ui/term: add line/cell/char handling for terminal pages

This commit introduces libsystemd-ui, a systemd-internal helper library
that will contain all the UI related functionality. It is going to be used
by systemd-welcomed, systemd-consoled, systemd-greeter and systemd-er.
Further use-cases may follow.

For now, this commit only adds terminal-page handling based on lines only.
Follow-up commits will add more functionality.

1 files changed, 253 insertions, 0 deletions

diff --git a/src/libsystemd-terminal/term-internal.h b/src/libsystemd-terminal/term-internal.h
new file mode 100644
index 0000000000..af1c723ade
--- /dev/null
+++ b/src/libsystemd-terminal/term-internal.h
@@ -0,0 +1,253 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include "util.h"
+
+typedef struct term_char term_char_t;
+typedef struct term_charbuf term_charbuf_t;
+
+typedef struct term_color term_color;
+typedef struct term_attr term_attr;
+typedef struct term_cell term_cell;
+typedef struct term_line term_line;
+
+/*
+ * Miscellaneous
+ * Sundry things and external helpers.
+ */
+
+int mk_wcwidth(wchar_t ucs4);
+int mk_wcwidth_cjk(wchar_t ucs4);
+int mk_wcswidth(const wchar_t *str, size_t len);
+int mk_wcswidth_cjk(const wchar_t *str, size_t len);
+
+/*
+ * Ageing
+ * Redrawing terminals is quite expensive. Therefore, we avoid redrawing on
+ * each single modification and mark modified cells instead. This way, we know
+ * which cells to redraw on the next frame. However, a single DIRTY flag is not
+ * enough for double/triple buffered screens, hence, we use an AGE field for
+ * each cell. If the cell is modified, we simply increase the age by one. Each
+ * framebuffer can then remember its last rendered age and request an update of
+ * all newer cells.
+ * TERM_AGE_NULL is special. If used as cell age, the cell must always be
+ * redrawn (forced update). If used as framebuffer age, all cells are drawn.
+ * This way, we can allow integer wrap-arounds.
+ */
+
+typedef uint64_t term_age_t;
+
+#define TERM_AGE_NULL 0
+
+/*
+ * Characters
+ * Each cell in a terminal page contains only a single character. This is
+ * usually a single UCS-4 value. However, Unicode allows combining-characters,
+ * therefore, the number of UCS-4 characters per cell must be unlimited. The
+ * term_char_t object wraps the internal combining char API so it can be
+ * treated as a single object.
+ */
+
+struct term_char {
+        /* never access this value directly */
+        uint64_t _value;
+};
+
+struct term_charbuf {
+        /* 3 bytes + zero-terminator */
+        uint32_t buf[4];
+};
+
+#define TERM_CHAR_INIT(_val) ((term_char_t){ ._value = (_val) })
+#define TERM_CHAR_NULL TERM_CHAR_INIT(0)
+
+term_char_t term_char_set(term_char_t previous, uint32_t append_ucs4);
+term_char_t term_char_merge(term_char_t base, uint32_t append_ucs4);
+term_char_t term_char_dup(term_char_t ch);
+term_char_t term_char_dup_append(term_char_t base, uint32_t append_ucs4);
+
+const uint32_t *term_char_resolve(term_char_t ch, size_t *s, term_charbuf_t *b);
+unsigned int term_char_lookup_width(term_char_t ch);
+
+/* true if @ch is TERM_CHAR_NULL, otherwise false */
+static inline bool term_char_is_null(term_char_t ch) {
+        return ch._value == 0;
+}
+
+/* true if @ch is dynamically allocated and needs to be freed */
+static inline bool term_char_is_allocated(term_char_t ch) {
+        return !term_char_is_null(ch) && !(ch._value & 0x1);
+}
+
+/* true if (a == b), otherwise false; this is (a == b), NOT (*a == *b) */
+static inline bool term_char_same(term_char_t a, term_char_t b) {
+        return a._value == b._value;
+}
+
+/* true if (*a == *b), otherwise false; this is implied by (a == b) */
+static inline bool term_char_equal(term_char_t a, term_char_t b) {
+        const uint32_t *sa, *sb;
+        term_charbuf_t ca, cb;
+        size_t na, nb;
+
+        sa = term_char_resolve(a, &na, &ca);
+        sb = term_char_resolve(b, &nb, &cb);
+        return na == nb && !memcmp(sa, sb, sizeof(*sa) * na);
+}
+
+/* free @ch in case it is dynamically allocated */
+static inline term_char_t term_char_free(term_char_t ch) {
+        if (term_char_is_allocated(ch))
+                term_char_set(ch, 0);
+
+        return TERM_CHAR_NULL;
+}
+
+/* gcc _cleanup_ helpers */
+#define _term_char_free_ _cleanup_(term_char_freep)
+static inline void term_char_freep(term_char_t *p) {
+        term_char_free(*p);
+}
+
+/*
+ * Attributes
+ * Each cell in a terminal page can have its own set of attributes. These alter
+ * the behavior of the renderer for this single cell. We use term_attr to
+ * specify attributes.
+ * The only non-obvious field is "ccode" for foreground and background colors.
+ * This field contains the terminal color-code in case no full RGB information
+ * was given by the host. It is also required for dynamic color palettes. If it
+ * is set to TERM_CCODE_RGB, the "red", "green" and "blue" fields contain the
+ * full RGB color.
+ */
+
+enum {
+        /* dark color-codes */
+        TERM_CCODE_BLACK,
+        TERM_CCODE_RED,
+        TERM_CCODE_GREEN,
+        TERM_CCODE_YELLOW,
+        TERM_CCODE_BLUE,
+        TERM_CCODE_MAGENTA,
+        TERM_CCODE_CYAN,
+        TERM_CCODE_WHITE,                                               /* technically: light grey */
+
+        /* light color-codes */
+        TERM_CCODE_LIGHT_BLACK          = TERM_CCODE_BLACK + 8,         /* technically: dark grey */
+        TERM_CCODE_LIGHT_RED            = TERM_CCODE_RED + 8,
+        TERM_CCODE_LIGHT_GREEN          = TERM_CCODE_GREEN + 8,
+        TERM_CCODE_LIGHT_YELLOW         = TERM_CCODE_YELLOW + 8,
+        TERM_CCODE_LIGHT_BLUE           = TERM_CCODE_BLUE + 8,
+        TERM_CCODE_LIGHT_MAGENTA        = TERM_CCODE_MAGENTA + 8,
+        TERM_CCODE_LIGHT_CYAN           = TERM_CCODE_CYAN + 8,
+        TERM_CCODE_LIGHT_WHITE          = TERM_CCODE_WHITE + 8,
+
+        /* pseudo colors */
+        TERM_CCODE_FG,                                                  /* selected foreground color */
+        TERM_CCODE_BG,                                                  /* selected background color */
+        TERM_CCODE_RGB,                                                 /* color is specified as RGB */
+
+        TERM_CCODE_CNT,
+};
+
+struct term_color {
+        uint8_t ccode;
+        uint8_t red;
+        uint8_t green;
+        uint8_t blue;
+};
+
+struct term_attr {
+        term_color fg;                          /* foreground color */
+        term_color bg;                          /* background color */
+
+        unsigned int bold : 1;                  /* bold font */
+        unsigned int italic : 1;                /* italic font */
+        unsigned int underline : 1;             /* underline text */
+        unsigned int inverse : 1;               /* inverse fg/bg */
+        unsigned int protect : 1;               /* protect from erase */
+        unsigned int blink : 1;                 /* blink text */
+};
+
+/*
+ * Cells
+ * The term_cell structure respresents a single cell in a terminal page. It
+ * contains the stored character, the age of the cell and all its attributes.
+ */
+
+struct term_cell {
+        term_char_t ch;         /* stored char or TERM_CHAR_NULL */
+        term_age_t age;         /* cell age or TERM_AGE_NULL */
+        term_attr attr;         /* cell attributes */
+        unsigned int cwidth;    /* cached term_char_lookup_width(cell->ch) */
+};
+
+/*
+ * Lines
+ * Instead of storing cells in a 2D array, we store them in an array of
+ * dynamically allocated lines. This way, scrolling can be implemented very
+ * fast without moving any cells at all. Similarly, the scrollback-buffer is
+ * much simpler to implement.
+ * We use term_line to store a single line. It contains an array of cells, a
+ * fill-state which remembers the amount of blanks on the right side, a
+ * separate age just for the line which can overwrite the age for all cells,
+ * and some management data.
+ */
+
+struct term_line {
+        term_line *lines_next;          /* linked-list for histories */
+        term_line *lines_prev;          /* linked-list for histories */
+
+        unsigned int width;             /* visible width of line */
+        unsigned int n_cells;           /* # of allocated cells */
+        term_cell *cells;               /* cell-array */
+
+        term_age_t age;                 /* line age */
+        unsigned int fill;              /* # of valid cells; starting left */
+};
+
+int term_line_new(term_line **out);
+term_line *term_line_free(term_line *line);
+
+#define _term_line_free_ _cleanup_(term_line_freep)
+DEFINE_TRIVIAL_CLEANUP_FUNC(term_line*, term_line_free);
+
+int term_line_reserve(term_line *line, unsigned int width, const term_attr *attr, term_age_t age, unsigned int protect_width);
+void term_line_set_width(term_line *line, unsigned int width);
+void term_line_write(term_line *line, unsigned int pos_x, term_char_t ch, unsigned int cwidth, const term_attr *attr, term_age_t age, bool insert_mode);
+void term_line_insert(term_line *line, unsigned int from, unsigned int num, const term_attr *attr, term_age_t age);
+void term_line_delete(term_line *line, unsigned int from, unsigned int num, const term_attr *attr, term_age_t age);
+void term_line_append_combchar(term_line *line, unsigned int pos_x, uint32_t ucs4, term_age_t age);
+void term_line_erase(term_line *line, unsigned int from, unsigned int num, const term_attr *attr, term_age_t age, bool keep_protected);
+void term_line_reset(term_line *line, const term_attr *attr, term_age_t age);
+
+void term_line_link(term_line *line, term_line **first, term_line **last);
+void term_line_link_tail(term_line *line, term_line **first, term_line **last);
+void term_line_unlink(term_line *line, term_line **first, term_line **last);
+
+#define TERM_LINE_LINK(_line, _head) term_line_link((_line), &(_head)->lines_first, &(_head)->lines_last)
+#define TERM_LINE_LINK_TAIL(_line, _head) term_line_link_tail((_line), &(_head)->lines_first, &(_head)->lines_last)
+#define TERM_LINE_UNLINK(_line, _head) term_line_unlink((_line), &(_head)->lines_first, &(_head)->lines_last)