teaching machines

CS 330 Lecture 19 – Abstracting a GUI

March 7, 2014 by Chris Johnson. Filed under cs330, lectures, spring 2014.

Agenda

• what ?s
• finishing GUI abstraction
• pitfalls of C
• C with Classes

TODO

• Compose a thoughtful and conceptual question that could appear on the midterm on Piazza. 1/4 sheet point, but just post.

Code

gui.xml

<?xml version="1.0" encoding="UTF-8"?>
<panel orientation="vertical">
 <panel orientation="horizontal">
  <label text="To:" />
  <textbox name="toBox" />
 </panel>
 <panel orientation="horizontal">
  <label text="Subject:" />
  <textbox name="subjectBox" />
 </panel>
 <textarea name="bodyBox" />
 <button text="Send" />
</panel>

gui_madness.c

#include <stdio.h>
#include <stdlib.h>
#include <expat.h>
#include <string.h>

void open_handler(void *data,
          const char *tag,
          const char **attributes) {
  /* printf("open tag: %s\n", tag); */
  int *ptag_counter = (int *) data;

  if (strcmp(tag, "panel") == 0) {
    int is_vertical = 1;
    for (int i = 0; attributes[i] != NULL; i += 2) {
      if (strcmp(attributes[i], "orientation") == 0) {
        if (strcmp(attributes[i + 1], "horizontal") == 0) {
          is_vertical = 0;
        }
      }
    }
    printf("{\nJPanel panel%d = new JPanel();\n", *ptag_counter);
    printf("panel%d.setLayout(new BoxLayout(panel%d, BoxLayout.%s));\n", *ptag_counter, *ptag_counter, is_vertical ? "PAGE_AXIS" : "LINE_AXIS");

    if (*ptag_counter == 0) {
      printf("add(panel%d);\n", *ptag_counter);
    } else {
      printf("panel%d.add(panel%d);\n", *ptag_counter - 1, *ptag_counter);
    }

    ++*ptag_counter;
  } else if (strcmp(tag, "button") == 0) {
    printf("panel%d.add(new JButton(\"%s\"));\n", *ptag_counter - 1, attributes[1]);
  } else if (strcmp(tag, "label") == 0) {
    printf("panel%d.add(new JLabel(\"%s\"));\n", *ptag_counter - 1, attributes[1]);
  } else if (strcmp(tag, "textbox") == 0) {
    printf("panel%d.add(new JTextField());\n", *ptag_counter - 1);
  } else if (strcmp(tag, "textarea") == 0) {
    printf("panel%d.add(new JTextArea());\n", *ptag_counter - 1);
  }
}

void close_handler(void *data,
           const char *tag) {
  int *ptag_counter = (int *) data;
  /* printf("close tag: %s\n", tag); */
  if (strcmp("panel", tag) == 0) {
    --*ptag_counter;
    printf("}\n");
  }
}

int main(int argc, char **argv) {
  int tag_counter = 0;

  XML_Parser parser = XML_ParserCreate(NULL);
  XML_SetElementHandler(parser, open_handler, close_handler);
  XML_SetUserData(parser, &tag_counter);

  const int BUFFER_SIZE = 8192;
  char buffer[BUFFER_SIZE];

  FILE *xml_file = fopen(argv[1], "r");
  int is_eof = 0;

  while (!is_eof) {
    int length = fread(buffer, sizeof(char), BUFFER_SIZE, xml_file);
    is_eof = feof(xml_file);
    XML_Parse(parser, buffer, length, is_eof);
  }

  fclose(xml_file);
  XML_ParserFree(parser);

  return 0;
}

EmailClient.java

package lecture12;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class EmailClient extends JFrame {
  public EmailClient() {
    super();

    {
      JPanel panel0 = new JPanel();
      panel0.setLayout(new BoxLayout(panel0, BoxLayout.PAGE_AXIS));
      add(panel0);
      {
        JPanel panel1 = new JPanel();
        panel1.setLayout(new BoxLayout(panel1, BoxLayout.LINE_AXIS));
        panel0.add(panel1);
        panel1.add(new JLabel("To:"));
        panel1.add(new JTextField());
      }
      {
        JPanel panel1 = new JPanel();
        panel1.setLayout(new BoxLayout(panel1, BoxLayout.LINE_AXIS));
        panel0.add(panel1);
        panel1.add(new JLabel("Subject:"));
        panel1.add(new JTextField());
      }
      panel0.add(new JTextArea());
      panel0.add(new JButton("Send"));
    }

    setSize(512, 600);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setVisible(true);
  }

  public static void main(String[] args) {
    new EmailClient();
  }
}

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