new(FALSE, borderSize);
    gtk_container_add(GTK_CONTAINER (vbox), current->box);

    current->toggle = gtk_toggle_button_new_with_label(buf);
    current->usageBar = gtk_progress_bar_new();
    gtk_progress_bar_update(GTK_PROGRESS_BAR (current->usageBar),
                            (gdouble) (i + 1) / CPUCount);

    gtk_box_pack_start(GTK_BOX (current->box), current->toggle, TRUE, FALSE, 0);
    gtk_box_pack_start(GTK_BOX (current->box), current->usageBar, TRUE, TRUE, 0);

    gtk_widget_show(current->toggle);
    gtk_widget_show(current->usageBar);
    gtk_widget_show(current->box);
  }

  /* show things */
  gtk_widget_show(vbox);
  gtk_widget_show(hbox);
  gtk_widget_show(window);

  /* add event handlers */
  g_signal_connect(window, "delete-event",
                   G_CALLBACK (deleteEventHandler), NULL);

  gtk_main();
  return 0;
}

Makefile

.POSIX:

CFLAGS = -Wall -Wextra -g
CC     = gcc

all: interface

interface: interface.c
	$(CC) interface.c -o interface $(CFLAGS) $$(pkg-config --cflags --libs gtk+-2.0)

clean:
	rm -f interface *~