Draw triangles and lines

4 files changed, 223 insertions, 35 deletions

diff --git a/examples/graph.c b/examples/graph.c
new file mode 100755
index 0000000..c7b2877
--- /dev/null
+++ b/examples/graph.c
@@ -0,0 +1,66 @@
+#if 0 /*
+#/  ================================================================
+#/
+#/    graph.c
+#/
+#/  ================================================================
+#/
+#/    Self-compilation shell script
+#/
+SRC=${0##*./}
+BIN=${SRC%.*}
+gcc                                         \
+  -Wall -Wextra -Werror -pedantic           \
+  -Wno-old-style-declaration                \
+  -Wno-missing-braces                       \
+  -Wno-unused-variable                      \
+  -Wno-unused-but-set-variable              \
+  -Wno-unused-parameter                     \
+  -Wno-overlength-strings                   \
+  -O3                                       \
+  -fsanitize=undefined,address,leak -mshstk \
+  -lX11 -lm                                 \
+  -o $BIN $SRC &&                           \
+  ./$BIN $@ && rm $BIN
+exit $? # */
+#endif
+
+#include "../graphics.c"
+
+i32 main(i32 argc, c8 **argv) {
+  (void) argc;
+  (void) argv;
+
+  platform = (Platform) {
+    .title        = "Graph",
+    .frame_width  = 960,
+    .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();
+
+    i64 x = platform.frame_width  / 2;
+    i64 y = platform.frame_height / 2;
+
+    fill_rectangle(OP_SET, WHITE, 0, 0, platform.frame_width, platform.frame_height);
+
+    fill_triangle(OP_SET, RED, 100, 100, 200, 100, 150, 200);
+
+    fill_line(OP_SET, BLUE, 100, 300, 300, 500, 30);
+
+    fill_ellipse(OP_SET, BLACK, x - 140, y - 100, 280, 200);
+
+    p_render_frame();
+  }  
+
+  p_cleanup();
+  return 0;
+}
diff --git a/examples/gravity.c b/examples/gravity.c
index 8bc45e0..246aab1 100755
--- a/examples/gravity.c
+++ b/examples/gravity.c
@@ -40,13 +40,6 @@ typedef struct {
   Entity entities[10 * 1024 * 1024];
 } World;
 
-i64 time_milliseconds() {
-  struct timespec t;
-  timespec_get(&t, TIME_UTC);
-
-  return (i64) t.tv_sec * 1000ll + (i64) t.tv_nsec / 1000000ll;
-}
-
 i32 main(i32 argc, c8 **argv) {
   (void) argc;
   (void) argv;
@@ -64,12 +57,12 @@ i32 main(i32 argc, c8 **argv) {
   srand(time(0));
 
   static World world  = {0};
-  i64          time_0 = time_milliseconds();
+  i64          time_0 = p_time();
 
   while (!platform.done) {
     p_handle_events();
 
-    i64 time_elapsed  = time_milliseconds() - time_0;
+    i64 time_elapsed  = p_time() - time_0;
     time_0           += time_elapsed;
 
     if (platform.key_pressed[BUTTON_LEFT]) {
diff --git a/examples/ui.c b/examples/ui.c
index 0847af3..4730a9d 100755
--- a/examples/ui.c
+++ b/examples/ui.c
@@ -59,12 +59,12 @@ i32 main(i32 argc, c8 **argv) {
     if (platform.cursor_x >= 40 && platform.cursor_x < 100 && platform.cursor_y >= 40 && platform.cursor_y < 100) {
       button_0_down = platform.key_down[BUTTON_LEFT];
       if (button_0_down)
-        draw_panel(OP_SET, 0xffffff, 40, 40, 60, 60);
+        fill_rectangle(OP_SET, 0xffffff, 40, 40, 60, 60);
       else
-        draw_panel(OP_SET, 0x00ff00, 40, 40, 60, 60);
+        fill_rectangle(OP_SET, 0x00ff00, 40, 40, 60, 60);
     } else {
       button_0_down = 0;
-      draw_panel(OP_SET, 0x208020, 40, 40, 60, 60);
+      fill_rectangle(OP_SET, 0x208020, 40, 40, 60, 60);
     }
 
     if (platform.cursor_x >= 40 && platform.cursor_x < 100 && platform.cursor_y >= 120 && platform.cursor_y < 180) {
@@ -72,17 +72,17 @@ i32 main(i32 argc, c8 **argv) {
       if (platform.key_pressed[BUTTON_LEFT])
         button_1_checked = !button_1_checked;
       if (button_1_down)
-        draw_panel(OP_SET, 0xffffff, 40, 120, 60, 60);
+        fill_rectangle(OP_SET, 0xffffff, 40, 120, 60, 60);
       else if (button_1_checked)
-        draw_panel(OP_SET, 0xff8080, 40, 120, 60, 60);
+        fill_rectangle(OP_SET, 0xff8080, 40, 120, 60, 60);
       else
-        draw_panel(OP_SET, 0x80ff80, 40, 120, 60, 60);
+        fill_rectangle(OP_SET, 0x80ff80, 40, 120, 60, 60);
     } else {
       button_1_down = 0;
       if (button_1_checked)
-        draw_panel(OP_SET, 0xff0000, 40, 120, 60, 60);
+        fill_rectangle(OP_SET, 0xff0000, 40, 120, 60, 60);
       else
-        draw_panel(OP_SET, 0x00ff00, 40, 120, 60, 60);
+        fill_rectangle(OP_SET, 0x00ff00, 40, 120, 60, 60);
     }
 
     i64 w  = platform.frame_width  / 2;
@@ -246,7 +246,7 @@ i32 main(i32 argc, c8 **argv) {
 
     draw_text_area(0, x0 + 8, y0 - 8, w, h, 10., 10., text_len, text);
     draw_text_area(color, x0, y0, w, h, 10., 10., text_len, text);
-    draw_text_cursor(0xffffff, x0, y0, w, h, 10., 10., cursor, selection, text_len, text);
+    draw_selection_cursor(0xffffff, x0, y0, w, h, 10., 10., cursor, selection, text_len, text);
 
     p_render_frame();
   }
diff --git a/graphics.c b/graphics.c
index b054db7..50f3b68 100644
--- a/graphics.c
+++ b/graphics.c
@@ -2,6 +2,12 @@
 //
 //    graphics.c
 //
+//  ----------------------------------------------------------------
+//
+//  TODO:
+//  - Blending.
+//  - Anti-aliasing.
+//
 //  ================================================================
 
 #ifndef GRAPHICS_HEADER_GUARD_
@@ -13,24 +19,53 @@
 
 #include "reduced_system_layer.c"
 
+#define EPSILON 1e-9
+
 enum {
   OP_SET,
   OP_XOR,
 };
 
-u32 u32_from_rgb(f32 red, f32 green, f32 blue);
-void draw_panel(u32 op, u32 color, f64 x0, f64 y0, f64 width, f64 height);
-void draw_text_area(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 num_chars, c32 *text);
-void draw_text_cursor(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 cursor, i64 selection, i64 num_chars, c32 *text);
+u32  u32_from_rgb         (f32 red, f32 green, f32 blue);
+void fill_rectangle       (u32 op, u32 color, f64 x0, f64 y0, f64 width, f64 height);
+void fill_triangle        (u32 op, u32 color, f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2);
+void fill_ellipse         (u32 op, u32 color, f64 x0, f64 y0, f64 width, f64 height);
+void fill_line            (u32 op, u32 color, f64 x0, f64 y0, f64 x1, f64 y1, f64 width);
+void draw_text_area       (u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 num_chars, c32 *text);
+void draw_selection_cursor(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 cursor, i64 selection, i64 num_chars, c32 *text);
 
 #endif // GRAPHICS_HEADER_GUARD_
 
+//  ================================================================
+
 #ifndef GRAPHICS_HEADER
 #ifndef GRAPHICS_IMPL_GUARD_
 #define GRAPHICS_IMPL_GUARD_
 
 #include <math.h>
 
+f64 min3(f64 a, f64 b, f64 c) {
+  if (a < b && a < c)
+    return a;
+  if (b < c)
+    return b;
+  return c;
+}
+
+f64 max3(f64 a, f64 b, f64 c) {
+  if (a > b && a > c)
+    return a;
+  if (b > c)
+    return b;
+  return c;
+}
+
+b8 same_sign(f64 a, f64 b) {
+  if (a >=  EPSILON && b <= -EPSILON) return 0;
+  if (a <= -EPSILON && b >=  EPSILON) return 0;
+  return 1;
+}
+
 u32 u32_from_rgb(f32 red, f32 green, f32 blue) {
   i32 r = (i32) floor(red   * 255.f);
   i32 g = (i32) floor(green * 255.f);
@@ -202,7 +237,7 @@ i64 enum_text_rows(i64 num_chars, c32 *text) {
   return rows;
 }
 
-void print_text(u32 color, f64 x0, f64 y0, f64 scale_x, f64 scale_y, i64 num_chars, c32 *text) {
+void draw_text(u32 color, f64 x0, f64 y0, f64 scale_x, f64 scale_y, i64 num_chars, c32 *text) {
   assert(text != NULL);
 
   f64 x = x0;
@@ -256,7 +291,16 @@ void print_text(u32 color, f64 x0, f64 y0, f64 scale_x, f64 scale_y, i64 num_cha
   }
 }
 
-void draw_panel(u32 op, u32 color, f64 x0, f64 y0, f64 width, f64 height) {
+void put_pixel(i64 i, i64 j, u32 op, u32 color) {
+  if (i < 0 || i >= platform.frame_width || j < 0 || j >= platform.frame_height)
+    return;
+  if (op == OP_XOR)
+    platform.pixels[j * platform.frame_width + i] ^= color;
+  else
+    platform.pixels[j * platform.frame_width + i]  = color;
+}
+
+void fill_rectangle(u32 op, u32 color, f64 x0, f64 y0, f64 width, f64 height) {
   i64 i0 = (i64) floor(x0 + .5);
   i64 j0 = (i64) floor(y0 + .5);
   i64 i1 = (i64) floor(x0 + width + .5);
@@ -269,10 +313,95 @@ void draw_panel(u32 op, u32 color, f64 x0, f64 y0, f64 width, f64 height) {
 
   for (i64 j = j0; j < j1; ++j)
     for (i64 i = i0; i < i1; ++i)
-      if (op == OP_XOR)
-        platform.pixels[j * platform.frame_width + i] ^= color;
-      else
-        platform.pixels[j * platform.frame_width + i] = color;
+      put_pixel(i, j, op, color);
+}
+
+void fill_triangle(u32 op, u32 color, f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2) {
+  i64 min_x = (i64) floor(min3(x0, x1, x2));
+  i64 min_y = (i64) floor(min3(y0, y1, y2));
+  i64 max_x = (i64) ceil (max3(x0, x1, x2));
+  i64 max_y = (i64) ceil (max3(y0, y1, y2));
+
+  //  Z-components of cross-products
+  //
+  f64 z0 = (x1 - x0) * (y2 - y0) - (x2 - x0) * (y1 - y0);
+  f64 z1 = (x2 - x1) * (y0 - y1) - (x0 - x1) * (y2 - y1);
+  f64 z2 = (x0 - x2) * (y1 - y2) - (x1 - x2) * (y0 - y2);
+
+  for (i64 j = min_y; j <= max_y; ++j)
+    for (i64 i = min_x; i <= max_x; ++i) {
+      f64 x = (f64) i;
+      f64 y = (f64) j;
+
+      //  Z-components of cross-products
+      //
+      f64 pz0 = (x - x0) * (y2 - y0) - (x2 - x0) * (y - y0);
+      f64 pz1 = (x - x1) * (y0 - y1) - (x0 - x1) * (y - y1);
+      f64 pz2 = (x - x2) * (y1 - y2) - (x1 - x2) * (y - y2);
+
+      //  Check signs
+      //
+      if (!same_sign(z0, pz0)) continue;
+      if (!same_sign(z1, pz1)) continue;
+      if (!same_sign(z2, pz2)) continue;
+
+      put_pixel(i, j, op, color);
+    }  
+}
+
+void fill_ellipse(u32 op, u32 color, f64 x0, f64 y0, f64 width, f64 height) {
+  //  FIXME PERF:
+  //  Implement better algorithm.
+
+  i64 i0 = (i64) floor(x0 + .5);
+  i64 j0 = (i64) floor(y0 + .5);
+  i64 i1 = (i64) floor(x0 + width + .5);
+  i64 j1 = (i64) floor(y0 + height + .5);
+
+  f64 dw = width  / 2;
+  f64 dh = height / 2;
+
+  if (dw < EPSILON || dh < EPSILON)
+    return;
+
+  f64 cx = x0 + dw;
+  f64 cy = y0 + dh;
+  f64 kx = 1. / dw;
+  f64 ky = 1. / dh;
+
+  for (i64 j = j0; j < j1; ++j) {
+    if (j < 0 || j >= platform.frame_height)
+      continue;
+    f64 dy   = (((f64) j) - cy) * ky;
+    f64 dydy = dy * dy;
+    for (i64 i = i0; i < i1; ++i) {
+      if (i < 0 || i >= platform.frame_width)
+        continue;
+      f64 dx = (((f64) i) - cx) * kx;
+      if (dx * dx + dydy <= 1.0)
+        put_pixel(i, j, op, color);
+    }
+  }
+}
+
+void fill_line(u32 op, u32 color, f64 x0, f64 y0, f64 x1, f64 y1, f64 width) {
+  f64 dx = x1 - x0;
+  f64 dy = y1 - y0;
+
+  //  Tangent
+  //
+  f64 tx = -dy;
+  f64 ty = dx;
+  f64 tl = sqrt(tx * tx + ty * ty);
+  if (tl >= EPSILON) {
+    tx /= tl;
+    ty /= tl;
+  }
+  tx *= width * .5;
+  ty *= width * .5;
+
+  fill_triangle(op, color, x0 - tx, y0 - ty, x0 + tx, y0 + ty, x1 + tx, y1 + ty);
+  fill_triangle(op, color, x0 - tx, y0 - ty, x1 + tx, y1 + ty, x1 - tx, y1 - ty);
 }
 
 void draw_text_area(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 num_chars, c32 *text) {
@@ -293,10 +422,10 @@ void draw_text_area(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_sc
   kx = k * max_scale_x;
   ky = k * max_scale_y;
 
-  print_text(color, x0, y0, kx, ky, num_chars, text);
+  draw_text(color, x0, y0, kx, ky, num_chars, text);
 }
 
-void draw_text_cursor(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 cursor, i64 selection, i64 num_chars, c32 *text) {
+void draw_selection_cursor(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 cursor, i64 selection, i64 num_chars, c32 *text) {
   assert(max_scale_x > 1e-6);
   assert(max_scale_y > 1e-6);
 
@@ -329,27 +458,27 @@ void draw_text_cursor(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_
     }
 
     if (cursor_y == selection_y)
-      draw_panel(OP_XOR, color,
+      fill_rectangle(OP_XOR, color,
         x0 + kx * cursor_x,
         y0 + ky * cursor_y - ky * (CHAR_NUM_BITS_Y + 1),
         kx * (selection_x - cursor_x),
         ky * (CHAR_NUM_BITS_Y + 1)
       );
     else {
-      draw_panel(OP_XOR, color,
+      fill_rectangle(OP_XOR, color,
         x0 + kx * cursor_x,
         y0 + ky * cursor_y - ky * (CHAR_NUM_BITS_Y + 1),
         kx * (num_columns - cursor_x),
         ky * (CHAR_NUM_BITS_Y + 1)
       );
       for (i64 j = cursor_y + CHAR_NUM_BITS_Y + 1; j < selection_y; j += CHAR_NUM_BITS_Y + 1)
-        draw_panel(OP_XOR, color,
+        fill_rectangle(OP_XOR, color,
           x0,
           y0 + ky * j - ky * (CHAR_NUM_BITS_Y + 1),
           kx * num_columns,
           ky * (CHAR_NUM_BITS_Y + 1)
         );
-      draw_panel(OP_XOR, color,
+      fill_rectangle(OP_XOR, color,
         x0,
         y0 + ky * selection_y - ky * (CHAR_NUM_BITS_Y + 1),
         kx * selection_x,
@@ -357,7 +486,7 @@ void draw_text_cursor(u32 color, f64 x0, f64 y0, f64 width, f64 height, f64 max_
       );
     }
   } else
-    draw_panel(OP_XOR, color, x0 + kx * cursor_x, y0 + ky * cursor_y - ky * CHAR_NUM_BITS_Y, kx * .5, ky * (CHAR_NUM_BITS_Y - 1));
+    fill_rectangle(OP_XOR, color, x0 + kx * cursor_x, y0 + ky * cursor_y - ky * CHAR_NUM_BITS_Y, kx * .5, ky * (CHAR_NUM_BITS_Y - 1));
 }
 
 #endif // GRAPHICS_IMPL_GUARD_