fixes

src/bg_shader.py

@@ -12,7 +12,7 @@ class BackgroundShader:
   self.ctx: Optional[nvg.Context] = None
 
  def render(self, width: float, height: float):
-  if not self.enabled:
+  if not self.enabled or width <= 0 or height <= 0:
    return
 
   # In imgui-bundle, hello_imgui handles the background.

src/gui_2.py

@@ -387,8 +387,10 @@ class App:
    curr_x = imgui.get_cursor_pos_x()
    drag_w = right_x - curr_x
    if drag_w > 0:
-    imgui.invisible_button("##drag_area", (drag_w, 0))
-    if imgui.is_item_hovered() and imgui.is_mouse_clicked(0):
+    # Use a small positive height to satisfy IM_ASSERT(size_arg.y != 0.0f)
+    # The menu bar naturally constrains the hit box height anyway.
+    imgui.invisible_button("##drag_area", (drag_w, 20.0))
+    if imgui.is_item_active() and imgui.is_mouse_dragging(0):
      win32gui.ReleaseCapture()
      win32gui.SendMessage(hwnd, win32con.WM_NCLBUTTONDOWN, win32con.HTCAPTION, 0)