* about **********************************************************************

tim.h is a portable library to create simple terminal applications
Demo video: https://asciinema.org/a/zn3p0dsVCOQOzwY1S9gDfyaxQ

* quick start ****************************************************************

#include "tim.h"                                // one header, no lib
int main(void) {                                //
    while (tim_run(0)) {                        // event loop
        scope (A, A, 24, 8) {                   // centered 24x8 scope
            uint64_t c = 0x0a060f;              // three colors
            frame(0, 0, ~0, ~0, c);             // draw frame for scope
            label("Greetings!", A, 2, A, A, c); // label in top center
            if (button("OK", A, ~1, 8, A, c))   // button in bottom center
                return 0;                       // exit on button click
            if (is_key_press('q'))              // ctrl-c is masked
                return 0;                       // exit on 'q' press
        }                                       //
    }                                           // atexit cleanup
}                                               //

* layout *********************************************************************

The terminal's columns (x) and rows (y) are addressed by their coordinates,
the origin is in the top left corner.

Scopes are the primary layout mechanism. They are used to group and place
multiple elements. Scopes can be nested.

The root scope is the full terminal screen. The scope macro is constructed
with a for loop, so statements like break or return inside the scope block
will probably give you a bad time.

Elements (widget, control, component) are elements of user interaction, such
as a button or edit box. Most elements take x/y/w/h arguments to control
placement. All positions are given in relation the element's parent scope.

Automatic (A) width and height are either based on the element's content, or
take the full available space from parent.

 arg | value | placement
-----|-------|---------------------------------
  x  |  n    | n columns to left
  x  | ~n    | n columns to right
  x  |  A    | center horizontally
  y  |  n    | n rows to top
  y  | ~n    | n rows to bottom
  y  |  A    | center vertically
  w  |  n    | n columns wide
  w  | ~n    | fit width to n columns to right
  w  |  A    | automatic width
  h  |  n    | n rows high
  h  | ~n    | fit height n rows to bottom
  h  |  A    | automatic height

The layout automatically adopts to terminal window resize events.

* colors *********************************************************************

Most elements have a uint64 color argument which holds up to eight colors.
Typically byte 0 is the text color and byte 1 is the background color.

For example 0x08040f encodes three colors. When used with a button the text
is white (0f), the background is blue (04), and the frame is gray (08).

The terminal should support xterm-256 colors. The TERM variable is ignored.
The lower 16 colors vary across different terminals, so the upper 240 colors
should be used if consistency is important.

xterm-256 color chart
https://upload.wikimedia.org/wikipedia/commons/1/15/Xterm_256color_chart.svg

* events *********************************************************************

tim_run blocks until it observes an event. Mouse and key events are always
immediately followed by a draw event in order to make changes visible.

Some elements need to consume events, for example edit consumes the key
event when focused in order to prevent other key handlers on acting on them.

The current event is stored in tim.event.

 event       | cause
-------------|-----------------------
 DRAW_EVENT  | input, timeout, resize
 KEY_EVENT   | key press
 MOUSE_EVENT | mouse click
 VOID_EVENT  | consumed event

* elements *******************************************************************

frame (x, y, w, h, color)

    Draw an empty frame and fill area.

    x/y/w/h see layout documentation
    color   background, frame

label (str, x, y, w, h, color)

    Draw text label. Automatic width and height are supported. Strings
    exceeding width or height are clipped.

    str     zero terminated string
    x/y/w/h see layout documentation
    color   background, text

button (str, x, y, w, h, color) -> bool

    Draw button. Automatic width and height are supported. Strings exceeding
    width or height are clipped. Returns true when clicked.

    str     zero terminated string
    x/y/w/h see layout documentation
    color   frame, background, text

edit (state, x, y, w, color) -> bool

    Draw text edit. Output is stored in state.str. Receives input events when
    focused by mouse click. Escape or return relinquish focus. Returns true
    when return is pressed.

    state   pointer to persistent edit state struct
    x/y/w   see layout documentation
    color   f   rame, background, text

check (str, state, x, y, w, color) -> bool

    Draw check box. State determines how the box is checked. [x] when state
    is non-zero, [ ] when state is zero, [-] when state is -1. A mouse click
    toggles the state between one and zero and returns true.

    str     zero terminated string
    state   pointer to persistent state variable
    x/y/w   see layout documentation
    color   check, background, text

radio (str, state, v, x, y, w, color) -> bool

    Draw radio box. If state equals v, the box is selected. Radios are
    grouped through a shared state. Within that group, each v must be unique.
    A mouse click assigns v to state and returns true.

    str     zero terminated string
    state   pointer to persistent state variable
    v       unique state value
    x/y/w   see layout documentation
    color   radio, background, text

* functions ******************************************************************

tim_run (fps) -> bool

    Process events and render frame. Blocks until input is received or the
    next frame is due. First call also initializes the terminal. When fps is
    zero the function blocks until input is received. Key and mouse events
    are immediately followed by a draw event, so the actual fps can be
    significantly greater than requested. Always returns true. To reset the
    terminal after a crash, run "reset".
    The Ctrl-C interrupt is masked, so make sure to put an exit condition
    like this at the end of the main loop:

        if (is_key_press(ESCAPE_KEY))
            exit(0);

    fps     frames per second

is_key_press (key) -> bool

    Returns true if key was pressed.

    key     char literal or one of the KEY constants, see constants

time_us () -> int64

    Returns monotonic clock value in microseconds. Not affected by summer
    time or leap seconds.

* useful links ***************************************************************

https://invisible-island.net/xterm/ctlseqs/ctlseqs.html
https://learn.microsoft.com/en-us/windows/console/

* bugs ***********************************************************************

- Double buffering is still new, set ENABLE_DBUF to 0 if you see glitches
- Double width characters like 彁 are not fully supported. Terminals do not
  handle these consistently and there is no portable way to reliably
  determine character width. The renderer can deal with some of the problems
  caused by this, but results may vary.
- Decomposed (NFD) UTF-8 is not supported and will cause havoc
- Zero width code points are not supported
- Windows cmd.exe resize events may be delayed

* compatibility **************************************************************

 emulator         | support | remarks
------------------|---------|----------------------------------
 Alacritty        | ?       |
 cmd.exe          | good    | resize may lag
 Cool Retro Term  | good    | wide character spill
 Deepin Terminal  | good    | wide character spill
 Eterm            | abysmal | garbled output
 GNOME Terminal   | full    |
 GNUstep Terminal | abysmal | garbled output
 iTerm2           | ?       |
 kitty            | full    |
 Konsole          | full    |
 LXTerminal       | full    |
 macOS Terminal   | ?       |
 PuTTY            | full    |
 QTerminal        | good    | wide character spill
 rxvt-unicode     | full    |
 GNU Screen       | good    | no alternate buffer, double esc
 st               | full    |
 Terminator       | full    |
 Terminology      | full    |
 tmux             | good    | esc lags
 Windows Terminal | full    |
 Xfce Terminal    | full    |
 XTerm            | full    | XTerm is law
 Zutty            | full    |

* license ********************************************************************

MIT License

Copyright (c) MMXXIV Chu'vok <chuvok@maeppi.e4ward.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

The software is provided "as is", without warranty of any kind, express or
implied, including but not limited to the warranties of merchantability,
fitness for a particular purpose and noninfringement. In no event shall the
authors or copyright holders be liable for any claim, damages or other
liability, whether in an action of contract, tort or otherwise, arising from,
out of or in connection with the software or the use or other dealings in the
software.