Improve handling of dead keys

When you press the dead key "^" followed by space on a German keyboard,
the applicaton receives the following two KeyDown events:
1. event.key = Key_Circumflex, event.character = ""
2. event.key = Key_Space, event.character = "^"

Under Gtk this should work for all dead keys by using GtkIMContext.
Under Windows it is implemented only for the scan code of the dead key
"^" on a German keyboard.

5 files changed, 113 insertions, 85 deletions

diff --git a/src/nigui.nim b/src/nigui.nim
index d0281b6..fef6fcc 100755
--- a/src/nigui.nim
+++ b/src/nigui.nim
@@ -68,59 +68,60 @@ type
 
   Key* = enum
     # Keys with same value than Unicode:
-    Key_None      = 0
-    Key_Backspace = 8
-    Key_Tab       = 9
-    Key_Return    = 13
-    Key_Escape    = 27
-    Key_Space     = 32
-    Key_Asterisk  = 42
-    Key_Plus      = 43
-    Key_Comma     = 44
-    Key_Minus     = 45
-    Key_Point     = 46
-    Key_Number0   = 48
-    Key_Number1   = 49
-    Key_Number2   = 50
-    Key_Number3   = 51
-    Key_Number4   = 52
-    Key_Number5   = 53
-    Key_Number6   = 54
-    Key_Number7   = 55
-    Key_Number8   = 56
-    Key_Number9   = 57
-    Key_A         = 65
-    Key_B         = 66
-    Key_C         = 67
-    Key_D         = 68
-    Key_E         = 69
-    Key_F         = 70
-    Key_G         = 71
-    Key_H         = 72
-    Key_I         = 73
-    Key_J         = 74
-    Key_K         = 75
-    Key_L         = 76
-    Key_M         = 77
-    Key_N         = 78
-    Key_O         = 79
-    Key_P         = 80
-    Key_Q         = 81
-    Key_R         = 82
-    Key_S         = 83
-    Key_T         = 84
-    Key_U         = 85
-    Key_V         = 86
-    Key_W         = 87
-    Key_X         = 88
-    Key_Y         = 89
-    Key_Z         = 90
-    Key_AE        = 196
-    Key_OE        = 214
-    Key_UE        = 220
-    Key_SharpS    = 223
+    Key_None       = 0
+    Key_Backspace  = 8
+    Key_Tab        = 9
+    Key_Return     = 13
+    Key_Escape     = 27
+    Key_Space      = 32
+    Key_Asterisk   = 42
+    Key_Plus       = 43
+    Key_Comma      = 44
+    Key_Minus      = 45
+    Key_Point      = 46
+    Key_Number0    = 48
+    Key_Number1    = 49
+    Key_Number2    = 50
+    Key_Number3    = 51
+    Key_Number4    = 52
+    Key_Number5    = 53
+    Key_Number6    = 54
+    Key_Number7    = 55
+    Key_Number8    = 56
+    Key_Number9    = 57
+    Key_A          = 65
+    Key_B          = 66
+    Key_C          = 67
+    Key_D          = 68
+    Key_E          = 69
+    Key_F          = 70
+    Key_G          = 71
+    Key_H          = 72
+    Key_I          = 73
+    Key_J          = 74
+    Key_K          = 75
+    Key_L          = 76
+    Key_M          = 77
+    Key_N          = 78
+    Key_O          = 79
+    Key_P          = 80
+    Key_Q          = 81
+    Key_R          = 82
+    Key_S          = 83
+    Key_T          = 84
+    Key_U          = 85
+    Key_V          = 86
+    Key_W          = 87
+    Key_X          = 88
+    Key_Y          = 89
+    Key_Z          = 90
+    Key_Circumflex = 94
+    Key_AE         = 196
+    Key_OE         = 214
+    Key_UE         = 220
+    Key_SharpS     = 223
     # Not part of Unicode:
-    Key_Insert    = 1000
+    Key_Insert     = 1000
     Key_Delete
     Key_Left
     Key_Right
diff --git a/src/nigui/private/gtk3/gtk3.nim b/src/nigui/private/gtk3/gtk3.nim
index b1e218f..1edf03c 100755
--- a/src/nigui/private/gtk3/gtk3.nim
+++ b/src/nigui/private/gtk3/gtk3.nim
@@ -421,6 +421,9 @@ proc gtk_clipboard_store*(clipboard: pointer) {.importc: "gtk_clipboard_store",
 
 proc gtk_accelerator_get_default_mod_mask*(): cint {.importc: "gtk_accelerator_get_default_mod_mask", libgtk3.}
 
+proc gtk_im_multicontext_new*(): pointer {.importc: "gtk_im_multicontext_new", libgtk3.}
+proc gtk_im_context_filter_keypress*(context: pointer, event: var GdkEventKey): bool {.importc: "gtk_im_context_filter_keypress", libgtk3.}
+
 
 # ----------------------------------------------------------------------------------------
 #                                   Drawing Related Procs
diff --git a/src/nigui/private/gtk3/platform_impl.nim b/src/nigui/private/gtk3/platform_impl.nim
index 6bf791a..e0635c1 100755
--- a/src/nigui/private/gtk3/platform_impl.nim
+++ b/src/nigui/private/gtk3/platform_impl.nim
@@ -62,6 +62,7 @@ proc pWindowConfigureSignal(windowHandle, event, data: pointer): bool {.cdecl.}
 
 proc pKeyvalToKey(keyval: cint): Key =
   result = case keyval
+  of 65106: Key_Circumflex
   of 65289: Key_Tab
   of 65293: Key_Return
   of 65307: Key_Escape
@@ -79,59 +80,68 @@ proc pKeyvalToKey(keyval: cint): Key =
   else: cast[Key](keyval.unicodeToUpper)
 
 proc pWindowKeyPressSignal(widget: pointer, event: var GdkEventKey, data: pointer): bool {.cdecl.} =
-  # echo "window keyPressCallback"
-
-  # echo event.keyval
-  # echo event.hardware_keycode
-
-  # echo $gdk_keyval_to_unicode(event.keyval)
-  var unicode = gdk_keyval_to_unicode(event.keyval)
-  # if unicode == 0:
-    # unicode = event.keyval
-
   let window = cast[WindowImpl](data)
+  window.fKeyPressed = pKeyvalToKey(event.keyval)
+  if gtk_im_context_filter_keypress(window.fIMContext, event) and window.fKeyPressed == Key_None:
+    return
   var evt = new WindowKeyEvent
   evt.window = window
-  evt.key = pKeyvalToKey(event.keyval)
+  evt.key = window.fKeyPressed
   if evt.key == Key_None:
     echo "Unkown key value: ", event.keyval
     return
-
   evt.character = $event.`string`
-  evt.unicode = unicode
-
+  evt.unicode = gdk_keyval_to_unicode(event.keyval)
   try:
     window.handleKeyDownEvent(evt)
-    result = evt.cancel
   except:
     handleException()
+  result = evt.cancel
 
 proc pControlKeyPressSignal(widget: pointer, event: var GdkEventKey, data: pointer): bool {.cdecl.} =
-
-  # echo "control keyPressCallback"
-
-  # echo $gdk_keyval_to_unicode(event.keyval)
-  var unicode = gdk_keyval_to_unicode(event.keyval)
-
-  # if unicode == 0:
-    # unicode = event.keyval
-
   let control = cast[ControlImpl](data)
+  control.fKeyPressed = pKeyvalToKey(event.keyval)
+  if gtk_im_context_filter_keypress(control.fIMContext, event) and control.fKeyPressed == Key_None:
+    return
   var evt = new ControlKeyEvent
   evt.control = control
-  evt.key = pKeyvalToKey(event.keyval)
+  evt.key = control.fKeyPressed
   if evt.key == Key_None:
     echo "Unkown key value: ", event.keyval
     return
   evt.character = $event.`string`
-  evt.unicode = unicode
-
+  evt.unicode = gdk_keyval_to_unicode(event.keyval)
   try:
     control.handleKeyDownEvent(evt)
   except:
     handleException()
+  result = evt.cancel
 
-  return evt.cancel
+proc pWindowIMContextCommitSignal(context: pointer, str: cstring, data: pointer) {.cdecl.} =
+  let window = cast[WindowImpl](data)
+  var evt = new WindowKeyEvent
+  evt.window = window
+  evt.character = $str
+  evt.unicode = evt.character.runeAt(0).toUpper().int
+  evt.key = window.fKeyPressed
+  window.fKeyPressed = Key_None
+  try:
+    window.handleKeyDownEvent(evt)
+  except:
+    handleException()
+
+proc pControlIMContextCommitSignal(context: pointer, str: cstring, data: pointer) {.cdecl.} =
+  let control = cast[ControlImpl](data)
+  var evt = new ControlKeyEvent
+  evt.control = control
+  evt.character = $str
+  evt.unicode = evt.character.runeAt(0).toUpper().int
+  evt.key = control.fKeyPressed
+  control.fKeyPressed = Key_None
+  try:
+    control.handleKeyDownEvent(evt)
+  except:
+    handleException()
 
 method focus(control: ControlImpl) =
   gtk_widget_grab_focus(control.fHandle)
@@ -618,6 +628,9 @@ proc init(window: WindowImpl) =
     gtk_scrolled_window_set_policy(window.fInnerHandle, GTK_POLICY_ALWAYS, GTK_POLICY_ALWAYS)
     discard g_signal_connect_data(window.fInnerHandle, "draw", pMainScrollbarDraw, nil)
 
+  window.fIMContext = gtk_im_multicontext_new()
+  discard g_signal_connect_data(window.fIMContext, "commit", pWindowIMContextCommitSignal, cast[pointer](window))
+
 method destroy(window: WindowImpl) =
   procCall window.Window.destroy()
   gtk_widget_destroy(window.fHandle)
@@ -758,6 +771,9 @@ proc init(control: ControlImpl) =
   gtk_widget_add_events(control.fHandle, GDK_BUTTON_RELEASE_MASK)
   discard g_signal_connect_data(control.fHandle, "button-release-event", pControlButtonReleaseSignal, cast[pointer](control))
 
+  control.fIMContext = gtk_im_multicontext_new()
+  discard g_signal_connect_data(control.fIMContext, "commit", pControlIMContextCommitSignal, cast[pointer](control))
+
   procCall control.Control.init()
 
 method destroy(control: ControlImpl) =
diff --git a/src/nigui/private/gtk3/platform_types1.nim b/src/nigui/private/gtk3/platform_types1.nim
index 505013b..5266e2f 100755
--- a/src/nigui/private/gtk3/platform_types1.nim
+++ b/src/nigui/private/gtk3/platform_types1.nim
@@ -6,6 +6,8 @@ type
   WindowImpl* = ref object of Window
     fHandle: pointer
     fInnerHandle: pointer
+    fIMContext: pointer
+    fKeyPressed: Key
 
   ControlImpl* = ref object of Control
     fHandle: pointer
@@ -14,6 +16,8 @@ type
     fHAdjust: pointer
     fVAdjust: pointer
     fDeadCornerHandle: pointer
+    fIMContext: pointer
+    fKeyPressed: Key
 
   CanvasImpl* = ref object of Canvas
     fSurface: pointer
diff --git a/src/nigui/private/windows/platform_impl.nim b/src/nigui/private/windows/platform_impl.nim
index 78dace3..8e072ff 100755
--- a/src/nigui/private/windows/platform_impl.nim
+++ b/src/nigui/private/windows/platform_impl.nim
@@ -20,6 +20,7 @@ const pCustomControlWindowClass = "3"
 
 var pDefaultParentWindow: pointer
 var pKeyState: KeyState
+var pKeyDownKey: Key
 
 # needed to calculate clicks:
 var pLastMouseButtonDownControl: Control
@@ -221,10 +222,10 @@ proc pVirtualKeyToKey(keyval: int): Key =
   of 46: Key_Delete
   else: cast[Key](keyval.unicodeToUpper)
 
-proc pHandleWMKEYDOWNOrWMCHAR(window: Window, control: Control, unicode: int, key: Key): bool =
+proc pHandleWMKEYDOWNOrWMCHAR(window: Window, control: Control, unicode: int): bool =
   var windowEvent = new WindowKeyEvent
   windowEvent.window = window
-  windowEvent.key = key
+  windowEvent.key = pKeyDownKey
   if windowEvent.key == Key_None:
     echo "WM_CHAR: Unkown key value: ", unicode
     return
@@ -252,19 +253,22 @@ proc pHandleWMKEYDOWNOrWMCHAR(window: Window, control: Control, unicode: int, ke
 
 proc pHandleWMKEYDOWN(window: Window, control: Control, wParam, lParam: pointer): bool =
   if not GetKeyboardState(pKeyState): pRaiseLastOSError()
+  pKeyDownKey = pVirtualKeyToKey(cast[int](wParam))
+  # Save the key for WM_CHAR, because WM_CHAR only gets the key combined with the dead key state
   var widestring = newString(2)
   let scancode = int32((cast[int](lParam) shr 8) and 0xFFFFFF00)
   if scancode == 10496:
     # When the dead key "^" on German keyboard is pressed, don't call ToUnicode(), because this would destroy the dead key state
-    return
+    pKeyDownKey = Key_Circumflex
+    return pHandleWMKEYDOWNOrWMCHAR(window, control, 0)
   let ret = ToUnicode(cast[int](wParam).int32, scancode, pKeyState, widestring, 1, 0)
   if ret == 1:
     return # Unicode characters are handled by WM_CHAR
-  result = pHandleWMKEYDOWNOrWMCHAR(window, control, 0, pVirtualKeyToKey(cast[int](wParam)))
+  result = pHandleWMKEYDOWNOrWMCHAR(window, control, 0)
 
 proc pHandleWMCHAR(window: Window, control: Control, wParam, lParam: pointer): bool =
   let unicode = cast[int](wParam)
-  result = pHandleWMKEYDOWNOrWMCHAR(window, control, unicode, cast[Key](unicode.unicodeToUpper))
+  result = pHandleWMKEYDOWNOrWMCHAR(window, control, unicode)
 
 proc pWindowWndProc(hWnd: pointer, uMsg: int32, wParam, lParam: pointer): pointer {.cdecl.} =
   case uMsg