From 3c772917dcdf0764b6d0a2729eec151877b85e8f Mon Sep 17 00:00:00 2001
From: Ivan Mahonin <bh@icystar.com>
Date: Feb 01 2019 12:12:19 +0000
Subject: c gtk3: calc-line


---

diff --git a/c/gtk3/calc-line/calcline.c b/c/gtk3/calc-line/calcline.c
new file mode 100644
index 0000000..4f6a929
--- /dev/null
+++ b/c/gtk3/calc-line/calcline.c
@@ -0,0 +1,56 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <gtk/gtk.h>
+
+
+void changed(GtkEditable *editable, gpointer data) {
+  const char *text = gtk_entry_get_text(GTK_ENTRY(editable));
+  double result = 0.0;
+  for(const char *c = text; c; ++c) {
+    if (*c == '+' || *c == '-' || *c == '*' || *c == '/') {
+      char *end;
+      double a = strtof(text, &end);
+      double b = strtof(c + 1, &end);
+      if (*c == '+') result = a + b;
+      if (*c == '-') result = a - b;
+      if (*c == '*') result = a * b;
+      if (*c == '/') result = a / b;
+    } else
+    if (*c == '=') {
+      int size = c - text + 1;
+      char *new_text = malloc(size + 20);
+      memcpy(new_text, text, size);
+      sprintf(new_text + size, "%g", result);
+      gtk_entry_set_text(GTK_ENTRY(editable), new_text);
+      free(new_text);
+      break;
+    }
+  }
+}
+
+void activate(GtkApplication* app, gpointer data) {
+  GtkWidget *window = gtk_application_window_new(app);
+  gtk_container_set_border_width(GTK_CONTAINER(window), 10);
+  
+  GtkWidget *vbox = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);
+  gtk_container_add(GTK_CONTAINER(window), vbox);
+
+  GtkWidget *label = gtk_label_new("Enter simple expression like: 2+3=");
+  gtk_container_add(GTK_CONTAINER(vbox), label);
+  
+  GtkWidget *entry = gtk_entry_new();
+  g_signal_connect(entry, "changed", G_CALLBACK(changed), NULL);
+  gtk_container_add(GTK_CONTAINER(vbox), entry);
+  
+  gtk_widget_show_all(window);
+}
+
+int main(int argc, char **argv) {
+  GtkApplication *application = gtk_application_new(NULL, 0);
+  g_signal_connect(application, "activate", G_CALLBACK(activate), NULL);
+  int status = g_application_run(G_APPLICATION(application), argc, argv);
+  g_object_unref(application);
+  return status;
+}
+