From 52fe7cdf6d86687cca4662a937b8e212cba94f6f Mon Sep 17 00:00:00 2001
From: Carl Worth <cworth@cworth.org>
Date: Thu, 5 Mar 2009 00:33:54 -0800
Subject: [PATCH] Add simplistic button-press handling

Right now this is just toggling a white ring on and off at
each location. The significant bit here is that the calculations
between board-index positions and screen coordinates are now
correct. Thanks to Keith Packard for helping me think through
some of the math here.
---
 dvonn.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 84 insertions(+), 10 deletions(-)

diff --git a/dvonn.c b/dvonn.c
index 43de664..616ebf3 100644
--- a/dvonn.c
+++ b/dvonn.c
@@ -80,6 +80,63 @@ loa_game_update_windows (loa_game_t *game)
 	gtk_widget_queue_draw (game->views[i]->window);
 }
 
+/* Convert from a board index to a device-pixel coordinate pair, (at
+ * the center of the ring). */
+static void
+layout_board_to_device (layout_t *layout, double *x_ret, double *y_ret)
+{
+    double x = *x_ret, y = *y_ret;
+
+    *x_ret = layout->x_offset + layout->cell_size *
+	(x + (y - DVONN_BOARD_Y_SIZE/2)/2.0 + 0.5);
+    *y_ret = layout->y_offset + layout->cell_size * (M_SQRT1_2 * y + 0.5);
+}
+
+/* Convert from a device-pixel coordinate pair to a board index. */
+static void
+layout_device_to_board (layout_t *layout, int *x_ret, int *y_ret)
+{
+    int x = *x_ret, y = *y_ret;
+    int x1, y1, x2, y2;
+    double x1_dev, y1_dev, x2_dev, y2_dev;
+    double dx, dy, d1, d2;
+
+    /* Because the vertical spacing between adjacent rows is less than
+     * layout->cell_size, the simple calculations here give us two
+     * candidate (x,y) pairs. We then choose the correct one based on
+     * a distance calculation.
+     */
+    y1 = (y - layout->y_offset) / (layout->cell_size * M_SQRT1_2);
+    x1 = (double) (x - layout->x_offset) / layout->cell_size - (y1 - DVONN_BOARD_Y_SIZE/2)/2.0;
+
+    y2 = y1 - 1;
+    x2 = (double) (x - layout->x_offset) / layout->cell_size - (y2 - DVONN_BOARD_Y_SIZE/2)/2.0;
+
+    x1_dev = x1;
+    y1_dev = y1;
+    layout_board_to_device (layout, &x1_dev, &y1_dev);
+
+    x2_dev = x2;
+    y2_dev = y2;
+    layout_board_to_device (layout, &x2_dev, &y2_dev);
+
+    dx = x - x1_dev;
+    dy = y - y1_dev;
+    d1 = sqrt (dx*dx + dy*dy);
+
+    dx = x - x2_dev;
+    dy = y - y2_dev;
+    d2 = sqrt (dx*dx + dy*dy);
+
+    if (d1 < d2) {
+	*x_ret = x1;
+	*y_ret = y1;
+    } else {
+	*x_ret = x2;
+	*y_ret = y2;
+    }
+}
+
 static gboolean
 on_button_press_event (GtkWidget	*widget,
 		       GdkEventButton	*event,
@@ -91,8 +148,29 @@ on_button_press_event (GtkWidget	*widget,
     int x, y;
     char *error;
 
-    x = (event->x - layout->x_offset) / layout->cell_size;
-    y = (event->y - layout->y_offset) / layout->cell_size;
+    x = event->x;
+    y = event->y;
+    layout_device_to_board (layout, &x, &y);
+
+    /* Do nothing for out-of-bounds clicks */
+    if (x < 0 || x >= DVONN_BOARD_X_SIZE ||
+	y < 0 || y >= DVONN_BOARD_Y_SIZE)
+    {
+	return TRUE;
+    }
+
+    /* Nor for cells which have array entries that are invalid. */
+    if (game->board.cells[x][y].type == DVONN_CELL_INVALID)
+	return TRUE;
+
+    if (game->board.cells[x][y].type == DVONN_CELL_EMPTY)
+	game->board.cells[x][y].type = DVONN_CELL_WHITE;
+    else if (game->board.cells[x][y].type == DVONN_CELL_WHITE)
+	game->board.cells[x][y].type = DVONN_CELL_EMPTY;
+
+    loa_game_update_windows (game);
+
+    return TRUE;
 
     if (! game->has_selected) {
 	if (game->board.cells[x][y].type == game->board.player) {
@@ -104,13 +182,6 @@ on_button_press_event (GtkWidget	*widget,
 	return TRUE;
     }
 
-    /* Do nothing for out-of-bounds clicks */
-    if (x < 0 || x >= DVONN_BOARD_X_SIZE ||
-	y < 0 || y >= DVONN_BOARD_Y_SIZE)
-    {
-	return TRUE;
-    }
-
     if (x == game->selected_x &&
 	y == game->selected_y)
     {
@@ -199,7 +270,10 @@ on_expose_event_draw (GtkWidget		*widget,
 			    x + (y - DVONN_BOARD_Y_SIZE/2) / 2.0,
 			    M_SQRT1_2 * y);
 	    ring_path (cr);
-	    cairo_set_source_rgba (cr, 0.0, 0.0, 0.2, 0.1);
+	    if (cell.type == DVONN_CELL_WHITE)
+		cairo_set_source_rgb (cr, 1.0, 1.0, 1.0); /* white */
+	    else
+		cairo_set_source_rgba (cr, 0.0, 0.0, 0.2, 0.1);
 	    cairo_fill (cr);
 
 	    cairo_restore (cr);
-- 
2.43.0