source: mainline/uspace/app/edit/edit.c@ 79ae36dd

/*
 * Copyright (c) 2009 Jiri Svoboda
 * 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 edit
 * @brief Text editor.
 * @{
 */
/**
 * @file
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <vfs/vfs.h>
#include <io/console.h>
#include <io/style.h>
#include <io/keycode.h>
#include <errno.h>
#include <align.h>
#include <macros.h>
#include <clipboard.h>
#include <bool.h>

#include "sheet.h"

enum redraw_flags {
        REDRAW_TEXT     = (1 << 0),
        REDRAW_ROW      = (1 << 1),
        REDRAW_STATUS   = (1 << 2),
        REDRAW_CARET    = (1 << 3)
};

/** Pane
 *
 * A rectangular area of the screen used to edit a document. Different
 * panes can be possibly used to edit the same document.
 */
typedef struct {
        /* Pane dimensions */
        int rows, columns;

        /* Position of the visible area */
        int sh_row, sh_column;

        /** Bitmask of components that need redrawing */
        enum redraw_flags rflags;

        /** Current position of the caret */
        tag_t caret_pos;

        /** Start of selection */
        tag_t sel_start;

        /** 
         * Ideal column where the caret should try to get. This is used
         * for maintaining the same column during vertical movement.
         */
        int ideal_column;
} pane_t;

/** Document
 *
 * Associates a sheet with a file where it can be saved to.
 */
typedef struct {
        char *file_name;
        sheet_t sh;
} doc_t;

static console_ctrl_t *con;
static doc_t doc;
static bool done;
static pane_t pane;
static bool cursor_visible;

static sysarg_t scr_rows;
static sysarg_t scr_columns;

#define ROW_BUF_SIZE 4096
#define BUF_SIZE 64
#define TAB_WIDTH 8
#define ED_INFTY 65536

/** Maximum filename length that can be entered. */
#define INFNAME_MAX_LEN 128

static void cursor_show(void);
static void cursor_hide(void);
static void cursor_setvis(bool visible);

static void key_handle_unmod(kbd_event_t const *ev);
static void key_handle_ctrl(kbd_event_t const *ev);
static void key_handle_shift(kbd_event_t const *ev);
static void key_handle_movement(unsigned int key, bool shift);

static int file_save(char const *fname);
static void file_save_as(void);
static int file_insert(char *fname);
static int file_save_range(char const *fname, spt_t const *spos,
    spt_t const *epos);
static char *filename_prompt(char const *prompt, char const *init_value);
static char *range_get_str(spt_t const *spos, spt_t const *epos);

static void pane_text_display(void);
static void pane_row_display(void);
static void pane_row_range_display(int r0, int r1);
static void pane_status_display(void);
static void pane_caret_display(void);

static void insert_char(wchar_t c);
static void delete_char_before(void);
static void delete_char_after(void);
static void caret_update(void);
static void caret_move(int drow, int dcolumn, enum dir_spec align_dir);

static bool selection_active(void);
static void selection_sel_all(void);
static void selection_get_points(spt_t *pa, spt_t *pb);
static void selection_delete(void);
static void selection_copy(void);
static void insert_clipboard_data(void);

static void pt_get_sof(spt_t *pt);
static void pt_get_eof(spt_t *pt);
static int tag_cmp(tag_t const *a, tag_t const *b);
static int spt_cmp(spt_t const *a, spt_t const *b);
static int coord_cmp(coord_t const *a, coord_t const *b);

static void status_display(char const *str);


int main(int argc, char *argv[])
{
        kbd_event_t ev;
        coord_t coord;
        bool new_file;

        spt_t pt;

        con = console_init(stdin, stdout);
        console_clear(con);

        console_get_size(con, &scr_columns, &scr_rows);

        pane.rows = scr_rows - 1;
        pane.columns = scr_columns;
        pane.sh_row = 1;
        pane.sh_column = 1;

        /* Start with an empty sheet. */
        sheet_init(&doc.sh);

        /* Place caret at the beginning of file. */
        coord.row = coord.column = 1;
        sheet_get_cell_pt(&doc.sh, &coord, dir_before, &pt);
        sheet_place_tag(&doc.sh, &pt, &pane.caret_pos);
        pane.ideal_column = coord.column;

        if (argc == 2) {
                doc.file_name = str_dup(argv[1]);
        } else if (argc > 1) {
                printf("Invalid arguments.\n");
                return -2;
        } else {
                doc.file_name = NULL;
        }

        new_file = false;

        if (doc.file_name == NULL || file_insert(doc.file_name) != EOK)
                new_file = true;

        /* Move to beginning of file. */
        caret_move(-ED_INFTY, -ED_INFTY, dir_before);

        /* Place selection start tag. */
        tag_get_pt(&pane.caret_pos, &pt);
        sheet_place_tag(&doc.sh, &pt, &pane.sel_start);

        /* Initial display */
        cursor_visible = true;

        cursor_hide();
        console_clear(con);
        pane_text_display();
        pane_status_display();
        if (new_file && doc.file_name != NULL)
                status_display("File not found. Starting empty file.");
        pane_caret_display();
        cursor_show();

        done = false;

        while (!done) {
                console_get_kbd_event(con, &ev);
                pane.rflags = 0;

                if (ev.type == KEY_PRESS) {
                        /* Handle key press. */
                        if (((ev.mods & KM_ALT) == 0) &&
                            ((ev.mods & KM_SHIFT) == 0) &&
                             (ev.mods & KM_CTRL) != 0) {
                                key_handle_ctrl(&ev);
                        } else if (((ev.mods & KM_ALT) == 0) &&
                            ((ev.mods & KM_CTRL) == 0) &&
                             (ev.mods & KM_SHIFT) != 0) {
                                key_handle_shift(&ev);
                        } else if ((ev.mods & (KM_CTRL | KM_ALT | KM_SHIFT)) == 0) {
                                key_handle_unmod(&ev);
                        }
                }

                /* Redraw as necessary. */

                cursor_hide();

                if (pane.rflags & REDRAW_TEXT)
                        pane_text_display();
                if (pane.rflags & REDRAW_ROW)
                        pane_row_display();
                if (pane.rflags & REDRAW_STATUS)
                        pane_status_display();
                if (pane.rflags & REDRAW_CARET)
                        pane_caret_display();

                cursor_show();
        }

        console_clear(con);

        return 0;
}

static void cursor_show(void)
{
        cursor_setvis(true);
}

static void cursor_hide(void)
{
        cursor_setvis(false);
}

static void cursor_setvis(bool visible)
{
        if (cursor_visible != visible) {
                console_cursor_visibility(con, visible);
                cursor_visible = visible;
        }
}

/** Handle key without modifier. */
static void key_handle_unmod(kbd_event_t const *ev)
{
        switch (ev->key) {
        case KC_ENTER:
                selection_delete();
                insert_char('\n');
                caret_update();
                break;
        case KC_LEFT:
        case KC_RIGHT:
        case KC_UP:
        case KC_DOWN:
        case KC_HOME:
        case KC_END:
        case KC_PAGE_UP:
        case KC_PAGE_DOWN:
                key_handle_movement(ev->key, false);
                break;
        case KC_BACKSPACE:
                if (selection_active())
                        selection_delete();
                else
                        delete_char_before();
                caret_update();
                break;
        case KC_DELETE:
                if (selection_active())
                        selection_delete();
                else
                        delete_char_after();
                caret_update();
                break;
        default:
                if (ev->c >= 32 || ev->c == '\t') {
                        selection_delete();
                        insert_char(ev->c);
                        caret_update();
                }
                break;
        }
}

/** Handle Shift-key combination. */
static void key_handle_shift(kbd_event_t const *ev)
{
        switch (ev->key) {
        case KC_LEFT:
        case KC_RIGHT:
        case KC_UP:
        case KC_DOWN:
        case KC_HOME:
        case KC_END:
        case KC_PAGE_UP:
        case KC_PAGE_DOWN:
                key_handle_movement(ev->key, true);
                break;
        default:
                if (ev->c >= 32 || ev->c == '\t') {
                        selection_delete();
                        insert_char(ev->c);
                        caret_update();
                }
                break;
        }
}

/** Handle Ctrl-key combination. */
static void key_handle_ctrl(kbd_event_t const *ev)
{
        switch (ev->key) {
        case KC_Q:
                done = true;
                break;
        case KC_S:
                if (doc.file_name != NULL)
                        file_save(doc.file_name);
                else
                        file_save_as();
                break;
        case KC_E:
                file_save_as();
                break;
        case KC_C:
                selection_copy();
                break;
        case KC_V:
                selection_delete();
                insert_clipboard_data();
                pane.rflags |= REDRAW_TEXT;
                caret_update();
                break;
        case KC_X:
                selection_copy();
                selection_delete();
                pane.rflags |= REDRAW_TEXT;
                caret_update();
                break;
        case KC_A:
                selection_sel_all();
                break;
        default:
                break;
        }
}

static void key_handle_movement(unsigned int key, bool select)
{
        spt_t pt;
        spt_t caret_pt;
        coord_t c_old, c_new;
        bool had_sel;

        /* Check if we had selection before. */
        tag_get_pt(&pane.caret_pos, &caret_pt);
        tag_get_pt(&pane.sel_start, &pt);
        had_sel = !spt_equal(&caret_pt, &pt);

        switch (key) {
        case KC_LEFT:
                caret_move(0, -1, dir_before);
                break;
        case KC_RIGHT:
                caret_move(0, 0, dir_after);
                break;
        case KC_UP:
                caret_move(-1, 0, dir_before);
                break;
        case KC_DOWN:
                caret_move(+1, 0, dir_before);
                break;
        case KC_HOME:
                caret_move(0, -ED_INFTY, dir_before);
                break;
        case KC_END:
                caret_move(0, +ED_INFTY, dir_before);
                break;
        case KC_PAGE_UP:
                caret_move(-pane.rows, 0, dir_before);
                break;
        case KC_PAGE_DOWN:
                caret_move(+pane.rows, 0, dir_before);
                break;
        default:
                break;
        }

        if (select == false) {
                /* Move sel_start to the same point as caret. */
                sheet_remove_tag(&doc.sh, &pane.sel_start);
                tag_get_pt(&pane.caret_pos, &pt);
                sheet_place_tag(&doc.sh, &pt, &pane.sel_start);
        }

        if (select) {
                tag_get_pt(&pane.caret_pos, &pt);
                spt_get_coord(&caret_pt, &c_old);
                spt_get_coord(&pt, &c_new);

                if (c_old.row == c_new.row)
                        pane.rflags |= REDRAW_ROW;
                else
                        pane.rflags |= REDRAW_TEXT;

        } else if (had_sel == true) {
                /* Redraw because text was unselected. */
                pane.rflags |= REDRAW_TEXT;
        }
}

/** Save the document. */
static int file_save(char const *fname)
{
        spt_t sp, ep;
        int rc;

        status_display("Saving...");
        pt_get_sof(&sp);
        pt_get_eof(&ep);

        rc = file_save_range(fname, &sp, &ep);

        switch (rc) {
        case EINVAL:
                status_display("Error opening file!");
                break;
        case EIO:
                status_display("Error writing data!");
                break;
        default:
                status_display("File saved.");
                break;
        }

        return rc;
}

/** Change document name and save. */
static void file_save_as(void)
{
        const char *old_fname = (doc.file_name != NULL) ? doc.file_name : "";
        char *fname;
        
        fname = filename_prompt("Save As", old_fname);
        if (fname == NULL) {
                status_display("Save cancelled.");
                return;
        }

        int rc = file_save(fname);
        if (rc != EOK)
                return;

        if (doc.file_name != NULL)
                free(doc.file_name);
        doc.file_name = fname;
}

/** Ask for a file name. */
static char *filename_prompt(char const *prompt, char const *init_value)
{
        kbd_event_t ev;
        char *str;
        wchar_t buffer[INFNAME_MAX_LEN + 1];
        int max_len;
        int nc;
        bool done;

        asprintf(&str, "%s: %s", prompt, init_value);
        status_display(str);
        console_set_pos(con, 1 + str_length(str), scr_rows - 1);
        free(str);

        console_set_style(con, STYLE_INVERTED);

        max_len = min(INFNAME_MAX_LEN, scr_columns - 4 - str_length(prompt));
        str_to_wstr(buffer, max_len + 1, init_value);
        nc = wstr_length(buffer);
        done = false;

        while (!done) {
                console_get_kbd_event(con, &ev);

                if (ev.type == KEY_PRESS) {
                        /* Handle key press. */
                        if (((ev.mods & KM_ALT) == 0) &&
                             (ev.mods & KM_CTRL) != 0) {
                                ;
                        } else if ((ev.mods & (KM_CTRL | KM_ALT)) == 0) {
                                switch (ev.key) {
                                case KC_ESCAPE:
                                        return NULL;
                                case KC_BACKSPACE:
                                        if (nc > 0) {
                                                putchar('\b');
                                                console_flush(con);
                                                --nc;
                                        }
                                        break;
                                case KC_ENTER:
                                        done = true;
                                        break;
                                default:
                                        if (ev.c >= 32 && nc < max_len) {
                                                putchar(ev.c);
                                                console_flush(con);
                                                buffer[nc++] = ev.c;
                                        }
                                        break;
                                }
                        }
                }
        }

        buffer[nc] = '\0';
        str = wstr_to_astr(buffer);

        console_set_style(con, STYLE_NORMAL);

        return str;
}

/** Insert file at caret position.
 *
 * Reads in the contents of a file and inserts them at the current position
 * of the caret.
 */
static int file_insert(char *fname)
{
        FILE *f;
        wchar_t c;
        char buf[BUF_SIZE];
        int bcnt;
        int n_read;
        size_t off;

        f = fopen(fname, "rt");
        if (f == NULL)
                return EINVAL;

        bcnt = 0;

        while (true) {
                if (bcnt < STR_BOUNDS(1)) {
                        n_read = fread(buf + bcnt, 1, BUF_SIZE - bcnt, f);
                        bcnt += n_read;
                }

                off = 0;
                c = str_decode(buf, &off, bcnt);
                if (c == '\0')
                        break;

                bcnt -= off;
                memcpy(buf, buf + off, bcnt);

                insert_char(c);
        }

        fclose(f);

        return EOK;
}

/** Save a range of text into a file. */
static int file_save_range(char const *fname, spt_t const *spos,
    spt_t const *epos)
{
        FILE *f;
        char buf[BUF_SIZE];
        spt_t sp, bep;
        size_t bytes, n_written;

        f = fopen(fname, "wt");
        if (f == NULL)
                return EINVAL;

        sp = *spos;

        do {
                sheet_copy_out(&doc.sh, &sp, epos, buf, BUF_SIZE, &bep);
                bytes = str_size(buf);

                n_written = fwrite(buf, 1, bytes, f);
                if (n_written != bytes) {
                        return EIO;
                }

                sp = bep;
        } while (!spt_equal(&bep, epos));

        if (fclose(f) != EOK)
                return EIO;

        return EOK;
}

/** Return contents of range as a new string. */
static char *range_get_str(spt_t const *spos, spt_t const *epos)
{
        char *buf;
        spt_t sp, bep;
        size_t bytes;
        size_t buf_size, bpos;

        buf_size = 1;

        buf = malloc(buf_size);
        if (buf == NULL)
                return NULL;

        bpos = 0;
        sp = *spos;

        while (true) {
                sheet_copy_out(&doc.sh, &sp, epos, &buf[bpos], buf_size - bpos,
                    &bep);
                bytes = str_size(&buf[bpos]);
                bpos += bytes;
                sp = bep;

                if (spt_equal(&bep, epos))
                        break;

                buf_size *= 2;
                buf = realloc(buf, buf_size);
                if (buf == NULL)
                        return NULL;
        }

        return buf;
}

static void pane_text_display(void)
{
        int sh_rows, rows;

        sheet_get_num_rows(&doc.sh, &sh_rows);
        rows = min(sh_rows - pane.sh_row + 1, pane.rows);

        /* Draw rows from the sheet. */

        console_set_pos(con, 0, 0);
        pane_row_range_display(0, rows);

        /* Clear the remaining rows if file is short. */
        
        int i;
        sysarg_t j;
        for (i = rows; i < pane.rows; ++i) {
                console_set_pos(con, 0, i);
                for (j = 0; j < scr_columns; ++j)
                        putchar(' ');
                console_flush(con);
        }

        pane.rflags |= (REDRAW_STATUS | REDRAW_CARET);
        pane.rflags &= ~REDRAW_ROW;
}

/** Display just the row where the caret is. */
static void pane_row_display(void)
{
        spt_t caret_pt;
        coord_t coord;
        int ridx;

        tag_get_pt(&pane.caret_pos, &caret_pt);
        spt_get_coord(&caret_pt, &coord);

        ridx = coord.row - pane.sh_row;
        pane_row_range_display(ridx, ridx + 1);
        pane.rflags |= (REDRAW_STATUS | REDRAW_CARET);
}

static void pane_row_range_display(int r0, int r1)
{
        int i, j, fill;
        spt_t rb, re, dep, pt;
        coord_t rbc, rec;
        char row_buf[ROW_BUF_SIZE];
        wchar_t c;
        size_t pos, size;
        int s_column;
        coord_t csel_start, csel_end, ctmp;

        /* Determine selection start and end. */

        tag_get_pt(&pane.sel_start, &pt);
        spt_get_coord(&pt, &csel_start);

        tag_get_pt(&pane.caret_pos, &pt);
        spt_get_coord(&pt, &csel_end);

        if (coord_cmp(&csel_start, &csel_end) > 0) {
                ctmp = csel_start;
                csel_start = csel_end;
                csel_end = ctmp;
        }

        /* Draw rows from the sheet. */

        console_set_pos(con, 0, 0);
        for (i = r0; i < r1; ++i) {
                /* Starting point for row display */
                rbc.row = pane.sh_row + i;
                rbc.column = pane.sh_column;
                sheet_get_cell_pt(&doc.sh, &rbc, dir_before, &rb);

                /* Ending point for row display */
                rec.row = pane.sh_row + i;
                rec.column = pane.sh_column + pane.columns;
                sheet_get_cell_pt(&doc.sh, &rec, dir_before, &re);

                /* Copy the text of the row to the buffer. */
                sheet_copy_out(&doc.sh, &rb, &re, row_buf, ROW_BUF_SIZE, &dep);

                /* Display text from the buffer. */

                if (coord_cmp(&csel_start, &rbc) <= 0 &&
                    coord_cmp(&rbc, &csel_end) < 0) {
                        console_flush(con);
                        console_set_style(con, STYLE_SELECTED);
                        console_flush(con);
                }

                console_set_pos(con, 0, i);
                size = str_size(row_buf);
                pos = 0;
                s_column = pane.sh_column;
                while (pos < size) {
                        if ((csel_start.row == rbc.row) && (csel_start.column == s_column)) {
                                console_flush(con);
                                console_set_style(con, STYLE_SELECTED);
                                console_flush(con);
                        }
        
                        if ((csel_end.row == rbc.row) && (csel_end.column == s_column)) {
                                console_flush(con);
                                console_set_style(con, STYLE_NORMAL);
                                console_flush(con);
                        }
        
                        c = str_decode(row_buf, &pos, size);
                        if (c != '\t') {
                                printf("%lc", (wint_t) c);
                                s_column += 1;
                        } else {
                                fill = 1 + ALIGN_UP(s_column, TAB_WIDTH)
                                    - s_column;

                                for (j = 0; j < fill; ++j)
                                        putchar(' ');
                                s_column += fill;
                        }
                }

                if ((csel_end.row == rbc.row) && (csel_end.column == s_column)) {
                        console_flush(con);
                        console_set_style(con, STYLE_NORMAL);
                        console_flush(con);
                }

                /* Fill until the end of display area. */

                if (str_length(row_buf) < (unsigned) scr_columns)
                        fill = scr_columns - str_length(row_buf);
                else
                        fill = 0;

                for (j = 0; j < fill; ++j)
                        putchar(' ');
                console_flush(con);
                console_set_style(con, STYLE_NORMAL);
        }

        pane.rflags |= REDRAW_CARET;
}

/** Display pane status in the status line. */
static void pane_status_display(void)
{
        spt_t caret_pt;
        coord_t coord;

        tag_get_pt(&pane.caret_pos, &caret_pt);
        spt_get_coord(&caret_pt, &coord);

        const char *fname = (doc.file_name != NULL) ? doc.file_name : "<unnamed>";

        console_set_pos(con, 0, scr_rows - 1);
        console_set_style(con, STYLE_INVERTED);
        int n = printf(" %d, %d: File '%s'. Ctrl-Q Quit  Ctrl-S Save  "
            "Ctrl-E Save As", coord.row, coord.column, fname);
        
        int pos = scr_columns - 1 - n;
        printf("%*s", pos, "");
        console_flush(con);
        console_set_style(con, STYLE_NORMAL);

        pane.rflags |= REDRAW_CARET;
}

/** Set cursor to reflect position of the caret. */
static void pane_caret_display(void)
{
        spt_t caret_pt;
        coord_t coord;

        tag_get_pt(&pane.caret_pos, &caret_pt);

        spt_get_coord(&caret_pt, &coord);
        console_set_pos(con, coord.column - pane.sh_column,
            coord.row - pane.sh_row);
}

/** Insert a character at caret position. */
static void insert_char(wchar_t c)
{
        spt_t pt;
        char cbuf[STR_BOUNDS(1) + 1];
        size_t offs;

        tag_get_pt(&pane.caret_pos, &pt);

        offs = 0;
        chr_encode(c, cbuf, &offs, STR_BOUNDS(1) + 1);
        cbuf[offs] = '\0';

        (void) sheet_insert(&doc.sh, &pt, dir_before, cbuf);

        pane.rflags |= REDRAW_ROW;
        if (c == '\n')
                pane.rflags |= REDRAW_TEXT;
}

/** Delete the character before the caret. */
static void delete_char_before(void)
{
        spt_t sp, ep;
        coord_t coord;

        tag_get_pt(&pane.caret_pos, &ep);
        spt_get_coord(&ep, &coord);

        coord.column -= 1;
        sheet_get_cell_pt(&doc.sh, &coord, dir_before, &sp);

        (void) sheet_delete(&doc.sh, &sp, &ep);

        pane.rflags |= REDRAW_ROW;
        if (coord.column < 1)
                pane.rflags |= REDRAW_TEXT;
}

/** Delete the character after the caret. */
static void delete_char_after(void)
{
        spt_t sp, ep;
        coord_t sc, ec;

        tag_get_pt(&pane.caret_pos, &sp);
        spt_get_coord(&sp, &sc);

        sheet_get_cell_pt(&doc.sh, &sc, dir_after, &ep);
        spt_get_coord(&ep, &ec);

        (void) sheet_delete(&doc.sh, &sp, &ep);

        pane.rflags |= REDRAW_ROW;
        if (ec.row != sc.row)
                pane.rflags |= REDRAW_TEXT;
}

/** Scroll pane after caret has moved.
 *
 * After modifying the position of the caret, this is called to scroll
 * the pane to ensure that the caret is in the visible area.
 */
static void caret_update(void)
{
        spt_t pt;
        coord_t coord;

        tag_get_pt(&pane.caret_pos, &pt);
        spt_get_coord(&pt, &coord);

        /* Scroll pane vertically. */

        if (coord.row < pane.sh_row) {
                pane.sh_row = coord.row;
                pane.rflags |= REDRAW_TEXT;
        }

        if (coord.row > pane.sh_row + pane.rows - 1) {
                pane.sh_row = coord.row - pane.rows + 1;
                pane.rflags |= REDRAW_TEXT;
        }

        /* Scroll pane horizontally. */

        if (coord.column < pane.sh_column) {
                pane.sh_column = coord.column;
                pane.rflags |= REDRAW_TEXT;
        }

        if (coord.column > pane.sh_column + pane.columns - 1) {
                pane.sh_column = coord.column - pane.columns + 1;
                pane.rflags |= REDRAW_TEXT;
        }

        pane.rflags |= (REDRAW_CARET | REDRAW_STATUS);
}

/** Change the caret position.
 *
 * Moves caret relatively to the current position. Looking at the first
 * character cell after the caret and moving by @a drow and @a dcolumn, we get
 * to a new character cell, and thus a new character. Then we either go to the
 * point before the the character or after it, depending on @a align_dir.
 */
static void caret_move(int drow, int dcolumn, enum dir_spec align_dir)
{
        spt_t pt;
        coord_t coord;
        int num_rows;
        bool pure_vertical;

        tag_get_pt(&pane.caret_pos, &pt);
        spt_get_coord(&pt, &coord);
        coord.row += drow; coord.column += dcolumn;

        /* Clamp coordinates. */
        if (drow < 0 && coord.row < 1) coord.row = 1;
        if (dcolumn < 0 && coord.column < 1) coord.column = 1;
        if (drow > 0) {
                sheet_get_num_rows(&doc.sh, &num_rows);
                if (coord.row > num_rows) coord.row = num_rows;
        }

        /* For purely vertical movement try attaining @c ideal_column. */
        pure_vertical = (dcolumn == 0 && align_dir == dir_before);
        if (pure_vertical)
                coord.column = pane.ideal_column;

        /*
         * Select the point before or after the character at the designated
         * coordinates. The character can be wider than one cell (e.g. tab).
         */
        sheet_get_cell_pt(&doc.sh, &coord, align_dir, &pt);
        sheet_remove_tag(&doc.sh, &pane.caret_pos);
        sheet_place_tag(&doc.sh, &pt, &pane.caret_pos);

        /* For non-vertical movement set the new value for @c ideal_column. */
        if (!pure_vertical) {
                spt_get_coord(&pt, &coord);
                pane.ideal_column = coord.column;
        }

        caret_update();
}

/** Check for non-empty selection. */
static bool selection_active(void)
{
        return (tag_cmp(&pane.caret_pos, &pane.sel_start) != 0);
}

static void selection_get_points(spt_t *pa, spt_t *pb)
{
        spt_t pt;

        tag_get_pt(&pane.sel_start, pa);
        tag_get_pt(&pane.caret_pos, pb);

        if (spt_cmp(pa, pb) > 0) {
                pt = *pa;
                *pa = *pb;
                *pb = pt;
        }
}

/** Delete selected text. */
static void selection_delete(void)
{
        spt_t pa, pb;
        coord_t ca, cb;
        int rel;

        tag_get_pt(&pane.sel_start, &pa);
        tag_get_pt(&pane.caret_pos, &pb);
        spt_get_coord(&pa, &ca);
        spt_get_coord(&pb, &cb);
        rel = coord_cmp(&ca, &cb);

        if (rel == 0)
                return;

        if (rel < 0)
                sheet_delete(&doc.sh, &pa, &pb);
        else
                sheet_delete(&doc.sh, &pb, &pa);

        if (ca.row == cb.row)
                pane.rflags |= REDRAW_ROW;
        else
                pane.rflags |= REDRAW_TEXT;
}

static void selection_sel_all(void)
{
        spt_t spt, ept;

        pt_get_sof(&spt);
        pt_get_eof(&ept);
        sheet_remove_tag(&doc.sh, &pane.sel_start);
        sheet_place_tag(&doc.sh, &spt, &pane.sel_start);
        sheet_remove_tag(&doc.sh, &pane.caret_pos);
        sheet_place_tag(&doc.sh, &ept, &pane.caret_pos);

        pane.rflags |= REDRAW_TEXT;
        caret_update();
}

static void selection_copy(void)
{
        spt_t pa, pb;
        char *str;

        selection_get_points(&pa, &pb);
        str = range_get_str(&pa, &pb);
        if (str == NULL || clipboard_put_str(str) != EOK) {
                status_display("Copying to clipboard failed!");
        }
        free(str);
}

static void insert_clipboard_data(void)
{
        char *str;
        size_t off;
        wchar_t c;
        int rc;

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

        off = 0;

        while (true) {
                c = str_decode(str, &off, STR_NO_LIMIT);
                if (c == '\0')
                        break;

                insert_char(c);
        }

        free(str);
}

/** Get start-of-file s-point. */
static void pt_get_sof(spt_t *pt)
{
        coord_t coord;

        coord.row = coord.column = 1;
        sheet_get_cell_pt(&doc.sh, &coord, dir_before, pt);
}

/** Get end-of-file s-point. */
static void pt_get_eof(spt_t *pt)
{
        coord_t coord;
        int num_rows;

        sheet_get_num_rows(&doc.sh, &num_rows);
        coord.row = num_rows + 1;
        coord.column = 1;

        sheet_get_cell_pt(&doc.sh, &coord, dir_after, pt);
}

/** Compare tags. */
static int tag_cmp(tag_t const *a, tag_t const *b)
{
        spt_t pa, pb;

        tag_get_pt(a, &pa);
        tag_get_pt(b, &pb);

        return spt_cmp(&pa, &pb);
}

/** Compare s-points. */
static int spt_cmp(spt_t const *a, spt_t const *b)
{
        coord_t ca, cb;

        spt_get_coord(a, &ca);
        spt_get_coord(b, &cb);

        return coord_cmp(&ca, &cb);
}

/** Compare coordinats. */
static int coord_cmp(coord_t const *a, coord_t const *b)
{
        if (a->row - b->row != 0)
                return a->row - b->row;

        return a->column - b->column;
}

/** Display text in the status line. */
static void status_display(char const *str)
{
        console_set_pos(con, 0, scr_rows - 1);
        console_set_style(con, STYLE_INVERTED);
        
        int pos = -(scr_columns - 3);
        printf(" %*s ", pos, str);
        console_flush(con);
        console_set_style(con, STYLE_NORMAL);

        pane.rflags |= REDRAW_CARET;
}

/** @}
 */