bugfixes and speedups

[swftools.git] / lib / gfxpoly / xrow.h

diff --git a/lib/gfxpoly/xrow.h b/lib/gfxpoly/xrow.h
index 8021085..e172920 100644 (file)
--- a/lib/gfxpoly/xrow.h
+++ b/lib/gfxpoly/xrow.h
@@ -13,7 +13,28 @@ typedef struct _xrow {
 } xrow_t;
 
 xrow_t* xrow_new();
+
+/* so the idea is this:
+   Before processing any events for a given y, store the list+tree of the current active
+   list (that might be useful anyway for adding xrow points to segments).
+   Then, for every starting segment and for every segment that receives a point, add a (x,segment)
+   tuple to a list which we later sort.
+   These segments will at that point have their *old* fill styles set.
+   Then, order that list, and also merge identical x values using left<->right comparisons on
+   the *old* active list, so that for every x coordinate we have the rightmost (old) segment. (For
+   small active lists, it might be faster to just mark the segments (and store the x in them), and
+   then walk the active list from left to right, collecting marked segments)
+   This list now gives us the information about what the fill areas look like above the scanline and to
+   the right of segments which received a point.
+   Now, apply fill style changes and resort the list, this time using the *new* active
+   list for merging identical x values. That gives us the information on what fill areas look like
+   *below* the scanline and to the right of segments which received a point.
+   Every time an "above" fillstyle differs from a "below" fillstyle, we need to draw a horizontal
+   line (from right to left, using the below fillstyle).
+*/
+
 void xrow_add(xrow_t*xrow, int32_t x);
+
 void xrow_sort(xrow_t*xrow);
 void xrow_dump(xrow_t*xrow);
 void xrow_reset(xrow_t*xrow);