x11: fix raw key down being sent repeatedly when holding key

Fixes #874

panda/src/x11display/x11GraphicsWindow.cxx

@@ -329,7 +329,7 @@ process_events() {
 
         // We thought about not generating the keypress event, but we need
         // that repeat for backspace.  Rethink later.
-        handle_keypress(event.xkey);
+        handle_keyrepeat(event.xkey);
         continue;
 
       } else {
@@ -1499,6 +1499,34 @@ handle_keypress(XKeyEvent &event) {
   }
 }
 
+/**
+ * Generates a keyrepeat corresponding to the indicated X KeyPress event.
+ */
+void x11GraphicsWindow::
+handle_keyrepeat(XKeyEvent &event) {
+  if (_properties.get_mouse_mode() != WindowProperties::M_relative) {
+    _input->set_pointer_in_window(event.x, event.y);
+  }
+
+  // Now get the raw unshifted button.
+  ButtonHandle button = get_button(event, false);
+  if (button != ButtonHandle::none()) {
+    if (button == KeyboardButton::lcontrol() || button == KeyboardButton::rcontrol()) {
+      _input->button_down(KeyboardButton::control());
+    }
+    if (button == KeyboardButton::lshift() || button == KeyboardButton::rshift()) {
+      _input->button_down(KeyboardButton::shift());
+    }
+    if (button == KeyboardButton::lalt() || button == KeyboardButton::ralt()) {
+      _input->button_down(KeyboardButton::alt());
+    }
+    if (button == KeyboardButton::lmeta() || button == KeyboardButton::rmeta()) {
+      _input->button_down(KeyboardButton::meta());
+    }
+    _input->button_down(button);
+  }
+}
+
 /**
  * Generates a keyrelease corresponding to the indicated X KeyRelease event.
  */

panda/src/x11display/x11GraphicsWindow.h

@@ -59,6 +59,7 @@ protected:
   virtual void setup_colormap(XVisualInfo *visual);
   void handle_keystroke(XKeyEvent &event);
   void handle_keypress(XKeyEvent &event);
+  void handle_keyrepeat(XKeyEvent &event);
   void handle_keyrelease(XKeyEvent &event);
 
   ButtonHandle get_button(XKeyEvent &key_event, bool allow_shift);