From 4754eda0991874c388d8a93517d579ed447d81e9 Mon Sep 17 00:00:00 2001
From: Francois Fleuret <francois@fleuret.org>
Date: Sun, 11 Sep 2016 19:17:59 +0200
Subject: [PATCH] Update.

---
 canvas.h        |  1 +
 canvas_cairo.cc |  8 ++++++--
 canvas_cairo.h  |  3 ++-
 generate.cc     | 42 +++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/canvas.h b/canvas.h
index a12dc74..b12823e 100644
--- a/canvas.h
+++ b/canvas.h
@@ -15,6 +15,7 @@
 
 class Canvas {
 public:
+  virtual void set_line_width(scalar_t w) = 0;
   virtual void set_drawing_color(scalar_t r, scalar_t g, scalar_t b) = 0;
   virtual void draw_polygon(int filled, int nb, scalar_t *x, scalar_t *y) = 0;
 };
diff --git a/canvas_cairo.cc b/canvas_cairo.cc
index f4c4acc..4bdcd2b 100644
--- a/canvas_cairo.cc
+++ b/canvas_cairo.cc
@@ -35,7 +35,7 @@ CanvasCairo::CanvasCairo(scalar_t scale, int width, int height) {
   cairo_scale(_context_resource, scale, scale);
 
   cairo_set_source_rgb(_context_resource, 1.0, 1.0, 1.0);
-  // cairo_set_source_rgb(_context_resource, 0.0, 0.0, 0.0);
+  cairo_set_line_width (_context_resource, 1.0);
 
   cairo_rectangle(_context_resource, 0, 0, width, height);
 
@@ -48,12 +48,16 @@ CanvasCairo::~CanvasCairo() {
   delete[] _data;
 }
 
+
+void CanvasCairo::set_line_width(scalar_t w) {
+  cairo_set_line_width (_context_resource, w);
+}
+
 void CanvasCairo::set_drawing_color(scalar_t r, scalar_t g, scalar_t b) {
   cairo_set_source_rgb(_context_resource, r, g, b);
 }
 
 void CanvasCairo::draw_polygon(int filled, int nb, scalar_t *x, scalar_t *y) {
-  cairo_set_line_width(_context_resource, 1.0);
   cairo_move_to(_context_resource, x[0], y[0]);
   for(int n = 0; n < nb; n++) {
     cairo_line_to(_context_resource, x[n], y[n]);
diff --git a/canvas_cairo.h b/canvas_cairo.h
index ab1d6ba..903b555 100644
--- a/canvas_cairo.h
+++ b/canvas_cairo.h
@@ -23,8 +23,9 @@ class CanvasCairo : public Canvas {
 
 public:
   CanvasCairo(scalar_t scale, int width, int height);
-
   ~CanvasCairo();
+
+  virtual void set_line_width(scalar_t w);
   virtual void set_drawing_color(scalar_t r, scalar_t g, scalar_t b);
   virtual void draw_polygon(int filled, int nb, scalar_t *x, scalar_t *y);
   virtual void write_png(FILE *file);
diff --git a/generate.cc b/generate.cc
index 6a8ee69..19e1518 100644
--- a/generate.cc
+++ b/generate.cc
@@ -31,6 +31,7 @@ using namespace std;
 
 void generate_png(Universe *universe, scalar_t scale, FILE *file) {
   CanvasCairo canvas(scale, universe->width(), universe->height());
+  canvas.set_line_width(2.0);
   universe->draw(&canvas);
   canvas.write_png(file);
 }
@@ -92,7 +93,7 @@ int main(int argc, char **argv) {
           scalar_t object_center_x = delta + (world_width - 2 * delta) * drand48();
           scalar_t object_center_y = delta + (world_height - 2 * delta) * drand48();
           scalar_t red, green, blue;
-          red = 0.75;
+          red = 0.90;
           green = red;
           blue = red;
           delete pol;
@@ -120,6 +121,8 @@ int main(int argc, char **argv) {
 
     const scalar_t scaling = 0.16;
 
+    CanvasCairo grab_trace(scaling, world_width, world_height);
+
     {
       char buffer[1024];
       sprintf(buffer, "/tmp/universe_%03d_0.png", n);
@@ -129,6 +132,21 @@ int main(int argc, char **argv) {
 
     scalar_t grab_relative_x = grabbed_polygon->relative_x(grab_start_x, grab_start_y);
     scalar_t grab_relative_y = grabbed_polygon->relative_y(grab_start_x, grab_start_y);
+    // scalar_t grab_previous_x = grab_start_x, grab_previous_y = grab_start_y;
+
+    {
+      int n = 36;
+      scalar_t xp[n], yp[n];
+      for(int k = 0; k < n; k++) {
+        scalar_t radius = 1/scaling;
+        scalar_t alpha = 2 * M_PI * scalar_t(k) / scalar_t(n);
+        xp[k] = grab_start_x + radius * cos(alpha);
+        yp[k] = grab_start_y + radius * sin(alpha);
+      }
+      grab_trace.set_drawing_color(0.0, 0.0, 0.0);
+      grab_trace.set_line_width(1.0);
+      grab_trace.draw_polygon(1, n, xp, yp);
+    }
 
     scalar_t dt = 0.1;
     for(int i = 0; i < 500; i++) {
@@ -136,6 +154,21 @@ int main(int argc, char **argv) {
       scalar_t yf = grabbed_polygon->absolute_y(grab_relative_x, grab_relative_y);
       grabbed_polygon->apply_force(dt, xf, yf, 0.0, -1.0);
       universe->update(dt);
+
+      /*
+        {
+        scalar_t xp[2], yp[2];
+        xp[0] = grab_previous_x;
+        yp[0] = grab_previous_y;
+        xp[1] = xf;
+        yp[1] = yf;
+        grab_previous_x = xf;
+        grab_previous_y = yf;
+
+        grab_trace.set_drawing_color(0.0, 0.0, 0.0);
+        grab_trace.draw_polygon(1, 2, xp, yp);
+        }
+      */
     }
 
     {
@@ -144,6 +177,13 @@ int main(int argc, char **argv) {
       FILE *file = fopen(buffer, "w");
       generate_png(universe, scaling, file);
     }
+
+    {
+      char buffer[1024];
+      sprintf(buffer, "/tmp/grab_trace_%03d.png", n);
+      FILE *file = fopen(buffer, "w");
+      grab_trace.write_png(file);
+    }
   }
 
   delete universe;
-- 
2.39.5