source: mainline/uspace/app/calculator/calculator.c@ 45004f3

/*
 * Copyright (c) 2021 Jiri Svoboda
 * Copyright (c) 2016 Martin Decky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup calculator
 * @{
 */
/** @file
 *
 * Inspired by the code released at https://github.com/osgroup/HelenOSProject
 *
 */

#include <clipboard.h>
#include <ctype.h>
#include <io/kbd_event.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <str.h>
#include <ui/entry.h>
#include <ui/fixed.h>
#include <ui/menubar.h>
#include <ui/menu.h>
#include <ui/menuentry.h>
#include <ui/pbutton.h>
#include <ui/ui.h>
#include <ui/window.h>

#define NAME  "calculator"

#define NULL_DISPLAY  "0"

#define SYNTAX_ERROR_DISPLAY   "Syntax error"
#define NUMERIC_ERROR_DISPLAY  "Numerical error"
#define UNKNOWN_ERROR_DISPLAY  "Unknown error"

#define EXPR_MAX_LEN 22

typedef enum {
        STATE_INITIAL = 0,
        STATE_FINISH,
        STATE_ERROR,
        STATE_DIGIT,
        STATE_VALUE
} parser_state_t;

typedef enum {
        ERROR_SYNTAX = 0,
        ERROR_NUMERIC
} error_type_t;

typedef enum {
        OPERATOR_NONE = 0,
        OPERATOR_ADD,
        OPERATOR_SUB,
        OPERATOR_MUL,
        OPERATOR_DIV
} operator_t;

typedef enum {
        ITEM_VALUE = 0,
        ITEM_OPERATOR
} stack_item_type_t;

typedef struct {
        link_t link;

        stack_item_type_t type;
        union {
                int64_t value;
                operator_t operator;
        } data;
} stack_item_t;

/** Dimensions. Most of this should not be needed with auto layout */
typedef struct {
        gfx_rect_t menubar_rect;
        gfx_rect_t entry_rect;
        gfx_coord2_t btn_orig;
        gfx_coord2_t btn_stride;
        gfx_coord2_t btn_dim;
} calc_geom_t;

typedef struct {
        ui_t *ui;
        ui_resource_t *ui_res;
        ui_pbutton_t *btn_eval;
        ui_pbutton_t *btn_clear;
        ui_pbutton_t *btn_add;
        ui_pbutton_t *btn_sub;
        ui_pbutton_t *btn_mul;
        ui_pbutton_t *btn_div;
        ui_pbutton_t *btn_0;
        ui_pbutton_t *btn_1;
        ui_pbutton_t *btn_2;
        ui_pbutton_t *btn_3;
        ui_pbutton_t *btn_4;
        ui_pbutton_t *btn_5;
        ui_pbutton_t *btn_6;
        ui_pbutton_t *btn_7;
        ui_pbutton_t *btn_8;
        ui_pbutton_t *btn_9;
        ui_menu_bar_t *menubar;
        calc_geom_t geom;
} calc_t;

static void display_update(void);

static void calc_file_exit(ui_menu_entry_t *, void *);
static void calc_edit_copy(ui_menu_entry_t *, void *);
static void calc_edit_paste(ui_menu_entry_t *, void *);

static void calc_pb_clicked(ui_pbutton_t *, void *);
static void calc_eval_clicked(ui_pbutton_t *, void *);
static void calc_clear_clicked(ui_pbutton_t *, void *);

static ui_pbutton_cb_t calc_pbutton_cb = {
        .clicked = calc_pb_clicked
};

static ui_pbutton_cb_t calc_clear_cb = {
        .clicked = calc_clear_clicked
};

static ui_pbutton_cb_t calc_eval_cb = {
        .clicked = calc_eval_clicked
};

static void wnd_close(ui_window_t *, void *);
static void wnd_kbd_event(ui_window_t *, void *, kbd_event_t *);

static ui_window_cb_t window_cb = {
        .close = wnd_close,
        .kbd = wnd_kbd_event
};

static char *expr = NULL;
static ui_entry_t *display;

/** Window close request
 *
 * @param window Window
 * @param arg Argument (calc_t *)
 */
static void wnd_close(ui_window_t *window, void *arg)
{
        calc_t *calc = (calc_t *) arg;

        ui_quit(calc->ui);
}

/** Window keyboard event
 *
 * @param window Window
 * @param arg Argument (calc_t *)
 * @param event Keyboard event
 */
static void wnd_kbd_event(ui_window_t *window, void *arg, kbd_event_t *event)
{
        calc_t *calc = (calc_t *) arg;

        if (event->type == KEY_PRESS && (event->mods & KM_CTRL) != 0) {
                switch (event->key) {
                case KC_C:
                        calc_edit_copy(NULL, calc);
                        break;
                case KC_V:
                        calc_edit_paste(NULL, calc);
                        break;
                default:
                        break;
                }
        }

        switch (event->key) {
        case KC_ENTER:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_eval);
                else
                        ui_pbutton_release(calc->btn_eval);
                break;
        case KC_BACKSPACE:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_clear);
                else
                        ui_pbutton_release(calc->btn_clear);
                break;
        case KC_MINUS:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_sub);
                else
                        ui_pbutton_release(calc->btn_sub);
                break;
        case KC_EQUALS:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_add);
                else
                        ui_pbutton_release(calc->btn_add);
                break;
        case KC_SLASH:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_div);
                else
                        ui_pbutton_release(calc->btn_div);
                break;
        case KC_0:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_0);
                else
                        ui_pbutton_release(calc->btn_0);
                break;
        case KC_1:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_1);
                else
                        ui_pbutton_release(calc->btn_1);
                break;
        case KC_2:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_2);
                else
                        ui_pbutton_release(calc->btn_2);
                break;
        case KC_3:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_3);
                else
                        ui_pbutton_release(calc->btn_3);
                break;
        case KC_4:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_4);
                else
                        ui_pbutton_release(calc->btn_4);
                break;
        case KC_5:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_5);
                else
                        ui_pbutton_release(calc->btn_5);
                break;
        case KC_6:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_6);
                else
                        ui_pbutton_release(calc->btn_6);
                break;
        case KC_7:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_7);
                else
                        ui_pbutton_release(calc->btn_7);
                break;
        case KC_8:
                if ((event->mods & KM_SHIFT) != 0) {
                        if (event->type == KEY_PRESS)
                                ui_pbutton_press(calc->btn_mul);
                        else
                                ui_pbutton_release(calc->btn_mul);
                } else {
                        if (event->type == KEY_PRESS)
                                ui_pbutton_press(calc->btn_8);
                        else
                                ui_pbutton_release(calc->btn_8);
                }
                break;
        case KC_9:
                if (event->type == KEY_PRESS)
                        ui_pbutton_press(calc->btn_9);
                else
                        ui_pbutton_release(calc->btn_9);
                break;
        default:
                break;
        }
}

/** File / Exit menu entry selected.
 *
 * @param mentry Menu entry
 * @param arg Argument (calc_t *)
 */
static void calc_file_exit(ui_menu_entry_t *mentry, void *arg)
{
        calc_t *calc = (calc_t *) arg;

        ui_quit(calc->ui);
}

/** Edit / Copy menu entry selected.
 *
 * @param mentry Menu entry
 * @param arg Argument (calc_t *)
 */
static void calc_edit_copy(ui_menu_entry_t *mentry, void *arg)
{
        const char *str;

        (void) arg;
        str = (expr != NULL) ? expr : NULL_DISPLAY;

        (void) clipboard_put_str(str);
}

/** Edit / Paste menu entry selected.
 *
 * @param mentry Menu entry
 * @param arg Argument (calc_t *)
 */
static void calc_edit_paste(ui_menu_entry_t *mentry, void *arg)
{
        char *str;
        char *old;
        char *cp;
        errno_t rc;

        (void) arg;

        rc = clipboard_get_str(&str);
        if (rc != EOK)
                return;

        /* Make sure string only contains allowed characters */
        cp = str;
        while (*cp != '\0') {
                if (!isdigit(*cp) && *cp != '+' && *cp != '-' &&
                    *cp != '*' && *cp != '/')
                        return;
                ++cp;
        }

        /* Update expression */
        old = expr;
        expr = str;
        free(old);

        display_update();
}

static bool is_digit(char c)
{
        return ((c >= '0') && (c <= '9'));
}

static int get_digit(char c)
{
        assert(is_digit(c));

        return (c - '0');
}

static bool is_plus(char c)
{
        return (c == '+');
}

static bool is_minus(char c)
{
        return (c == '-');
}

static bool is_finish(char c)
{
        return (c == 0);
}

static operator_t get_operator(char c)
{
        switch (c) {
        case '+':
                return OPERATOR_ADD;
        case '-':
                return OPERATOR_SUB;
        case '*':
                return OPERATOR_MUL;
        case '/':
                return OPERATOR_DIV;
        default:
                return OPERATOR_NONE;
        }
}

static bool is_operator(char c)
{
        return (get_operator(c) != OPERATOR_NONE);
}

static bool stack_push_value(list_t *stack, int64_t value, bool value_neg)
{
        stack_item_t *item = malloc(sizeof(stack_item_t));
        if (!item)
                return false;

        link_initialize(&item->link);
        item->type = ITEM_VALUE;

        if (value_neg)
                item->data.value = -value;
        else
                item->data.value = value;

        list_prepend(&item->link, stack);

        return true;
}

static bool stack_push_operator(list_t *stack, operator_t operator)
{
        stack_item_t *item = malloc(sizeof(stack_item_t));
        if (!item)
                return false;

        link_initialize(&item->link);
        item->type = ITEM_OPERATOR;
        item->data.operator = operator;
        list_prepend(&item->link, stack);

        return true;
}

static bool stack_pop_value(list_t *stack, int64_t *value)
{
        link_t *link = list_first(stack);
        if (!link)
                return false;

        stack_item_t *item = list_get_instance(link, stack_item_t, link);
        if (item->type != ITEM_VALUE)
                return false;

        *value = item->data.value;

        list_remove(link);
        free(item);

        return true;
}

static bool stack_pop_operator(list_t *stack, operator_t *operator)
{
        link_t *link = list_first(stack);
        if (!link)
                return false;

        stack_item_t *item = list_get_instance(link, stack_item_t, link);
        if (item->type != ITEM_OPERATOR)
                return false;

        *operator = item->data.operator;

        list_remove(link);
        free(item);

        return true;
}

static void stack_cleanup(list_t *stack)
{
        while (!list_empty(stack)) {
                link_t *link = list_first(stack);
                if (link) {
                        stack_item_t *item = list_get_instance(link, stack_item_t,
                            link);

                        list_remove(link);
                        free(item);
                }
        }
}

static bool compute(int64_t a, operator_t operator, int64_t b, int64_t *value)
{
        switch (operator) {
        case OPERATOR_ADD:
                *value = a + b;
                break;
        case OPERATOR_SUB:
                *value = a - b;
                break;
        case OPERATOR_MUL:
                *value = a * b;
                break;
        case OPERATOR_DIV:
                if (b == 0)
                        return false;

                *value = a / b;
                break;
        default:
                return false;
        }

        return true;
}

static unsigned int get_priority(operator_t operator)
{
        switch (operator) {
        case OPERATOR_ADD:
                return 0;
        case OPERATOR_SUB:
                return 0;
        case OPERATOR_MUL:
                return 1;
        case OPERATOR_DIV:
                return 1;
        default:
                return 0;
        }
}

static void evaluate(list_t *stack, int64_t *value, parser_state_t *state,
    error_type_t *error_type)
{
        while (!list_empty(stack)) {
                if (!stack_pop_value(stack, value)) {
                        *state = STATE_ERROR;
                        *error_type = ERROR_SYNTAX;
                        break;
                }

                if (!list_empty(stack)) {
                        operator_t operator;
                        if (!stack_pop_operator(stack, &operator)) {
                                *state = STATE_ERROR;
                                *error_type = ERROR_SYNTAX;
                                break;
                        }

                        int64_t value_a;
                        if (!stack_pop_value(stack, &value_a)) {
                                *state = STATE_ERROR;
                                *error_type = ERROR_SYNTAX;
                                break;
                        }

                        if (!compute(value_a, operator, *value, value)) {
                                *state = STATE_ERROR;
                                *error_type = ERROR_NUMERIC;
                                break;
                        }

                        if (!stack_push_value(stack, *value, false)) {
                                *state = STATE_ERROR;
                                *error_type = ERROR_SYNTAX;
                                break;
                        }
                }
        }
}

static void display_update(void)
{
        if (expr != NULL)
                (void) ui_entry_set_text(display, (void *) expr);
        else
                (void) ui_entry_set_text(display, (void *) NULL_DISPLAY);

        ui_entry_paint(display);
}

static void display_error(error_type_t error_type)
{
        if (expr != NULL) {
                free(expr);
                expr = NULL;
        }

        switch (error_type) {
        case ERROR_SYNTAX:
                (void) ui_entry_set_text(display,
                    (void *) SYNTAX_ERROR_DISPLAY);
                break;
        case ERROR_NUMERIC:
                (void) ui_entry_set_text(display,
                    (void *) NUMERIC_ERROR_DISPLAY);
                break;
        default:
                (void) ui_entry_set_text(display,
                    (void *) UNKNOWN_ERROR_DISPLAY);
                break;
        }

        ui_entry_paint(display);
}

static void calc_pb_clicked(ui_pbutton_t *pbutton, void *arg)
{
        const char *subexpr = (const char *) arg;

        if (expr != NULL) {
                char *new_expr;

                if (str_length(expr) < EXPR_MAX_LEN) {
                        asprintf(&new_expr, "%s%s", expr, subexpr);
                        free(expr);
                        expr = new_expr;
                }
        } else {
                expr = str_dup(subexpr);
        }

        display_update();
}

static void calc_clear_clicked(ui_pbutton_t *pbutton, void *arg)
{
        if (expr != NULL) {
                free(expr);
                expr = NULL;
        }

        display_update();
}

static void calc_eval_clicked(ui_pbutton_t *pbutton, void *arg)
{
        if (expr == NULL)
                return;

        list_t stack;
        list_initialize(&stack);

        error_type_t error_type = ERROR_SYNTAX;
        size_t i = 0;
        parser_state_t state = STATE_INITIAL;
        int64_t value = 0;
        bool value_neg = false;
        operator_t last_operator = OPERATOR_NONE;

        while ((state != STATE_FINISH) && (state != STATE_ERROR)) {
                switch (state) {
                case STATE_INITIAL:
                        if (is_digit(expr[i])) {
                                value = get_digit(expr[i]);
                                i++;
                                state = STATE_VALUE;
                        } else if (is_plus(expr[i])) {
                                i++;
                                value_neg = false;
                                state = STATE_DIGIT;
                        } else if (is_minus(expr[i])) {
                                i++;
                                value_neg = true;
                                state = STATE_DIGIT;
                        } else
                                state = STATE_ERROR;
                        break;

                case STATE_DIGIT:
                        if (is_digit(expr[i])) {
                                value = get_digit(expr[i]);
                                i++;
                                state = STATE_VALUE;
                        } else
                                state = STATE_ERROR;
                        break;

                case STATE_VALUE:
                        if (is_digit(expr[i])) {
                                value *= 10;
                                value += get_digit(expr[i]);
                                i++;
                        } else if (is_operator(expr[i])) {
                                if (!stack_push_value(&stack, value, value_neg)) {
                                        state = STATE_ERROR;
                                        break;
                                }

                                value = 0;
                                value_neg = false;

                                operator_t operator = get_operator(expr[i]);

                                if (get_priority(operator) <= get_priority(last_operator)) {
                                        evaluate(&stack, &value, &state, &error_type);
                                        if (state == STATE_ERROR)
                                                break;

                                        if (!stack_push_value(&stack, value, value_neg)) {
                                                state = STATE_ERROR;
                                                break;
                                        }
                                }

                                if (!stack_push_operator(&stack, operator)) {
                                        state = STATE_ERROR;
                                        break;
                                }

                                last_operator = operator;
                                i++;
                                state = STATE_DIGIT;
                        } else if (is_finish(expr[i])) {
                                if (!stack_push_value(&stack, value, value_neg)) {
                                        state = STATE_ERROR;
                                        break;
                                }

                                state = STATE_FINISH;
                        } else
                                state = STATE_ERROR;
                        break;

                default:
                        state = STATE_ERROR;
                }
        }

        evaluate(&stack, &value, &state, &error_type);
        stack_cleanup(&stack);

        if (state == STATE_ERROR) {
                display_error(error_type);
                return;
        }

        free(expr);
        asprintf(&expr, "%" PRId64, value);
        display_update();
}

static errno_t calc_button_create(calc_t *calc, ui_fixed_t *fixed,
    int x, int y, const char *text, ui_pbutton_cb_t *cb, void *arg,
    ui_pbutton_t **rbutton)
{
        ui_pbutton_t *pb;
        gfx_rect_t rect;
        errno_t rc;

        rc = ui_pbutton_create(calc->ui_res, text, &pb);
        if (rc != EOK) {
                printf("Error creating button.\n");
                return rc;
        }

        ui_pbutton_set_cb(pb, cb, arg);

        rect.p0.x = calc->geom.btn_orig.x + calc->geom.btn_stride.x * x;
        rect.p0.y = calc->geom.btn_orig.y + calc->geom.btn_stride.y * y;
        rect.p1.x = rect.p0.x + calc->geom.btn_dim.x;
        rect.p1.y = rect.p0.y + calc->geom.btn_dim.y;
        ui_pbutton_set_rect(pb, &rect);

        rc = ui_fixed_add(fixed, ui_pbutton_ctl(pb));
        if (rc != EOK) {
                printf("Error adding control to layout.\n");
                return rc;
        }

        if (rbutton != NULL)
                *rbutton = pb;
        return EOK;
}

static void print_syntax(void)
{
        printf("Syntax: %s [-d <display-spec>]\n", NAME);
}

int main(int argc, char *argv[])
{
        const char *display_spec = UI_DISPLAY_DEFAULT;
        ui_t *ui;
        ui_resource_t *ui_res;
        ui_fixed_t *fixed;
        ui_wnd_params_t params;
        ui_window_t *window;
        ui_menu_t *mfile;
        ui_menu_entry_t *mexit;
        ui_menu_t *medit;
        ui_menu_entry_t *mcopy;
        ui_menu_entry_t *mpaste;
        calc_t calc;
        errno_t rc;
        int i;

        i = 1;
        while (i < argc) {
                if (str_cmp(argv[i], "-d") == 0) {
                        ++i;
                        if (i >= argc) {
                                printf("Argument missing.\n");
                                print_syntax();
                                return 1;
                        }

                        display_spec = argv[i++];
                } else {
                        printf("Invalid option '%s'.\n", argv[i]);
                        print_syntax();
                        return 1;
                }
        }

        rc = ui_create(display_spec, &ui);
        if (rc != EOK) {
                printf("Error creating UI on display %s.\n", display_spec);
                return rc;
        }

        ui_wnd_params_init(&params);
        params.caption = "Calculator";
        params.rect.p0.x = 0;
        params.rect.p0.y = 0;

        if (ui_is_textmode(ui)) {
                params.rect.p1.x = 38;
                params.rect.p1.y = 18;

                calc.geom.menubar_rect.p0.x = 1;
                calc.geom.menubar_rect.p0.y = 1;
                calc.geom.menubar_rect.p1.x = params.rect.p1.x - 1;
                calc.geom.menubar_rect.p1.y = 2;
                calc.geom.entry_rect.p0.x = 4;
                calc.geom.entry_rect.p0.y = 3;
                calc.geom.entry_rect.p1.x = 34;
                calc.geom.entry_rect.p1.y = 4;
                calc.geom.btn_orig.x = 4;
                calc.geom.btn_orig.y = 5;
                calc.geom.btn_dim.x = 6;
                calc.geom.btn_dim.y = 2;
                calc.geom.btn_stride.x = 8;
                calc.geom.btn_stride.y = 3;
        } else {
                params.rect.p1.x = 250;
                params.rect.p1.y = 270;

                calc.geom.menubar_rect.p0.x = 4;
                calc.geom.menubar_rect.p0.y = 30;
                calc.geom.menubar_rect.p1.x = params.rect.p1.x - 4;
                calc.geom.menubar_rect.p1.y = 52;
                calc.geom.entry_rect.p0.x = 10;
                calc.geom.entry_rect.p0.y = 51;
                calc.geom.entry_rect.p1.x = 240;
                calc.geom.entry_rect.p1.y = 76;
                calc.geom.btn_orig.x = 10;
                calc.geom.btn_orig.y = 90;
                calc.geom.btn_dim.x = 50;
                calc.geom.btn_dim.y = 35;
                calc.geom.btn_stride.x = 60;
                calc.geom.btn_stride.y = 45;
        }

        rc = ui_window_create(ui, &params, &window);
        if (rc != EOK) {
                printf("Error creating window.\n");
                return rc;
        }

        ui_window_set_cb(window, &window_cb, (void *) &calc);
        calc.ui = ui;

        ui_res = ui_window_get_res(window);
        calc.ui_res = ui_res;

        rc = ui_fixed_create(&fixed);
        if (rc != EOK) {
                printf("Error creating fixed layout.\n");
                return rc;
        }

        rc = ui_menu_bar_create(ui, window, &calc.menubar);
        if (rc != EOK) {
                printf("Error creating menu bar.\n");
                return rc;
        }

        rc = ui_menu_create(calc.menubar, "File", &mfile);
        if (rc != EOK) {
                printf("Error creating menu.\n");
                return rc;
        }

        rc = ui_menu_entry_create(mfile, "Exit", "Alt-F4", &mexit);
        if (rc != EOK) {
                printf("Error creating menu.\n");
                return rc;
        }

        ui_menu_entry_set_cb(mexit, calc_file_exit, (void *) &calc);

        rc = ui_menu_create(calc.menubar, "Edit", &medit);
        if (rc != EOK) {
                printf("Error creating menu.\n");
                return rc;
        }

        rc = ui_menu_entry_create(medit, "Copy", "Ctrl-C", &mcopy);
        if (rc != EOK) {
                printf("Error creating menu.\n");
                return rc;
        }

        ui_menu_entry_set_cb(mcopy, calc_edit_copy, (void *) &calc);

        rc = ui_menu_entry_create(medit, "Paste", "Ctrl-V", &mpaste);
        if (rc != EOK) {
                printf("Error creating menu.\n");
                return rc;
        }

        ui_menu_entry_set_cb(mpaste, calc_edit_paste, (void *) &calc);

        ui_menu_bar_set_rect(calc.menubar, &calc.geom.menubar_rect);

        rc = ui_fixed_add(fixed, ui_menu_bar_ctl(calc.menubar));
        if (rc != EOK) {
                printf("Error adding control to layout.\n");
                return rc;
        }

        rc = ui_entry_create(window, NULL_DISPLAY, &display);
        if (rc != EOK) {
                printf("Error creating text lentry.\n");
                return rc;
        }

        ui_entry_set_rect(display, &calc.geom.entry_rect);
        ui_entry_set_halign(display, gfx_halign_right);
        ui_entry_set_read_only(display, true);

        rc = ui_fixed_add(fixed, ui_entry_ctl(display));
        if (rc != EOK) {
                printf("Error adding control to layout.\n");
                return rc;
        }

        rc = calc_button_create(&calc, fixed, 0, 0, "7", &calc_pbutton_cb,
            (void *) "7", &calc.btn_7);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 1, 0, "8", &calc_pbutton_cb,
            (void *) "8", &calc.btn_8);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 2, 0, "9", &calc_pbutton_cb,
            (void *) "9", &calc.btn_9);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 3, 0, "/", &calc_pbutton_cb,
            (void *) "/", &calc.btn_div);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 0, 1, "4", &calc_pbutton_cb,
            (void *) "4", &calc.btn_4);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 1, 1, "5", &calc_pbutton_cb,
            (void *) "5", &calc.btn_5);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 2, 1, "6", &calc_pbutton_cb,
            (void *) "6", &calc.btn_6);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 3, 1, "*", &calc_pbutton_cb,
            (void *) "*", &calc.btn_mul);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 0, 2, "1", &calc_pbutton_cb,
            (void *) "1", &calc.btn_1);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 1, 2, "2", &calc_pbutton_cb,
            (void *) "2", &calc.btn_2);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 2, 2, "3", &calc_pbutton_cb,
            (void *) "3", &calc.btn_3);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 3, 2, "-", &calc_pbutton_cb,
            (void *) "-", &calc.btn_sub);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 0, 3, "0", &calc_pbutton_cb,
            (void *) "0", &calc.btn_0);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 1, 3, "C", &calc_clear_cb,
            (void *) "C", &calc.btn_clear);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 2, 3, "=", &calc_eval_cb,
            (void *) "=", &calc.btn_eval);
        if (rc != EOK)
                return rc;

        rc = calc_button_create(&calc, fixed, 3, 3, "+", &calc_pbutton_cb,
            (void *) "+", &calc.btn_add);
        if (rc != EOK)
                return rc;

        ui_pbutton_set_default(calc.btn_eval, true);

        ui_window_add(window, ui_fixed_ctl(fixed));

        rc = ui_window_paint(window);
        if (rc != EOK) {
                printf("Error painting window.\n");
                return rc;
        }

        ui_run(ui);
        ui_window_destroy(window);
        ui_destroy(ui);

        return 0;
}