1 files changed, 113 insertions, 0 deletions
diff --git a/pen-fix/main.cpp b/pen-fix/main.cpp
new file mode 100644
index 0000000..4688f28
--- /dev/null
+++ b/pen-fix/main.cpp
@@ -0,0 +1,113 @@
+#include <algorithm>
+#include <cstdio>
+#include <linux/input-event-codes.h>
+#include <linux/input.h>
+#include <poll.h>
+#include <sys/poll.h>
+#include <unistd.h>
+#include <utility>
+#include <vector>
+
+auto flush(std::vector<input_event> & frame) -> void
+{
+  std::ranges::for_each(frame, [](auto event) { std::fwrite(&event, sizeof(event), 1, stdout); });
+
+  std::fflush(stdout);
+  frame.clear();
+}
+
+auto main() -> int
+{
+  auto poll_descriptor = pollfd{.fd = STDIN_FILENO, .events = POLLIN, .revents = 0};
+
+  auto current_frame = std::vector<struct input_event>{};
+  auto deferred_frame = std::vector<struct input_event>{};
+  auto waiting_for_rubber_tool = false;
+
+  while (true)
+  {
+    auto timeout_ms = waiting_for_rubber_tool ? 50 : -1;
+    auto ret = poll(&poll_descriptor, 1, timeout_ms);
+
+    if (ret == 0)
+    {
+      if (waiting_for_rubber_tool)
+      {
+        flush(deferred_frame);
+        waiting_for_rubber_tool = false;
+      }
+      continue;
+    }
+
+    if (ret < 0)
+    {
+      break;
+    }
+
+    auto event = input_event{};
+    if (std::fread(&event, sizeof(event), 1, stdin) != 1)
+    {
+      break;
+    }
+
+    current_frame.push_back(event);
+
+    if (event.type == EV_SYN && event.code == SYN_REPORT)
+    {
+      auto has_pen_leave = false;
+      auto has_rubber_enter = false;
+      auto has_rubber_leave = false;
+
+      std::ranges::for_each(current_frame, [&](auto event) {
+        if (event.type == EV_KEY && event.code == BTN_TOOL_PEN && event.value == 0)
+          has_pen_leave = true;
+        if (event.type == EV_KEY && event.code == BTN_TOOL_RUBBER && event.value == 1)
+          has_rubber_enter = true;
+        if (event.type == EV_KEY && event.code == BTN_TOOL_RUBBER && event.value == 0)
+          has_rubber_leave = true;
+      });
+
+      if (has_pen_leave)
+      {
+        deferred_frame = std::move(current_frame);
+        waiting_for_rubber_tool = true;
+      }
+      else if (has_rubber_enter || has_rubber_leave)
+      {
+        auto mutated_frame = std::vector<input_event>{};
+
+        for (auto const & e : current_frame)
+        {
+          if (e.type == EV_KEY && e.code == BTN_TOOL_RUBBER)
+          {
+            struct input_event mutated_btn = e;
+            mutated_btn.code = BTN_STYLUS2;
+            mutated_frame.push_back(mutated_btn);
+          }
+          else if (e.type == EV_ABS)
+          {
+            continue;
+          }
+          else
+          {
+            mutated_frame.push_back(e);
+          }
+        }
+        deferred_frame.clear();
+        waiting_for_rubber_tool = false;
+        flush(mutated_frame);
+      }
+      else
+      {
+        if (waiting_for_rubber_tool)
+        {
+          flush(deferred_frame);
+          waiting_for_rubber_tool = false;
+        }
+        flush(current_frame);
+      }
+      current_frame.clear();
+    }
+  }
+  return 0;
+}