Refactor code to make rounded rectangles accessible (#553)

This adds fl_rounded_rect and fl_rounded_rectf so the
user can draw rounded rectangles. This uses existing and
optimised code that is rearranged.

2 files changed, 48 insertions, 21 deletions

diff --git a/src/Fl_Graphics_Driver.cxx b/src/Fl_Graphics_Driver.cxx
index 95f79ee22..9d120961e 100644
--- a/src/Fl_Graphics_Driver.cxx
+++ b/src/Fl_Graphics_Driver.cxx
@@ -455,6 +455,50 @@ void Fl_Graphics_Driver::rect(int x, int y, int w, int h) {}
 /** see fl_rectf() */
 void Fl_Graphics_Driver::rectf(int x, int y, int w, int h) {}
 
+void Fl_Graphics_Driver::_rbox(int fill, int x, int y, int w, int h, int r) {
+  static double lut[] = { 0.0, 0.07612, 0.29289, 0.61732, 1.0};
+  if (r == 5) r = 4;  // use only even sizes for small corners (STR #2943)
+  if (r == 7) r = 8;  // note: 8 is better than 6 (really)
+  double xd = x, yd = y, rd = (x+w-1), bd = (y+h-1);
+  double rr = r;
+  if (fill) begin_polygon(); else begin_loop();
+  // top left
+  transformed_vertex(xd+lut[0]*rr, yd+lut[4]*rr);
+  transformed_vertex(xd+lut[1]*rr, yd+lut[3]*rr);
+  transformed_vertex(xd+lut[2]*rr, yd+lut[2]*rr);
+  transformed_vertex(xd+lut[3]*rr, yd+lut[1]*rr);
+  transformed_vertex(xd+lut[4]*rr, yd+lut[0]*rr);
+  // top right
+  transformed_vertex(rd-lut[4]*rr, yd+lut[0]*rr);
+  transformed_vertex(rd-lut[3]*rr, yd+lut[1]*rr);
+  transformed_vertex(rd-lut[2]*rr, yd+lut[2]*rr);
+  transformed_vertex(rd-lut[1]*rr, yd+lut[3]*rr);
+  transformed_vertex(rd-lut[0]*rr, yd+lut[4]*rr);
+  // bottom right
+  transformed_vertex(rd-lut[0]*rr, bd-lut[4]*rr);
+  transformed_vertex(rd-lut[1]*rr, bd-lut[3]*rr);
+  transformed_vertex(rd-lut[2]*rr, bd-lut[2]*rr);
+  transformed_vertex(rd-lut[3]*rr, bd-lut[1]*rr);
+  transformed_vertex(rd-lut[4]*rr, bd-lut[0]*rr);
+  // bottom left
+  transformed_vertex(xd+lut[4]*rr, bd-lut[0]*rr);
+  transformed_vertex(xd+lut[3]*rr, bd-lut[1]*rr);
+  transformed_vertex(xd+lut[2]*rr, bd-lut[2]*rr);
+  transformed_vertex(xd+lut[1]*rr, bd-lut[3]*rr);
+  transformed_vertex(xd+lut[0]*rr, bd-lut[4]*rr);
+  if (fill) fl_end_polygon(); else fl_end_loop();
+}
+
+/** see fl_rrect() */
+void Fl_Graphics_Driver::rounded_rect(int x, int y, int w, int h, int r) {
+  _rbox(0, x, y, w, h, r);
+}
+
+/** see fl_rrectf() */
+void Fl_Graphics_Driver::rounded_rectf(int x, int y, int w, int h, int r) {
+  _rbox(1, x, y, w, h, r);
+}
+
 void Fl_Graphics_Driver::colored_rectf(int x, int y, int w, int h, uchar r, uchar g, uchar b) {
   color(r, g, b);
   rectf(x, y, w, h);
diff --git a/src/fl_rounded_box.cxx b/src/fl_rounded_box.cxx
index df41b4f6e..f1b351144 100644
--- a/src/fl_rounded_box.cxx
+++ b/src/fl_rounded_box.cxx
@@ -23,35 +23,18 @@
 //  RS = max. corner radius
 //  BW = box shadow width
 
-#define RN 5
 #define RS (Fl::box_border_radius_max())
 #define BW (Fl::box_shadow_width())
 
-static double offset[RN] = { 0.0, 0.07612, 0.29289, 0.61732, 1.0};
-
-static inline void fl_vertex_r(double x, double y) {
-  fl_vertex(x + 0.5, y + 0.5);
-}
-
 static void rbox(int fill, int x, int y, int w, int h) {
-  int i;
   int rs, rsy;
   rs = w*2/5; rsy = h*2/5;
   if (rs > rsy) rs = rsy; // use smaller radius
   if (rs > RS) rs = RS;
-  if (rs == 5) rs = 4;  // use only even sizes for small corners (STR #2943)
-  if (rs == 7) rs = 8;  // note: 8 is better than 6 (really)
-
-  if (fill) fl_begin_polygon(); else fl_begin_loop();
-  for (i=0; i<RN; i++)
-    fl_vertex_r(x + offset[RN-i-1]*rs, y + offset[i] * rs);
-  for (i=0; i<RN; i++)
-    fl_vertex_r(x + offset[i]*rs, y + h-1 - offset[RN-i-1] * rs);
-  for (i=0; i<RN; i++)
-    fl_vertex_r(x + w-1 - offset[RN-i-1]*rs, y + h-1 - offset[i] * rs);
-  for (i=0; i<RN; i++)
-    fl_vertex_r(x + w-1 - offset[i]*rs, y + offset[RN-i-1] * rs);
-  if (fill) fl_end_polygon(); else fl_end_loop();
+  if (fill)
+    fl_rounded_rectf(x, y, w, h, rs);
+  else
+    fl_rounded_rect(x, y, w, h, rs);
 }
 
 static void fl_rflat_box(int x, int y, int w, int h, Fl_Color c) {