diff --git a/gltools/@include/glfwLib.pxd b/gltools/@include/glfwLib.pxd
index 1696054..3f08461 100644
--- a/gltools/@include/glfwLib.pxd
+++ b/gltools/@include/glfwLib.pxd
@@ -135,6 +135,12 @@ cdef extern from "GLFW/glfw3.h":
         GLFW_KEY_MENU
         GLFW_KEY_LAST
         
+        # Modifiers
+        GLFW_MOD_SHIFT
+        GLFW_MOD_CONTROL
+        GLFW_MOD_ALT
+        GLFW_MOD_SUPER
+
         # Mouse button definitions
         GLFW_MOUSE_BUTTON_1
         GLFW_MOUSE_BUTTON_2
diff --git a/gltools/@src/Constants.pxi b/gltools/@src/Constants.pxi
index fbce906..bcf1ba6 100644
--- a/gltools/@src/Constants.pxi
+++ b/gltools/@src/Constants.pxi
@@ -4,6 +4,53 @@ class ACTION:
     PRESS = GLFW_PRESS
         
 class KEY:
+    SPACE = GLFW_KEY_SPACE
+    APOSTROPHE = GLFW_KEY_APOSTROPHE
+    COMMA = GLFW_KEY_COMMA
+    MINUS = GLFW_KEY_MINUS
+    PERIOD = GLFW_KEY_PERIOD
+    SLASH = GLFW_KEY_SLASH
+    ZERO = GLFW_KEY_0
+    ONE = GLFW_KEY_1
+    TWO = GLFW_KEY_2
+    THREE = GLFW_KEY_3
+    FOUR = GLFW_KEY_4
+    FIVE = GLFW_KEY_5
+    SIX = GLFW_KEY_6
+    SEVEN = GLFW_KEY_7
+    EIGHT = GLFW_KEY_8
+    NINE = GLFW_KEY_9
+    SEMICOLON = GLFW_KEY_SEMICOLON
+    EQUAL = GLFW_KEY_EQUAL
+    A = GLFW_KEY_A
+    B = GLFW_KEY_B
+    C = GLFW_KEY_C
+    D = GLFW_KEY_D
+    E = GLFW_KEY_E
+    F = GLFW_KEY_F
+    G = GLFW_KEY_G
+    H = GLFW_KEY_H
+    I = GLFW_KEY_I
+    J = GLFW_KEY_J
+    K = GLFW_KEY_K
+    L = GLFW_KEY_L
+    M = GLFW_KEY_M
+    N = GLFW_KEY_N
+    O = GLFW_KEY_O
+    P = GLFW_KEY_P
+    Q = GLFW_KEY_Q
+    R = GLFW_KEY_R
+    S = GLFW_KEY_S
+    T = GLFW_KEY_T
+    U = GLFW_KEY_U
+    V = GLFW_KEY_V
+    W = GLFW_KEY_W
+    X = GLFW_KEY_X
+    Y = GLFW_KEY_Y
+    Z = GLFW_KEY_Z
+    LEFT_BRACKET = GLFW_KEY_LEFT_BRACKET
+    BACKSLASH = GLFW_KEY_BACKSLASH
+    RIGHT_BRACKET = GLFW_KEY_RIGHT_BRACKET
     SPACE = GLFW_KEY_SPACE
     ESCAPE = GLFW_KEY_ESCAPE
     ENTER = GLFW_KEY_ENTER
@@ -43,6 +90,12 @@ class KEY:
     RIGHT_CONTROL = GLFW_KEY_RIGHT_CONTROL
     RIGHT_ALT = GLFW_KEY_RIGHT_ALT
 
+class MOD:
+    SHIFT = GLFW_MOD_SHIFT
+    CONTROL = GLFW_MOD_CONTROL
+    ALT = GLFW_MOD_ALT
+    SUPER = GLFW_MOD_SUPER
+        
 class MOUSE:
     LEFT = GLFW_MOUSE_BUTTON_LEFT
     RIGHT = GLFW_MOUSE_BUTTON_RIGHT
diff --git a/gltools/@src/Image.pxi b/gltools/@src/Image.pxi
index 2355ac3..2ea0be8 100644
--- a/gltools/@src/Image.pxi
+++ b/gltools/@src/Image.pxi
@@ -74,7 +74,7 @@ cdef class Image:
                 for i in range(self.bytesPerPixel):
                     pixels[swapOffset + i], pixels[offset + i] = pixels[offset + i], pixels[swapOffset + i]
     
-    cpdef writePNG(self, char *filename, int stride = 0):
+    cpdef writePNG(self, filename, int stride = 0):
         '''
         Write image to PNG file. Note that the file
         will be overwritten if not locked.
@@ -84,7 +84,11 @@ cdef class Image:
         
         Raises GLError on failure.
         '''
-        if not stbi_write_png(filename, self.width, self.height, self.bytesPerPixel,
+        cdef char *c_filename
+        bytetext = unicode(filename).encode('UTF-8','ignore')
+        c_filename = bytetext
+        
+        if not stbi_write_png(c_filename, self.width, self.height, self.bytesPerPixel,
                               self._buffer, stride):
             raise GLError("failed to write to PNG '%s'" % filename)
             
diff --git a/gltools/gltools.pxd b/gltools/gltools.pxd
index f4bd64b..5ec460a 100644
--- a/gltools/gltools.pxd
+++ b/gltools/gltools.pxd
@@ -142,7 +142,7 @@ cdef class Image:
     cdef __cythonbufferdefaults__ = {"ndim": 1, "mode": "c"}
     
     cpdef flipY(self)
-    cpdef writePNG(self, char *filename, int stride = ?)
+    cpdef writePNG(self, filename, int stride = ?)
     
 cpdef InitGLExt()
 cpdef int Check()
diff --git a/gltools/test.py b/gltools/test.py
index 8080b51..9bb093c 100644
--- a/gltools/test.py
+++ b/gltools/test.py
@@ -310,6 +310,9 @@ class MainWindow(gl.Window):
         #print('onKey ', key, action)
         if key == gl.KEY.ESCAPE:
             self.running = False
+        elif key == gl.KEY.F:
+            self.cam.zoomExtents(self.near, self.far)
+            self.onRefresh()
         elif key == gl.KEY.F1:
             self.makeContextCurrent()
             img = gl.Image(self.width, self.height, gl.RGBA)
@@ -317,12 +320,6 @@ class MainWindow(gl.Window):
             img.flipY()
             img.writePNG('screenshot01.png')
             
-    def onChar(self, ch):
-        #print('onChar ', ch)
-        if ch == 'f':
-            self.cam.zoomExtents(self.near, self.far)
-            self.onRefresh()
-        
     def onScroll(self, scx, scy):
         x, y = self.lastPos
         self.uiScroll = -int(scy)