fish-shell/src/screen.h

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// High level library for handling the terminal screen
//
// The screen library allows the interactive reader to write its output to screen efficiently by
// keeping an internal representation of the current screen contents and trying to find a reasonably
// efficient way for transforming that to the desired screen content.
//
// The current implementation is less smart than ncurses allows and can not for example move blocks
// of text around to handle text insertion.
#ifndef FISH_SCREEN_H
#define FISH_SCREEN_H
#include "config.h" // IWYU pragma: keep
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#include <stddef.h>
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#include <sys/stat.h>
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#include <wchar.h>
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#include <algorithm>
#include <cstddef>
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#include <map>
#include <memory>
#include <set>
#include <vector>
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#include "common.h"
#include "highlight.h"
class page_rendering_t;
/// A class representing a single line of a screen.
struct line_t {
std::vector<wchar_t> text;
std::vector<highlight_spec_t> colors;
bool is_soft_wrapped;
line_t() : text(), colors(), is_soft_wrapped(false) {}
void clear(void) {
text.clear();
colors.clear();
}
void append(wchar_t txt, highlight_spec_t color) {
text.push_back(txt);
colors.push_back(color);
}
void append(const wchar_t *txt, highlight_spec_t color) {
for (size_t i = 0; txt[i]; i++) {
text.push_back(txt[i]);
colors.push_back(color);
}
}
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size_t size(void) const { return text.size(); }
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wchar_t char_at(size_t idx) const { return text.at(idx); }
highlight_spec_t color_at(size_t idx) const { return colors.at(idx); }
void append_line(const line_t &line) {
text.insert(text.end(), line.text.begin(), line.text.end());
colors.insert(colors.end(), line.colors.begin(), line.colors.end());
}
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wcstring to_string() const { return wcstring(this->text.begin(), this->text.end()); }
};
/// A class representing screen contents.
class screen_data_t {
std::vector<line_t> line_datas;
public:
struct cursor_t {
int x;
int y;
cursor_t() : x(0), y(0) {}
cursor_t(int a, int b) : x(a), y(b) {}
} cursor;
line_t &add_line(void) {
line_datas.resize(line_datas.size() + 1);
return line_datas.back();
}
void resize(size_t size) { line_datas.resize(size); }
line_t &create_line(size_t idx) {
if (idx >= line_datas.size()) {
line_datas.resize(idx + 1);
}
return line_datas.at(idx);
}
line_t &insert_line_at_index(size_t idx) {
assert(idx <= line_datas.size());
return *line_datas.insert(line_datas.begin() + idx, line_t());
}
line_t &line(size_t idx) { return line_datas.at(idx); }
const line_t &line(size_t idx) const { return line_datas.at(idx); }
size_t line_count() const { return line_datas.size(); }
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void append_lines(const screen_data_t &d) {
this->line_datas.insert(this->line_datas.end(), d.line_datas.begin(), d.line_datas.end());
}
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bool empty() const { return line_datas.empty(); }
};
/// The class representing the current and desired screen contents.
class screen_t {
public:
/// Constructor
screen_t();
/// The internal representation of the desired screen contents.
screen_data_t desired;
/// The internal representation of the actual screen contents.
screen_data_t actual;
/// A string containing the prompt which was last printed to the screen.
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wcstring actual_left_prompt;
/// Last right prompt width.
size_t last_right_prompt_width;
/// The actual width of the screen at the time of the last screen write.
int actual_width;
/// If we support soft wrapping, we can output to this location without any cursor motion.
screen_data_t::cursor_t soft_wrap_location;
/// Whether the last-drawn autosuggestion (if any) is truncated, or hidden entirely.
bool autosuggestion_is_truncated;
/// This flag is set to true when there is reason to suspect that the parts of the screen lines
/// where the actual content is not filled in may be non-empty. This means that a clr_eol
/// command has to be sent to the terminal at the end of each line, including
/// actual_lines_before_reset.
bool need_clear_lines;
/// Whether there may be yet more content after the lines, and we issue a clr_eos if possible.
bool need_clear_screen;
/// If we need to clear, this is how many lines the actual screen had, before we reset it. This
/// is used when resizing the window larger: if the cursor jumps to the line above, we need to
/// remember to clear the subsequent lines.
size_t actual_lines_before_reset;
/// These status buffers are used to check if any output has occurred other than from fish's
/// main loop, in which case we need to redraw.
struct stat prev_buff_1, prev_buff_2, post_buff_1, post_buff_2;
};
/// This is the main function for the screen putput library. It is used to define the desired
/// contents of the screen. The screen command will use it's knowlege of the current contents of the
/// screen in order to render the desired output using as few terminal commands as possible.
///
/// \param s the screen on which to write
/// \param left_prompt the prompt to prepend to the command line
/// \param right_prompt the right prompt, or NULL if none
/// \param commandline the command line
/// \param explicit_len the number of characters of the "explicit" (non-autosuggestion) portion of
/// the command line
/// \param colors the colors to use for the comand line
/// \param indent the indent to use for the command line
/// \param cursor_pos where the cursor is
/// \param pager_data any pager data, to append to the screen
/// \param cursor_is_within_pager whether the position is within the pager line (first line)
void s_write(screen_t *s, const wcstring &left_prompt, const wcstring &right_prompt,
const wcstring &commandline, size_t explicit_len, const highlight_spec_t *colors,
const int *indent, size_t cursor_pos, const page_rendering_t &pager_data,
bool cursor_is_within_pager);
/// This function resets the screen buffers internal knowledge about the contents of the screen. Use
/// this function when some other function than s_write has written to the screen.
///
/// \param s the screen to reset
/// \param reset_cursor whether the line on which the cursor has changed should be assumed to have
/// changed. If \c reset_cursor is false, the library will attempt to make sure that the screen area
/// does not seem to move up or down on repaint.
/// \param reset_prompt whether to reset the prompt as well.
///
/// If reset_cursor is incorrectly set to false, this may result in screen contents being erased. If
/// it is incorrectly set to true, it may result in one or more lines of garbage on screen on the
/// next repaint. If this happens during a loop, such as an interactive resizing, there will be one
/// line of garbage for every repaint, which will quickly fill the screen.
void s_reset(screen_t *s, bool reset_cursor, bool reset_prompt = true);
enum screen_reset_mode_t {
/// Do not make a new line, do not repaint the prompt.
screen_reset_current_line_contents,
/// Do not make a new line, do repaint the prompt.
screen_reset_current_line_and_prompt,
/// Abandon the current line, go to the next one, repaint the prompt.
screen_reset_abandon_line,
/// Abandon the current line, go to the next one, clear the rest of the screen.
screen_reset_abandon_line_and_clear_to_end_of_screen
};
void s_reset(screen_t *s, screen_reset_mode_t mode);
/// Issues an immediate clr_eos, returning if it existed.
bool screen_force_clear_to_end();
/// Returns the length of an escape code. Exposed for testing purposes only.
size_t escape_code_length(const wchar_t *code);
// Maintain a mapping of escape sequences to their length for fast lookup.
class cached_esc_sequences_t {
private:
// Cached escape sequences we've already detected in the prompt and similar strings.
std::set<wcstring> cache;
// The escape sequence lengths we've cached. My original implementation used min and max
// length variables. The cache was then iterated over using a loop like this:
// `for (size_t l = min; l <= max; l++)`.
//
// However that is inefficient when there are big gaps in the lengths. This has been observed
// with the BobTheFish theme which has a bunch of 5 and 6 char sequences and 16 to 19 char
// sequences and almost nothing in between. So instead we keep track of only those escape
// sequence lengths we've actually cached to avoid checking for matches of lengths we know are
// not in our cache.
std::vector<size_t> lengths;
std::map<size_t, size_t> lengths_match_count;
size_t cache_hits;
public:
explicit cached_esc_sequences_t() : cache(), lengths(), lengths_match_count(), cache_hits(0) {}
void add_entry(const wchar_t *entry, size_t len) {
auto str = wcstring(entry, len);
#if 0
// This is a can't happen scenario. I only wrote this to validate during testing that it
// wouldn't be triggered. I'm leaving it in but commented out in case someone feels the need
// to re-enable the check.
auto match = cache.find(str);
if (match != cache.end()) {
debug(0, "unexpected add_entry() call of a value already in the cache: '%ls'",
escape(str.c_str(), ESCAPE_ALL).c_str());
return;
}
#endif
cache.emplace(str);
if (std::find(lengths.begin(), lengths.end(), len) == lengths.end()) {
lengths.push_back(len);
lengths_match_count[len] = 0;
}
}
size_t find_entry(const wchar_t *entry) {
size_t entry_len = wcslen(entry);
for (auto len : lengths) {
if (len > entry_len) continue;
auto match = cache.find(wcstring(entry, len));
if (match != cache.end()) { // we found a matching cached sequence
// Periodically sort the sequence lengths so we check for matches going from the
// most frequently matching lengths to least frequent.
lengths_match_count[len]++;
if (++cache_hits % 1000 == 0) {
// std::sort(lengths.begin(), lengths.end(), custom_cmp(lengths_match_count));
std::sort(lengths.begin(), lengths.end(), [&](size_t l1, size_t l2) {
return lengths_match_count[l1] > lengths_match_count[l2];
});
}
return len; // return the length of the matching cached sequence
}
}
return 0; // no cached sequence matches the entry
}
void clear() {
cache.clear();
lengths.clear();
lengths_match_count.clear();
cache_hits = 0;
}
};
// Singleton that is exposed so that the cache can be invalidated when terminal related variables
// change by calling `cached_esc_sequences.clear()`.
extern cached_esc_sequences_t cached_esc_sequences;
#endif