Proportional sizes of 100% are apparently allowed too

[rodin/chimara.git] / libchimara / window.c

#include "window.h"
#include "magic.h"
#include "chimara-glk-private.h"

extern ChimaraGlkPrivate *glk_data;

/**
 * glk_window_iterate:
 * @win: A window, or %NULL.
 * @rockptr: Return location for the next window's rock, or %NULL.
 *
 * This function can be used to iterate through the list of all open windows
 * (including pair windows.) See <link 
 * linkend="chimara-Iterating-Through-Opaque-Objects">Iterating Through Opaque
 * Objects</link>.
 *
 * As that section describes, the order in which windows are returned is
 * arbitrary. The root window is not necessarily first, nor is it necessarily
 * last.
 *
 * Returns: the next window, or %NULL if there are no more.
 */
winid_t
glk_window_iterate(winid_t win, glui32 *rockptr)
{
        VALID_WINDOW_OR_NULL(win, return NULL);
        
        GNode *retnode;
        
        if(win == NULL)
                retnode = glk_data->root_window;
        else
        {
                GNode *node = win->window_node;
                if( G_NODE_IS_LEAF(node) )
                {
                        while(node && node->next == NULL)
                                node = node->parent;
                        if(node)
                                retnode = node->next;
                        else
                                retnode = NULL;
                }
                else
                        retnode = g_node_first_child(node);
        }
        winid_t retval = retnode? (winid_t)retnode->data : NULL;
                
        /* Store the window's rock in rockptr */
        if(retval && rockptr)
                *rockptr = glk_window_get_rock(retval);
                
        return retval;
}

/**
 * glk_window_get_rock:
 * @win: A window.
 * 
 * Returns @win's rock value. Pair windows always have rock 0; all other windows
 * return whatever rock value you created them with.
 *
 * Returns: A rock value.
 */
glui32
glk_window_get_rock(winid_t win)
{
        VALID_WINDOW(win, return 0);
        return win->rock;
}

/**
 * glk_window_get_type:
 * @win: A window.
 *
 * Returns @win's type, one of #wintype_Blank, #wintype_Pair,
 * #wintype_TextBuffer, #wintype_TextGrid, or #wintype_Graphics.
 *
 * Returns: The window's type.
 */
glui32
glk_window_get_type(winid_t win)
{
        VALID_WINDOW(win, return 0);
        return win->type;
}

/**
 * glk_window_get_parent:
 * @win: A window.
 *
 * Returns the window which is the parent of @win. If @win is the root window,
 * this returns %NULL, since the root window has no parent. Remember that the
 * parent of every window is a pair window; other window types are always
 * childless.
 *
 * Returns: A window, or %NULL.
 */
winid_t
glk_window_get_parent(winid_t win)
{
        VALID_WINDOW(win, return NULL);
        /* Value will also be NULL if win is the root window */
        return (winid_t)win->window_node->parent->data;
}

/**
 * glk_window_get_sibling:
 * @win: A window.
 *
 * Returns the other child of @win's parent. If @win is the root window, this
 * returns %NULL.
 *
 * Returns: A window, or %NULL.
 */
winid_t
glk_window_get_sibling(winid_t win)
{
        VALID_WINDOW(win, return NULL);
        
        if(G_NODE_IS_ROOT(win->window_node))
                return NULL;
        if(win->window_node->next)
                return (winid_t)win->window_node->next;
        return (winid_t)win->window_node->prev;
}

/**
 * glk_window_get_root:
 * 
 * Returns the root window. If there are no windows, this returns %NULL.
 *
 * Returns: A window, or %NULL.
 */
winid_t
glk_window_get_root()
{
        if(glk_data->root_window == NULL)
                return NULL;
        return (winid_t)glk_data->root_window->data;
}

/**
 * glk_window_open:
 * @split: The window to split to create the new window. Must be 0 if there
 * are no windows yet.
 * @method: Position of the new window and method of size computation. One of
 * #winmethod_Above, #winmethod_Below, #winmethod_Left, or #winmethod_Right
 * OR'ed with #winmethod_Fixed or #winmethod_Proportional. If @wintype is
 * #wintype_Blank, then #winmethod_Fixed is not allowed.
 * @size: Size of the new window, in percentage points if @method is
 * #winmethod_Proportional, otherwise in characters if @wintype is 
 * #wintype_TextBuffer or #wintype_TextGrid, or pixels if @wintype is
 * #wintype_Graphics.
 * @wintype: Type of the new window. One of #wintype_Blank, #wintype_TextGrid,
 * #wintype_TextBuffer, or #wintype_Graphics.
 * @rock: The new window's rock value.
 *
 * Creates a new window. If there are no windows, the first three arguments are
 * meaningless. @split <emphasis>must</emphasis> be 0, and @method and @size
 * are ignored. @wintype is the type of window you're creating, and @rock is
 * the rock (see <link linkend="chimara-Rocks">Rocks</link>).
 *
 * If any windows exist, new windows must be created by splitting existing
 * ones. @split is the window you want to split; this <emphasis>must 
 * not</emphasis> be zero. @method is a mask of constants to specify the
 * direction and the split method (see below). @size is the size of the split.
 * @wintype is the type of window you're creating, and @rock is the rock.
 *
 * Remember that it is possible that the library will be unable to create a new
 * window, in which case glk_window_open() will return %NULL.
 * 
 * <note><para>
 *   It is acceptable to gracefully exit, if the window you are creating is an
 *   important one &mdash; such as your first window. But you should not try to
 *   perform any window operation on the id until you have tested to make sure
 *   it is non-zero.
 * </para></note>
 * 
 * The examples we've seen so far have the simplest kind of size control. (Yes,
 * this is <quote>below</quote>.) Every pair is a percentage split, with 
 * <inlineequation>
 *   <alt>X</alt>
 *   <mathphrase>X</mathphrase>
 * </inlineequation>
 * percent going to one side, and 
 * <inlineequation>
 *   <alt>(100-X)</alt>
 *   <mathphrase>(100 - X)</mathphrase>
 * </inlineequation> 
 * percent going to the other side. If the player resizes the window, the whole
 * mess expands, contracts, or stretches in a uniform way.
 * 
 * As I said above, you can also make fixed-size splits. This is a little more
 * complicated, because you have to know how this fixed size is measured.
 * 
 * Sizes are measured in a way which is different for each window type. For
 * example, a text grid window is measured by the size of its fixed-width font.
 * You can make a text grid window which is fixed at a height of four rows, or
 * ten columns. A text buffer window is measured by the size of its font.
 * 
 * <note><para>
 *   Remember that different windows may use different size fonts. Even two
 *   text grid windows may use fixed-size fonts of different sizes.
 * </para></note>
 *
 * Graphics windows are measured in pixels, not characters. Blank windows
 * aren't measured at all; there's no meaningful way to measure them, and
 * therefore you can't create a blank window of a fixed size, only of a
 * proportional (percentage) size.
 * 
 * So to create a text buffer window which takes the top 40% of the original
 * window's space, you would execute
 * |[ newwin = #glk_window_open(win, #winmethod_Above | #winmethod_Proportional, 40, #wintype_TextBuffer, 0); ]|
 *
 * To create a text grid which is always five lines high, at the bottom of the
 * original window, you would do
 * |[ newwin = #glk_window_open(win, #winmethod_Below | #winmethod_Fixed, 5, #wintype_TextGrid, 0); ]|
 * 
 * Note that the meaning of the @size argument depends on the @method argument.
 * If the method is #winmethod_Fixed, it also depends on the @wintype argument.
 * The new window is then called the <quote>key window</quote> of this split,
 * because its window type determines how the split size is computed.
 * 
 * <note><para>
 *   For #winmethod_Proportional splits, you can still call the new window the
 *   <quote>key window</quote>. But the key window is not important for
 *   proportional splits, because the size will always be computed as a simple
 *   ratio of the available space, not a fixed size of one child window.
 * </para></note>
 * 
 * This system is more or less peachy as long as all the constraints work out.
 * What happens when there is a conflict? The rules are simple. Size control
 * always flows down the tree, and the player is at the top. Let's bring out an
 * example:
 * <informaltable frame="none"><tgroup cols="2"><tbody><row>
 * <entry><mediaobject><imageobject><imagedata fileref="fig5-7a.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><textobject><literallayout class="monospaced">
 *      O
 *     / \
 *    O   B
 *   / \
 *  A   C
 * </literallayout></textobject></mediaobject></entry>
 * </row></tbody></tgroup></informaltable>
 * 
 * First we split A into A and B, with a 50% proportional split. Then we split
 * A into A and C, with C above, C being a text grid window, and C gets a fixed
 * size of two rows (as measured in its own font size). A gets whatever remains
 * of the 50% it had before.
 * 
 * Now the player stretches the window vertically.
 * <informalfigure><mediaobject><imageobject><imagedata fileref="fig6.png"/>
 * </imageobject></mediaobject></informalfigure>
 * 
 * The library figures: the topmost split, the original A/B split, is 50-50. So
 * B gets half the screen space, and the pair window next to it (the lower
 * <quote>O</quote>) gets the other half. Then it looks at the lower 
 * <quote>O</quote>. C gets two rows; A gets the rest. All done.
 * 
 * Then the user maliciously starts squeezing the window down, in stages:
 * <informaltable frame="none"><tgroup cols="5"><tbody><row valign="top">
 * <entry><mediaobject><imageobject><imagedata fileref="fig5-7a.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><imageobject><imagedata fileref="fig7b.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><imageobject><imagedata fileref="fig7c.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><imageobject><imagedata fileref="fig7d.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><imageobject><imagedata fileref="fig7e.png"/>
 * </imageobject></mediaobject></entry>
 * </row></tbody></tgroup></informaltable>
 * 
 * The logic remains the same. B always gets half the space. At stage 3,
 * there's no room left for A, so it winds up with zero height. Nothing
 * displayed in A will be visible. At stage 4, there isn't even room in the
 * upper 50% to give C its two rows; so it only gets one. Finally, C is
 * squashed out of existence as well.
 * 
 * When a window winds up undersized, it remembers what size it should be. In
 * the example above, A remembers that it should be two rows; if the user
 * expands the window to the original size, it would return to the original
 * layout.
 * 
 * The downward flow of control is a bit harsh. After all, in stage 4, there's
 * room for C to have its two rows if only B would give up some of its 50%. But
 * this does not happen.
 * 
 * <note><para>
 *   This makes life much easier for the Glk library. To determine the
 *   configuration of a window, it only needs to look at the window's
 *   ancestors, never at its descendants. So window layout is a simple
 *   recursive algorithm, no backtracking.
 * </para></note>
 * 
 * What happens when you split a fixed-size window? The resulting pair window
 * &mdash; that is, the two new parts together &mdash; retain the same size
 * constraint as the original window that was split. The key window for the
 * original split is still the key window for that split, even though it's now
 * a grandchild instead of a child.
 * 
 * The easy, and correct, way to think about this is that the size constraint
 * is stored by a window's parent, not the window itself; and a constraint
 * consists of a pointer to a key window plus a size value.
 * 
 * <informaltable frame="none"><tgroup cols="6"><tbody><row>
 * <entry><mediaobject><imageobject><imagedata fileref="fig8a.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><textobject><literallayout class="monospaced">
 *  A   
 * </literallayout></textobject></mediaobject></entry>
 * <entry><mediaobject><imageobject><imagedata fileref="fig8b.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><textobject><literallayout class="monospaced">
 *    O1  
 *   / \  
 *  A   B 
 * </literallayout></textobject></mediaobject></entry> 
 * <entry><mediaobject><imageobject><imagedata fileref="fig8c.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><textobject><literallayout class="monospaced">
 *      O1  
 *     / \  
 *    O2  B 
 *   / \    
 *  A   C   
 * </literallayout></textobject></mediaobject></entry> 
 * </row></tbody></tgroup></informaltable>
 * After the first split, the new pair window (O1, which covers the whole
 * screen) knows that its first child (A) is above the second, and gets 50% of
 * its own area. (A is the key window for this split, but a proportional split
 * doesn't care about key windows.)
 * 
 * After the second split, all this remains true; O1 knows that its first child
 * gets 50% of its space, and A is O1's key window. But now O1's first child is
 * O2 instead of A. The newer pair window (O2) knows that its first child (C)
 * is above the second, and gets a fixed size of two rows. (As measured in C's
 * font, because C is O2's key window.)
 * 
 * If we split C, now, the resulting pair will still be two C-font rows high
 * &mdash; that is, tall enough for two lines of whatever font C displays. For
 * the sake of example, we'll do this vertically.
 * <informaltable frame="none"><tgroup cols="2"><tbody><row>
 * <entry><mediaobject><imageobject><imagedata fileref="fig9.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><textobject><literallayout class="monospaced">
 *      O1
 *     / \
 *    O2  B
 *   / \
 *  A   O3
 *     / \
 *    C   D
 * </literallayout></textobject></mediaobject></entry> 
 * </row></tbody></tgroup></informaltable>
 * 
 * O3 now knows that its children have a 50-50 left-right split. O2 is still
 * committed to giving its upper child, O3, two C-font rows. Again, this is
 * because C is O2's key window. 
 *
 * <note><para>
 *   This turns out to be a good idea, because it means that C, the text grid
 *   window, is still two rows high. If O3 had been a upper-lower split, things
 *   wouldn't work out so neatly. But the rules would still apply. If you don't
 *   like this, don't do it.
 * </para></note>
 *
 * Returns: the new window, or %NULL on error.
 */
winid_t
glk_window_open(winid_t split, glui32 method, glui32 size, glui32 wintype, 
                glui32 rock)
{
        VALID_WINDOW_OR_NULL(split, return NULL);
        g_return_val_if_fail(method == (method & (winmethod_DirMask | winmethod_DivisionMask)), NULL);
        g_return_val_if_fail(!(((method & winmethod_DivisionMask) == winmethod_Proportional) && size > 100), NULL);     

        if(split == NULL && glk_data->root_window != NULL)
        {
                ILLEGAL("Tried to open a new root window, but there is already a root window");
                return NULL;
        }
        
        gdk_threads_enter();
        
        /* Create the new window */
        winid_t win = g_new0(struct glk_window_struct, 1);
        win->magic = MAGIC_WINDOW;
        win->rock = rock;
        win->type = wintype;
        win->window_node = g_node_new(win);

        switch(wintype)
        {
                case wintype_Blank:
                {
                        /* A blank window will be a label without any text */
                        GtkWidget *label = gtk_label_new("");
                        gtk_widget_show(label);
                        
                        win->widget = label;
                        win->frame = label;
                        /* A blank window has no size */
                        win->unit_width = 0;
                        win->unit_height = 0;
                        /* You can print to a blank window's stream, but it does nothing */
                        win->window_stream = window_stream_new(win);
                        win->echo_stream = NULL;
                }
                        break;
                
                case wintype_TextGrid:
                {
                    GtkWidget *textview = gtk_text_view_new();

                    gtk_text_view_set_wrap_mode( GTK_TEXT_VIEW(textview), GTK_WRAP_NONE );
                    gtk_text_view_set_editable( GTK_TEXT_VIEW(textview), FALSE );
                        gtk_widget_show(textview);
                                
                        /* Set the window's font */
                        gtk_widget_modify_font(textview, glk_data->monospace_font_desc);
                    
                    win->widget = textview;
                    win->frame = textview;
                        
                        /* Determine the size of a "0" character in pixels */
                        PangoLayout *zero = gtk_widget_create_pango_layout(textview, "0");
                        pango_layout_set_font_description(zero, glk_data->monospace_font_desc);
                        pango_layout_get_pixel_size(zero, &(win->unit_width), &(win->unit_height));
                        g_object_unref(zero);
                        
                        /* Set the other parameters (width and height are set later) */
                        win->window_stream = window_stream_new(win);
                        win->echo_stream = NULL;
                        win->input_request_type = INPUT_REQUEST_NONE;
                        win->line_input_buffer = NULL;
                        win->line_input_buffer_unicode = NULL;
                        
                        /* Connect signal handlers */
                        win->keypress_handler = g_signal_connect( G_OBJECT(textview), "key-press-event", G_CALLBACK(on_window_key_press_event), win );
                        g_signal_handler_block( G_OBJECT(textview), win->keypress_handler );
                }
                    break;
                
                case wintype_TextBuffer:
                {
                        GtkWidget *scrolledwindow = gtk_scrolled_window_new(NULL, NULL);
                        GtkWidget *textview = gtk_text_view_new();
                        GtkTextBuffer *textbuffer = gtk_text_view_get_buffer( GTK_TEXT_VIEW(textview) );

                        gtk_scrolled_window_set_policy( GTK_SCROLLED_WINDOW(scrolledwindow), GTK_POLICY_NEVER, GTK_POLICY_AUTOMATIC );
                        
                        gtk_text_view_set_wrap_mode( GTK_TEXT_VIEW(textview), GTK_WRAP_WORD_CHAR );
                        gtk_text_view_set_editable( GTK_TEXT_VIEW(textview), FALSE );

                        gtk_container_add( GTK_CONTAINER(scrolledwindow), textview );
                        gtk_widget_show_all(scrolledwindow);

                        /* Set the window's font */
                        gtk_widget_modify_font(textview, glk_data->default_font_desc);
                        
                        win->widget = textview;
                        win->frame = scrolledwindow;
                        
                        /* Determine the size of a "0" character in pixels */
                        PangoLayout *zero = gtk_widget_create_pango_layout(textview, "0");
                        pango_layout_set_font_description(zero, glk_data->default_font_desc);
                        pango_layout_get_pixel_size(zero, &(win->unit_width), &(win->unit_height));
                        g_object_unref(zero);
                        
                        /* Set the other parameters */
                        win->window_stream = window_stream_new(win);
                        win->echo_stream = NULL;
                        win->input_request_type = INPUT_REQUEST_NONE;
                        win->line_input_buffer = NULL;
                        win->line_input_buffer_unicode = NULL;

                        /* Connect signal handlers */
                        win->keypress_handler = g_signal_connect( G_OBJECT(textview), "key-press-event", G_CALLBACK(on_window_key_press_event), win );
                        g_signal_handler_block( G_OBJECT(textview), win->keypress_handler );

                        win->insert_text_handler = g_signal_connect_after( G_OBJECT(textbuffer), "insert-text", G_CALLBACK(after_window_insert_text), win );
                        g_signal_handler_block( G_OBJECT(textbuffer), win->insert_text_handler );

                        /* Create an editable tag to indicate uneditable parts of the window
                        (for line input) */
                        gtk_text_buffer_create_tag(textbuffer, "uneditable", "editable", FALSE, "editable-set", TRUE, NULL);

                        /* Create the default styles available to the window stream */
                        style_init_textbuffer(textbuffer);

                        /* Mark the position where the user will input text */
                        GtkTextIter end;
                        gtk_text_buffer_get_end_iter(textbuffer, &end);
                        gtk_text_buffer_create_mark(textbuffer, "input_position", &end, TRUE);
                }
                        break;
                        
                default:
                        gdk_threads_leave();
                        ILLEGAL_PARAM("Unknown window type: %u", wintype);
                        g_free(win);
                        g_node_destroy(glk_data->root_window);
                        glk_data->root_window = NULL;
                        return NULL;
        }

        /* Set the minimum size to "as small as possible" so it doesn't depend on
         the size of the window contents */
        gtk_widget_set_size_request(win->widget, 0, 0);
        gtk_widget_set_size_request(win->frame, 0, 0);
        
        if(split)
        {
                /* When splitting, construct a new parent window
                 * copying most characteristics from the window that is being split */
                winid_t pair = g_new0(struct glk_window_struct, 1);
                pair->magic = MAGIC_WINDOW;
                pair->rock = 0;
                pair->type = wintype_Pair;
                pair->window_node = g_node_new(pair);
                /* You can print to a pair window's window stream, but it has no effect */
                pair->window_stream = window_stream_new(pair);
                pair->echo_stream = NULL;

                /* The pair window must know about its children's split method */
                pair->key_window = win;
                pair->split_method = method;
                pair->constraint_size = size;
                
                /* Insert the new window into the window tree */
                if(split->window_node->parent == NULL)
                        glk_data->root_window = pair->window_node;
                else 
                {
                        if( split->window_node == g_node_first_sibling(split->window_node) )
                                g_node_prepend(split->window_node->parent, pair->window_node);
                        else
                                g_node_append(split->window_node->parent, pair->window_node);
                        g_node_unlink(split->window_node);
                }
                /* Place the windows in the correct order */
                switch(method & winmethod_DirMask)
                {
                        case winmethod_Left:
                        case winmethod_Above:
                                g_node_append(pair->window_node, win->window_node);
                                g_node_append(pair->window_node, split->window_node);
                                break;
                        case winmethod_Right:
                        case winmethod_Below:
                                g_node_append(pair->window_node, split->window_node);
                                g_node_append(pair->window_node, win->window_node);
                                break;
                }

        } else {
                /* Set the window as root window */
                glk_data->root_window = win->window_node;
        }

        /* Set the window as a child of the Glk widget */
        gtk_widget_set_parent(win->frame, GTK_WIDGET(glk_data->self));
        gtk_widget_queue_resize(GTK_WIDGET(glk_data->self));
        
        gdk_threads_leave();
        
        /* For blank or pair windows, this is almost a no-op. For text grid and
         text buffer windows, this will wait for GTK to draw the window. Otherwise,
         opening a window and getting its size immediately will give you the wrong
         size. */
        glk_window_get_size(win, NULL, NULL);
        
    /* For text grid windows, fill the buffer with blanks. */
    if(wintype == wintype_TextGrid)
    {
        /* Create the cursor position mark */
                gdk_threads_enter();
        GtkTextIter begin;
        GtkTextBuffer *buffer = gtk_text_view_get_buffer( GTK_TEXT_VIEW(win->widget) );
        gtk_text_buffer_get_start_iter(buffer, &begin);
        gtk_text_buffer_create_mark(buffer, "cursor_position", &begin, TRUE);
        gdk_threads_leave();
                
        /* Fill the buffer with blanks and move the cursor to the upper left */
        glk_window_clear(win);
    }

        return win;
}

/* Internal function: if node's key window is closing_win or one of its
 children, set node's key window to NULL. */
static gboolean 
remove_key_windows(GNode *node, winid_t closing_win)
{
        winid_t win = (winid_t)node->data;
        if(win->key_window && (win->key_window == closing_win || g_node_is_ancestor(closing_win->window_node, win->key_window->window_node)))
                win->key_window = NULL;
        return FALSE; /* Don't stop the traversal */
}

/* Internal function: destroy this window's GTK widgets, window streams, 
 and those of all its children */
static void
destroy_windows_below(winid_t win, stream_result_t *result)
{
        switch(win->type)
        {
                case wintype_Blank:
                        gdk_threads_enter();
                        gtk_widget_unparent(win->widget);
                        gdk_threads_leave();
                        break;
        
            case wintype_TextGrid:
                case wintype_TextBuffer:
                        gdk_threads_enter();
                        gtk_widget_unparent(win->frame);
                        gdk_threads_leave();
                        /* TODO: Cancel all input requests */
                        break;

                case wintype_Pair:
                        destroy_windows_below(win->window_node->children->data, NULL);
                        destroy_windows_below(win->window_node->children->next->data, NULL);
                        break;

                default:
                        ILLEGAL_PARAM("Unknown window type: %u", win->type);
                        return;
        }
        stream_close_common(win->window_stream, result);
}

/* Internal function: free the winid_t structure of this window and those of all its children */
static void
free_winids_below(winid_t win)
{
        if(win->type == wintype_Pair) {
                free_winids_below(win->window_node->children->data);
                free_winids_below(win->window_node->children->next->data);
        }
        win->magic = MAGIC_FREE;
        g_free(win);
}

/**
 * glk_window_close:
 * @win: Window to close.
 * @result: Pointer to a #stream_result_t in which to store the write count.
 *
 * Closes @win, which is pretty much exactly the opposite of opening a window.
 * It is legal to close all your windows, or to close the root window (which is
 * the same thing.) 
 *
 * The @result argument is filled with the output character count of the window
 * stream. See <link linkend="chimara-Streams">Streams</link> and <link
 * linkend="chimara-Closing-Streams">Closing Streams</link>.
 * 
 * When you close a window (and it is not the root window), the other window
 * in its pair takes over all the freed-up area. Let's close D, in the current
 * example:
 * <informaltable frame="none"><tgroup cols="2"><tbody><row>
 * <entry><mediaobject><imageobject><imagedata fileref="fig10.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><textobject><literallayout class="monospaced">
 *      O1
 *     / \
 *    O2  B
 *   / \
 *  A   C
 * </literallayout></textobject></mediaobject></entry> 
 * </row></tbody></tgroup></informaltable>
 * 
 * Notice what has happened. D is gone. O3 is gone, and its 50-50 left-right
 * split has gone with it. The other size constraints are unchanged; O2 is
 * still committed to giving its upper child two rows, as measured in the font
 * of O2's key window, which is C. Conveniently, O2's upper child is C, just as
 * it was before we created D. In fact, now that D is gone, everything is back
 * to the way it was before we created D.
 * 
 * But what if we had closed C instead of D? We would have gotten this:
 * <informaltable frame="none"><tgroup cols="2"><tbody><row>
 * <entry><mediaobject><imageobject><imagedata fileref="fig11.png"/>
 * </imageobject></mediaobject></entry>
 * <entry><mediaobject><textobject><literallayout class="monospaced">
 *      O1
 *     / \
 *    O2  B
 *   / \
 *  A   D
 * </literallayout></textobject></mediaobject></entry> 
 * </row></tbody></tgroup></informaltable>
 * 
 * Again, O3 is gone. But D has collapsed to zero height. This is because its
 * height is controlled by O2, and O2's key window was C, and C is now gone. O2
 * no longer has a key window at all, so it cannot compute a height for its
 * upper child, so it defaults to zero.
 * 
 * <note><para>
 *   This may seem to be an inconvenient choice. That is deliberate. You should
 *   not leave a pair window with no key, and the zero-height default reminds
 *   you not to. You can use glk_window_set_arrangement() to set a new split
 *   measurement and key window. See <link 
 *   linkend="chimara-Changing-Window-Constraints">Changing Window
 *   Constraints</link>.
 * </para></note>
 */
void
glk_window_close(winid_t win, stream_result_t *result)
{
        VALID_WINDOW(win, return);
        
        /* If any pair windows have this window or its children as a key window,
         set their key window to NULL */
        g_node_traverse(glk_data->root_window, G_IN_ORDER, G_TRAVERSE_NON_LEAVES, -1, (GNodeTraverseFunc)remove_key_windows, win);
        
        /* Close all the window streams and destroy the widgets of this window
         and below, before trashing the window tree */
        destroy_windows_below(win, result);
        
        /* Then free the winid_t structures below this node, but not this one itself */
        if(win->type == wintype_Pair) {
                free_winids_below(win->window_node->children->data);
                free_winids_below(win->window_node->children->next->data);
        }
        /* So now we should be left with a skeleton tree hanging off this node */       
        
        /* Parent window changes from a split window into the sibling window */
        /* The parent of any window is either a pair window or NULL */
        GNode *pair_node = win->window_node->parent;
        g_node_destroy(win->window_node);
        /* If win was not the root window: */
        if(pair_node != NULL)
        {
                gboolean new_child_on_left = ( pair_node == g_node_first_sibling(pair_node) );
                GNode *sibling_node = pair_node->children; /* only one child left */
                GNode *new_parent_node = pair_node->parent;
                g_node_unlink(pair_node);
                g_node_unlink(sibling_node);
                /* pair_node and sibling_node should now be totally unconnected to the tree */
                
                if(new_parent_node == NULL)
                {
                        glk_data->root_window = sibling_node;
                } 
                else 
                {
                        if(new_child_on_left)
                                g_node_prepend(new_parent_node, sibling_node);
                        else
                                g_node_append(new_parent_node, sibling_node);
                }

                winid_t pair = (winid_t) pair_node->data;
                g_node_destroy(pair_node);
                
                pair->magic = MAGIC_FREE;
                g_free(pair);
        } 
        else /* it was the root window */
        {
                glk_data->root_window = NULL;
        }

        win->magic = MAGIC_FREE;
        g_free(win);

        /* Schedule a redraw */
        gdk_threads_enter();
        gtk_widget_queue_resize( GTK_WIDGET(glk_data->self) );
        gdk_window_process_all_updates();
        gdk_threads_leave();
}

/**
 * glk_window_clear:
 * @win: A window.
 *
 * Erases @win. The meaning of this depends on the window type.
 * <variablelist>
 * <varlistentry>
 *  <term>Text buffer</term>
 *  <listitem><para>
 *   This may do any number of things, such as delete all text in the window, or
 *   print enough blank lines to scroll all text beyond visibility, or insert a
 *   page-break marker which is treated specially by the display part of the
 *   library.
 *  </para></listitem>
 * </varlistentry>
 * <varlistentry>
 *  <term>Text grid</term>
 *  <listitem><para>
 *   This will clear the window, filling all positions with blanks. The window
 *   cursor is moved to the top left corner (position 0,0).
 *  </para></listitem>
 * </varlistentry>
 * <varlistentry>
 *  <term>Graphics</term>
 *  <listitem><para>
 *   Clears the entire window to its current background color. See <link
 *   linkend="chimara-Graphics-Windows">Graphics Windows</link>.
 *  </para></listitem>
 * </varlistentry>
 * <varlistentry>
 *  <term>Other window types</term>
 *  <listitem><para>No effect.</para></listitem>
 * </varlistentry>
 * </variablelist>
 *
 * It is illegal to erase a window which has line input pending. 
 */
void
glk_window_clear(winid_t win)
{
        VALID_WINDOW(win, return);
        g_return_if_fail(win->input_request_type != INPUT_REQUEST_LINE && win->input_request_type != INPUT_REQUEST_LINE_UNICODE);
        
        switch(win->type)
        {
                case wintype_Blank:
                case wintype_Pair:
                        /* do nothing */
                        break;
                
                case wintype_TextGrid:
                    /* fill the buffer with blanks */
                {
                    gdk_threads_enter();
                    
            /* Manually put newlines at the end of each row of characters in the buffer; manual newlines make resizing the window's grid easier. */
            gchar *blanks = g_strnfill(win->width, ' ');
            gchar **blanklines = g_new0(gchar *, win->height + 1);
            int count;
            for(count = 0; count < win->height; count++)
                blanklines[count] = blanks;
            blanklines[win->height] = NULL;
            gchar *text = g_strjoinv("\n", blanklines);
            g_free(blanklines); /* not g_strfreev() */
            g_free(blanks);
            
            GtkTextBuffer *textbuffer = gtk_text_view_get_buffer( GTK_TEXT_VIEW(win->widget) );
            gtk_text_buffer_set_text(textbuffer, text, -1);
            g_free(text);
            
            GtkTextIter begin;
            gtk_text_buffer_get_start_iter(textbuffer, &begin);
            gtk_text_buffer_move_mark_by_name(textbuffer, "cursor_position", &begin);
                    
                    gdk_threads_leave();
                }
                    break;
                
                case wintype_TextBuffer:
                        /* delete all text in the window */
                {
                        gdk_threads_enter();

                        GtkTextBuffer *buffer = gtk_text_view_get_buffer( GTK_TEXT_VIEW(win->widget) );
                        GtkTextIter start, end;
                        gtk_text_buffer_get_bounds(buffer, &start, &end);
                        gtk_text_buffer_delete(buffer, &start, &end);

                        gdk_threads_leave();
                }
                        break;
                
                default:
                        ILLEGAL_PARAM("Unknown window type: %d", win->type);
        }
}

/**
 * glk_set_window:
 * @win: A window.
 *
 * Sets the current stream to @win's window stream. It is exactly equivalent to
 * <code>#glk_stream_set_current(#glk_window_get_stream(@win))</code>.
 */
void
glk_set_window(winid_t win)
{
        VALID_WINDOW_OR_NULL(win, return);
        glk_stream_set_current( glk_window_get_stream(win) );
}

/**
 * glk_window_get_stream:
 * @win: A window.
 *
 * Returns the stream which is associated with @win. (See <link 
 * linkend="chimara-Window-Streams">Window Streams</link>.) Every window has a
 * stream which can be printed to, but this may not be useful, depending on the
 * window type.
 * 
 * <note><para>
 *   For example, printing to a blank window's stream has no effect.
 * </para></note>
 *
 * Returns: A window stream.
 */
strid_t glk_window_get_stream(winid_t win)
{
        VALID_WINDOW(win, return NULL);
        return win->window_stream;
}

/**
 * glk_window_set_echo_stream:
 * @win: A window.
 * @str: A stream to attach to the window, or %NULL.
 *
 * Sets @win's echo stream to @str, which can be any valid output stream. You
 * can reset a window to stop echoing by calling 
 * <code>#glk_window_set_echo_stream(@win, %NULL)</code>.
 *
 * It is illegal to set a window's echo stream to be its 
 * <emphasis>own</emphasis> window stream. That would create an infinite loop,
 * and is nearly certain to crash the Glk library. It is similarly illegal to
 * create a longer loop (two or more windows echoing to each other.)
 */
void
glk_window_set_echo_stream(winid_t win, strid_t str)
{
        VALID_WINDOW(win, return);
        VALID_STREAM_OR_NULL(str, return);
        
        /* Test for an infinite loop */
        strid_t next = str;
        for(; next && next->type == STREAM_TYPE_WINDOW; next = next->window->echo_stream)
        {
                if(next == win->window_stream)
                {
                        ILLEGAL("Infinite loop detected");
                        win->echo_stream = NULL;
                        return;
                }
        }
        
        win->echo_stream = str;
}

/**
 * glk_window_get_echo_stream:
 * @win: A window.
 *
 * Returns the echo stream of window @win. Initially, a window has no echo
 * stream, so <code>#glk_window_get_echo_stream(@win)</code> will return %NULL.
 *
 * Returns: A stream, or %NULL.
 */
strid_t
glk_window_get_echo_stream(winid_t win)
{
        VALID_WINDOW(win, return NULL);
        return win->echo_stream;
}

/**
 * glk_window_get_size:
 * @win: A window.
 * @widthptr: Pointer to a location to store the window's width, or %NULL.
 * @heightptr: Pointer to a location to store the window's height, or %NULL.
 *
 * Simply returns the actual size of the window, in its measurement system.
 * As described in <link linkend="chimara-Other-API-Conventions">Other API 
 * Conventions</link>, either @widthptr or @heightptr can be %NULL, if you
 * only want one measurement. 
 *
 * <note><para>Or, in fact, both, if you want to waste time.</para></note>
 */
void
glk_window_get_size(winid_t win, glui32 *widthptr, glui32 *heightptr)
{
        VALID_WINDOW(win, return);

    switch(win->type)
    {
        case wintype_Blank:
                case wintype_Pair:
            if(widthptr != NULL)
                *widthptr = 0;
            if(heightptr != NULL)
                *heightptr = 0;
            break;
            
        case wintype_TextGrid:
                        gdk_threads_enter();
                        /* Wait for the window to be drawn, and then cache the width and height */
                        gdk_window_process_all_updates();
                        while(win->widget->allocation.width == 1 && win->widget->allocation.height == 1)
                    {
                        /* Release the GDK lock momentarily */
                        gdk_threads_leave();
                        gdk_threads_enter();
                        while(gtk_events_pending())
                            gtk_main_iteration();
                    }
                    
                        win->width = (glui32)(win->widget->allocation.width / win->unit_width);
                    win->height = (glui32)(win->widget->allocation.height / win->unit_height);
            gdk_threads_leave();
                        
            if(widthptr != NULL)
                *widthptr = win->width;
            if(heightptr != NULL)
                *heightptr = win->height;
            break;
            
        case wintype_TextBuffer:
            /* TODO: Glk wants to be able to get its windows' sizes as soon as they are created, but GTK doesn't decide on their sizes until they are drawn. The drawing happens somewhere in an idle function. A good method would be to make an educated guess of the window's size using the ChimaraGlk widget's size. */
            gdk_threads_enter();
            /*if(win->widget->allocation.width == 1 && win->widget->allocation.height == 1)
            {
                g_warning("glk_window_get_size: The Glk program requested the size of a window before it was allocated screen space by GTK. The window size is just an educated guess.");
                guess the size from the parent window;
                break;
            } */
            
            /* Instead, we wait for GTK to draw the widget. This is probably very slow and should be fixed. */
            gdk_window_process_all_updates();
                        while(win->widget->allocation.width == 1 && win->widget->allocation.height == 1)
            {
                /* Release the GDK lock momentarily */
                gdk_threads_leave();
                gdk_threads_enter();
                while(gtk_events_pending())
                    gtk_main_iteration();
            }
                
            if(widthptr != NULL)
                *widthptr = (glui32)(win->widget->allocation.width / win->unit_width);
            if(heightptr != NULL)
                *heightptr = (glui32)(win->widget->allocation.height / win->unit_height);
            gdk_threads_leave();
            
            break;
            
        default:
            ILLEGAL_PARAM("Unknown window type: %u", win->type);
    }
}

/**
 * glk_window_set_arrangement:
 * @win: a pair window to rearrange.
 * @method: new method of size computation. One of #winmethod_Above, 
 * #winmethod_Below, #winmethod_Left, or #winmethod_Right OR'ed with 
 * #winmethod_Fixed or #winmethod_Proportional.
 * @size: new size constraint, in percentage points if @method is
 * #winmethod_Proportional, otherwise in characters if @win's type is 
 * #wintype_TextBuffer or #wintype_TextGrid, or pixels if @win's type is
 * #wintype_Graphics.
 * @keywin: new key window, or %NULL to leave the key window unchanged.
 *
 * Changes the size of an existing split &mdash; that is, it changes the 
 * constraint of a given pair window.
 * 
 * Consider the example above, where D has collapsed to zero height. Say D was a
 * text buffer window. You could make a more useful layout by doing
 * |[
 * #winid_t o2;
 * o2 = #glk_window_get_parent(d);
 * glk_window_set_arrangement(o2, #winmethod_Above | #winmethod_Fixed, 3, d);
 * ]|
 * That would set D (the upper child of O2) to be O2's key window, and give it a
 * fixed size of 3 rows.
 * 
 * If you later wanted to expand D, you could do
 * |[ glk_window_set_arrangement(o2, #winmethod_Above | #winmethod_Fixed, 5, NULL); ]|
 * That expands D to five rows. Note that, since O2's key window is already set 
 * to D, it is not necessary to provide the @keywin argument; you can pass %NULL
 * to mean <quote>leave the key window unchanged.</quote>
 * 
 * If you do change the key window of a pair window, the new key window 
 * <emphasis>must</emphasis> be a descendant of that pair window. In the current
 * example, you could change O2's key window to be A, but not B. The key window
 * also cannot be a pair window itself.
 * 
 * |[ glk_window_set_arrangement(o2, #winmethod_Below | #winmethod_Fixed, 3, NULL); ]|
 * This changes the constraint to be on the <emphasis>lower</emphasis> child of 
 * O2, which is A. The key window is still D; so A would then be three rows high
 * as measured in D's font, and D would get the rest of O2's space. That may not
 * be what you want. To set A to be three rows high as measured in A's font, you
 * would do
 * |[ glk_window_set_arrangement(o2, #winmethod_Below | #winmethod_Fixed, 3, a); ]|
 * 
 * Or you could change O2 to a proportional split:
 * |[ glk_window_set_arrangement(o2, #winmethod_Below | #winmethod_Proportional, 30, NULL); ]|
 * or
 * |[ glk_window_set_arrangement(o2, #winmethod_Above | #winmethod_Proportional, 70, NULL); ]|
 * These do exactly the same thing, since 30&percnt; above is the same as 
 * 70&percnt; below. You don't need to specify a key window with a proportional
 * split, so the @keywin argument is %NULL. (You could actually specify either A
 * or D as the key window, but it wouldn't affect the result.)
 * 
 * Whatever constraint you set, glk_window_get_size() will tell you the actual 
 * window size you got.
 * 
 * Note that you can resize windows, but you can't flip or rotate them. You 
 * can't move A above D, or change O2 to a vertical split where A is left or 
 * right of D. 
 * <note><para>
 *   To get this effect you could close one of the windows, and re-split the 
 *   other one with glk_window_open().
 * </para></note>
 */
void
glk_window_set_arrangement(winid_t win, glui32 method, glui32 size, winid_t keywin)
{
        VALID_WINDOW(win, return);
        VALID_WINDOW_OR_NULL(keywin, return);
        g_return_if_fail(win->type == wintype_Pair);
        if(keywin)
        {
                g_return_if_fail(keywin->type != wintype_Pair);
                g_return_if_fail(g_node_is_ancestor(win->window_node, keywin->window_node));
        }
        g_return_if_fail(method == (method & (winmethod_DirMask | winmethod_DivisionMask)));
        g_return_if_fail(!(((method & winmethod_DivisionMask) == winmethod_Proportional) && size > 100));
        
        win->split_method = method;
        win->constraint_size = size;
        if(keywin)
                win->key_window = keywin;

        /* Tell GTK to rearrange the windows */
        gdk_threads_enter();
        gtk_widget_queue_resize(GTK_WIDGET(glk_data->self));
        gdk_window_process_all_updates();
        gdk_threads_leave();
}

/**
 * glk_window_get_arrangement:
 * @win: a pair window.
 * @methodptr: return location for the constraint flags of @win, or %NULL.
 * @sizeptr: return location for the constraint size of @win, or %NULL.
 * @keywinptr: return location for the key window of @win, or %NULL.
 *
 * Queries the constraint of a given pair window.
 */
void
glk_window_get_arrangement(winid_t win, glui32 *methodptr, glui32 *sizeptr, winid_t *keywinptr)
{
        VALID_WINDOW(win, return);
        g_return_if_fail(win->type == wintype_Pair);
        
        if(methodptr)
                *methodptr = win->split_method;
        if(sizeptr)
                *sizeptr = win->constraint_size;
        if(keywinptr)
                *keywinptr = win->key_window;
}

/**
 * glk_window_move_cursor:
 * @win: A text grid window.
 * @xpos: Horizontal cursor position.
 * @ypos: Vertical cursor position.
 * 
 * Sets the cursor position. If you move the cursor right past the end of a 
 * line, it wraps; the next character which is printed will appear at the
 * beginning of the next line.
 * 
 * If you move the cursor below the last line, or when the cursor reaches the
 * end of the last line, it goes <quote>off the screen</quote> and further
 * output has no effect. You must call glk_window_move_cursor() or
 * glk_window_clear() to move the cursor back into the visible region.
 * 
 * <note><para>
 *  Note that the arguments of glk_window_move_cursor() are <type>unsigned 
 *  int</type>s. This is okay, since there are no negative positions. If you try
 *  to pass a negative value, Glk will interpret it as a huge positive value,
 *  and it will wrap or go off the last line.
 * </para></note>
 *
 * <note><para>
 *  Also note that the output cursor is not necessarily visible. In particular,
 *  when you are requesting line or character input in a grid window, you cannot
 *  rely on the cursor position to prompt the player where input is indicated.
 *  You should print some character prompt at that spot &mdash; a 
 *  <quote>&gt;</quote> character, for example.
 * </para></note>
 */
void
glk_window_move_cursor(winid_t win, glui32 xpos, glui32 ypos)
{
        VALID_WINDOW(win, return);
        g_return_if_fail(win->type == wintype_TextGrid);
        
        /* Calculate actual position if cursor is moved past the right edge */
        if(xpos >= win->width)
        {
            ypos += xpos / win->width;
            xpos %= win->width;
        }
        /* Go to the end if the cursor is moved off the bottom edge */
        if(ypos >= win->height)
        {
            xpos = win->width - 1;
            ypos = win->height - 1;
        }
        
        gdk_threads_enter();
        
        GtkTextBuffer *buffer = gtk_text_view_get_buffer( GTK_TEXT_VIEW(win->widget) );
        GtkTextIter newpos;
        /* There must actually be a character at xpos, or the following function will choke */
        gtk_text_buffer_get_iter_at_line_offset(buffer, &newpos, ypos, xpos);
        gtk_text_buffer_move_mark_by_name(buffer, "cursor_position", &newpos);
        
        gdk_threads_leave();
}