Report touch events on MS-Windows

* etc/NEWS: Announce change.

* src/w32fns.c (RegisterTouchWindow_fn): New function.
(w32_createwindow): Assign a base value for touch event
identifiers to the frame, and register for touch input.
(w32_wnd_proc): Forward WM_TOUCH/WM_TOUCHMOVE messages to the
main thread.
(globals_of_w32fns): Load RegisterTouchWindow from user32.dll.

* src/w32term.c (w32_read_socket) <WM_TOUCH>: Detect WM_TOUCH
events, compare and record their touch points with and into the
frame's record of their prior state, and report the same to Lisp.
(pfnCloseTouchInputHandle, pfnGetTouchInputInfo): New variables.
(w32_initialize): Load the above functions from user32.dll.

* src/w32term.h (MAX_TOUCH_POINTS): New definition.
(struct w32_output) <touch_ids, touch_x, touch_y, touch_base>:
New fields.

3 files changed, 217 insertions, 1 deletions

diff --git a/src/w32fns.c b/src/w32fns.c
index 8b61b54bdc5..4437c1fb2b5 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -216,6 +216,8 @@ typedef BOOL (WINAPI * WTSRegisterSessionNotification_Proc)
   (HWND hwnd, DWORD dwFlags);
 typedef BOOL (WINAPI * WTSUnRegisterSessionNotification_Proc) (HWND hwnd);
 
+typedef BOOL (WINAPI * RegisterTouchWindow_proc) (HWND, ULONG);
+
 TrackMouseEvent_Proc track_mouse_event_fn = NULL;
 ImmGetCompositionString_Proc get_composition_string_fn = NULL;
 ImmGetContext_Proc get_ime_context_fn = NULL;
@@ -234,6 +236,7 @@ SetWindowTheme_Proc SetWindowTheme_fn = NULL;
 DwmSetWindowAttribute_Proc DwmSetWindowAttribute_fn = NULL;
 WTSUnRegisterSessionNotification_Proc WTSUnRegisterSessionNotification_fn = NULL;
 WTSRegisterSessionNotification_Proc WTSRegisterSessionNotification_fn = NULL;
+RegisterTouchWindow_proc RegisterTouchWindow_fn = NULL;
 
 extern AppendMenuW_Proc unicode_append_menu;
 
@@ -2455,6 +2458,7 @@ w32_createwindow (struct frame *f, int *coords)
   RECT rect;
   int top, left;
   Lisp_Object border_width = Fcdr (Fassq (Qborder_width, f->param_alist));
+  static EMACS_INT touch_base;
 
   if (FRAME_PARENT_FRAME (f) && FRAME_W32_P (FRAME_PARENT_FRAME (f)))
     {
@@ -2517,6 +2521,8 @@ w32_createwindow (struct frame *f, int *coords)
 
   if (hwnd)
     {
+      int i;
+
       if (FRAME_SKIP_TASKBAR (f))
         SetWindowLong (hwnd, GWL_EXSTYLE,
                        GetWindowLong (hwnd, GWL_EXSTYLE) | WS_EX_NOACTIVATE);
@@ -2545,6 +2551,20 @@ w32_createwindow (struct frame *f, int *coords)
            parent.  */
         MapWindowPoints (HWND_DESKTOP, parent_hwnd, (LPPOINT) &rect, 2);
 
+      /* Enable touch-screen input.  */
+      if (RegisterTouchWindow_fn)
+        (*RegisterTouchWindow_fn) (hwnd, 0);
+
+      /* Reset F's touch point array.  */
+      for (i = 0; i < ARRAYELTS (f->output_data.w32->touch_ids); ++i)
+        f->output_data.w32->touch_ids[i] = -1;
+
+      /* Assign an offset for touch points reported to F.  */
+      if (FIXNUM_OVERFLOW_P (touch_base + MAX_TOUCH_POINTS - 1))
+        touch_base = 0;
+      f->output_data.w32->touch_base = touch_base;
+      touch_base += MAX_TOUCH_POINTS;
+
       f->left_pos = rect.left;
       f->top_pos = rect.top;
     }
@@ -5370,6 +5390,19 @@ w32_wnd_proc (HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
       my_post_msg (&wmsg, hwnd, msg, wParam, lParam);
       goto dflt;
 
+#ifdef WM_TOUCHMOVE
+    case WM_TOUCHMOVE:
+#else /* not WM_TOUCHMOVE */
+#ifndef WM_TOUCH
+#define WM_TOUCH 576
+#endif /* WM_TOUCH */
+    case WM_TOUCH:
+#endif /* not WM_TOUCHMOVE */
+      my_post_msg (&wmsg, hwnd, msg, wParam, lParam);
+      /* It is said that DefWindowProc will release the touch
+         information in the event.  */
+      return 0;
+
 #ifdef WINDOWSNT
     case WM_CREATE:
       setup_w32_kbdhook (hwnd);
@@ -11405,6 +11438,9 @@ globals_of_w32fns (void)
   system_parameters_info_w_fn = (SystemParametersInfoW_Proc)
     get_proc_addr (user32_lib, "SystemParametersInfoW");
 #endif
+  RegisterTouchWindow_fn
+    = (RegisterTouchWindow_proc) get_proc_addr (user32_lib,
+                                                "RegisterTouchWindow");
 
   {
     HMODULE imm32_lib = GetModuleHandle ("imm32.dll");
diff --git a/src/w32term.c b/src/w32term.c
index 3ef6d0f11f1..45f94ab76bd 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -120,6 +120,13 @@ BOOL (WINAPI *pfnSetLayeredWindowAttributes) (HWND, COLORREF, BYTE, DWORD);
 /* PlgBlt is available since Windows 2000.  */
 BOOL (WINAPI *pfnPlgBlt) (HDC, const POINT *, HDC, int, int, int, int, HBITMAP, int, int);
 
+/* Functions that extract data from touch-screen events.  */
+typedef BOOL (WINAPI * CloseTouchInputHandle_proc) (HANDLE);
+typedef BOOL (WINAPI * GetTouchInputInfo_proc) (HANDLE, UINT, PTOUCHINPUT, int);
+
+CloseTouchInputHandle_proc pfnCloseTouchInputHandle;
+GetTouchInputInfo_proc pfnGetTouchInputInfo;
+
 
 #ifndef LWA_ALPHA
 #define LWA_ALPHA 0x02
@@ -139,6 +146,35 @@ BOOL (WINAPI *pfnPlgBlt) (HDC, const POINT *, HDC, int, int, int, int, HBITMAP,
 #define SM_CYVIRTUALSCREEN 79
 #endif
 
+/* Define required types and constants on systems with older headers
+   lest they be absent.  */
+
+#if _WIN32_WINNT < 0x0601
+#define TOUCHEVENTF_DOWN                               0x0001
+#define TOUCHEVENTF_MOVE                               0x0002
+#define TOUCHEVENTF_UP                                 0x0004
+
+#define TOUCHEVENTMASKF_CONTACTAREA                    0x0004
+#define TOUCHEVENTMASKF_EXTRAINFO                      0x0002
+#define TOUCHEVENTMASKF_TIMEFROMSYSTEM                 0x0001
+
+#define WM_TOUCHMOVE                                      576
+
+typedef struct _TOUCHINPUT
+{
+  LONG x;
+  LONG y;
+  HANDLE hSource;
+  DWORD dwID;
+  DWORD dwFlags;
+  DWORD dwMask;
+  DWORD dwTime;
+  ULONG_PTR dwExtraInfo;
+  DWORD cxContact;
+  DWORD cyContact;
+} TOUCHINPUT, *PTOUCHINPUT;
+#endif /* _WIN32_WINNT < 0x0601 */
+
 /* The handle of the frame that currently owns the system caret.  */
 HWND w32_system_caret_hwnd;
 int w32_system_caret_height;
@@ -6056,6 +6092,137 @@ w32_read_socket (struct terminal *terminal,
           break;
 #endif
 
+#if 0
+          /* These messages existed in prerelease versions of Windows 7,
+             yet, though superseded by just WM_TOUCHMOVE (renamed
+             WM_TOUCH) in the release, are still defined by MinGW's
+             winuser.h.  */
+        case WM_TOUCHDOWN:
+        case WM_TOUCHUP:
+#endif /* 0 */
+#ifdef WM_TOUCHMOVE
+        case WM_TOUCHMOVE:
+#else /* not WM_TOUCHMOVE */
+        case WM_TOUCH:
+#endif /* not WM_TOUCHMOVE */
+          f = w32_window_to_frame (dpyinfo, msg.msg.hwnd);
+
+          /* WM_TOUCH should never be received when touch input
+             functions are unavailable.  */
+          if (!pfnGetTouchInputInfo)
+            break;
+
+          if (f)
+            {
+              TOUCHINPUT points[MAX_TOUCH_POINTS];
+              int i, x;
+
+              if ((*pfnGetTouchInputInfo) ((HANDLE) msg.msg.lParam,
+                                           MAX_TOUCH_POINTS,
+                                           points, sizeof (TOUCHINPUT)))
+                {
+                  bool movement_p = false;
+                  EMACS_INT base = FRAME_OUTPUT_DATA (f)->touch_base;
+
+                  /* Iterate over the list of touch points in the
+                     structure, and for each, enter or remove
+                     information into and from F->touch_ids, and
+                     generate events correspondingly.  */
+                  for (i = 0; i < MAX_TOUCH_POINTS; ++i)
+                    {
+                      if (!points[i].dwID)
+                        continue;
+
+                      /* Search for a slot in touch_ids that is either
+                         empty or matches dwID.  */
+                      for (x = 0; x < MAX_TOUCH_POINTS; x++)
+                        {
+                          if (FRAME_OUTPUT_DATA (f)->touch_ids[x] == -1
+                              || (FRAME_OUTPUT_DATA (f)->touch_ids[x]
+                                  == points[i].dwID))
+                            break;
+                        }
+                      if (x == MAX_TOUCH_POINTS)
+                        continue;
+
+                      if (points[i].dwFlags & TOUCHEVENTF_UP)
+                        {
+                          /* Clear the entry in touch_ids and report the
+                             change.  Unless, of course, the entry be
+                             empty.  */
+                          if (FRAME_OUTPUT_DATA (f)->touch_ids[x] == -1)
+                            continue;
+                          FRAME_OUTPUT_DATA (f)->touch_ids[x] = -1;
+
+                          inev.kind = TOUCHSCREEN_END_EVENT;
+                          inev.timestamp = msg.msg.time;
+                          XSETFRAME (inev.frame_or_window, f);
+                          XSETINT (inev.x, points[i].x);
+                          XSETINT (inev.y, points[i].y);
+                          XSETINT (inev.arg, x + base);
+                          kbd_buffer_store_event (&inev);
+                          EVENT_INIT (inev);
+                        }
+                      else if (points[i].dwFlags & TOUCHEVENTF_DOWN)
+                        {
+                          bool recorded_p
+                            = FRAME_OUTPUT_DATA (f)->touch_ids[x] != -1;
+
+                          /* Report and record (if not already recorded)
+                             the addition.  */
+                          FRAME_OUTPUT_DATA (f)->touch_ids[x] = points[i].dwID;
+                          FRAME_OUTPUT_DATA (f)->touch_x[x] = points[i].x;
+                          FRAME_OUTPUT_DATA (f)->touch_y[x] = points[i].y;
+
+                          if (recorded_p)
+                            movement_p = true;
+                          else
+                            {
+                              inev.kind = TOUCHSCREEN_BEGIN_EVENT;
+                              inev.timestamp = msg.msg.time;
+                              XSETFRAME (inev.frame_or_window, f);
+                              XSETINT (inev.x, points[i].x);
+                              XSETINT (inev.y, points[i].y);
+                              XSETINT (inev.arg, x + base);
+                              kbd_buffer_store_event (&inev);
+                              EVENT_INIT (inev);
+                            }
+                        }
+                      else
+                        {
+                          FRAME_OUTPUT_DATA (f)->touch_ids[x] = points[i].dwID;
+                          FRAME_OUTPUT_DATA (f)->touch_x[x] = points[i].x;
+                          FRAME_OUTPUT_DATA (f)->touch_y[x] = points[i].y;
+                          movement_p = true;
+                        }
+                    }
+
+                  /* Report updated positions of touchpoints if some
+                     changed.  */
+                  if (movement_p)
+                    {
+                      Lisp_Object arg;
+
+                      inev.kind = TOUCHSCREEN_UPDATE_EVENT;
+                      inev.timestamp = msg.msg.time;
+                      XSETFRAME (inev.frame_or_window, f);
+                      arg = Qnil;
+
+                      for (i = 0; i < MAX_TOUCH_POINTS; ++i)
+                        arg
+                          = Fcons (list3i (FRAME_OUTPUT_DATA (f)->touch_x[i],
+                                           FRAME_OUTPUT_DATA (f)->touch_y[i],
+                                           i + base),
+                                   arg);
+
+                      inev.arg = arg;
+                    }
+                }
+            }
+
+          (*CloseTouchInputHandle) ((HANDLE) msg.msg.lParam);
+          break;
+
         default:
           /* Check for messages registered at runtime.  */
           if (msg.msg.message == msh_mousewheel)
@@ -7893,12 +8060,13 @@ w32_initialize (void)
 #define LOAD_PROC(lib, fn) pfn##fn = (void *) GetProcAddress (lib, #fn)
 
     LOAD_PROC (user_lib, SetLayeredWindowAttributes);
+    LOAD_PROC (user_lib, CloseTouchInputHandle);
+    LOAD_PROC (user_lib, GetTouchInputInfo);
 
     /* PlgBlt is not available on Windows 9X.  */
     HMODULE hgdi = LoadLibrary ("gdi32.dll");
     if (hgdi)
       LOAD_PROC (hgdi, PlgBlt);
-
 #undef LOAD_PROC
 
     /* Ensure scrollbar handles are at least 5 pixels.  */
diff --git a/src/w32term.h b/src/w32term.h
index 38eac4230dd..1cdb165d2ed 100644
--- a/src/w32term.h
+++ b/src/w32term.h
@@ -434,6 +434,18 @@ struct w32_output
 
   /* Whether or not this frame should be double buffered.  */
   unsigned want_paint_buffer : 1;
+
+#define MAX_TOUCH_POINTS 10
+  /* Array of dwIDs of presently active touch points, or -1 when
+     unpopulated.  */
+  int touch_ids[MAX_TOUCH_POINTS];
+
+  /* X and Y coordinates of active touchpoints.  */
+  LONG touch_x[MAX_TOUCH_POINTS], touch_y[MAX_TOUCH_POINTS];
+
+  /* Base value for touch point identifiers registered by this
+     frame.  */
+  EMACS_INT touch_base;
 };
 
 extern struct w32_output w32term_display;