initial commit: basic parsing, flow, rendering and some nodes

.gitignore

@@ -0,0 +1,19 @@
+# Files generated by configuration
+Makefile.cfg
+
+# Other working files
+exclude/
+
+# Build files
+build/
+
+# Target files
+TeX-cli
+TeX-SDL
+libTeX-fx.a
+libTeX-cg.a
+
+# Sublime Text files
+*.sublime-workspace
+*.sublime-project
+

Makefile

@@ -0,0 +1,94 @@
+#! /usr/bin/make -f
+
+# Require the configuration file if we're not cleaning
+ifeq "$(filter clean distclean,$(MAKECMDGOALS))" ""
+ifeq ($(wildcard Makefile.cfg),)
+$(error "Makefile.cfg is missing. Did you ./configure ?")
+endif
+endif
+
+include Makefile.cfg
+include config/$(PLATFORM).cfg
+
+parser := src/TeX.y
+src    := $(wildcard src/*.c) $(wildcard src/platform/$(PLATFORM).c)
+obj    := $(src:src/%.c=build/%.c.o) $(parser:src/%.y=build/%.tab.c.o)
+
+cflags := -Wall -Wextra -std=c11 -I include -D_GNU_SOURCE $(CFLAGS)
+dflags  = -MMD -MT $@ -MF $(@:.o=.d) -MP
+bflags := -L C
+
+#
+#  Building
+#
+
+all: $(TARGET)
+
+TeX-SDL TeX-cli: $(obj)
+	$(CC) $^ -o $@ $(cflags) $(LDFLAGS)
+
+libTeX-fx.a libTeX-cg.a: $(obj)
+	$(AR) rcs $@ $^
+
+build/%.c.o: src/%.c Makefile.cfg
+	@ mkdir -p $(dir $@)
+	$(CC) -c $< -o $@ $(dflags) $(cflags)
+build/%.tab.c.o: build/%.tab.c
+	@ mkdir -p $(dir $@)
+	$(CC) -c $< -o $@ $(dflags) $(cflags)
+
+build/%.tab.c: src/%.y Makefile.cfg
+	@ mkdir -p $(dir $@)
+	bison $< -o $@ $(bflags)
+
+#
+#  Dependency management
+#
+
+
+.PRECIOUS: build/%.tab.c
+
+.PRECIOUS: build/%.d
+
+build/%.d: ;
+
+include $(wildcard build/*.d)
+
+#
+#  Install
+#
+
+ifeq "$(PLATFORM)" "fx9860g"
+install: $(TARGET)
+	install -d $(PREFIX)
+	install $(TARGET) -m 644 $(PREFIX)
+	cp -r include/TeX $(PREFIX)/include
+
+uninstall: $(TARGET)
+	rm -f $(PREFIX)/$(TARGET)
+	rm -rf $(PREFIX)/include/TeX
+endif
+
+ifeq "$(PLATFORM)" "fxcg50"
+install: $(TARGET)
+	install -d $(PREFIX)
+	install $(TARGET) -m 644 $(PREFIX)
+	cp -r include/TeX $(PREFIX)/include
+
+uninstall: $(TARGET)
+	rm -f $(PREFIX)/$(TARGET)
+	rm -rf $(PREFIX)/include/TeX
+endif
+
+#
+#  Cleaning
+#
+
+clean:
+	rm -rf build
+distclean: clean
+	rm -f Makefile.cfg
+	rm -f TeX-cli TeX-SDL libTeX-fx.a libTeX-cg.a
+
+.PHONY: all clean distclean install
+.SUFFIXES:

TODO

@@ -0,0 +1,11 @@
+*  Support angle brackets, and honor TEX_LEFTRIGHT_MAX_ANGLE
+*  Write real error messages
+*  Support Unicode symbols (probably requires help from the font side, urgh)
+*  Don't use TEX_LAYOUT_SPACING for everything, just make it the default
+
+*  Add sum and products
+*  Add square roots, and honor TEX_SQRT_SLANTED and TEX_SQRT_BAR_LENGTH
+*  Add vectors
+*  Add limits
+*  Add integrals, and honor TEX_INT_DISPLAY
+*  Add matrices

config/cli.cfg

@@ -0,0 +1,4 @@
+# Simple command-line parsing and layout troubleshooter
+TARGET = TeX-cli
+CFLAGS = -D TEX_PLATFORM_CLI -D TEX_DEBUG -g
+CC = gcc

config/fx9860g.cfg

@@ -0,0 +1,5 @@
+# Casio fx9860g library
+TARGET = libTeX-fx.a
+CFLAGS = -m3 -mb -D TEX_PLATFORM_FX9860G -D FX9860G -Os -ffreestanding
+CC = sh3eb-elf-gcc
+AR = sh3eb-elf-ar

config/fxcg50.cfg

@@ -0,0 +1,5 @@
+# Casio fxcg50 library
+TARGET = libTeX-cg.a
+CFLAGS = -m4-nofpu -mb -D TEX_PLATFORM_FXCG50 -D FXCG50 -Os -ffreestanding
+CC = sh4eb-elf-gcc
+AR = sh4eb-elf-ar

config/sdl2.cfg

@@ -0,0 +1,6 @@
+# SDL2 layout and rendering (not interactive)
+SRC = main-SDL.c
+TARGET = TeX-SDL
+CFLAGS = -D TEX_PLATFORM_SDL -D TEX_DEBUG -g
+LDFLAGS = -lSDL2
+CC = gcc

configure

@@ -0,0 +1,99 @@
+#! /usr/bin/bash
+
+usage() {
+  echo "usage: $0 --platform=<platform> [options...]"
+  echo ""
+  echo "Available platforms:"
+
+  for file in config/*.cfg; do
+    platform="${file#config/}"
+    platform="${platform%.cfg}"
+
+    printf '  %-10s' "$platform"
+    head -1 "$file" | sed 's/^# *//'
+  done
+
+  echo ""
+  echo "Options for fx9860g and fxcg50:"
+  echo "  --toolchain=<toolchain>"
+  echo "    Target triplet; default is 'sh3eb-elf' for fx9860g and 'sh4eb-elf'"
+  echo "    for fxcg50"
+  echo "  --prefix=<path>"
+  echo "    Library install path, guessed automatically by asking the compiler"
+  echo "    if not specified"
+
+  exit ${1:-1}
+}
+
+platform=
+toolchain=
+
+# Parse command-line arguments
+
+for arg in "$@"; do case "$arg" in
+  -h|--help|"-?")
+    usage 0;;
+  --platform=*)
+    platform=${arg#*=};;
+  --toolchain=*)
+    toolchain=${arg#*=};;
+  --prefix=*)
+    prefix=${arg#*=};;
+  *)
+    echo "error: unrecognized option '$arg'" 2>&1
+    error=1;;
+esac; done
+
+# Check validity
+
+if [ -z "$platform" ]; then
+  echo "error: please specify a platform" 2>&1
+  echo "Try '$0 --help' for more information."
+  exit 1
+fi
+
+if [ ! -f "config/$platform.cfg" ]; then
+  echo "error: unknown platform '$platform'" 2>&1
+  echo "Try '$0 --help' for a list of available platforms."
+  exit 1
+fi
+
+# Guess toolchains
+
+[[ $platform == fx9860g && -z $toolchain ]] && toolchain=sh3eb-elf
+[[ $platform == fxcg50  && -z $toolchain ]] && toolchain=sh4eb-elf
+
+# Guess compiler paths
+
+if [[ ( $platform == fx9860g || $platform == fxcg50 ) && -z $prefix ]]; then
+  echo "No prefix specified, let's ask the compiler:"
+  echo "  $toolchain-gcc --print-search-dirs | grep install | sed 's/install: //'"
+  inst=$($toolchain-gcc --print-search-dirs | grep install | sed 's/install: //')
+
+  if [[ $? != 0 ]]; then
+    echo "Call returned $?, giving up."
+  fi
+
+  echo "Got '$inst'".
+
+  if [[ ! -d $inst ]]; then
+    echo "Directory does not exist (or is not a directory), giving up."
+  fi
+
+  echo ""
+  prefix=$inst
+fi
+
+# Output configuration
+
+output_config() {
+  echo "PLATFORM=$platform"
+
+  if [[ $platform == fx9860g || $platform == fxcg50 ]]; then
+    echo "TOOLCHAIN=$toolchain"
+    echo "PREFIX=$prefix"
+  fi
+}
+
+output_config > Makefile.cfg
+echo "Makefile.cfg now links to the platform file 'config/$platform.cfg'."

include/TeX/TeX.h

@@ -0,0 +1,153 @@
+//---
+//	TeX: Natural rendering for mathematical formulae
+//---
+
+#ifndef TEX_H
+#define TEX_H
+
+#include <stddef.h>
+
+//---
+//	Graphical settings
+//	A few quirks that can be adjusted to your needs.
+//---
+
+/* Thickness and horizontal margin of fraction bars */
+#define TEX_FRACTION_BAR_THICKNESS 1
+#define TEX_FRACTION_BAR_MARGIN 1
+
+/* Vertical placement of subscripts and superscripts (relative to object) */
+#define TEX_SUBSCRIPT_ELEVATION 3
+#define TEX_SUPERSCRIPT_DEPTH 3
+
+/* Align the center of the resizable brackets with the baseline */
+#define TEX_LEFTRIGHT_ALIGNED 0
+/* Make them extend symmetrically around baseline */
+#define TEX_LEFTRIGHT_SYMMETRICAL 0
+/* Maximum angle for resizable "<" and ">" delimiters (radians) */
+#define TEX_LEFTRIGHT_MAX_ANGLE 2.50
+
+/* Spacing: between layout elements, letters, and width of space character */
+#define TEX_LAYOUT_SPACING 1
+#define TEX_LETTER_SPACING 1
+#define TEX_WORD_SPACING 6
+
+/* Whether to place bounds above and below integrals (display mode) */
+#define TEX_INT_DISPLAY 0
+
+/* Make the vertical part of the square root symbol slanted at low heights */
+#define TEX_SQRT_SLANTED 1
+/* Length of the top-right bar of square roots (0 to disable) */
+#define TEX_SQRT_BAR_LENGTH 0
+
+//---
+//	Implementation settings
+//---
+
+/* Size of the lexer buffer; must be large enough to hold all command names.
+   Longer than the longest literal string is a waste of space */
+#define TEX_LEXER_BUFSIZE 64
+
+/* Maximum number of nested left/right pairs */
+#define TEX_LEFTRIGHT_NESTING 16
+
+/* Enable or disable debugging functions with TEX_DEBUG. Currently this is
+   enabled (and used) by all computer targets and disabled on calculator. */
+#if defined(TEX_PLATFORM_FX9860G) || defined(TEX_PLATFORM_FXCG50)
+#undef TEX_DEBUG
+#elif !defined(TEX_DEBUG)
+#define TEX_DEBUG
+#endif
+
+//---
+//	Module interface
+//	This TeX module does not have its own primitive rendering methods;
+//	instead it relies on a few user-provided functions.
+//	This gives a certain amount on freedom on rendering. For instance, you
+//	can render a formula in a scrollable sub-rectangle of the screen by
+//	having pixel() and text() translate coordinates and check bounds.
+//---
+
+/* Opaque declaration - see <TeX/structure.h> for the details */
+struct TeX_Flow;
+
+/* TeX_intf_pixel() - Set a single pixel
+   This function configures the pixel-rendering procedure used by the module.
+   The argument should expect three parameters:
+   @x      Horizontal position of the pixel (left --> right)
+   @y      Vertical position of the pixel (top --> bottom)
+   @color  Requested color */
+void TeX_intf_pixel(void (*draw_pixel)(int x, int y, int color));
+
+/* TeX_intf_line() - Draw a line
+   This function sets the line drawing procedure of the module. The argument
+   should take give parameters:
+   @x1 @y1  Location of the first endpoint of the line
+   @x2 @y2  Location of the second endpoint of the line
+   @color   Requested color */
+void TeX_intf_line(void (*draw_line)(int x1, int y1, int x2, int y2,
+	int color));
+
+/* TeX_intf_size() - Get the dimensions of a string
+   This function configures the procedure used by the module to compute the
+   size of a string node. The argument should expect three parameters:
+   @str     String whose dimensions are requested
+   @width   Pointer to width value (must be updated by function)
+   @height  Pointer to height value (must be updated by function) */
+void TeX_intf_size(void (*text_size)(char const *str, int *width,int *height));
+
+/* TeX_intf_text() - Draw variable-width text
+   This function configures the text-rendering procedure used by the module.
+   Four arguments will be passed:
+   @x      x coordinate of the left-side of the bounding box (included)
+   @y      y coordinate of the top-size of the bounding box (included)
+   @str    String to render
+   @color  Requested color for the rendered pixels
+   The rendering function must honor the size estimates provided by the
+   procedure assigned to TeX_intf_size() and never draw pixel outside the
+   announced bounding box. */
+void TeX_intf_text(void (*draw_text)(char const *str, int x, int y,int color));
+
+//---
+//	Parsing
+//	The following functions create recursive TeX_Flow objects that
+//	represent the structure of the formulae. Once parsed, TeX_Node objects
+//	are rendered very quickly.
+//---
+
+/* TeX_parse() - Parse a TeX formula
+   @formula   TeX formula to parse
+   Returns a dynamically-allocated TeX_Flow object that can be used in further
+   calls to TeX_draw() and must be freed by a call to TeX_free(). */
+struct TeX_Flow *TeX_parse(char const *formula);
+
+/* TeX_free() - Free an allocated TeX formula
+   Freed formulas become dangling and must not be used in any further call.
+   @formula  Formula to free, assumed allocated by TeX_parse() */
+void TeX_free(struct TeX_Flow *formula);
+
+//---
+//	Rendering
+//	These functions are used to draw formulae on the screen. As doing
+//	parsing several times is inefficient, it is advised to use TeX_draw()
+//	as much as possible by reusing the same TeX_Flow object.
+//---
+
+/* TeX_draw() - Render a parsed formula
+   @formula  Formula to render
+   @x        x coordinate of the left-side of the bounding box (included)
+   @y        y coordinate of the top-size of the bounding box (included)
+   @color    Requested color for the rendered pixels */
+void TeX_draw(struct TeX_Flow *formula, int x, int y, int color);
+
+/* TeX_interpret() - Parse and render, in sequence
+   This function parses the provided formula, renders it and then frees it.
+   Only use it if you're going to render the formula only once or if you're
+   very short on memory.
+   @formula  Formula to render (textual form)
+   @x        x coordinate of the left-side of the bounding box (included)
+   @y        y coordinate of the top-size of the bounding box (included)
+   @color    Requested color for the rendered pixels */
+void TeX_interpret(char const *formula, int x, int y, int color);
+
+#endif /* TEX_H */

include/TeX/defs.h

@@ -0,0 +1,23 @@
+//---
+//	defs: Just generic definitions
+//---
+
+#ifndef DEFS_H
+#define DEFS_H
+
+/* uint type for bit fields */
+typedef unsigned int uint;
+
+/* min(), max() - But don't duplicate side-effects */
+#define	min(a, b) ({			\
+	__auto_type _a = (a);		\
+	__auto_type _b = (b);		\
+	_a < _b ? _a : _b;		\
+})
+#define	max(a, b) ({			\
+	__auto_type _a = (a);		\
+	__auto_type _b = (b);		\
+	_a > _b ? _a : _b;		\
+})
+
+#endif /* DEFS_H */

include/TeX/parser.h

@@ -0,0 +1,44 @@
+//---
+//	parser: interface to the TeX parser
+//---
+
+#ifndef TEX_PARSER
+#define TEX_PARSER
+
+#include <TeX/TeX.h>
+#include <TeX/structure.h>
+
+/* parse_start(): Configure parser to run on a string
+   @str  Input data, must be NULL-terminated */
+void parse_start(const char *str);
+
+/* parse(): Parse into a TeX flow
+   Uses input data set by parse_start(). Returns a flow object on success (free
+   with TeX_free()), NULL on error (generally syntax issues).
+   TODO: Fine-grained error detection? */
+struct TeX_Flow *parse(void);
+
+#ifdef TEX_DEBUG
+
+/* TeX_debug_lex(): Display the result of lexing
+   Makes a lexical analysis of the given formula and prints the stream of
+   tokens to standard output. */
+void TeX_debug_lex(const char *formula);
+
+/* TeX_debug_node(): Recursively display the structure of a node
+   Displays the nature and dimensions of the given node and its children,
+   making recursive calls to TeX_debug_flow().
+   @node    Displayed node
+   @indent  Indent level, in spaces (goes up by groups of 4) */
+void TeX_debug_node(struct TeX_Node *node, int indent);
+
+/* TeX_debug_flow(): Recursively display the structure of a flow
+   Displays the dimensions of the given flow and its contents, making recursive
+   calls to TeX_debug_node().
+   @flow    Displayed flow
+   @indent  Indent level, in spaces (goes up by groups of 4) */
+void TeX_debug_flow(struct TeX_Flow *flow, int indent);
+
+#endif /* TEX_DEBUG */
+
+#endif /* TEX_PARSER */

include/TeX/render.h

@@ -0,0 +1,23 @@
+//---
+//	render: Rendering functions
+//---
+
+#ifndef TEX_RENDER
+#define TEX_RENDER
+
+/* Rendering-related interface functions */
+extern void (*TeX_pixel)(int x, int y, int color);
+extern void (*TeX_line)(int x1, int y1, int x2, int y2, int color);
+extern void (*TeX_size)(char const * str, int *width, int *height);
+extern void (*TeX_text)(char const * str, int x, int y, int color);
+
+/* render_node() - Recursively render a node
+   This function all nodes types (including text). The node's size must have
+   been computed first. */
+void render_node(struct TeX_Node const * node, int x, int y, int color);
+
+/* render_flow() - Render a flow and all its components
+   This function arranges and renders all horizontal objects in a flow. */
+void render_flow(struct TeX_Flow const * flow, int x, int y, int color);
+
+#endif /* TEX_RENDER */

include/TeX/structure.h

@@ -0,0 +1,153 @@
+//---
+//	structure: Recursive node/flow data structure
+//---
+
+#ifndef TEX_STRUCTURE
+#define TEX_STRUCTURE
+
+#include <TeX/defs.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/* Maximum number of command arguments allowed by the library (each node has
+   exactly this number of children; memory usage is better if this is small) */
+#define TEX_MAX_CHILDREN 2
+
+/* A special class number for nodes that contain plain text. Class numbers from
+   1 onwards are used by TeX_Class. See also the class array in nodes.c. */
+#define TEX_NODECLASS_TEXT 0
+
+//---
+//	Data structures
+//	The structure mixes linked lists (text flow along a line, TeX_Flow) and
+//	trees (arguments to commands, TeX_Node) in a mutually-recursive way.
+//---
+
+/* TeX_Flow
+   This object represents a horizontal line of nodes following the flow of the
+   text; each node can be a plain string or a functional node. All share the
+   same base line when rendered. */
+struct TeX_Flow
+{
+	/* Pointer to first and last elements of the line */
+	struct TeX_Node *first;
+	struct TeX_Node *last;
+
+	uint16_t width;
+	uint16_t height;
+	uint16_t line;
+
+} __attribute__((packed, aligned(sizeof (void *))));
+
+/* TeX_Node
+   Here's the main deal. TeX_Flow objects handle the flow and TeX_Node objects
+   handle the content and its structure. */
+struct TeX_Node
+{
+	/* Pointer to next element in the flow */
+	struct TeX_Node *next;
+
+	union {
+		/* Plain text content encoded as UTF-8 */
+		uint8_t *text;
+		/* Functional arguments */
+		struct TeX_Flow *args[TEX_MAX_CHILDREN];
+	};
+
+	/* Invalid or hidden node */
+	uint hidden   :1;
+	/* Node class identifier */
+	uint type     :7;
+	/* Class variant or fixed argument */
+	uint subtype  :8;
+
+	/* Size and placement */
+	uint16_t width;
+	uint16_t height;
+	uint16_t line;
+
+	/* Location withing flow, as x and baseline displacement */
+	uint16_t x;
+	int16_t l;
+
+} __attribute__((packed, aligned(sizeof (void *))));
+
+//---
+//	Class nodes
+//	These are the nodes that have arguments, and specific size-calculation
+//	and rendering methods. Most interesting nodes (fractions, sums,
+//	matrices...) fall into this category.
+//---
+
+/* TeX_Class
+   A class of nodes (ie. "\name{arg}{arg}..."): function name, size-calculation
+   method, rendering method. */
+struct TeX_Class
+{
+	/* Most of the time this name appears in the formula using the "\name"
+	   notation, but some classes (superscript, parentheses, matrices...)
+	   have special syntax and their names are hardcoded. To avoid
+	   conflicts, built-in class names start with a backslash. */
+	const char *name;
+
+	/* size()
+	   This function must calculate the width, height and base line of the
+	   node and store the results in the structure fields. It is allowed to
+	   access the .width, .height and .line fields of its children because
+	   they will have had their size calculated beforehand.
+
+	   This TeX module provides classes with a primitive function that
+	   calculates the size of raw strings:
+	     void text_size(const char *str, int *width, int *height);
+
+	   @node  A node of the described class, for size calculation */
+	void (*size)(struct TeX_Node *node);
+
+	/* render()
+	   This function must render the given node at the provided (x, y)
+	   coordinates. The (x, y) point is the top-left corner of the bounding
+	   box of the expression and is inside the box (ie. it can be drawn
+	   to). This function must honor the size estimates provided by
+	   calculate_size() and not draw outside the bounding box.
+
+	   This TeX module provides two primitive functions for rendering:
+	     void pixel(int x, int y, int color);
+	     void text(const char *str, int x, int y, int color);
+
+	   @node   A node of the described class, for rendering
+	   @x      Horizontal coordinate of the requested rendering position
+	   @y      Vertical coordinate of the requested rendering position
+	   @color  Requested rendering color */
+	void (*render)(struct TeX_Node const * node, int x, int y, int color);
+};
+
+/* class_find() - Find a class using a command name
+   @name  Command name
+   Returns a positive class id representing the requested TeX_Class object (if
+   a class with this name is found in the table, a negative number otherwise.
+   This function never returns 0, which is reserved for TEX_NODECLASS_TEXT. */
+int class_find(const char *name);
+
+/* Class table. This is an array that can be indexed by class_id - 1 where
+   class_id is an id returned by class_find(). It is terminated by a class
+   with a NULL command name. Be careful because the first element in this array
+   has class id 1. */
+extern struct TeX_Class TeX_table[];
+
+//---
+//	Recursive size computation
+//---
+
+/* size_node() - Calculate the size of node
+   This function handles all node classes (including text) and computes the
+   size of the children in advance, as required by the class' calculate_size()
+   method. Modifies the node structure. */
+void size_node(struct TeX_Node *node);
+
+/* size_flow() - Calculate the size of a flow
+   This function calculates the size taken by nodes sharing the same baseline.
+   It heeds for special size and alignment exceptions such as parenthesis-type
+   characters and subscripts/superscripts. Modifies the flow structure. */
+void size_flow(struct TeX_Flow *flow);
+
+#endif /* TEX_STRUCTURE */

src/TeX.c

@@ -0,0 +1,147 @@
+#include <TeX/TeX.h>
+#include <TeX/defs.h>
+#include <TeX/structure.h>
+#include <TeX/parser.h>
+#include <TeX/render.h>
+#include <stdlib.h>
+#include <string.h>
+
+//---
+//	Interface functions
+//---
+
+/* Rendering-related interface functions */
+void (*TeX_pixel)(int x, int y, int color) = NULL;
+void (*TeX_line)(int x1, int y1, int x2, int y2, int color) = NULL;
+void (*TeX_size)(char const *str, int *width, int *height) = NULL;
+void (*TeX_text)(char const *str, int x, int y, int color) = NULL;
+
+/* TeX_intf_pixel() - Set a single pixel */
+void TeX_intf_pixel(void (*draw_pixel)(int x, int y, int color))
+{
+	TeX_pixel = draw_pixel;
+}
+
+/* TeX_intf_line() - Draw a line */
+void TeX_intf_line(void (*draw_line)(int x1, int y1, int x2, int y2,
+	int color))
+{
+	TeX_line = draw_line;
+}
+
+/* TeX_intf_size() - Get the dimensions of a string */
+void TeX_intf_size(void (*text_size)(const char *str, int *width,int *height))
+{
+	TeX_size = text_size;
+}
+
+/* TeX_intf_text() - Draw variable-width text */
+void TeX_intf_text(void (*draw_text)(const char *str, int x, int y,int color))
+{
+	TeX_text = draw_text;
+}
+
+//---
+//	Object management
+//---
+
+/* TeX_free_node() - Free TeX_Node objects
+   @node  Node to free. Its parameters will also be freed */
+static void TeX_free_node(struct TeX_Node *node)
+{
+	/* Text nodes: free the allocated string */
+	if(node->type == TEX_NODECLASS_TEXT) free(node->text);
+
+	/* Class nodes: recursively free children */
+	else for(int i = 0; i < TEX_MAX_CHILDREN; i++)
+	{
+		if(node->args[i]) TeX_free(node->args[i]);
+	}
+
+	free(node);
+}
+
+/* TeX_free() - Free an allocated TeX formula */
+void TeX_free(struct TeX_Flow *flow)
+{
+	if(!flow) return;
+
+	struct TeX_Node *node, *next = NULL;
+
+	for(node = flow->first; node; node = next)
+	{
+		next = node->next;
+		TeX_free_node(node);
+	}
+
+	free(flow);
+}
+
+//---
+//	Node operations: size computation and rendering
+//---
+
+/* size_node() - Calculate the size of node */
+void size_node(struct TeX_Node *node)
+{
+	/* Text nodes */
+	if(node->type == TEX_NODECLASS_TEXT)
+	{
+		int w, h;
+		TeX_size((char const *)node->text, &w, &h);
+
+		node->width = w;
+		node->height = h;
+		node->line = (h+1) >> 1;
+
+		return;
+	}
+
+	/* For other classes, first compute the size of children */
+	for(int i = 0; i < TEX_MAX_CHILDREN && node->args[i]; i++)
+		size_flow(node->args[i]);
+
+	/* Then use the class' special size computation function */
+	if(TeX_table[node->type - 1].size)
+		TeX_table[node->type - 1].size(node);
+}
+
+/* render_node() - Recursively render a node */
+void render_node(struct TeX_Node const * node, int x, int y, int color)
+{
+	/* Don't render hidden or invalid elements */
+	if(node->hidden) return;
+
+	if(node->type == TEX_NODECLASS_TEXT)
+	{
+		TeX_text((void *)node->text, x, y, color);
+		return;
+	}
+
+	/* For non trivial classes, use the class' special function */
+	if(TeX_table[node->type - 1].render)
+		TeX_table[node->type - 1].render(node, x, y, color);
+}
+
+//---
+//	Module functions
+//---
+
+/* TeX_parse() - Parse a TeX formula */
+struct TeX_Flow *TeX_parse(const char *formula)
+{
+	struct TeX_Flow *flow;
+
+	parse_start(formula);
+	flow = parse();
+	if(!flow) return NULL;
+
+	size_flow(flow);
+	return flow;
+}
+
+/* TeX_draw() - Render a parsed formula */
+void TeX_draw(struct TeX_Flow *formula, int x, int y, int color)
+{
+	render_flow(formula, x, y, color);
+}

src/TeX.y

@@ -0,0 +1,589 @@
+/* TODO Notes for the calculator version.
+   Don't use GLR (= non-deterministic forks)
+   Provide <alloca.h>, <malloc.h>, <stddef.h>, <stdlib.h>
+   To access semantic value of an object, use "-> value"
+   To suppress locations on-calc: #define YYLLOC_DEFAULT(Cur, Rhs, N)
+   (or just don't pass --locations) */
+
+%{
+
+#include <TeX/TeX.h>
+#include <TeX/parser.h>
+#include <TeX/structure.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+/* yylex() - The lexer, as usual */
+int yylex(void);
+/* yyerror() - The error function */
+void yyerror(const char *);
+
+static struct TeX_Flow *result = NULL;
+
+//---
+//	Node allocation functions
+//---
+
+/* mkflow_cons() - Add a new node at the right edge of a flow
+   @flow  Updated flow
+   @node  New node to add
+   Returns the new flow, which my be a different pointer if [flow] is NULL. */
+static struct TeX_Flow *mkflow_cons(struct TeX_Flow*flow, struct TeX_Node*node)
+{
+	if(!node) return flow;
+
+	if(!flow)
+	{
+		flow = calloc(1, sizeof *flow);
+		if(!flow) { yyerror("[[out of memory]]"); return NULL; }
+
+		flow->first = flow->last = node;
+		return flow;
+	}
+
+	flow->last->next = node;
+	flow->last = node;
+	return flow;
+}
+
+/* mknode_text() - Create a new text container node
+   @str  8-byte contained string
+   Returns a new node with an internal format for the string. The original
+   string may disappear. */
+static struct TeX_Node *mknode_text(const char *str)
+{
+	struct TeX_Node *node = calloc(1, sizeof *node);
+	if(!node) { yyerror("[[out of memory]]"); return NULL; }
+
+	/* TODO: Don't use strdup(); use a format conversion instead */
+	node->text = malloc(strlen(str) + 1);
+	if(!node->text) {
+		yyerror("[[out of memory]]"); free(node); return NULL; }
+	strcpy((void *)node->text, str);
+	node->type = TEX_NODECLASS_TEXT;
+
+	return node;
+}
+
+/* mknode_command() - Create a new command node
+   @name  Command name
+   This function looks up the command name in the class table and returns NULL
+   if the command is not available. Otherwise it returns a new node without
+   arguments for this command. */
+static struct TeX_Node *mknode_command(const char *name)
+{
+	/* Get the class id from the class table */
+	int type = class_find(name);
+	if(type < 0) { yyerror("[[ unknown command ]]"); return NULL; }
+
+	struct TeX_Node *node = calloc(1, sizeof *node);
+	if(!node) { yyerror("[[out of memory]]"); return NULL; }
+
+	node->type = type;
+	node->next = NULL;
+	return node;
+}
+
+/* mknode_arg() - Add an argument to a command node
+   @node  Node to add an argument to
+   @arg   Argument flow
+   Always returns node. If node is not a plain text node and has at least one
+   free argument slot, then arg is added at the first free slot. Otherwise,
+   arg is freed and node is returned unchanged. */
+static struct TeX_Node *mknode_arg(struct TeX_Node *node, struct TeX_Flow *arg)
+{
+	if(!node || !arg) return node;
+
+	/* Drop the argument if it's for a plain text node */
+	if(node->type == TEX_NODECLASS_TEXT)
+	{
+		yyerror("[[dropping argument of plain text node]]");
+		TeX_free(arg);
+		return node;
+	}
+
+	/* Otherwise look up a free slot in the argument array of node */
+	int i = 0;
+	while(i < TEX_MAX_CHILDREN && node->args[i]) i++;
+
+	if(i >= TEX_MAX_CHILDREN)
+	{
+		yyerror("[[too much arguments for node]]");
+		TeX_free(arg);
+	}
+	else node->args[i] = arg;
+
+	return node;
+}
+
+/* mknode_absarg() - Add an absorbed argument to a command node
+   @node  Command node
+   @arg   Text argument
+   For special cases such as left/right, sets the subtype, otherwise creates
+   a text flow as usual. */
+static struct TeX_Node *mknode_absarg(struct TeX_Node *node, char const *text)
+{
+	char const *class = "";
+	if(node->type != TEX_NODECLASS_TEXT)
+		class = TeX_table[node->type - 1].name;
+
+	if(!strcmp(class, "left") || !strcmp(class, "right"))
+	{
+		node->subtype = text[0];
+		return node;
+	}
+
+	return mknode_arg(node, mkflow_cons(NULL, mknode_text(text)));
+}
+
+/* mknode_f() - Make a function node with a flow argument
+   @name  Command name; intended for built-in nodes only
+   @flow  Flow argument
+   Returns a node for command [name] with as argument [flow]. */
+static struct TeX_Node *mknode_f(const char *name, struct TeX_Flow *flow)
+{
+	struct TeX_Node *node = mknode_command(name);
+	return mknode_arg(node, flow);
+}
+
+/* mknode_t() - Make a function node with a text argument */
+#define mknode_t(name, text) \
+	mknode_f((name), mkflow_cons(NULL, mknode_text((text))))
+
+%}
+
+%define api.value.type union
+
+%token <const char *> TEXT
+%token <const char *> COMMAND
+%token <const char *> COMMAND_ABS
+%left '^' '_'
+
+%type <struct TeX_Flow *> flow
+%type <struct TeX_Node *> node
+%type <struct TeX_Node *> node_abs
+
+%%
+
+main:
+	flow			{ result = $1; }
+
+flow:
+	%empty			{ $$ = NULL; }
+	| flow node		{ $$ = mkflow_cons($1, $2); }
+
+node:
+	TEXT			{ $$ = mknode_text($1); }
+	| COMMAND		{ $$ = mknode_command($1); }
+	| node_abs		{ $$ = $1; }
+	| node '{' flow '}'	{ $$ = mknode_arg($1, $3); }
+	/* Special shortcuts for the superscript and subscript classes */
+	| '^' TEXT		{ $$ = mknode_t("\\sup", $2); }
+	| '_' TEXT		{ $$ = mknode_t("\\sub", $2); }
+	| '^' '{' flow '}'	{ $$ = mknode_f("\\sup", $3); }
+	| '_' '{' flow '}'	{ $$ = mknode_f("\\sub", $3); }
+
+/* TODO: shift/reduce for [COMMAND_ABS TEXT] - could split in two nodes */
+
+node_abs:
+	COMMAND_ABS		{ $$ = mknode_command($1); }
+	| node_abs TEXT		{ $$ = mknode_absarg($1, $2); }
+%%
+
+//---
+//	The lexer
+//
+//	The lexical analysis is actually the subtle part in this program,
+//	because we want to preserve text sections without cutting them to avoid
+//	merging string tokens later on.
+//
+//	The program below is a lexer with some hybrid parser features that
+//	accomplishes this task.
+//	- It has a lookahead character and never retracts.
+//	- It has a notion of context (notably single-character mode).
+//	This machinery, however, can only be edited by hand.
+//
+//	The good side of this is that it's much more efficient because we don't
+//	break sections without commands, so there are less allocations and less
+//	tokens to parse.
+//---
+
+/* Character source (input formula) */
+static const char *lex;
+
+/* Accumulator. This buffer contains text that will be emitted in the next
+   token, more precisely everything between the start of the token and [lex]
+   (the [lex] pointer will move forward during lexing), but with escape
+   characters decoded.
+
+   Note that this buffer is static *and* unique, so every token will make its
+   way through the accumulator. As a consequence, we must apply a parsing rule
+   that copies the accumulated string every time we flush the buffer. If a
+   parsing rule has several parameters with data in the accumulator, then all
+   except the last will have their data overridden before the semantic rule is
+   executed. */
+static char acc_buffer[TEX_LEXER_BUFSIZE];
+
+/* Position of the next free character in [acc_buffer] */
+static char *acc;
+
+/* enum state - Lexer automaton states.
+   The automaton state represents what has been discovered at the previous
+   step; the state is changed to store instructions for the next character
+   input round. Often, when a character is read, previously-lexed input is
+   emitted and the character is stored in the accumulator. Possibly the state
+   is changed. */
+static enum {
+	/* Reached end-of-file (continuously emits $end tokens) */
+	eof = 0,
+	/* When reading text sections to be displayed on the screen, possibly
+	   with escapes - this is the part we don't want to cut. */
+	text,
+	/* When reading a command name after a '\' */
+	command,
+	/* The following states are transitioned into when their characters are
+	   read from input. The associated token will only be emitted in the
+	   next character input round. */
+	superscript	= '^',
+	subscript	= '_',
+	lbrace		= '{',
+	rbrace		= '}',
+} state = text;
+
+/* Single-character mode. When a command name, '^' or '_' is not followed by a
+   '{', the argument is taken to be the next input character. This mode alters
+   the behavior of the [text] state (mainly) to emit a token at the next
+   character instead of storing data in the accumulator. */
+int single;
+/* Lookahead symbol. The combination of the lookahead character with the
+   delayed-emission described in [enum state] gives this lexer two characters
+   to make decisions. For example, when lexing "ab^2", at the third character
+   input round:
+   * '^' is read from the input
+   * "ab" is released as a TEXT token and the accumulator is emptied
+   * '2' is seen as lookahead and single-character mode is activated */
+static int la;
+
+/* forward() - Maybe return
+   Returns the value of @expr if it's nonnegative; does nothing otherwise. */
+#define forward(expr) do {		\
+	int v = expr;			\
+	if(v >= 0) return v;		\
+} while(0)
+
+/* lexer_init() - TODO: Document lexer_init() */
+void lexer_init(const char *formula)
+{
+	acc = acc_buffer;
+
+	/* When the formula is empty, don't let the lexer read a lookahead! */
+	if(!formula || !formula[0])
+	{
+		lex = NULL;
+		state = eof;
+		la = 0;
+		single = 0;
+		return;
+	}
+
+	lex = formula + 1;
+	state = text;
+	la = formula[0];
+	single = 0;
+}
+
+/* release() - Release the lexer buffer as a textual token
+   This function returns produces a text token of the requested types using the
+   contents of the lexer buffer, but only if the buffer is not empty. Thus the
+   call must be wrapped into forward() and not return if there is a fallback
+   action.
+   @token  Requested token type
+   Returns a nonnegative token number if the buffer is not empty, or -1. */
+static int release(int token)
+{
+	if(acc == acc_buffer) return -1;
+
+	*acc++ = 0;
+	acc = acc_buffer;
+
+	/* After all we don't need to switch on token */
+	/* WARN: may be fragile, look for appropriate flags */
+	yylval.TEXT = yylval.COMMAND = yylval.COMMAND_ABS = acc_buffer;
+	return token;
+}
+
+/* accumulate() - Accumulate characters in the lexer buffer
+   Adds a new character @c to the lexer buffer. If the buffer is full or if
+   single-character mode is active, emits a token and empties the buffer. For
+   this return to work, the call to accumulate() must be wrapped in forward().
+   @c  Character to add (1 byte)
+   Returns a nonnegative token number if one is emitted, -1 otherwise. */
+static int accumulate(int c)
+{
+	*acc++ = c;
+
+	/* Send a token if the buffer is full or single-character mode is on */
+	if(acc >= acc_buffer + TEX_LEXER_BUFSIZE - 1 || single)
+	{
+		single = 0;
+
+		switch(state)
+		{
+		case text:	return release(TEXT);
+		case command:	return release(COMMAND);
+		default:	break;
+		}
+	}
+
+	/* Continue lexing for now */
+	return -1;
+}
+
+/* acccmp() - String comparison with the accumulator
+   Like strcmp(), but uses the non-NUL-terminated accumulator as one input. */
+static int acccmp(const char *str)
+{
+	return strncmp(acc_buffer, str, acc - acc_buffer);
+}
+
+/* lexer_text() - Execute a step of lexing from the text state
+
+   In text state, we are accumulating characters as long as possible without
+   releasing tokens. Longer chunks of text render faster on monochrome
+   calculators and need less memory.
+
+   This mode is exited whenever a metacharacter, that is '{', '}', '^' or '_'.
+   The backslash character '\' is treated with more care because escaped
+   metacharacters such as '\{' still count as text and don't need us to release
+   the accumulator.
+
+   Returns a token ID if one is emitted, -1 otherwise. */
+static int lexer_text(void)
+{
+	/* Feed lexer: this is safe thanks because I heed for c = EOF */
+	int c = la;
+	if(!c) { state = eof; return release(TEXT); }
+	la = *lex++;
+
+	/* Escapes and command names */
+	if(c == '\\')
+	{
+		/* Command name: release current buffer and move */
+		if(la >= 'a' && la <= 'z')
+		{
+			state = command;
+			return release(TEXT);
+		}
+
+		/* Escaped character: accumulate lookahead and feed lexer.
+		   Feeding is safe because current lookahead is not EOF */
+		if(strchr("\\{}^_", la))
+		{
+			c = la;
+			la = *lex++;
+
+			/* Intentional fall-through */
+		}
+		/* TODO: Emit a warning in an "else" clause? */
+
+		return accumulate(c);
+	}
+
+	/* Opening and closing braces are always syntactic elements */
+	else if(c == '{' || c == '}')
+	{
+		state = c;
+		return release(TEXT);
+	}
+
+	/* Superscript and subscript: heed for various input modes */
+	else if(c == '^' || c == '_')
+	{
+		/* In all cases, prepare to emit c at next lexing round */
+		state = c;
+
+		/* If the next character is not '{', then we don't have a {}
+		   for the argument; enable single-character mode */
+		if(la != '{') single = 1;
+
+		/* Then emit what was already in the buffer, as text */
+		return release(TEXT);
+	}
+
+	/* Accumulate the current character in the buffer until it's full */
+	return accumulate(c);
+}
+
+/* lexer_command() - Execute of step of lexing from the command state
+
+   This state is transitioned into when a '\' followed by a letter is
+   encountered. The lexer remains there until the end of the command, signaled
+   by a non-letter character, is reached.
+
+   At this point, the lexer can either enter the text mode again and wait for a
+   '{' to start arguments, or enter the text mode with the single-character
+   argument flag so any character that comes next is treated as the argument.
+
+   The original TeX does this conditionally, using single-character arguments
+   if and only if the argument does not start with a '{'. However, in this
+   program, because the number of arguments is not known at parse time, this
+   would make dumb commands such as '\alpha' gobble an unbounded amount of
+   arguments. So all commands use brace-only arguments, except for a designated
+   set. Typically this includes \left and \right which are mainly used without
+   braces in practice.
+
+   Returns a token ID if one is emitted, -1 otherwise. */
+static int lexer_command(void)
+{
+	/* Feed lexer; this is safe because I heed for la = EOF */
+	int c = la;
+	if(!c) { state = eof; return release(COMMAND); }
+	la = *lex++;
+
+	/* In this state, c is always in the range a .. z */
+	int ret = accumulate(c);
+
+	/* Continue if next character is a command continuation */
+	if(la >= 'a' && la <= 'z') return ret;
+
+	/* Otherwise, release command name */
+	state = text;
+
+	/* Absorbing commands include "left" and "right" */
+	if(!acccmp("left") || !acccmp("right"))
+	{
+		single = 1;
+		return release(COMMAND_ABS);
+	}
+
+	return release(COMMAND);
+}
+
+/* yylex() - The lexer
+   Returns the token type of the next token in the string initialized by the
+   last call to parse_start(). */
+int yylex(void)
+{
+	while(1)
+	{
+		if(state == text) forward(lexer_text());
+		else if(state == command) forward(lexer_command());
+		else break;
+	}
+
+	/* End-of-File: give up */
+	if(state == eof) return 0;
+
+	/* Character-specific states: feed and return state number */
+	int c = state;
+	state = text;
+	return c;
+}
+
+//---
+//	Parser interface
+//---
+
+/* parse_start(): Configure parser to run on a string */
+void parse_start(const char *str)
+{
+	lexer_init(str);
+}
+
+/* parse(): Parse into a TeX flow */
+struct TeX_Flow *parse(void)
+{
+	int x = yyparse();
+	return x ? NULL: result;
+}
+
+#ifdef TEX_DEBUG
+
+#include <stdio.h>
+
+void yyerror(const char *error)
+{
+	fprintf(stderr, "Parsing failed: %s\n", error);
+}
+
+#else /* TEX_DEBUG */
+
+void yyerror(__attribute__((unused)) const char *error)
+{
+}
+
+#endif /* TEX_DEBUG */
+
+//---
+//	Debugging functions
+//---
+
+#ifdef TEX_DEBUG
+
+#define GRAY "\e[30;1m"
+#define END "\e[0m"
+
+/* TeX_debug_lex(): Display the result of lexing on stdout */
+void TeX_debug_lex(const char *formula)
+{
+	lexer_init(formula);
+	int token;
+
+	do
+	{
+		token = yylex();
+
+		printf("%-3d ", token);
+		if(strchr("{}^_", token)) printf("%c", token);
+		if(token == 258) printf("TEXT        %s", yylval.TEXT);
+		if(token == 259) printf("COMMAND     %s", yylval.COMMAND);
+		if(token == 260) printf("COMMAND_ABS %s", yylval.COMMAND_ABS);
+		printf("\n");
+	}
+	while(token != 0);
+}
+
+/* TeX_debug_node(): Recursively display the structure of a node */
+void TeX_debug_node(struct TeX_Node *node, int indent)
+{
+	printf("%*s", indent, "");
+	if(!node) { puts("node (null)"); return; }
+
+	if(node->type == TEX_NODECLASS_TEXT)
+	{
+		printf("\"%s\"", node->text);
+		printf(GRAY " %dx%d,%d %+d%+d" END "\n", node->width,
+			node->height, node->line, node->x, node->l);
+	}
+	else
+	{
+		printf("<%s>", TeX_table[node->type - 1].name);
+		if(node->subtype)
+			printf(" subtype '%c'", node->subtype);
+		printf(" "GRAY "%dx%d,%d %+d%+d" END "\n", node->width,
+			node->height, node->line, node->x, node->l);
+		for(int i = 0; i < TEX_MAX_CHILDREN && node->args[i]; i++)
+			TeX_debug_flow(node->args[i], indent + 4);
+	}
+}
+
+/* TeX_debug_flow(): Recursively display the structure of a flow */
+void TeX_debug_flow(struct TeX_Flow *flow, int indent)
+{
+	printf("%*s", indent, "");
+	if(!flow) { puts("flow (null)"); return; }
+
+	printf("flow " GRAY "%dx%d,%d" END "\n", flow->width, flow->height,
+		flow->line);
+
+	struct TeX_Node *node = flow->first;
+
+	while(node)
+	{
+		TeX_debug_node(node, indent + 4);
+		node = node->next;
+	}
+}
+
+#endif /* TEX_DEBUG */

src/classes.c

@@ -0,0 +1,255 @@
+//---
+//	classes: Node classes used for mathematical notations
+//---
+
+#include <TeX/TeX.h>
+#include <TeX/structure.h>
+#include <TeX/render.h>
+#include <TeX/defs.h>
+#include <string.h>
+
+
+/* Some quick macros to access parameters and their size */
+#define args ((node)->args)
+#define w(n) (args[n]->width)
+#define h(n) (args[n]->height)
+#define l(n) (args[n]->line)
+
+//---
+//	Fractions.
+//	* args: 2 (<2 invalidate, >2 ignore)
+//	* flow: normal
+//
+//	Graphical parameters:
+//
+//	TEX_LAYOUT_SPACING (inherited):
+//	  Spacing between bar and operands
+//	TEX_FRACTION_BAR_THICKNESS:
+//	  Thickness (pixels) of fraction bar
+//	TEX_FRACTION_BAR_MARGIN:
+//	  Additional bar length that extends beyond the operands
+//
+//	     1
+//	          ] TEX_LAYOUT_SPACING
+//	  ####### ] TEX_FRACTION_BAR_THICKNESS
+//	          ] TEX_LAYOUT_SPACING
+//	     2
+//        |_| |_|
+//	TEX_FRACTION_BAR_MARGIN
+//---
+
+void frac_size(struct TeX_Node *node)
+{
+	/* Drop the fraction if there are less than two arguments */
+	if(!args[1]) { node->hidden = 1; return; }
+
+	int margin    = TEX_FRACTION_BAR_MARGIN;
+	int thickness = TEX_FRACTION_BAR_THICKNESS;
+	int spacing   = TEX_LAYOUT_SPACING;
+
+	node->width  = max(w(0), w(1)) + 2 * margin;
+	node->height = h(0) + h(1) + 2 * spacing + thickness;
+	node->line   = h(0) + spacing + thickness / 2;
+}
+
+void frac_render(struct TeX_Node const * node, int x, int y, int color)
+{
+	/* Fraction bar */
+	for(int i = 0; i < TEX_FRACTION_BAR_THICKNESS; i++)
+	{
+		int y0 = y + h(0) + TEX_LAYOUT_SPACING + i;
+		TeX_line(x, y0, x + node->width - 1, y0, color);
+	}
+
+	/* First argument */
+	render_flow(args[0],
+		x + ((node->width - w(0)) >> 1),
+		y,
+		color);
+
+	/* Second argument */
+	render_flow(args[1],
+		x + ((node->width - w(1)) >> 1),
+		y + h(0) + 2 * TEX_LAYOUT_SPACING + TEX_FRACTION_BAR_THICKNESS,
+		color);
+}
+
+//---
+//	Left and right delimiters.
+//	* args: 1 (<1 invalidate, >1 ignore)
+//	* flow: adapt width and height to contents until matching delimiter
+//
+//	Left and right delimiters are resizable bracket-like elements used to
+//	parenthesize or decorate terms. They serve a special flow purpose and
+//	are matched together by the size_flow() routine.
+//
+//	Graphical parameters:
+//
+//	TEX_LEFTRIGHT_ALIGNED:
+//	  Forces the middle of the decoration to be aligned with the baseline
+//	TEX_LEFTRIGHT_SYMMETRICAL:
+//	  Makes the size of the delimiter symmetrical around the baseline
+//	TEX_LEFTRIGHT_MAX_ANGLE:
+//	  Maximum angle allowed for "<" and ">" delimiters, radians (causes
+//	  these delimiters to grow in width if their content is tall)
+//
+//	Default:       Aligned:      Aligned symmetrical:
+//	 /  x           /  x                /  x
+//       |  -           |  -                |  -
+//      <   y           |  y                |  y
+//       | ---         <  ---              <  ---
+//	 \  z           \  z                |  z
+//                                          |
+//                                          \.
+//
+//	LaTeX's behavior on this is essentially centered symmetrical, but it
+//	seems to resize the contents to make it smoother. Not possible here.
+//---
+
+void leftright_size(struct TeX_Node *node)
+{
+	int width, height;
+	TeX_size("#", &width, &height);
+
+	/* TODO: Not the same on fxcg50 */
+	node->width = 3;
+	node->height = height;
+	node->line = (height+1) >> 1;
+}
+
+void leftright_render(struct TeX_Node const * node, int x, int y, int color)
+{
+	int h = node->height, l = node->line;
+
+	switch(node->subtype)
+	{
+	case '(':
+		TeX_pixel(x + 2, y, color);
+		TeX_pixel(x + 1, y + 1, color);
+		TeX_line(x, y + 2, x, y + h - 3, color);
+		TeX_pixel(x + 1, y + h - 2, color);
+		TeX_pixel(x + 2, y + h - 1, color);
+		break;
+
+	case ')':
+		TeX_pixel(x, y, color);
+		TeX_pixel(x + 1, y + 1, color);
+		TeX_line(x + 2, y + 2, x + 2, y + h - 3, color);
+		TeX_pixel(x + 1, y + h - 2, color);
+		TeX_pixel(x, y + h - 1, color);
+		break;
+
+	case '[':
+		TeX_pixel(x + 1, y, color);
+		TeX_pixel(x + 2, y, color);
+		TeX_line(x, y, x, y + h - 1, color);
+		TeX_pixel(x + 1, y + h - 1, color);
+		TeX_pixel(x + 2, y + h - 1, color);
+		break;
+
+	case ']':
+		TeX_pixel(x, y, color);
+		TeX_pixel(x + 1, y, color);
+		TeX_line(x + 2, y, x + 2, y + h - 1, color);
+		TeX_pixel(x, y + h - 1, color);
+		TeX_pixel(x + 1, y + h - 1, color);
+		break;
+
+	case '{':
+		TeX_pixel(x + 2, y, color);
+		TeX_line(x + 1, y + 1, x + 1, y + l - 1, color);
+		TeX_pixel(x, y + l, color);
+		TeX_line(x + 1, y + l + 1, x + 1, y + h - 2, color);
+		TeX_pixel(x + 2, y + h - 1, color);
+		break;
+
+	case '}':
+		TeX_pixel(x, y, color);
+		TeX_line(x + 1, y + 1, x + 1, y + l - 1, color);
+		TeX_pixel(x + 2, y + l, color);
+		TeX_line(x + 1, y + l + 1, x + 1, y + h - 2, color);
+		TeX_pixel(x, y + h - 1, color);
+		break;
+	}
+}
+
+//---
+//	Superscripts and subscripts.
+//	* args: 1 (<1 invalidate, >1 ignore)
+//	* flow: elevated or lowered to extend the previous node
+//
+//	Superscript and subscripts are very common elements. The class itself
+//	does nothing but name them and render its argument. The only special
+//	thing about them is their behavior in a flow, which depends on the
+//	context and is handled by flow functions in [TeX.c].
+//
+//	Graphical parameters:
+//
+//	TEX_SUPERSCRIPT_DEPTH:
+//	  Distance between bottom of superscript and top of base
+//	TEX_SUBSCRIPT_ELEVATION:
+//	  Distance between top of subscript and bottom of base
+//
+//	       +-----+
+//	       |     |
+//	+------+  1  |  --,
+//	| Base |     |    |  TEX_SUPERSCRIPT_DEPTH
+//	|      +-----+  --'
+//	+------+
+//
+//	+------+
+//	|      +-----+  --,
+//	| Base |     |    |  TEX_SUBSCRIPT_ELEVATION
+//	+------|  1  |  --'
+//	       |     |
+//	       +-----+
+//---
+
+void supsubscript_size(struct TeX_Node *node)
+{
+	/* Invalidate node if no argument is provided */
+	if(!args[0]) { node->hidden = 1; return; }
+
+	node->width  = w(0);
+	node->height = h(0);
+	node->line   = l(0);
+}
+
+void supsubscript_render(struct TeX_Node const * node, int x, int y,
+	int color)
+{
+	render_flow(args[0], x, y, color);
+}
+
+//---
+//	The class table and lookup functions
+//---
+
+struct TeX_Class TeX_table[] = {
+	/* Text is omitted from the table and has ID 0 */
+
+	/* Fractions */
+	{ "frac", frac_size, frac_render },
+	/* Size-aware opening and closing elements */
+	{ "left",  leftright_size, leftright_render },
+	{ "right", leftright_size, leftright_render },
+	/* Superscripts and subscripts */
+	{ "\\sup", supsubscript_size, supsubscript_render },
+	{ "\\sub", supsubscript_size, supsubscript_render },
+	/* Integral */
+	{ "int",     NULL,                   NULL          },
+	/* NULL terminator */
+	{ NULL,	     NULL,                   NULL          },
+};
+
+/* class_find() - Find a class using a command name */
+int class_find(const char *name)
+{
+	/* TODO: Do a binary search instead of a linear one */
+	for(int i = 0; TeX_table[i].name; i++)
+	{
+		if(!strcmp(TeX_table[i].name, name)) return i + 1;
+	}
+
+	return -1;
+}

src/flow.c

@@ -0,0 +1,314 @@
+#include <TeX/TeX.h>
+#include <TeX/structure.h>
+#include <TeX/render.h>
+#include <string.h>
+
+//---
+//	Chunks to place subscripts and superscripts
+//---
+
+#define TEX_CHUNK_INLINE 0
+#define TEX_CHUNK_DISPLAY 1
+#define TEX_CHUNK_SLANTED 2
+
+/* struct chunk: Chunk of nodes positioned relative to each other
+   The notion of "chunk" comprises a base with a subscript and a superscript.
+   Together they can be arranged in three different ways:
+
+   * TEX_CHUNK_INLINE:
+     Normal inline setting, subscript and superscript are placed to the right
+     of the base and moved below and above the baseline.
+   * TEX_CHUNK_DISPLAY:
+     Similar to LaTeX's display style, subscript and superscript are placed
+     under and above the base, and are centered horizontally.
+   * TEX_CHUNK_SLANTED:
+     Similar to inline mode, but subscript is slightly moved to the left and
+     superscript is slightly moved to the right. Looks good on integrals.
+
+   The user of a chunk sets the [x] and [l] members of the [base] node, then
+   selects the display mode and optionally adds subscript and superscript. When
+   the chunk_finalize() function is called, the position of the elements is
+   computed and the [x] and [l] members of the [sub] and [sup] nodes, as well
+   as the geometry of the chunk, are set. */
+struct chunk
+{
+	/* Base node, baseline aligned on the flow */
+	struct TeX_Node *base;
+	/* Subscript and superscript (might both be NULL) */
+	struct TeX_Node *sub, *sup;
+	/* Display mode */
+	int mode;
+
+	/* Chunk geometry */
+	int width;
+	int height;
+	int line;
+};
+
+/* chunk_make(): Make a new chunk for a base node */
+void chunk_make(struct chunk *chunk, struct TeX_Node *base, int mode)
+{
+	chunk->base = base;
+	chunk->mode = mode;
+
+	chunk->sub = NULL;
+	chunk->sup = NULL;
+
+	chunk->width = 0;
+	chunk->height = 0;
+	chunk->line = 0;
+}
+
+/* chunk_reset(): Empty a chunk */
+void chunk_reset(struct chunk *chunk)
+{
+	memset(chunk, 0, sizeof *chunk);
+}
+
+/* chunk_set(): Check whether a chunk is empty */
+int chunk_set(struct chunk *chunk)
+{
+	return chunk->base != NULL;
+}
+
+/* chunk_set_subscript(): Add a subscript on a chunk */
+void chunk_set_subscript(struct chunk *chunk, struct TeX_Node *sub)
+{
+	/* Silently refuse double index */
+	if(chunk->sub) return;
+
+	chunk->sub = sub;
+}
+
+/* chunk_set_superscript(): Add a superscript on a chunk */
+void chunk_set_superscript(struct chunk *chunk, struct TeX_Node *sup)
+{
+	/* Silently refuse double exponent */
+	if(chunk->sup) return;
+
+	chunk->sup = sup;
+}
+
+/* chunk_compute_inline(): Compute chunk layout for inline mode */
+void chunk_compute_inline(struct chunk *chunk)
+{
+	struct TeX_Node *base = chunk->base;
+	struct TeX_Node *sup = chunk->sup;
+	struct TeX_Node *sub = chunk->sub;
+
+	/* Height over and below baseline */
+	int over = base->line;
+	int under = base->height - base->line;
+	/* Additional width */
+	int right = 0;
+
+	if(sub)
+	{
+		int elevation = TEX_SUBSCRIPT_ELEVATION;
+
+		sub->x = base->x + base->width + TEX_LAYOUT_SPACING;
+		sub->l = base->l + (base->height - base->line + sub->line -
+			elevation);
+
+		under = max(under, under + sub->height - elevation);
+		right = max(right, sub->width);
+	}
+	if(sup)
+	{
+		int depth = TEX_SUPERSCRIPT_DEPTH;
+
+		sup->x = base