How can I create a user input box and output area in a GTK C program, similar to a shell or terminal?

Question

I am trying to make a shell-ish thing in C using GTK. I want to make a box where:

1. the user types something
2. the output appears in a box
3. The output moves upwards and you can scroll (basically like a regular terminal.)

How would I go about doing this? Here is my code so far:

#include <gtk/gtk.h>
static GtkWidget *entry1 = 0;
void button_clicked(GtkWidget *widget,gpointer data)
{
    const gchar *entry_text1;
    entry_text1 = gtk_entry_get_text (GTK_ENTRY (entry1));
    g_print ("%s\n", entry_text1);
}

void destroy(GtkWidget* widget, gpointer data)
{
    gtk_main_quit();
}
int main(int argc,char *argv[])
{
    gtk_init(&argc,&argv);
    GtkWidget *win = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size (GTK_WINDOW (win), 680, 460);

    entry1 = gtk_entry_new();

    GtkWidget *btn2 = gtk_button_new_with_label("Click Here2");

    GtkWidget *grd = gtk_grid_new();


    g_signal_connect(btn2,"clicked",G_CALLBACK(button_clicked),NULL);

    gtk_grid_attach(grd, entry1, 1,1,1,1);
    gtk_grid_attach(grd, btn2, 2,1,1,1);

    gtk_container_add(GTK_CONTAINER(win),grd);
    gtk_container_set_border_width(GTK_CONTAINER(win), 20);
    g_signal_connect(win, "destroy",G_CALLBACK(destroy), NULL);
    gtk_widget_show_all(win);
    gtk_main();
    return 0;
}

I have no clue what type of widget to use to do something like this.

Answer 1

I think you should use GtkScrolledWindow to achieve this. For example:

#include <gtk/gtk.h>

// User adds contents to this entry.
static GtkWidget *input = NULL;

// The text buffer containing all previous user entries.
static GtkTextBuffer *buffer = NULL;

// When the "userText" button is clicked, all the user added to the
// entry is transfered to the text area.
void button_clicked(GtkWidget *widget, gpointer data)
{
    // Get the text added to the entry by the user:
    const gchar *userText;
    userText = gtk_entry_get_text(GTK_ENTRY(input));
    
    // Insert in the text view (at the end):
    GtkTextIter end; // Notice how this is created on the stack! Passing a pointer as usual is not working.
                     // See : https://stackoverflow.com/questions/52182527/iterators-do-not-belong-to-their-assigned-text-buffer
    gtk_text_buffer_get_end_iter(buffer, &end);
    
    gtk_text_buffer_insert(buffer, &end, userText, -1);
    gtk_text_buffer_insert(buffer, &end, "\n", -1);
    
    // Clear the user input entry for the next input:
    gtk_entry_set_text(GTK_ENTRY(input), "");
}

void destroy(GtkWidget* widget, gpointer data)
{
    gtk_main_quit();
}

int main(int argc,char *argv[])
{
    gtk_init(&argc,&argv);
    
    GtkWidget *mainWindow = gtk_window_new(GTK_WINDOW_TOPLEVEL);

    input = gtk_entry_new();
    
    GtkWidget *send = gtk_button_new_with_label("Send");
 
    // A text view is used to show the user's past input (in terminal
    // fashion). We wrap the text view in a GtkScrollmainWindowdow, which
    // makes the text view's content scrollable:   
    GtkWidget *scrollWindow = gtk_scrolled_window_new(NULL, NULL);
    buffer = gtk_text_buffer_new(NULL);
    GtkWidget *textArea = gtk_text_view_new_with_buffer(buffer);
    gtk_container_add(GTK_CONTAINER(scrollWindow), textArea);

    g_signal_connect(send,"clicked", G_CALLBACK(button_clicked), NULL);

    GtkWidget *layout = gtk_grid_new();
    gtk_grid_attach(GTK_GRID(layout), scrollWindow, 1, 1, 2, 1);
    gtk_grid_attach(GTK_GRID(layout), input, 1, 2, 1, 1);
    gtk_grid_attach(GTK_GRID(layout), send, 2, 2, 1, 1);
    gtk_container_set_focus_child(GTK_CONTAINER(layout), input);

    gtk_container_add(GTK_CONTAINER(mainWindow),layout);
    gtk_container_set_border_width(GTK_CONTAINER(mainWindow), 20);
    g_signal_connect(mainWindow, "destroy", G_CALLBACK(destroy), NULL);
    gtk_widget_show_all(mainWindow);
    
    gtk_main();
    
    return 0;
}

Here is what it looks like after having added "text 1", "text 2", "text 3" and "text 4", in that order:

At first, it seems like there are no scrollbars (at least on my setup), but hovering the mouse on the right side of the text view makes them appear: