fix stuck keys on ubuntu and on focus loss #142

In the `OnKeyDown` event handler, check if the key is actually pressed
using `wxGetKeyState()`, because for some reason on Ubuntu 18
spurious events are generated when the key is not actually pressed.

Also, if a game is paused by the frontend while a key is being pressed,
the key will remain active for the game when unpaused. This is an
issue because the key will likely be released outside of the game zone;
therefore, we would not process the key release for the game itself.

The same bug happens if clicking outside of the game zone while
holding a key.

For the case of a directional key, this means a continuous movement
in the direction of the key pressed before the pause until the key
is pressed and released.

src/wx/panel.cpp

@@ -16,6 +16,9 @@
 #include "filters.h"
 #include "wxvbam.h"
 
+// release all buttons currently pressed
+static void clear_input_press();
+
 int emulating;
 
 IMPLEMENT_DYNAMIC_CLASS(GameArea, wxPanel)
@@ -919,6 +922,12 @@ GameArea::~GameArea()
     }
 }
 
+void GameArea::OnKillFocus(wxFocusEvent& ev)
+{
+    clear_input_press();
+    ev.Skip(true);
+}
+
 void GameArea::Pause()
 {
     if (paused)
@@ -932,6 +941,11 @@ void GameArea::Pause()
 
     paused = was_paused = true;
 
+    // when the game is paused like this, we should not allow any
+    // input to remain pressed, because they could be released
+    // outside of the game zone and we would not know about it. 
+    clear_input_press();
+
     if (loaded != IMAGE_UNKNOWN)
         soundPause();
 }
@@ -1022,6 +1036,9 @@ void GameArea::OnIdle(wxIdleEvent& event)
         // the userdata is freed on disconnect/destruction
         this->Connect(wxEVT_SIZE,          wxSizeEventHandler(GameArea::OnSize),           NULL, this);
 
+	// we need to check if the buttons stayed pressed when focus the panel
+	w->Connect(wxEVT_KILL_FOCUS,       wxFocusEventHandler(GameArea::OnKillFocus),     NULL, this);
+
         w->SetBackgroundStyle(wxBG_STYLE_CUSTOM);
         w->SetSize(wxSize(basic_width, basic_height));
 
@@ -1141,6 +1158,16 @@ static uint32_t bmask[NUM_KEYS] = {
 
 static wxJoyKeyBinding_v keys_pressed;
 
+static void clear_input_press()
+{
+    int i;
+    for (i = 0; i < 4; ++i)
+    {
+	joypress[i] = 0;
+    }
+    keys_pressed.clear();
+}
+
 struct game_key {
     int player;
     int key_num;
@@ -1257,7 +1284,9 @@ static void draw_black_background(wxWindow* win) {
 
 void GameArea::OnKeyDown(wxKeyEvent& ev)
 {
-    if (process_key_press(true, ev.GetKeyCode(), ev.GetModifiers())) {
+    // check if the key is pressed indeed and then process it
+    wxKeyCode keyCode = (wxKeyCode)ev.GetKeyCode();
+    if (wxGetKeyState(keyCode) && process_key_press(true, ev.GetKeyCode(), ev.GetModifiers())) {
         ev.Skip(false);
         ev.StopPropagation();
         wxWakeUpIdle();

src/wx/wxvbam.h

@@ -621,6 +621,7 @@ class GameArea : public wxPanel, public HiDPIAware {
     void PaintEv(wxPaintEvent& ev);
     void EraseBackground(wxEraseEvent& ev);
     void OnSize(wxSizeEvent& ev);
+    void OnKillFocus(wxFocusEvent& ev);
 
 #ifndef NO_FFMPEG
     MediaRecorder snd_rec, vid_rec;