Add non-linear undo/redo design documentation and improve UndoSystem with backspace batching and GUI integration fixes.

TerminalInputHandler.cc

@@ -18,7 +18,17 @@ TerminalInputHandler::~TerminalInputHandler() = default;
 
 
 static bool
-map_key_to_command(const int ch, bool &k_prefix, bool &esc_meta, MappedInput &out)
+map_key_to_command(const int ch,
+                   bool &k_prefix,
+                   bool &esc_meta,
+                   // universal-argument state (by ref)
+                   bool &uarg_active,
+                   bool &uarg_collecting,
+                   bool &uarg_negative,
+                   bool &uarg_had_digits,
+                   int &uarg_value,
+                   std::string &uarg_text,
+                   MappedInput &out)
 {
 	// Handle special keys from ncurses
 	switch (ch) {
@@ -75,8 +85,15 @@ map_key_to_command(const int ch, bool &k_prefix, bool &esc_meta, MappedInput &ou
 	// 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
+		k_prefix = false;
+		esc_meta = true; // next key will be considered meta-modified
+		// Cancel any universal argument collection
+		uarg_active     = false;
+		uarg_collecting = false;
+		uarg_negative   = false;
+		uarg_had_digits = false;
+		uarg_value      = 0;
+		uarg_text.clear();
 		out.hasCommand = false; // no command yet
 		return true;
 	}
@@ -92,7 +109,46 @@ map_key_to_command(const int ch, bool &k_prefix, bool &esc_meta, MappedInput &ou
 		// cancel
 		k_prefix = false;
 		esc_meta = false;
-		out      = {true, CommandId::Refresh, "", 0};
+		// cancel universal argument as well
+		uarg_active     = false;
+		uarg_collecting = false;
+		uarg_negative   = false;
+		uarg_had_digits = false;
+		uarg_value      = 0;
+		uarg_text.clear();
+		out = {true, CommandId::Refresh, "", 0};
+		return true;
+	}
+	// Universal argument: C-u
+	if (ch == CTRL('U')) {
+		// Start or extend universal argument
+		if (!uarg_active) {
+			uarg_active     = true;
+			uarg_collecting = true;
+			uarg_negative   = false;
+			uarg_had_digits = false;
+			uarg_value      = 4; // default
+			// Reset collected text and emit status update
+			uarg_text.clear();
+			out = {true, CommandId::UArgStatus, uarg_text, 0};
+			return true;
+		} else if (uarg_collecting && !uarg_had_digits && !uarg_negative) {
+			// Bare repeated C-u multiplies by 4
+			if (uarg_value <= 0)
+				uarg_value = 4;
+			else
+				uarg_value *= 4;
+			// Keep showing status (no digits yet)
+			out = {true, CommandId::UArgStatus, uarg_text, 0};
+			return true;
+		} else {
+			// If digits or '-' have been entered, C-u ends the argument (ready for next command)
+			uarg_collecting = false;
+			if (!uarg_had_digits && !uarg_negative && uarg_value <= 0)
+				uarg_value = 4;
+		}
+		// No command produced by C-u itself
+		out.hasCommand = false;
 		return true;
 	}
 	// Tab (note: terminals encode Tab and C-i as the same code 9)
@@ -115,12 +171,13 @@ map_key_to_command(const int ch, bool &k_prefix, bool &esc_meta, MappedInput &ou
 			ctrl      = true;
 			ascii_key = 'a' + (ch - 1);
 		}
-		ascii_key = KLowerAscii(ascii_key);
+		// Do NOT lowercase here; KLookupKCommand handles case-sensitive bindings
 		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) : '?';
+			int shown = KLowerAscii(ascii_key);
+			char c    = (shown >= 0x20 && shown <= 0x7e) ? static_cast<char>(shown) : '?';
 			std::string arg(1, c);
 			out = {true, CommandId::UnknownKCommand, arg, 0};
 		}
@@ -167,6 +224,36 @@ map_key_to_command(const int ch, bool &k_prefix, bool &esc_meta, MappedInput &ou
 
 	// k_prefix handled earlier
 
+	// If collecting universal arg, handle digits and optional leading '-'
+	if (uarg_active && uarg_collecting) {
+		if (ch >= '0' && ch <= '9') {
+			int d = ch - '0';
+			if (!uarg_had_digits) {
+				// First digit overrides any 4^n default
+				uarg_value      = 0;
+				uarg_had_digits = true;
+			}
+			if (uarg_value < 100000000) {
+				// avoid overflow
+				uarg_value = uarg_value * 10 + d;
+			}
+			// Update raw text and status to reflect collected digits
+			uarg_text.push_back(static_cast<char>(ch));
+			out = {true, CommandId::UArgStatus, uarg_text, 0};
+			return true;
+		}
+		if (ch == '-' && !uarg_had_digits && !uarg_negative) {
+			uarg_negative = true;
+			// Show leading minus in status
+			uarg_text = "-";
+			out       = {true, CommandId::UArgStatus, uarg_text, 0};
+			return true;
+		}
+		// Any other key will be processed as a command; fall through to mapping below
+		// but mark collection finished so we apply the argument to that command
+		uarg_collecting = false;
+	}
+
 	// Printable ASCII
 	if (ch >= 0x20 && ch <= 0x7E) {
 		out.hasCommand = true;
@@ -188,7 +275,33 @@ TerminalInputHandler::decode_(MappedInput &out)
 	if (ch == ERR) {
 		return false; // no input
 	}
-	return map_key_to_command(ch, k_prefix_, esc_meta_, out);
+	bool consumed = map_key_to_command(
+		ch,
+		k_prefix_, esc_meta_,
+		uarg_active_, uarg_collecting_, uarg_negative_, uarg_had_digits_, uarg_value_, uarg_text_,
+		out);
+	if (!consumed)
+		return false;
+	// If a command was produced and a universal argument is active, attach it and clear state
+	if (out.hasCommand && uarg_active_ && out.id != CommandId::UArgStatus) {
+		int count = 0;
+		if (!uarg_had_digits_ && !uarg_negative_) {
+			// No explicit digits: use current value (default 4 or 4^n)
+			count = (uarg_value_ > 0) ? uarg_value_ : 4;
+		} else {
+			count = uarg_value_;
+			if (uarg_negative_)
+				count = -count;
+		}
+		out.count = count;
+		// Clear state
+		uarg_active_     = false;
+		uarg_collecting_ = false;
+		uarg_negative_   = false;
+		uarg_had_digits_ = false;
+		uarg_value_      = 0;
+	}
+	return true;
 }