1 files changed, 205 insertions, 13 deletions

diff --git a/examples/graph.c b/examples/graph.c
index c7b2877..7f9870f 100755
--- a/examples/graph.c
+++ b/examples/graph.c
@@ -27,6 +27,167 @@ exit $? # */
 
 #include "../graphics.c"
 
+enum {
+  MAX_NUM_NODES = 1024,
+  MAX_NUM_EDGES = 1024,
+};
+
+typedef struct {
+  b8  enabled;
+  f64 x;
+  f64 y;
+  f64 radius;
+  b8  hover;
+} Node;
+
+typedef struct {
+  b8  enabled;
+  i64 src;
+  i64 dst;
+  f64 width;
+  b8  hover;
+} Edge;
+
+typedef struct {
+  Node nodes[MAX_NUM_NODES];
+  Edge edges[MAX_NUM_EDGES];
+} World;
+
+World world = {0};
+
+b8 check_node_index(i64 node_index) {
+  return
+       node_index >= 0 && node_index < MAX_NUM_NODES
+    && world.nodes[node_index].enabled;
+}
+
+b8 check_edge_index(i64 edge_index) {
+  return
+       edge_index >= 0 && edge_index < MAX_NUM_EDGES
+    && world.edges[edge_index].enabled
+    && check_node_index(world.edges[edge_index].src)
+    && check_node_index(world.edges[edge_index].dst);
+}
+
+void draw_node(i64 node_index) {
+  assert(check_node_index(node_index));
+
+  Node n = world.nodes[node_index];
+
+  u32 color = 0; // black color
+
+  if (n.hover)
+    color = 0x007f00; // green color
+
+  fill_ellipse(
+    OP_SET, // set pixels
+    color,
+    n.x - n.radius,
+    n.y - n.radius,
+    n.radius * 2,
+    n.radius * 2
+  );
+}
+
+void draw_edge(i64 edge_index) {
+  assert(check_edge_index(edge_index));
+
+  Edge e  = world.edges[edge_index];
+  Node n0 = world.nodes[e.src];
+  Node n1 = world.nodes[e.dst];
+
+  u32 color = 0x7f7f7f; // grey color
+
+  if (e.hover)
+    color = 0x007f00; // green color
+
+  fill_line(
+    OP_SET, // set pixels
+    color,
+    n0.x,
+    n0.y,
+    n1.x,
+    n1.y,
+    e.width
+  );
+}
+
+void draw_graph(void) {
+  //  draw all edges
+  for (i64 i = 0; i < MAX_NUM_EDGES; ++i)
+    if (world.edges[i].enabled)
+      draw_edge(i);
+
+  //  draw all nodes
+  for (i64 i = 0; i < MAX_NUM_NODES; ++i)
+    if (world.nodes[i].enabled)
+      draw_node(i);
+}
+
+void update_node(i64 node_index) {
+  assert(check_node_index(node_index));
+
+  Node n = world.nodes[node_index];
+
+  f64 cx = platform.cursor_x - n.x;
+  f64 cy = platform.cursor_y - n.y;
+
+  world.nodes[node_index].hover = cx * cx + cy * cy <= n.radius * n.radius;
+}
+
+void update_edge(i64 edge_index) {
+  assert(check_edge_index(edge_index));
+
+  Edge e  = world.edges[edge_index];
+  Node n0 = world.nodes[e.src];
+  Node n1 = world.nodes[e.dst];
+
+  f64 cx = platform.cursor_x - n0.x;
+  f64 cy = platform.cursor_y - n0.y;
+
+  // normalized line direction vector
+  f64 rx = n1.x - n0.x;
+  f64 ry = n1.y - n0.y;
+  f64 r  = sqrt(rx * rx + ry * ry);
+  if (r >= EPSILON) {
+    rx /= r;
+    ry /= r;
+  }
+
+  // tangent
+  f64 tx = -ry;
+  f64 ty = rx;
+
+  // distance to the line (dot-product)
+  f64 d = cx * tx + cy * ty;
+
+  // distance to the tangent line
+  f64 l = cx * rx + cy * ry;
+
+  world.edges[edge_index].hover = d <= e.width / 2 && d >= -e.width / 2 && l >= 0 && l <= r;
+}
+
+void update_graph(void) {
+  b8 hover_node = 0;
+
+  //  update all nodes
+  for (i64 i = 0; i < MAX_NUM_NODES; ++i)
+    if (world.nodes[i].enabled) {
+      update_node(i);
+      if (world.nodes[i].hover)
+        hover_node = 1;
+    }
+
+  //  update all edges
+  for (i64 i = 0; i < MAX_NUM_EDGES; ++i)
+    if (world.edges[i].enabled) {
+      if (hover_node)
+        world.edges[i].hover = 0;
+      else
+        update_edge(i);
+    }
+}
+
 i32 main(i32 argc, c8 **argv) {
   (void) argc;
   (void) argv;
@@ -37,26 +198,57 @@ i32 main(i32 argc, c8 **argv) {
     .frame_height = 720,
   };
 
-  u32 WHITE = u32_from_rgb(1.f, 1.f, 1.f);
-  u32 BLACK = u32_from_rgb(0.f, 0.f, 0.f);
-  u32 RED   = u32_from_rgb(1.f, 0.f, 0.f);
-  u32 BLUE  = u32_from_rgb(0.f, 0.f, 1.f);
-
   p_init();
 
-  while (!platform.done) {
-    p_wait_events();
+  world.nodes[0] = (Node) {
+    .enabled = 1,
+    .x       = 100,
+    .y       = 100,
+    .radius  = 50,
+  };
+
+  world.nodes[1] = (Node) {
+    .enabled = 1,
+    .x       = 300,
+    .y       = 100,
+    .radius  = 50,
+  };
+
+  world.nodes[2] = (Node) {
+    .enabled = 1,
+    .x       = 120,
+    .y       = 300,
+    .radius  = 60,
+  };
 
-    i64 x = platform.frame_width  / 2;
-    i64 y = platform.frame_height / 2;
+  world.edges[0] = (Edge) {
+    .enabled = 1,
+    .src     = 0,
+    .dst     = 1,
+    .width   = 30,
+  };
 
-    fill_rectangle(OP_SET, WHITE, 0, 0, platform.frame_width, platform.frame_height);
+  world.edges[1] = (Edge) {
+    .enabled = 1,
+    .src     = 0,
+    .dst     = 2,
+    .width   = 30,
+  };
 
-    fill_triangle(OP_SET, RED, 100, 100, 200, 100, 150, 200);
+  world.edges[2] = (Edge) {
+    .enabled = 1,
+    .src     = 1,
+    .dst     = 2,
+    .width   = 30,
+  };
+
+  while (!platform.done) {
+    p_wait_events();
 
-    fill_line(OP_SET, BLUE, 100, 300, 300, 500, 30);
+    fill_rectangle(OP_SET, 0xffffff, 0, 0, platform.frame_width, platform.frame_height);
 
-    fill_ellipse(OP_SET, BLACK, x - 140, y - 100, 280, 200);
+    update_graph();
+    draw_graph();
 
     p_render_frame();
   }