upgrade button example

examples/button.c

@@ -2,14 +2,30 @@
 #include <ptk.h>
 #include <ptk_log.h>
 
+#include <GLFW/glfw3.h>
+
+static const float color_step = 10.0f;
+
 static PtkRect *r;
 
 static void on_press(const int button, const int action, const int mods) {
-    (void)button; (void)action; (void)mods;
-    PTK_DEBUG("pressed!");
-    r->color.r = r->color.r + (1.0f / 255.0f);
-    if (r->color.r == 256.0f) {
-        r->color.r = 0.0f;
+    (void)button; (void)mods;
+    if (action == GLFW_PRESS) {
+        PTK_DEBUG("pressed!");
+        r->color.b += color_step / 255.0f;
+        if (r->color.b > 1.0f) {
+            r->color.b = 0.0f;
+
+            r->color.g += color_step / 255.0f;
+            if (r->color.g > 1.0f) {
+                r->color.g = 0.0f;
+
+                r->color.r += color_step / 255.0f;
+                if (r->color.r > 1.0f) {
+                    r->color.r = 0.0f;
+                }
+            }
+        }
     }
 }
 
@@ -21,7 +37,7 @@ int main(void) {
     r = (PtkRect *)ptk_rect(
         (PtkPos){ .x = 100.0f, .y = 100.0f },
         (PtkSize){ .w = 100.0f, .h = 50.0f },
-        (PtkColor){ .r = 1.0f, .g = 0.0f, .b = 0.0f }
+        (PtkColor){ .r = 1.0f, .g = 1.0f, .b = 1.0f }
     );
 
     return ptk_run(