add curve to pen pressure on windows

src/canvas_modes.cpp

@@ -111,6 +111,12 @@ void CanvasModePen::on_MouseEvent(MouseEvent* me, glm::vec2& loc)
     if (Canvas::I->m_touch_lock && me->m_source == kEventSource::Touch)
         return;
 
+#if _WIN32
+    // curve https://www.wolframalpha.com/input/?i=plot+(1-(x-1)%5E2)%5E2+from+x%3D0+to+1
+    auto curve = [](float x, float max) { return x > max ? 1.f : glm::pow(1.f - glm::pow(x / max - 1.f, 2.f), 2.f); };
+    me->m_pressure = curve(me->m_pressure, 0.95f);
+#endif
+
     switch (me->m_type)
     {
         case kEventType::MouseDownL: