2 files changed, 293 insertions, 0 deletions
diff --git a/calendar/gui/layout.c b/calendar/gui/layout.c
new file mode 100644
index 0000000000..03fac94cc6
--- /dev/null
+++ b/calendar/gui/layout.c
@@ -0,0 +1,268 @@
+/* Event layout engine for Gnomecal
+ *
+ * Copyright (C) 1998 The Free Software Foundation
+ *
+ * Authors: Miguel de Icaza <miguel@nuclecu.unam.mx>
+ *          Federico Mena <federico@nuclecu.unam.mx>
+ */
+
+#include "layout.h"
+
+
+/* This defines the maximum number of events to overlap per row.  More than that number of events
+ * will not be displayed.  This is not ideal, so sue me.
+ */
+#define MAX_EVENTS_PER_ROW 32
+
+
+/* Compares two time_t values, used for qsort() */
+static int
+compare_time_t (const void *a, const void *b)
+{
+	time_t ta, tb;
+
+	ta = *((time_t *) a);
+	tb = *((time_t *) b);
+
+	if (ta < tb)
+		return -1;
+	else if (ta > tb)
+		return 1;
+	else
+		return 0;
+}
+
+/* Builds a partition of the time range occupied by the events in the list.  It returns an array
+ * with the times that define the partition and the number of items in the partition.
+ */
+static time_t *
+build_partition (GList *events, int num_events, int *num_rows)
+{
+	time_t *rows, *p, *q;
+	GList *list;
+	CalendarObject *co;
+	int i, unique_vals;
+
+	/* This is the maximum number of rows we would need */
+
+	*num_rows = num_events * 2;
+
+	/* Fill the rows with the times */
+
+	rows = g_new (time_t, *num_rows);
+
+	for (list = events, p = rows; list; list = list->next) {
+		co = list->data;
+		*p++ = co->ev_start;
+		*p++ = co->ev_end;
+	}
+
+	/* Do a sort | uniq on the array */
+
+	qsort (rows, *num_rows, sizeof (time_t), compare_time_t);
+
+	p = rows;
+	q = rows + 1;
+	unique_vals = 1;
+
+	for (i = 1; i < *num_rows; i++, q++)
+		if (*q != *p) {
+			unique_vals++;
+			p++;
+			*p = *q;
+		}
+
+	/* Return the number of unique values in the partition and the partition array itself */
+
+	*num_rows = unique_vals;
+	return rows;
+}
+
+/* Returns the index of the element in the partition that corresponds to the specified time */
+int
+find_index (time_t *partition, time_t t)
+{
+	int i;
+
+	for (i = 0; ; i++)
+		if (partition[i] == t)
+			return i;
+}
+
+#define xy(slot_array, x, y) slot_array[(y * MAX_EVENTS_PER_ROW) + (x)]
+
+/* Checks that all the cells in the slot array at the specified slot column are free to use by an
+ * event that has the specified range.
+ */
+static int
+range_is_empty (time_t *partition, int *slot_array, int slot, time_t start, time_t end)
+{
+	int i;
+
+	for (i = find_index (partition, start); partition[i] < end; i++)
+		if (xy (slot_array, slot, i) != -1)
+			return FALSE;
+
+	return TRUE;
+}
+
+/* Allocates a time in the slot array for the specified event's index */
+static void
+range_allocate (time_t *partition, int *slot_array, int slot, time_t start, time_t end, int ev_num)
+{
+	int i;
+
+	for (i = find_index (partition, start); partition[i] < end; i++)
+		xy (slot_array, slot, i) = ev_num;
+}
+
+/* Performs the initial allocation of slots for events.  Each event gets one column; they will be
+ * expanded in a later stage.  Returns the number of columns used.
+ */
+static int
+initial_allocate (GList *events, time_t *partition, int *slot_array, int *allocations, int *columns_used)
+{
+	CalendarObject *co;
+	int i;
+	int slot;
+	int num_slots;
+
+	num_slots = 0;
+
+	for (i = 0; events; events = events->next, i++) {
+		co = events->data;
+
+		/* Start with no allocation, no columns */
+
+		allocations[i] = -1;
+		columns_used[i] = 0;
+
+		/* Find a free column for the event */
+
+		for (slot = 0; slot < MAX_EVENTS_PER_ROW; slot++)
+			if (range_is_empty (partition, slot_array, slot, co->ev_start, co->ev_end)) {
+				range_allocate (partition, slot_array, slot, co->ev_start, co->ev_end, i);
+
+				allocations[i] = slot;
+				columns_used[i] = 1;
+
+				if ((slot + 1) > num_slots)
+					num_slots = slot + 1;
+
+				break;
+			}
+	}
+
+	return num_slots;
+}
+
+/* Returns the maximum number of columns that an event can expanded by in the slot array */
+static int
+columns_to_expand (time_t *partition, int *slot_array, int *allocations, int num_slots, int ev_num,
+		   time_t start, time_t end)
+{
+	int cols;
+	int slot;
+	int i_start;
+	int i;
+
+	cols = 0;
+
+	i_start = find_index (partition, start);
+
+	for (slot = allocations[ev_num] + 1; slot < num_slots; slot++) {
+		for (i = i_start; partition[i] < end; i++)
+			if (xy (slot_array, slot, i) != -1)
+				return cols;
+
+		cols++;
+	}
+
+	return cols;
+}
+
+/* Expands an event to occupy the specified number of columns */
+static void
+do_expansion (time_t *partition, int *slot_array, int *allocations, int ev_num, time_t start, time_t end, int num_cols)
+{
+	int i, j;
+	int slot;
+
+	for (i = find_index (partition, start); partition[i] < end; i++) {
+		slot = allocations[ev_num] + 1;
+
+		for (j = 0; j < num_cols; j++)
+			xy (slot_array, slot + j, i) = ev_num;
+	}
+}
+
+/* Expands the events in the slot array to occupy as many columns as possible.  This is the second
+ * pass of the layout algorithm.
+ */
+static void
+expand_events (GList *events, time_t *partition, int *slot_array, int num_slots, int *allocations, int *columns_used)
+{
+	int i;
+	CalendarObject *co;
+	int cols;
+
+	for (i = 0; events; events = events->next, i++) {
+		co = events->data;
+
+		cols = columns_to_expand (partition, slot_array, allocations, num_slots, i, co->ev_start, co->ev_end);
+
+		if (cols == 0)
+			continue; /* We can't expand this event */
+
+		do_expansion (partition, slot_array, allocations, i, co->ev_start, co->ev_end, cols);
+
+		columns_used[i] += cols;
+	}
+}
+
+void
+layout_events (GList *events, int *num_slots, int **allocations, int **slots)
+{
+	time_t *time_partition;
+	int *slot_array;
+	int num_events;
+	int num_rows;
+	int i;
+
+	g_return_if_fail (num_slots != NULL);
+	g_return_if_fail (allocations != NULL);
+	g_return_if_fail (slots != NULL);
+
+	if (!events) {
+		*num_slots = 0;
+		*allocations = NULL;
+		*slots = NULL;
+
+		return;
+	}
+
+	num_events = g_list_length (events);
+
+	/* Build the partition of the time range, and then build the array of slots */
+
+	time_partition = build_partition (events, num_events, &num_rows);
+
+	slot_array = g_new (int, num_rows * MAX_EVENTS_PER_ROW);
+	for (i = 0; i < (num_rows * MAX_EVENTS_PER_ROW); i++)
+		slot_array[i] = -1; /* This is our 'empty' value */
+
+	/* Build the arrays for allocations and columns used */
+
+	*allocations = g_new (int, num_events);
+	*slots = g_new (int, num_events);
+
+	/* Perform initial allocation -- each event gets one column */
+
+	*num_slots = initial_allocate (events, time_partition, slot_array, *allocations, *slots);
+
+	/* Expand the events to as many columns as possible */
+
+	expand_events (events, time_partition, slot_array, *num_slots, *allocations, *slots);
+
+	g_free (slot_array);
+}
diff --git a/calendar/gui/layout.h b/calendar/gui/layout.h
new file mode 100644
index 0000000000..b87cf7e36b
--- /dev/null
+++ b/calendar/gui/layout.h
@@ -0,0 +1,25 @@
+/* Event layout engine for Gnomecal
+ *
+ * Copyright (C) 1998 The Free Software Foundation
+ *
+ * Authors: Miguel de Icaza <miguel@nuclecu.unam.mx>
+ *          Federico Mena <federico@nuclecu.unam.mx>
+ */
+
+#ifndef LAYOUT_H
+#define LAYOUT_H
+
+#include "calendar.h"
+
+
+/* This is the main layout function for overlapping events.  You pass in a list of CalendarObject
+ * structures and it will calculate a nice non-overlapping layout for them.
+ *
+ * It returns the number of slots ("columns") that you need to take into account when actually
+ * painting the events, the array of the first slot index that each event occupies, and the array of
+ * number of slots that each event occupies.  You have to free both arrays.
+ */
+void layout_events (GList *events, int *num_slots, int **allocations, int **slots);
+
+
+#endif