kte/TerminalInputHandler.cc

#include <ncurses.h>
#include <cstdio>

#include "KKeymap.h"
#include "TerminalInputHandler.h"

namespace {
constexpr int
CTRL(char c)
{
	return c & 0x1F;
}
}

TerminalInputHandler::TerminalInputHandler() = default;

TerminalInputHandler::~TerminalInputHandler() = default;


static bool
map_key_to_command(const int ch, bool &k_prefix, bool &esc_meta, MappedInput &out)
{
	// Handle special keys from ncurses
	switch (ch) {
	case KEY_MOUSE: {
		MEVENT ev{};
		if (getmouse(&ev) == OK) {
			// React to left button click/press
			if (ev.bstate & (BUTTON1_CLICKED | BUTTON1_PRESSED | BUTTON1_RELEASED)) {
				char buf[64];
				// Use screen coordinates; command handler will translate via offsets
				std::snprintf(buf, sizeof(buf), "@%d:%d", ev.y, ev.x);
				out = {true, CommandId::MoveCursorTo, std::string(buf), 0};
				return true;
			}
		}
		// No actionable mouse event
		out.hasCommand = false;
		return true;
	}
	case KEY_LEFT:
		out = {true, CommandId::MoveLeft, "", 0};
		return true;
	case KEY_RIGHT:
		out = {true, CommandId::MoveRight, "", 0};
		return true;
	case KEY_UP:
		out = {true, CommandId::MoveUp, "", 0};
		return true;
	case KEY_DOWN:
		out = {true, CommandId::MoveDown, "", 0};
		return true;
	case KEY_HOME:
		out = {true, CommandId::MoveHome, "", 0};
		return true;
	case KEY_END:
		out = {true, CommandId::MoveEnd, "", 0};
		return true;
	case KEY_PPAGE:
		out = {true, CommandId::PageUp, "", 0};
		return true;
	case KEY_NPAGE:
		out = {true, CommandId::PageDown, "", 0};
		return true;
	case KEY_DC:
		out = {true, CommandId::DeleteChar, "", 0};
		return true;
	case KEY_RESIZE:
		out = {true, CommandId::Refresh, "", 0};
		return true;
	default:
		break;
	}

	// ESC as cancel of prefix; many terminals send meta sequences as ESC+...
	if (ch == 27) {
		// ESC
		k_prefix       = false;
		esc_meta       = true; // next key will be considered meta-modified
		out.hasCommand = false; // no command yet
		return true;
	}

	// Control keys
	if (ch == CTRL('K')) {
		// C-k prefix
		k_prefix = true;
		out      = {true, CommandId::KPrefix, "", 0};
		return true;
	}
	if (ch == CTRL('G')) {
		// cancel
		k_prefix = false;
		esc_meta = false;
		out      = {true, CommandId::Refresh, "", 0};
		return true;
	}
	// Tab (note: terminals encode Tab and C-i as the same code 9)
	if (ch == '\t') {
		k_prefix       = false;
		out.hasCommand = true;
		out.id         = CommandId::InsertText;
		out.arg        = "\t";
		out.count      = 0;
		return true;
	}
	// Generic Control-chord lookup (after handling special prefixes/cancel)
	// IMPORTANT: if we're in k-prefix, the very next key must be interpreted
	// via the C-k keymap first, even if it's a Control chord like C-d.
	if (k_prefix) {
		k_prefix      = false; // consume the prefix for this one key
		bool ctrl     = false;
		int ascii_key = ch;
		if (ch >= 1 && ch <= 26) {
			ctrl      = true;
			ascii_key = 'a' + (ch - 1);
		}
		ascii_key = KLowerAscii(ascii_key);
		CommandId id;
		if (KLookupKCommand(ascii_key, ctrl, id)) {
			out = {true, id, "", 0};
		} else {
			char c = (ascii_key >= 0x20 && ascii_key <= 0x7e) ? static_cast<char>(ascii_key) : '?';
			std::string arg(1, c);
			out = {true, CommandId::UnknownKCommand, arg, 0};
		}
		return true;
	}

	if (ch >= 1 && ch <= 26) {
		int ascii_key = 'a' + (ch - 1);
		CommandId id;
		if (KLookupCtrlCommand(ascii_key, id)) {
			out = {true, id, "", 0};
			return true;
		}
	}

	// Enter
	if (ch == '\n' || ch == '\r') {
		k_prefix = false;
		out      = {true, CommandId::Newline, "", 0};
		return true;
	}
	// Backspace in ncurses can be KEY_BACKSPACE or 127
	if (ch == KEY_BACKSPACE || ch == 127 || ch == CTRL('H')) {
		k_prefix = false;
		out      = {true, CommandId::Backspace, "", 0};
		return true;
	}

	// If previous key was ESC, interpret as meta and use ESC keymap
	if (esc_meta) {
		esc_meta      = false;
		int ascii_key = ch;
		if (ascii_key >= 'A' && ascii_key <= 'Z')
			ascii_key = ascii_key - 'A' + 'a';
		CommandId id;
		if (KLookupEscCommand(ascii_key, id)) {
			out = {true, id, "", 0};
			return true;
		}
		// Unhandled meta key: no command
		out.hasCommand = false;
		return true;
	}

	// k_prefix handled earlier

	// Printable ASCII
	if (ch >= 0x20 && ch <= 0x7E) {
		out.hasCommand = true;
		out.id         = CommandId::InsertText;
		out.arg.assign(1, static_cast<char>(ch));
		out.count = 0;
		return true;
	}

	out.hasCommand = false;
	return true; // consumed a key
}


bool
TerminalInputHandler::decode_(MappedInput &out)
{
	int ch = getch();
	if (ch == ERR) {
		return false; // no input
	}
	return map_key_to_command(ch, k_prefix_, esc_meta_, out);
}


bool
TerminalInputHandler::Poll(MappedInput &out)
{
	out = {};
	return decode_(out) && out.hasCommand;
}