+ for (i = 0; i < g->num_dots; i++) {
+ dot_bbox(ds, g, &g->dots[i], &bx, &by, &bw, &bh);
+ if (boxes_intersect(x, y, w, h, bx, by, bw, bh))
+ game_redraw_dot(dr, ds, state, i);
+ }
+
+ unclip(dr);
+ draw_update(dr, x, y, w, h);
+}
+
+static void game_redraw(drawing *dr, game_drawstate *ds, game_state *oldstate,
+ game_state *state, int dir, game_ui *ui,
+ float animtime, float flashtime)
+{
+#define REDRAW_OBJECTS_LIMIT 16 /* Somewhat arbitrary tradeoff */
+
+ grid *g = state->game_grid;
+ int border = BORDER(ds->tilesize);
+ int i;
+ int flash_changed;
+ int redraw_everything = FALSE;
+
+ int edges[REDRAW_OBJECTS_LIMIT], nedges = 0;
+ int faces[REDRAW_OBJECTS_LIMIT], nfaces = 0;
+
+ /* Redrawing is somewhat involved.
+ *
+ * An update can theoretically affect an arbitrary number of edges
+ * (consider, for example, completing or breaking a cycle which doesn't
+ * satisfy all the clues -- we'll switch many edges between error and
+ * normal states). On the other hand, redrawing the whole grid takes a
+ * while, making the game feel sluggish, and many updates are actually
+ * quite well localized.
+ *
+ * This redraw algorithm attempts to cope with both situations gracefully
+ * and correctly. For localized changes, we set a clip rectangle, fill
+ * it with background, and then redraw (a plausible but conservative
+ * guess at) the objects which intersect the rectangle; if several
+ * objects need redrawing, we'll do them individually. However, if lots
+ * of objects are affected, we'll just redraw everything.
+ *
+ * The reason for all of this is that it's just not safe to do the redraw
+ * piecemeal. If you try to draw an antialiased diagonal line over
+ * itself, you get a slightly thicker antialiased diagonal line, which
+ * looks rather ugly after a while.
+ *
+ * So, we take two passes over the grid. The first attempts to work out
+ * what needs doing, and the second actually does it.
+ */
+
+ if (!ds->started)
+ redraw_everything = TRUE;
+ else {
+
+ /* First, trundle through the faces. */
+ for (i = 0; i < g->num_faces; i++) {
+ grid_face *f = g->faces + i;
+ int sides = f->order;
+ int clue_mistake;
+ int clue_satisfied;
+ int n = state->clues[i];
+ if (n < 0)
+ continue;
+
+ clue_mistake = (face_order(state, i, LINE_YES) > n ||
+ face_order(state, i, LINE_NO ) > (sides-n));
+ clue_satisfied = (face_order(state, i, LINE_YES) == n &&
+ face_order(state, i, LINE_NO ) == (sides-n));
+
+ if (clue_mistake != ds->clue_error[i] ||
+ clue_satisfied != ds->clue_satisfied[i]) {
+ ds->clue_error[i] = clue_mistake;
+ ds->clue_satisfied[i] = clue_satisfied;
+ if (nfaces == REDRAW_OBJECTS_LIMIT)
+ redraw_everything = TRUE;
+ else
+ faces[nfaces++] = i;
+ }
+ }
+
+ /* Work out what the flash state needs to be. */
+ if (flashtime > 0 &&
+ (flashtime <= FLASH_TIME/3 ||
+ flashtime >= FLASH_TIME*2/3)) {
+ flash_changed = !ds->flashing;
+ ds->flashing = TRUE;
+ } else {
+ flash_changed = ds->flashing;
+ ds->flashing = FALSE;
+ }
+
+ /* Now, trundle through the edges. */
+ for (i = 0; i < g->num_edges; i++) {
+ char new_ds =
+ state->line_errors[i] ? DS_LINE_ERROR : state->lines[i];
+ if (new_ds != ds->lines[i] ||
+ (flash_changed && state->lines[i] == LINE_YES)) {
+ ds->lines[i] = new_ds;
+ if (nedges == REDRAW_OBJECTS_LIMIT)
+ redraw_everything = TRUE;
+ else
+ edges[nedges++] = i;
+ }
+ }
+ }
+
+ /* Pass one is now done. Now we do the actual drawing. */
+ if (redraw_everything) {
+ int grid_width = g->highest_x - g->lowest_x;
+ int grid_height = g->highest_y - g->lowest_y;
+ int w = grid_width * ds->tilesize / g->tilesize;
+ int h = grid_height * ds->tilesize / g->tilesize;
+
+ game_redraw_in_rect(dr, ds, state,
+ 0, 0, w + 2*border + 1, h + 2*border + 1);
+ } else {
+
+ /* Right. Now we roll up our sleeves. */
+
+ for (i = 0; i < nfaces; i++) {
+ grid_face *f = g->faces + faces[i];
+ int x, y, w, h;
+
+ face_text_bbox(ds, g, f, &x, &y, &w, &h);
+ game_redraw_in_rect(dr, ds, state, x, y, w, h);
+ }
+
+ for (i = 0; i < nedges; i++) {
+ grid_edge *e = g->edges + edges[i];
+ int x, y, w, h;
+
+ edge_bbox(ds, g, e, &x, &y, &w, &h);
+ game_redraw_in_rect(dr, ds, state, x, y, w, h);
+ }
+ }
+
+ ds->started = TRUE;