Android: added function to optimize complex regions

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12760 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

src/drivers/Android/Fl_Android_Graphics_Clipping.H

@@ -69,6 +69,7 @@ public:
   void set_ltrb(int l, int t, int r, int b);
   virtual void set(const Fl_Rect_Region &r);
   virtual int intersect_with(const Fl_Rect_Region &r);
+  void add_to_bbox(const Fl_Rect_Region &r);
 
   virtual void print(const char*) const;
 
@@ -87,14 +88,29 @@ private:
  * rectangular, is_simple() returns 1 and the rectangle can be used just
  * as in Fl_Rect_Region.
  *
- * If a more complex representation is needed, the first list of
- * subregions is organizen in horizontal strips. The root region rect
- * will contain the outline of all subregions, and the subregions
- * will either be simple rectangles, or they will contain a second
- * level of subregions, subdividing the horizontal region into vertical
- * columns.
+ * If a more complex representation is needed, subregions are created which are
+ * guaranteed to lie within the bounding box of the current region. Subregions
+ * themselves can again contain sub-subregions to describe the entire clipping
+ * region, effectively creating a tree where the leafs contain the rectangles
+ * that together describe the clipping area.
+ *
+ * To make life easier, Fl_Complex_Region provides two types of iterator to
+ * travers the entire tree.
+ *
+ * 1. Fl_Complex_Region itself is compatible to C++11 range-based loops and
+ *    can bewalked simply by writing ``for (auto &&it: rgn) { ... }``.
+ *
+ * 2. Fl_Complex_Region provides an alternative iterator that loop only through
+ *    leafs that intersects with a given rectangle. The returned object
+ *    provides access to the readily clipped rectangle.
+ *
+ * @code
+ * Fl_Complex_Region rgn(something);
+ * for (auto &&it: rgn.iterate(Fl_Rect_Region(0, 0, 100, 100)) {
+ *    draw_something(it->rect());
+ * }
+ * @endcode
  *
- * When reading, the tree can be easily walked using recursion.
  */
 class Fl_Complex_Region : public Fl_Rect_Region
 {
@@ -156,6 +172,7 @@ protected:
   void print_data(int indent) const;
   int subtract_smaller_region(const Fl_Rect_Region &r);
   Fl_Complex_Region *add_subregion();
+  void compress();
 
   Fl_Complex_Region *pSubregion = 0L;
   Fl_Complex_Region *pParent = 0L;

src/drivers/Android/Fl_Android_Graphics_Clipping.cxx

@@ -167,6 +167,17 @@ int Fl_Rect_Region::intersect_with(const Fl_Rect_Region &r)
   return LESS;
 }
 
+/**
+ * Use rectangle as a bounding box and add the outline of another rect.
+ */
+void Fl_Rect_Region::add_to_bbox(const Fl_Rect_Region &r)
+{
+  if (r.pLeft<pLeft) pLeft = r.pLeft;
+  if (r.pTop<pTop) pTop = r.pTop;
+  if (r.pRight>pRight) pRight = r.pRight;
+  if (r.pBottom>pBottom) pBottom = r.pBottom;
+}
+
 /**
  * Print the coordinates of the rect to the log.
  * @param label some text that is logged with this message.
@@ -237,8 +248,8 @@ void Fl_Complex_Region::print_data(int indent) const
  */
 void Fl_Complex_Region::set(const Fl_Rect_Region &r)
 {
-  delete pSubregion; pSubregion = 0;
   Fl_Rect_Region::set(r);
+  delete pSubregion; pSubregion = 0;
 }
 
 /**
@@ -307,9 +318,48 @@ int Fl_Complex_Region::subtract(const Fl_Rect_Region &r)
       pNext->subtract(r);
     }
   }
+  compress();
   return 0;
 }
 
+/**
+ * Compress the subregion of this region if possible and update the bounding
+ * box of this region.
+ *
+ * Does not recurse down the tree!
+ */
+void Fl_Complex_Region::compress()
+{
+  // Can't compress anything that does not have a subregion
+  if (!pSubregion) return;
+
+  // remove all empty regions, because the really don't add anything (literally)
+  Fl_Complex_Region *rgn = pSubregion, **rgnPtr = &pSubregion;
+  while (rgn) {
+    if (rgn->is_empty()) {
+      *rgnPtr = rgn->pNext;
+      delete rgn;
+    }
+    rgnPtr = &rgn->pNext;
+    rgn = *rgnPtr;
+  }
+  if (!pSubregion) return;
+
+  // find rectangles that can be merged into a single new rectangle
+
+  // if there is only a single subregion left, merge it into this region
+  if (pSubregion->pNext==nullptr) {
+    set((Fl_Rect_Region&)*pSubregion); // deletes subregion for us
+  }
+  if (!pSubregion) return;
+
+  // finally, update the boudning box
+  Fl_Rect_Region::set((Fl_Rect_Region&)*pSubregion);
+  for (rgn=pSubregion->pNext; rgn; rgn=rgn->pNext) {
+    add_to_bbox(*rgn);
+  }
+}
+
 /**
  * Subtract a rect from another rect, potentially creating four new rectangles.
  * This assumes that the calling region is NOT complex.

src/drivers/Android/Fl_Android_Graphics_Driver.cxx

@@ -544,6 +544,9 @@ void Fl_GDI_Graphics_Driver::set_current_() {
 
 #endif
 
+/*
+
+ */
 
 //
 // End of "$Id$".