From d9a85a167e9d824937c46a85b332263ae91316c8 Mon Sep 17 00:00:00 2001
From: blink1073 <steven.silvester@ieee.org>
Date: Sat, 12 Jul 2014 20:32:20 -0500
Subject: [PATCH 1/9] Move handling of blit behavior to axes object.

---
 skimage/viewer/canvastools/base.py | 58 +++++++++++++++++++++++-------
 1 file changed, 45 insertions(+), 13 deletions(-)

diff --git a/skimage/viewer/canvastools/base.py b/skimage/viewer/canvastools/base.py
index 29e6099d..284e2bd6 100644
--- a/skimage/viewer/canvastools/base.py
+++ b/skimage/viewer/canvastools/base.py
@@ -11,6 +11,31 @@ def _pass(*args):
     pass
 
 
+class BlitManager(object):
+    """Object that manages blits on an axes"""
+    def __init__(self, ax):
+        self.ax = ax
+        self.canvas = ax.figure.canvas
+        self.canvas.mpl_connect('draw_event', self.on_draw_event)
+        self.ax = ax
+        self.background = None
+        self.artists = []
+
+    def on_draw_event(self, event=None):
+        self.background = self.canvas.copy_from_bbox(self.ax.bbox)
+        self.draw_artists()
+
+    def redraw(self):
+        if self.background is not None:
+            self.canvas.restore_region(self.background)
+            self.draw_artists()
+            self.canvas.blit(self.ax.bbox)
+
+    def draw_artists(self):
+        for artist in self.artists:
+            self.ax.draw_artist(artist)
+
+
 class CanvasToolBase(object):
     """Base canvas tool for matplotlib axes.
 
@@ -28,26 +53,31 @@ class CanvasToolBase(object):
     useblit : bool
         If True, update canvas by blitting, which is much faster than normal
         redrawing (turn off for debugging purposes).
+    nograb_draw : bool
+        If a mouse click is detected, but it does not grab a handle,
+        redraw the line from scratch.  True by default.
     """
+
     def __init__(self, ax, on_move=None, on_enter=None, on_release=None,
                  useblit=True):
         self.ax = ax
         self.canvas = ax.figure.canvas
-        self.img_background = None
         self.cids = []
         self._artists = []
         self.active = True
 
+        self.connect_event('draw_event', self._on_draw_event)
         if useblit:
-            self.connect_event('draw_event', self._blit_on_draw_event)
+            if not hasattr(ax, 'blit_manager'):
+                ax.blit_manager = BlitManager(ax)
+            ax.blit_manager.artists.extend(self._artists)
+
         self.useblit = useblit
 
         self.callback_on_move = _pass if on_move is None else on_move
         self.callback_on_enter = _pass if on_enter is None else on_enter
         self.callback_on_release = _pass if on_release is None else on_release
 
-        self.connect_event('key_press_event', self._on_key_press)
-
     def connect_event(self, event, callback):
         """Connect callback with an event.
 
@@ -74,9 +104,13 @@ class CanvasToolBase(object):
         for artist in self._artists:
             artist.set_visible(val)
 
-    def _blit_on_draw_event(self, event=None):
-        self.img_background = self.canvas.copy_from_bbox(self.ax.bbox)
-        self._draw_artists()
+    def _on_draw_event(self, event=None):
+        if self.useblit:
+            for artist in self._artists:
+                if not artist in self.ax.blit_manager.artists:
+                    self.ax.blit_manager.artists.append(artist)
+        else:
+            self._draw_artists()
 
     def _draw_artists(self):
         for artist in self._artists:
@@ -97,14 +131,12 @@ class CanvasToolBase(object):
 
         This method should be called by subclasses when artists are updated.
         """
-        if self.useblit and self.img_background is not None:
-            self.canvas.restore_region(self.img_background)
-            self._draw_artists()
-            self.canvas.blit(self.ax.bbox)
+        if not self.useblit:
+            self.canvas.draw()
         else:
-            self.canvas.draw_idle()
+            self.ax.blit_manager.redraw()
 
-    def _on_key_press(self, event):
+    def on_key_press(self, event):
         if event.key == 'enter':
             self.callback_on_enter(self.geometry)
             self.set_visible(False)

From 410f3926e4b7fce9645506054b5dfd1668502811 Mon Sep 17 00:00:00 2001
From: blink1073 <steven.silvester@ieee.org>
Date: Sat, 12 Jul 2014 20:32:43 -0500
Subject: [PATCH 2/9] Push handling of line tools to axes level for better
 coordination.

---
 skimage/viewer/canvastools/linetool.py | 84 +++++++++++++++++++++++---
 1 file changed, 74 insertions(+), 10 deletions(-)

diff --git a/skimage/viewer/canvastools/linetool.py b/skimage/viewer/canvastools/linetool.py
index 61d94825..4b53ebad 100644
--- a/skimage/viewer/canvastools/linetool.py
+++ b/skimage/viewer/canvastools/linetool.py
@@ -10,6 +10,63 @@ from skimage.viewer.canvastools.base import CanvasToolBase, ToolHandles
 __all__ = ['LineTool', 'ThickLineTool']
 
 
+class EventManager(object):
+    """Object that manages events on a canvas"""
+    def __init__(self, ax):
+        self.canvas = ax.figure.canvas
+        self.connect_event('button_press_event', self.on_mouse_press)
+        self.connect_event('key_press_event', self.on_key_press)
+        self.connect_event('button_release_event', self.on_mouse_release)
+        self.connect_event('motion_notify_event', self.on_move)
+
+        self.tools = []
+        self.active_tool = None
+
+    def connect_event(self, name, handler):
+        self.canvas.mpl_connect(name, handler)
+
+    def attach(self, tool):
+        self.tools.append(tool)
+        self.active_tool = tool
+
+    def on_mouse_press(self, event):
+        for tool in self.tools:
+            if not tool.ignore(event) and tool.hit_test(event):
+                self.active_tool = tool
+                tool.on_mouse_press(event)
+                return
+        if self.active_tool and not self.active_tool.ignore(event):
+            self.active_tool.on_mouse_press(event)
+            return
+        for tool in self.tools:
+            if not tool.ignore(event):
+                self.active_tool = tool
+                tool.on_mouse_press(event)
+                return
+
+    def on_key_press(self, event):
+        tool = self.get_tool()
+        if not tool is None and not tool.ignore(event):
+            tool.on_key_press(event)
+
+    def get_tool(self):
+        if not self.tools:
+            return
+        if self.active_tool is None:
+            self.active_tool = self.tools[0]
+        return self.active_tool
+
+    def on_mouse_release(self, event):
+        tool = self.get_tool()
+        if not tool is None and not tool.ignore(event):
+            tool.on_mouse_release(event)
+
+    def on_move(self, event):
+        tool = self.get_tool()
+        if not tool is None and not tool.ignore(event):
+            tool.on_move(event)
+
+
 class LineTool(CanvasToolBase):
     """Widget for line selection in a plot.
 
@@ -35,9 +92,10 @@ class LineTool(CanvasToolBase):
         End points of line ((x1, y1), (x2, y2)).
     """
     def __init__(self, ax, on_move=None, on_release=None, on_enter=None,
-                 maxdist=10, line_props=None):
+                 maxdist=10, line_props=None,
+                 **kwargs):
         super(LineTool, self).__init__(ax, on_move=on_move, on_enter=on_enter,
-                                       on_release=on_release)
+                                       on_release=on_release, **kwargs)
 
         props = dict(color='r', linewidth=1, alpha=0.4, solid_capstyle='butt')
         props.update(line_props if line_props is not None else {})
@@ -56,16 +114,16 @@ class LineTool(CanvasToolBase):
         self._handles.set_visible(False)
         self._artists = [self._line, self._handles.artist]
 
+        if not hasattr(ax, 'event_manager'):
+            ax.event_manager = EventManager(ax)
+        ax.event_manager.attach(self)
+
         if on_enter is None:
             def on_enter(pts):
                 x, y = np.transpose(pts)
                 print("length = %0.2f" % np.sqrt(np.diff(x)**2 + np.diff(y)**2))
         self.callback_on_enter = on_enter
 
-        self.connect_event('button_press_event', self.on_mouse_press)
-        self.connect_event('button_release_event', self.on_mouse_release)
-        self.connect_event('motion_notify_event', self.on_move)
-
     @property
     def end_points(self):
         return self._end_pts.astype(int)
@@ -76,19 +134,24 @@ class LineTool(CanvasToolBase):
 
         self._line.set_data(np.transpose(pts))
         self._handles.set_data(np.transpose(pts))
-        self._line.set_linewidth(self.linewidth)
 
         self.set_visible(True)
         self.redraw()
 
-    def on_mouse_press(self, event):
+    def hit_test(self, event):
         if event.button != 1 or not self.ax.in_axes(event):
-            return
-        self.set_visible(True)
+            return False
         idx, px_dist = self._handles.closest(event.x, event.y)
         if px_dist < self.maxdist:
             self._active_pt = idx
+            return True
         else:
+            self._active_pt = None
+            return False
+
+    def on_mouse_press(self, event):
+        self.set_visible(True)
+        if self._active_pt is None:
             self._active_pt = 0
             x, y = event.xdata, event.ydata
             self._end_pts = np.array([[x, y], [x, y]])
@@ -98,6 +161,7 @@ class LineTool(CanvasToolBase):
             return
         self._active_pt = None
         self.callback_on_release(self.geometry)
+        self.redraw()
 
     def on_move(self, event):
         if event.button != 1 or self._active_pt is None:

From 1799846be9552c7d13586e5ad4b147a121329a87 Mon Sep 17 00:00:00 2001
From: blink1073 <steven.silvester@ieee.org>
Date: Sat, 12 Jul 2014 20:44:21 -0500
Subject: [PATCH 3/9] Remove unused parameter from docstring

---
 skimage/viewer/canvastools/base.py | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/skimage/viewer/canvastools/base.py b/skimage/viewer/canvastools/base.py
index 284e2bd6..fce163f3 100644
--- a/skimage/viewer/canvastools/base.py
+++ b/skimage/viewer/canvastools/base.py
@@ -53,9 +53,6 @@ class CanvasToolBase(object):
     useblit : bool
         If True, update canvas by blitting, which is much faster than normal
         redrawing (turn off for debugging purposes).
-    nograb_draw : bool
-        If a mouse click is detected, but it does not grab a handle,
-        redraw the line from scratch.  True by default.
     """
 
     def __init__(self, ax, on_move=None, on_enter=None, on_release=None,

From 2d9d8bb94ce8f32ff8d07feab60a509c16d21cdb Mon Sep 17 00:00:00 2001
From: blink1073 <steven.silvester@ieee.org>
Date: Sun, 20 Jul 2014 18:39:49 -0500
Subject: [PATCH 4/9] Refactor blit manager and event manager to viewer

---
 skimage/viewer/canvastools/base.py      | 115 +++++-------------------
 skimage/viewer/canvastools/linetool.py  |  83 +++--------------
 skimage/viewer/canvastools/painttool.py |  20 ++---
 skimage/viewer/canvastools/recttool.py  |  25 +++---
 skimage/viewer/viewers/core.py          | 102 ++++++++++++++++++++-
 5 files changed, 153 insertions(+), 192 deletions(-)

diff --git a/skimage/viewer/canvastools/base.py b/skimage/viewer/canvastools/base.py
index fce163f3..a1a06360 100644
--- a/skimage/viewer/canvastools/base.py
+++ b/skimage/viewer/canvastools/base.py
@@ -11,38 +11,13 @@ def _pass(*args):
     pass
 
 
-class BlitManager(object):
-    """Object that manages blits on an axes"""
-    def __init__(self, ax):
-        self.ax = ax
-        self.canvas = ax.figure.canvas
-        self.canvas.mpl_connect('draw_event', self.on_draw_event)
-        self.ax = ax
-        self.background = None
-        self.artists = []
-
-    def on_draw_event(self, event=None):
-        self.background = self.canvas.copy_from_bbox(self.ax.bbox)
-        self.draw_artists()
-
-    def redraw(self):
-        if self.background is not None:
-            self.canvas.restore_region(self.background)
-            self.draw_artists()
-            self.canvas.blit(self.ax.bbox)
-
-    def draw_artists(self):
-        for artist in self.artists:
-            self.ax.draw_artist(artist)
-
-
 class CanvasToolBase(object):
     """Base canvas tool for matplotlib axes.
 
     Parameters
     ----------
-    ax : :class:`matplotlib.axes.Axes`
-        Matplotlib axes where tool is displayed.
+    viewer : :class:`skimage.viewer.Viewer`
+        Skimage viewer object.
     on_move : function
         Function called whenever a control handle is moved.
         This function must accept the end points of line as the only argument.
@@ -50,45 +25,19 @@ class CanvasToolBase(object):
         Function called whenever the control handle is released.
     on_enter : function
         Function called whenever the "enter" key is pressed.
-    useblit : bool
-        If True, update canvas by blitting, which is much faster than normal
-        redrawing (turn off for debugging purposes).
     """
 
-    def __init__(self, ax, on_move=None, on_enter=None, on_release=None,
+    def __init__(self, viewer, on_move=None, on_enter=None, on_release=None,
                  useblit=True):
-        self.ax = ax
-        self.canvas = ax.figure.canvas
-        self.cids = []
-        self._artists = []
+        self.viewer = viewer
+        self.ax = viewer.ax
+        self.artists = []
         self.active = True
 
-        self.connect_event('draw_event', self._on_draw_event)
-        if useblit:
-            if not hasattr(ax, 'blit_manager'):
-                ax.blit_manager = BlitManager(ax)
-            ax.blit_manager.artists.extend(self._artists)
-
-        self.useblit = useblit
-
         self.callback_on_move = _pass if on_move is None else on_move
         self.callback_on_enter = _pass if on_enter is None else on_enter
         self.callback_on_release = _pass if on_release is None else on_release
 
-    def connect_event(self, event, callback):
-        """Connect callback with an event.
-
-        This should be used in lieu of `figure.canvas.mpl_connect` since this
-        function stores call back ids for later clean up.
-        """
-        cid = self.canvas.mpl_connect(event, callback)
-        self.cids.append(cid)
-
-    def disconnect_events(self):
-        """Disconnect all events created by this widget."""
-        for c in self.cids:
-            self.canvas.mpl_disconnect(c)
-
     def ignore(self, event):
         """Return True if event should be ignored.
 
@@ -97,47 +46,30 @@ class CanvasToolBase(object):
         """
         return not self.active
 
+    def redraw(self):
+        self.viewer.redraw()
+
     def set_visible(self, val):
         for artist in self._artists:
             artist.set_visible(val)
 
-    def _on_draw_event(self, event=None):
-        if self.useblit:
-            for artist in self._artists:
-                if not artist in self.ax.blit_manager.artists:
-                    self.ax.blit_manager.artists.append(artist)
-        else:
-            self._draw_artists()
-
-    def _draw_artists(self):
-        for artist in self._artists:
-            self.ax.draw_artist(artist)
-
-    def remove(self):
-        """Remove artists and events from axes.
-
-        Note that the naming here mimics the interface of Matplotlib artists.
-        """
-        #TODO: For some reason, RectangleTool doesn't get properly removed
-        self.disconnect_events()
-        for a in self._artists:
-            a.remove()
-
-    def redraw(self):
-        """Redraw image and canvas artists.
-
-        This method should be called by subclasses when artists are updated.
-        """
-        if not self.useblit:
-            self.canvas.draw()
-        else:
-            self.ax.blit_manager.redraw()
-
     def on_key_press(self, event):
         if event.key == 'enter':
             self.callback_on_enter(self.geometry)
             self.set_visible(False)
-            self.redraw()
+            self.viewer.redraw()
+
+    def on_mouse_press(self, event):
+        pass
+
+    def on_mouse_release(self, event):
+        pass
+
+    def on_move(self, event):
+        pass
+
+    def on_scroll(self, event):
+        pass
 
     @property
     def geometry(self):
@@ -190,9 +122,6 @@ class ToolHandles(object):
     def set_animated(self, val):
         self._markers.set_animated(val)
 
-    def draw(self):
-        self.ax.draw_artist(self._markers)
-
     def closest(self, x, y):
         """Return index and pixel distance to closest index."""
         pts = np.transpose((self.x, self.y))
diff --git a/skimage/viewer/canvastools/linetool.py b/skimage/viewer/canvastools/linetool.py
index 4b53ebad..e1b48c05 100644
--- a/skimage/viewer/canvastools/linetool.py
+++ b/skimage/viewer/canvastools/linetool.py
@@ -10,70 +10,13 @@ from skimage.viewer.canvastools.base import CanvasToolBase, ToolHandles
 __all__ = ['LineTool', 'ThickLineTool']
 
 
-class EventManager(object):
-    """Object that manages events on a canvas"""
-    def __init__(self, ax):
-        self.canvas = ax.figure.canvas
-        self.connect_event('button_press_event', self.on_mouse_press)
-        self.connect_event('key_press_event', self.on_key_press)
-        self.connect_event('button_release_event', self.on_mouse_release)
-        self.connect_event('motion_notify_event', self.on_move)
-
-        self.tools = []
-        self.active_tool = None
-
-    def connect_event(self, name, handler):
-        self.canvas.mpl_connect(name, handler)
-
-    def attach(self, tool):
-        self.tools.append(tool)
-        self.active_tool = tool
-
-    def on_mouse_press(self, event):
-        for tool in self.tools:
-            if not tool.ignore(event) and tool.hit_test(event):
-                self.active_tool = tool
-                tool.on_mouse_press(event)
-                return
-        if self.active_tool and not self.active_tool.ignore(event):
-            self.active_tool.on_mouse_press(event)
-            return
-        for tool in self.tools:
-            if not tool.ignore(event):
-                self.active_tool = tool
-                tool.on_mouse_press(event)
-                return
-
-    def on_key_press(self, event):
-        tool = self.get_tool()
-        if not tool is None and not tool.ignore(event):
-            tool.on_key_press(event)
-
-    def get_tool(self):
-        if not self.tools:
-            return
-        if self.active_tool is None:
-            self.active_tool = self.tools[0]
-        return self.active_tool
-
-    def on_mouse_release(self, event):
-        tool = self.get_tool()
-        if not tool is None and not tool.ignore(event):
-            tool.on_mouse_release(event)
-
-    def on_move(self, event):
-        tool = self.get_tool()
-        if not tool is None and not tool.ignore(event):
-            tool.on_move(event)
-
-
 class LineTool(CanvasToolBase):
     """Widget for line selection in a plot.
 
     Parameters
     ----------
-    ax : :class:`matplotlib.axes.Axes`
-        Matplotlib axes where tool is displayed.
+    viewer : :class:`skimage.viewer.Viewer`
+        Skimage viewer object.
     on_move : function
         Function called whenever a control handle is moved.
         This function must accept the end points of line as the only argument.
@@ -91,7 +34,7 @@ class LineTool(CanvasToolBase):
     end_points : 2D array
         End points of line ((x1, y1), (x2, y2)).
     """
-    def __init__(self, ax, on_move=None, on_release=None, on_enter=None,
+    def __init__(self, viewer, on_move=None, on_release=None, on_enter=None,
                  maxdist=10, line_props=None,
                  **kwargs):
         super(LineTool, self).__init__(ax, on_move=on_move, on_enter=on_enter,
@@ -108,21 +51,18 @@ class LineTool(CanvasToolBase):
         self._end_pts = np.transpose([x, y])
 
         self._line = lines.Line2D(x, y, visible=False, animated=True, **props)
-        ax.add_line(self._line)
+        self.ax.add_line(self._line)
 
-        self._handles = ToolHandles(ax, x, y)
+        self._handles = ToolHandles(self.ax, x, y)
         self._handles.set_visible(False)
-        self._artists = [self._line, self._handles.artist]
-
-        if not hasattr(ax, 'event_manager'):
-            ax.event_manager = EventManager(ax)
-        ax.event_manager.attach(self)
+        self.artists = [self._line, self._handles.artist]
 
         if on_enter is None:
             def on_enter(pts):
                 x, y = np.transpose(pts)
                 print("length = %0.2f" % np.sqrt(np.diff(x)**2 + np.diff(y)**2))
         self.callback_on_enter = on_enter
+        viewer.add_tool(self)
 
     @property
     def end_points(self):
@@ -189,8 +129,8 @@ class ThickLineTool(LineTool):
 
     Parameters
     ----------
-    ax : :class:`matplotlib.axes.Axes`
-        Matplotlib axes where tool is displayed.
+    viewer : :class:`skimage.viewer.Viewer`
+        Skimage viewer object.
     on_move : function
         Function called whenever a control handle is moved.
         This function must accept the end points of line as the only argument.
@@ -211,7 +151,7 @@ class ThickLineTool(LineTool):
         End points of line ((x1, y1), (x2, y2)).
     """
 
-    def __init__(self, ax, on_move=None, on_enter=None, on_release=None,
+    def __init__(self, viewer, on_move=None, on_enter=None, on_release=None,
                  on_change=None, maxdist=10, line_props=None):
         super(ThickLineTool, self).__init__(ax,
                                             on_move=on_move,
@@ -225,9 +165,6 @@ class ThickLineTool(LineTool):
                 pass
         self.callback_on_change = on_change
 
-        self.connect_event('scroll_event', self.on_scroll)
-        self.connect_event('key_press_event', self.on_key_press)
-
     def on_scroll(self, event):
         if not event.inaxes:
             return
diff --git a/skimage/viewer/canvastools/painttool.py b/skimage/viewer/canvastools/painttool.py
index 9b94e0a2..8d3c9449 100644
--- a/skimage/viewer/canvastools/painttool.py
+++ b/skimage/viewer/canvastools/painttool.py
@@ -17,8 +17,8 @@ class PaintTool(CanvasToolBase):
 
     Parameters
     ----------
-    ax : :class:`matplotlib.axes.Axes`
-        Matplotlib axes where tool is displayed.
+    viewer : :class:`skimage.viewer.Viewer`
+        Skimage viewer object.
     overlay_shape : shape tuple
         2D shape tuple used to initialize overlay image.
     alpha : float (between [0, 1])
@@ -41,8 +41,9 @@ class PaintTool(CanvasToolBase):
     label : int
         Current paint color.
     """
-    def __init__(self, ax, overlay_shape, radius=5, alpha=0.3, on_move=None,
-                 on_release=None, on_enter=None, rect_props=None):
+    def __init__(self, viewer, overlay_shape, radius=5, alpha=0.3,
+                 on_move=None, on_release=None, on_enter=None,
+                 rect_props=None):
         super(PaintTool, self).__init__(ax, on_move=on_move, on_enter=on_enter,
                                         on_release=on_release)
 
@@ -63,11 +64,8 @@ class PaintTool(CanvasToolBase):
         self.radius = radius
 
         # Note that the order is important: Redraw cursor *after* overlay
-        self._artists = [self._overlay_plot, self._cursor]
-
-        self.connect_event('button_press_event', self.on_mouse_press)
-        self.connect_event('button_release_event', self.on_mouse_release)
-        self.connect_event('motion_notify_event', self.on_move)
+        self.artists = [self._overlay_plot, self._cursor]
+        view.add_tool(self)
 
     @property
     def label(self):
@@ -123,7 +121,7 @@ class PaintTool(CanvasToolBase):
             self.radius = self._radius
         self.overlay = np.zeros(shape, dtype='uint8')
 
-    def _on_key_press(self, event):
+    def on_key_press(self, event):
         if event.key == 'enter':
             self.callback_on_enter(self.geometry)
             self.redraw()
@@ -140,7 +138,7 @@ class PaintTool(CanvasToolBase):
         self.callback_on_release(self.geometry)
 
     def on_move(self, event):
-        if not self.ax.in_axes(event):
+        if not self.viewer.ax.in_axes(event):
             self._cursor.set_visible(False)
             self.redraw() # make sure cursor is not visible
             return
diff --git a/skimage/viewer/canvastools/recttool.py b/skimage/viewer/canvastools/recttool.py
index 929fe939..d3724bf9 100644
--- a/skimage/viewer/canvastools/recttool.py
+++ b/skimage/viewer/canvastools/recttool.py
@@ -18,8 +18,8 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
 
     Parameters
     ----------
-    ax : :class:`matplotlib.axes.Axes`
-        Matplotlib axes where tool is displayed.
+    viewer : :class:`skimage.viewer.Viewer`
+        Skimage viewer object.
     on_move : function
         Function called whenever a control handle is moved.
         This function must accept the rectangle extents as the only argument.
@@ -39,7 +39,7 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
         Rectangle extents: (xmin, xmax, ymin, ymax).
     """
 
-    def __init__(self, ax, on_move=None, on_release=None, on_enter=None,
+    def __init__(self, viewer, on_move=None, on_release=None, on_enter=None,
                  maxdist=10, rect_props=None):
         CanvasToolBase.__init__(self, ax, on_move=on_move,
                                 on_enter=on_enter, on_release=on_release)
@@ -48,9 +48,9 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
         props.update(rect_props if rect_props is not None else {})
         if props['edgecolor'] is None:
             props['edgecolor'] = props['facecolor']
-        RectangleSelector.__init__(self, ax, lambda *args: None,
-                                   rectprops=props,
-                                   useblit=self.useblit)
+        RectangleSelector.__init__(self, self.ax, lambda *args: None,
+                                   rectprops=props)
+        self.disconnect_events()  # events are handled by the viewer
         # Alias rectangle attribute, which is initialized in RectangleSelector.
         self._rect = self.to_draw
         self._rect.set_animated(True)
@@ -74,9 +74,10 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
         self._edge_handles = ToolHandles(ax, xe, ye, marker='s',
                                          marker_props=props)
 
-        self._artists = [self._rect,
-                         self._corner_handles.artist,
-                         self._edge_handles.artist]
+        self.artists = [self._rect,
+                        self._corner_handles.artist,
+                        self._edge_handles.artist]
+        viewer.add_tool(self)
 
     @property
     def _rect_bbox(self):
@@ -129,7 +130,7 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
         self.set_visible(True)
         self.redraw()
 
-    def release(self, event):
+    def on_mouse_release(self, event):
         if event.button != 1:
             return
         if not self.ax.in_axes(event):
@@ -142,7 +143,7 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
         self.redraw()
         self.callback_on_release(self.geometry)
 
-    def press(self, event):
+    def on_mouse_press(self, event):
         if event.button != 1 or not self.ax.in_axes(event):
             return
         self._set_active_handle(event)
@@ -177,7 +178,7 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
             y1, y2 = y2, event.ydata
         self._extents_on_press = x1, x2, y1, y2
 
-    def onmove(self, event):
+    def on_move(self, event):
         if self.eventpress is None or not self.ax.in_axes(event):
             return
 
diff --git a/skimage/viewer/viewers/core.py b/skimage/viewer/viewers/core.py
index 52ac073a..afd3ff2b 100644
--- a/skimage/viewer/viewers/core.py
+++ b/skimage/viewer/viewers/core.py
@@ -12,7 +12,6 @@ else:
 from skimage import io, img_as_float
 from skimage.util.dtype import dtype_range
 from skimage.exposure import rescale_intensity
-from skimage._shared.testing import doctest_skip_parser
 import numpy as np
 from .. import utils
 from ..widgets import Slider
@@ -51,6 +50,88 @@ def mpl_image_to_rgba(mpl_image):
     return img_as_float(image)
 
 
+class BlitManager(object):
+    """Object that manages blits on an axes"""
+    def __init__(self, ax):
+        self.ax = ax
+        self.canvas = ax.figure.canvas
+        self.canvas.mpl_connect('draw_event', self.on_draw_event)
+        self.ax = ax
+        self.background = None
+        self.artists = []
+
+    def on_draw_event(self, event=None):
+        self.background = self.canvas.copy_from_bbox(self.ax.bbox)
+        self.draw_artists()
+
+    def redraw(self):
+        if self.background is not None:
+            self.canvas.restore_region(self.background)
+            self.draw_artists()
+            self.canvas.blit(self.ax.bbox)
+
+    def draw_artists(self):
+        for artist in self.artists:
+            self.ax.draw_artist(artist)
+
+
+class EventManager(object):
+    """Object that manages events on a canvas"""
+    def __init__(self, ax):
+        self.canvas = ax.figure.canvas
+        self.connect_event('button_press_event', self.on_mouse_press)
+        self.connect_event('key_press_event', self.on_key_press)
+        self.connect_event('button_release_event', self.on_mouse_release)
+        self.connect_event('motion_notify_event', self.on_move)
+
+        self.tools = []
+        self.active_tool = None
+
+    def connect_event(self, name, handler):
+        self.canvas.mpl_connect(name, handler)
+
+    def attach(self, tool):
+        self.tools.append(tool)
+        self.active_tool = tool
+
+    def on_mouse_press(self, event):
+        for tool in self.tools:
+            if not tool.ignore(event) and tool.hit_test(event):
+                self.active_tool = tool
+                tool.on_mouse_press(event)
+                return
+        if self.active_tool and not self.active_tool.ignore(event):
+            self.active_tool.on_mouse_press(event)
+            return
+        for tool in reversed(self.tools):
+            if not tool.ignore(event):
+                self.active_tool = tool
+                tool.on_mouse_press(event)
+                return
+
+    def on_key_press(self, event):
+        tool = self.get_tool()
+        if not tool is None and not tool.ignore(event):
+            tool.on_key_press(event)
+
+    def get_tool(self):
+        if not self.tools:
+            return
+        if self.active_tool is None:
+            self.active_tool = self.tools[0]
+        return self.active_tool
+
+    def on_mouse_release(self, event):
+        tool = self.get_tool()
+        if not tool is None and not tool.ignore(event):
+            tool.on_mouse_release(event)
+
+    def on_move(self, event):
+        tool = self.get_tool()
+        if not tool is None and not tool.ignore(event):
+            tool.on_move(event)
+
+
 class ImageViewer(QtGui.QMainWindow):
     """Viewer for displaying images.
 
@@ -91,7 +172,7 @@ class ImageViewer(QtGui.QMainWindow):
     # Signal that the original image has been changed
     original_image_changed = Signal(np.ndarray)
 
-    def __init__(self, image):
+    def __init__(self, image, useblit=True):
         # Start main loop
         utils.init_qtapp()
         super(ImageViewer, self).__init__()
@@ -125,6 +206,12 @@ class ImageViewer(QtGui.QMainWindow):
         self.canvas.setParent(self)
         self.ax.autoscale(enable=False)
 
+        self._tools = []
+        self.useblit = useblit
+        if useblit:
+            self._blit_manager = BlitManager(self.ax)
+        self._event_manager = EventManager(self.ax)
+
         self._image_plot = self.ax.images[0]
         self._update_original_image(image)
         self.plugins = []
@@ -238,7 +325,10 @@ class ImageViewer(QtGui.QMainWindow):
         return [p.output() for p in self.plugins]
 
     def redraw(self):
-        self.canvas.draw_idle()
+        if self.useblit:
+            self._blit_manager.redraw()
+        else:
+            self.canvas.draw_idle()
 
     @property
     def image(self):
@@ -280,6 +370,12 @@ class ImageViewer(QtGui.QMainWindow):
         else:
             self.status_message('')
 
+    def add_tool(self, tool):
+        if self.blit:
+            self._blit_manager.artists.extend(tool.artists)
+        self._tools.append(tool)
+        self._event_manager.attach(tool)
+
     def _format_coord(self, x, y):
         # callback function to format coordinate display in status bar
         x = int(x + 0.5)

From 1775e959d6bec18bf97ee3e42810e02aa4e2d06a Mon Sep 17 00:00:00 2001
From: blink1073 <steven.silvester@ieee.org>
Date: Sun, 20 Jul 2014 19:08:14 -0500
Subject: [PATCH 5/9] Switch plugins to use new tool api

---
 skimage/viewer/plugins/color_histogram.py | 3 ++-
 skimage/viewer/plugins/crop.py            | 2 +-
 skimage/viewer/plugins/labelplugin.py     | 2 +-
 skimage/viewer/plugins/lineprofile.py     | 2 +-
 skimage/viewer/plugins/measure.py         | 2 +-
 5 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/skimage/viewer/plugins/color_histogram.py b/skimage/viewer/plugins/color_histogram.py
index 4826fc44..99205c41 100644
--- a/skimage/viewer/plugins/color_histogram.py
+++ b/skimage/viewer/plugins/color_histogram.py
@@ -21,7 +21,8 @@ class ColorHistogram(PlotPlugin):
     def attach(self, image_viewer):
         super(ColorHistogram, self).attach(image_viewer)
 
-        self.rect_tool = RectangleTool(self.ax, on_release=self.ab_selected)
+        self.rect_tool = RectangleTool(image_viewer,
+                                       on_release=self.ab_selected)
         self._on_new_image(image_viewer.image)
 
     def _on_new_image(self, image):
diff --git a/skimage/viewer/plugins/crop.py b/skimage/viewer/plugins/crop.py
index 61f61034..29ad5866 100644
--- a/skimage/viewer/plugins/crop.py
+++ b/skimage/viewer/plugins/crop.py
@@ -18,7 +18,7 @@ class Crop(Plugin):
     def attach(self, image_viewer):
         super(Crop, self).attach(image_viewer)
 
-        self.rect_tool = RectangleTool(self.image_viewer.ax,
+        self.rect_tool = RectangleTool(image_viewer,
                                        maxdist=self.maxdist,
                                        on_enter=self.crop)
         self.artists.append(self.rect_tool)
diff --git a/skimage/viewer/plugins/labelplugin.py b/skimage/viewer/plugins/labelplugin.py
index 06ba2dd9..fa2b1940 100644
--- a/skimage/viewer/plugins/labelplugin.py
+++ b/skimage/viewer/plugins/labelplugin.py
@@ -37,7 +37,7 @@ class LabelPainter(Plugin):
         super(LabelPainter, self).attach(image_viewer)
 
         image = image_viewer.original_image
-        self.paint_tool = PaintTool(self.image_viewer.ax, image.shape,
+        self.paint_tool = PaintTool(image_viewer, image.shape,
                                     on_enter=self.on_enter)
         self.paint_tool.radius = self.radius
         self.paint_tool.label = self._label_widget.index = 1
diff --git a/skimage/viewer/plugins/lineprofile.py b/skimage/viewer/plugins/lineprofile.py
index 6e5b2c1f..46a0f1d2 100644
--- a/skimage/viewer/plugins/lineprofile.py
+++ b/skimage/viewer/plugins/lineprofile.py
@@ -59,7 +59,7 @@ class LineProfile(PlotPlugin):
         x = [w / 3, 2 * w / 3]
         y = [h / 2] * 2
 
-        self.line_tool = ThickLineTool(self.image_viewer.ax,
+        self.line_tool = ThickLineTool(self.image_viewer,
                                        maxdist=self.maxdist,
                                        on_move=self.line_changed,
                                        on_change=self.line_changed)
diff --git a/skimage/viewer/plugins/measure.py b/skimage/viewer/plugins/measure.py
index eeaa13b0..7e29a796 100644
--- a/skimage/viewer/plugins/measure.py
+++ b/skimage/viewer/plugins/measure.py
@@ -32,7 +32,7 @@ class Measure(Plugin):
 
         image = image_viewer.original_image
         h, w = image.shape
-        self.line_tool = LineTool(self.image_viewer.ax,
+        self.line_tool = LineTool(self.image_viewer,
                                   maxdist=self.maxdist,
                                   on_move=self.line_changed)
         self.artists.append(self.line_tool)

From 778f62de6a76e5eae0b0c78b66ab9567e326412a Mon Sep 17 00:00:00 2001
From: blink1073 <steven.silvester@ieee.org>
Date: Sun, 20 Jul 2014 19:15:40 -0500
Subject: [PATCH 6/9] Updates to get all tools tested and working

---
 skimage/viewer/canvastools/base.py      |  5 ++++-
 skimage/viewer/canvastools/linetool.py  | 15 +++++++--------
 skimage/viewer/canvastools/painttool.py | 13 +++++++------
 skimage/viewer/canvastools/recttool.py  | 15 +++++++--------
 skimage/viewer/viewers/core.py          |  2 +-
 5 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/skimage/viewer/canvastools/base.py b/skimage/viewer/canvastools/base.py
index a1a06360..5412198b 100644
--- a/skimage/viewer/canvastools/base.py
+++ b/skimage/viewer/canvastools/base.py
@@ -46,11 +46,14 @@ class CanvasToolBase(object):
         """
         return not self.active
 
+    def hit_test(self, event):
+        return False
+
     def redraw(self):
         self.viewer.redraw()
 
     def set_visible(self, val):
-        for artist in self._artists:
+        for artist in self.artists:
             artist.set_visible(val)
 
     def on_key_press(self, event):
diff --git a/skimage/viewer/canvastools/linetool.py b/skimage/viewer/canvastools/linetool.py
index e1b48c05..0b6de5a4 100644
--- a/skimage/viewer/canvastools/linetool.py
+++ b/skimage/viewer/canvastools/linetool.py
@@ -37,7 +37,8 @@ class LineTool(CanvasToolBase):
     def __init__(self, viewer, on_move=None, on_release=None, on_enter=None,
                  maxdist=10, line_props=None,
                  **kwargs):
-        super(LineTool, self).__init__(ax, on_move=on_move, on_enter=on_enter,
+        super(LineTool, self).__init__(viewer, on_move=on_move,
+                                       on_enter=on_enter,
                                        on_release=on_release, **kwargs)
 
         props = dict(color='r', linewidth=1, alpha=0.4, solid_capstyle='butt')
@@ -153,7 +154,7 @@ class ThickLineTool(LineTool):
 
     def __init__(self, viewer, on_move=None, on_enter=None, on_release=None,
                  on_change=None, maxdist=10, line_props=None):
-        super(ThickLineTool, self).__init__(ax,
+        super(ThickLineTool, self).__init__(viewer,
                                             on_move=on_move,
                                             on_enter=on_enter,
                                             on_release=on_release,
@@ -192,16 +193,14 @@ class ThickLineTool(LineTool):
 
 
 if __name__ == '__main__':  # pragma: no cover
-    import matplotlib.pyplot as plt
     from skimage import data
+    from skimage.viewer import ImageViewer
 
     image = data.camera()
 
-    f, ax = plt.subplots()
-    ax.imshow(image, interpolation='nearest')
+    viewer = ImageViewer(image)
     h, w = image.shape
 
-    # line_tool = LineTool(ax)
-    line_tool = ThickLineTool(ax)
+    line_tool = ThickLineTool(viewer)
     line_tool.end_points = ([w/3, h/2], [2*w/3, h/2])
-    plt.show()
+    viewer.show()
diff --git a/skimage/viewer/canvastools/painttool.py b/skimage/viewer/canvastools/painttool.py
index 8d3c9449..953f6ebe 100644
--- a/skimage/viewer/canvastools/painttool.py
+++ b/skimage/viewer/canvastools/painttool.py
@@ -44,7 +44,8 @@ class PaintTool(CanvasToolBase):
     def __init__(self, viewer, overlay_shape, radius=5, alpha=0.3,
                  on_move=None, on_release=None, on_enter=None,
                  rect_props=None):
-        super(PaintTool, self).__init__(ax, on_move=on_move, on_enter=on_enter,
+        super(PaintTool, self).__init__(viewer, on_move=on_move,
+                                        on_enter=on_enter,
                                         on_release=on_release)
 
         props = dict(edgecolor='r', facecolor='0.7', alpha=0.5, animated=True)
@@ -65,7 +66,7 @@ class PaintTool(CanvasToolBase):
 
         # Note that the order is important: Redraw cursor *after* overlay
         self.artists = [self._overlay_plot, self._cursor]
-        view.add_tool(self)
+        viewer.add_tool(self)
 
     @property
     def label(self):
@@ -201,10 +202,10 @@ class CenteredWindow(object):
 if __name__ == '__main__':  # pragma: no cover
     np.testing.rundocs()
     from skimage import data
+    from skimage.viewer import ImageViewer
 
     image = data.camera()
 
-    f, ax = plt.subplots()
-    ax.imshow(image, interpolation='nearest')
-    paint_tool = PaintTool(ax, image.shape)
-    plt.show()
+    viewer = ImageViewer(image)
+    paint_tool = PaintTool(viewer, image.shape)
+    viewer.show()
diff --git a/skimage/viewer/canvastools/recttool.py b/skimage/viewer/canvastools/recttool.py
index d3724bf9..5d658533 100644
--- a/skimage/viewer/canvastools/recttool.py
+++ b/skimage/viewer/canvastools/recttool.py
@@ -41,7 +41,7 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
 
     def __init__(self, viewer, on_move=None, on_release=None, on_enter=None,
                  maxdist=10, rect_props=None):
-        CanvasToolBase.__init__(self, ax, on_move=on_move,
+        CanvasToolBase.__init__(self, viewer, on_move=on_move,
                                 on_enter=on_enter, on_release=on_release)
 
         props = dict(edgecolor=None, facecolor='r', alpha=0.15)
@@ -67,11 +67,11 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
         props = dict(mec=props['edgecolor'])
         self._corner_order = ['NW', 'NE', 'SE', 'SW']
         xc, yc = self.corners
-        self._corner_handles = ToolHandles(ax, xc, yc, marker_props=props)
+        self._corner_handles = ToolHandles(self.ax, xc, yc, marker_props=props)
 
         self._edge_order = ['W', 'N', 'E', 'S']
         xe, ye = self.edge_centers
-        self._edge_handles = ToolHandles(ax, xe, ye, marker='s',
+        self._edge_handles = ToolHandles(self.ax, xe, ye, marker='s',
                                          marker_props=props)
 
         self.artists = [self._rect,
@@ -202,13 +202,12 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
 
 
 if __name__ == '__main__':  # pragma: no cover
-    import matplotlib.pyplot as plt
+    from skimage.viewer import ImageViewer
     from skimage import data
 
-    f, ax = plt.subplots()
-    ax.imshow(data.camera(), interpolation='nearest')
+    viewer = ImageViewer(data.camera())
 
-    rect_tool = RectangleTool(ax)
-    plt.show()
+    rect_tool = RectangleTool(viewer)
+    viewer.show()
     print("Final selection:")
     rect_tool.callback_on_enter(rect_tool.extents)
diff --git a/skimage/viewer/viewers/core.py b/skimage/viewer/viewers/core.py
index afd3ff2b..6dc4a7a5 100644
--- a/skimage/viewer/viewers/core.py
+++ b/skimage/viewer/viewers/core.py
@@ -371,7 +371,7 @@ class ImageViewer(QtGui.QMainWindow):
             self.status_message('')
 
     def add_tool(self, tool):
-        if self.blit:
+        if self.useblit:
             self._blit_manager.artists.extend(tool.artists)
         self._tools.append(tool)
         self._event_manager.attach(tool)

From 7864adbc0c36f81c614e3a7c11c8b9a553ee2583 Mon Sep 17 00:00:00 2001
From: blink1073 <steven.silvester@ieee.org>
Date: Sun, 20 Jul 2014 19:29:39 -0500
Subject: [PATCH 7/9] Make other suggested style changes

---
 skimage/viewer/viewers/core.py | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/skimage/viewer/viewers/core.py b/skimage/viewer/viewers/core.py
index 6dc4a7a5..52e2259f 100644
--- a/skimage/viewer/viewers/core.py
+++ b/skimage/viewer/viewers/core.py
@@ -98,8 +98,7 @@ class EventManager(object):
         for tool in self.tools:
             if not tool.ignore(event) and tool.hit_test(event):
                 self.active_tool = tool
-                tool.on_mouse_press(event)
-                return
+                break
         if self.active_tool and not self.active_tool.ignore(event):
             self.active_tool.on_mouse_press(event)
             return
@@ -110,25 +109,23 @@ class EventManager(object):
                 return
 
     def on_key_press(self, event):
-        tool = self.get_tool()
-        if not tool is None and not tool.ignore(event):
+        tool = self._get_tool(event)
+        if not tool is None:
             tool.on_key_press(event)
 
-    def get_tool(self):
-        if not self.tools:
-            return
-        if self.active_tool is None:
-            self.active_tool = self.tools[0]
+    def _get_tool(self, event):
+        if not self.tools or self.active_tool.ignore(event):
+            return None
         return self.active_tool
 
     def on_mouse_release(self, event):
-        tool = self.get_tool()
-        if not tool is None and not tool.ignore(event):
+        tool = self._get_tool(event)
+        if not tool is None:
             tool.on_mouse_release(event)
 
     def on_move(self, event):
-        tool = self.get_tool()
-        if not tool is None and not tool.ignore(event):
+        tool = self._get_tool(event)
+        if not tool is None:
             tool.on_move(event)
 
 

From 17403921101f1fd55e263fd90172a23ef3b1dc18 Mon Sep 17 00:00:00 2001
From: Steven Silvester <steven.silvester@ieee.org>
Date: Mon, 1 Sep 2014 10:28:28 -0500
Subject: [PATCH 8/9] Add on_scroll behavior and allow line to change width.

---
 skimage/viewer/canvastools/linetool.py | 1 +
 skimage/viewer/viewers/core.py         | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/skimage/viewer/canvastools/linetool.py b/skimage/viewer/canvastools/linetool.py
index 0b6de5a4..6dbda97b 100644
--- a/skimage/viewer/canvastools/linetool.py
+++ b/skimage/viewer/canvastools/linetool.py
@@ -75,6 +75,7 @@ class LineTool(CanvasToolBase):
 
         self._line.set_data(np.transpose(pts))
         self._handles.set_data(np.transpose(pts))
+        self._line.set_linewidth(self.linewidth)
 
         self.set_visible(True)
         self.redraw()
diff --git a/skimage/viewer/viewers/core.py b/skimage/viewer/viewers/core.py
index 52e2259f..f1e541a1 100644
--- a/skimage/viewer/viewers/core.py
+++ b/skimage/viewer/viewers/core.py
@@ -83,6 +83,7 @@ class EventManager(object):
         self.connect_event('key_press_event', self.on_key_press)
         self.connect_event('button_release_event', self.on_mouse_release)
         self.connect_event('motion_notify_event', self.on_move)
+        self.connect_event('scroll_event', self.on_scroll)
 
         self.tools = []
         self.active_tool = None
@@ -128,6 +129,11 @@ class EventManager(object):
         if not tool is None:
             tool.on_move(event)
 
+    def on_scroll(self, event):
+        tool = self._get_tool(event)
+        if not tool is None:
+            tool.on_scroll(event)
+
 
 class ImageViewer(QtGui.QMainWindow):
     """Viewer for displaying images.

From 7ac6323210fbab64a417c1cf0f09ed8e5030f77e Mon Sep 17 00:00:00 2001
From: Steven Silvester <steven.silvester@ieee.org>
Date: Mon, 1 Sep 2014 13:30:07 -0500
Subject: [PATCH 9/9] Fix failing tests

---
 skimage/viewer/canvastools/base.py   |  4 ++
 skimage/viewer/tests/test_tools.py   | 90 +++++++++++++---------------
 skimage/viewer/tests/test_utils.py   |  4 +-
 skimage/viewer/tests/test_widgets.py |  8 ++-
 skimage/viewer/viewers/core.py       | 23 ++++++-
 5 files changed, 73 insertions(+), 56 deletions(-)

diff --git a/skimage/viewer/canvastools/base.py b/skimage/viewer/canvastools/base.py
index 5412198b..197800c0 100644
--- a/skimage/viewer/canvastools/base.py
+++ b/skimage/viewer/canvastools/base.py
@@ -33,6 +33,7 @@ class CanvasToolBase(object):
         self.ax = viewer.ax
         self.artists = []
         self.active = True
+        viewer.add_tool(self)
 
         self.callback_on_move = _pass if on_move is None else on_move
         self.callback_on_enter = _pass if on_enter is None else on_enter
@@ -74,6 +75,9 @@ class CanvasToolBase(object):
     def on_scroll(self, event):
         pass
 
+    def remove(self):
+        self.viewer.remove_tool(self)
+
     @property
     def geometry(self):
         """Geometry information that gets passed to callback functions."""
diff --git a/skimage/viewer/tests/test_tools.py b/skimage/viewer/tests/test_tools.py
index 6663c465..8cc6bd0d 100644
--- a/skimage/viewer/tests/test_tools.py
+++ b/skimage/viewer/tests/test_tools.py
@@ -19,7 +19,7 @@ def get_end_points(image):
     return np.transpose([x, y])
 
 
-def create_mouse_event(ax, button=1, xdata=0, ydata=0, key=None):
+def do_event(viewer, etype, button=1, xdata=0, ydata=0, key=None):
     """
      *name*
         the event name
@@ -56,6 +56,7 @@ def create_mouse_event(ax, button=1, xdata=0, ydata=0, key=None):
     *step*
         number of scroll steps (positive for 'up', negative for 'down')
     """
+    ax = viewer.ax
     event = namedtuple('Event',
                        ('name canvas guiEvent x y inaxes xdata ydata '
                         'button key step'))
@@ -68,7 +69,9 @@ def create_mouse_event(ax, button=1, xdata=0, ydata=0, key=None):
     event.step = 1
     event.guiEvent = None
     event.name = 'Custom'
-    return event
+
+    func = getattr(viewer._event_manager, 'on_%s' % etype)
+    func(event)
 
 
 @skipif(not viewer_available)
@@ -76,24 +79,22 @@ def test_line_tool():
     img = data.camera()
     viewer = ImageViewer(img)
 
-    tool = LineTool(viewer.ax, maxdist=10)
+    tool = LineTool(viewer, maxdist=10)
     tool.end_points = get_end_points(img)
     assert_equal(tool.end_points, np.array([[170, 256], [341, 256]]))
 
     # grab a handle and move it
-    grab = create_mouse_event(viewer.ax, xdata=170, ydata=256)
-    tool.on_mouse_press(grab)
-    move = create_mouse_event(viewer.ax, xdata=180, ydata=260)
-    tool.on_move(move)
-    tool.on_mouse_release(move)
+    do_event(viewer, 'mouse_press', xdata=170, ydata=256)
+    do_event(viewer, 'move', xdata=180, ydata=260)
+    do_event(viewer, 'mouse_release')
+
     assert_equal(tool.geometry, np.array([[180, 260], [341, 256]]))
 
     # create a new line
-    new = create_mouse_event(viewer.ax, xdata=10, ydata=10)
-    tool.on_mouse_press(new)
-    move = create_mouse_event(viewer.ax, xdata=100, ydata=100)
-    tool.on_move(move)
-    tool.on_mouse_release(move)
+    do_event(viewer, 'mouse_press', xdata=10, ydata=10)
+    do_event(viewer, 'move', xdata=100, ydata=100)
+    do_event(viewer, 'mouse_release')
+
     assert_equal(tool.geometry, np.array([[100, 100], [10, 10]]))
 
 
@@ -102,23 +103,20 @@ def test_thick_line_tool():
     img = data.camera()
     viewer = ImageViewer(img)
 
-    tool = ThickLineTool(viewer.ax, maxdist=10)
+    tool = ThickLineTool(viewer, maxdist=10)
     tool.end_points = get_end_points(img)
 
-    scroll_up = create_mouse_event(viewer.ax, button='up')
-    tool.on_scroll(scroll_up)
+    do_event(viewer, 'scroll', button='up')
     assert_equal(tool.linewidth, 2)
 
-    scroll_down = create_mouse_event(viewer.ax, button='down')
-    tool.on_scroll(scroll_down)
+    do_event(viewer, 'scroll', button='down')
+
     assert_equal(tool.linewidth, 1)
 
-    key_up = create_mouse_event(viewer.ax, key='+')
-    tool.on_key_press(key_up)
+    do_event(viewer, 'key_press',  key='+')
     assert_equal(tool.linewidth, 2)
 
-    key_down = create_mouse_event(viewer.ax, key='-')
-    tool.on_key_press(key_down)
+    do_event(viewer, 'key_press', key='-')
     assert_equal(tool.linewidth, 1)
 
 
@@ -127,7 +125,7 @@ def test_rect_tool():
     img = data.camera()
     viewer = ImageViewer(img)
 
-    tool = RectangleTool(viewer.ax, maxdist=10)
+    tool = RectangleTool(viewer, maxdist=10)
     tool.extents = (100, 150, 100, 150)
 
     assert_equal(tool.corners,
@@ -138,19 +136,15 @@ def test_rect_tool():
     assert_equal(tool.geometry, (100, 150, 100, 150))
 
     # grab a corner and move it
-    grab = create_mouse_event(viewer.ax, xdata=100, ydata=100)
-    tool.press(grab)
-    move = create_mouse_event(viewer.ax, xdata=120, ydata=120)
-    tool.onmove(move)
-    tool.release(move)
+    do_event(viewer, 'mouse_press', xdata=100, ydata=100)
+    do_event(viewer, 'move', xdata=120, ydata=120)
+    do_event(viewer, 'mouse_release')
     assert_equal(tool.geometry, [120, 150, 120, 150])
 
     # create a new line
-    new = create_mouse_event(viewer.ax, xdata=10, ydata=10)
-    tool.press(new)
-    move = create_mouse_event(viewer.ax, xdata=100, ydata=100)
-    tool.onmove(move)
-    tool.release(move)
+    do_event(viewer, 'mouse_press', xdata=10, ydata=10)
+    do_event(viewer, 'move', xdata=100, ydata=100)
+    do_event(viewer, 'mouse_release')
     assert_equal(tool.geometry, [10, 100,  10, 100])
 
 
@@ -159,7 +153,7 @@ def test_paint_tool():
     img = data.moon()
     viewer = ImageViewer(img)
 
-    tool = PaintTool(viewer.ax, img.shape)
+    tool = PaintTool(viewer, img.shape)
 
     tool.radius = 10
     assert_equal(tool.radius, 10)
@@ -167,24 +161,21 @@ def test_paint_tool():
     assert_equal(tool.label, 2)
     assert_equal(tool.shape, img.shape)
 
-    start = create_mouse_event(viewer.ax, xdata=100, ydata=100)
-    tool.on_mouse_press(start)
-    move = create_mouse_event(viewer.ax, xdata=110, ydata=110)
-    tool.on_move(move)
-    tool.on_mouse_release(move)
+    do_event(viewer, 'mouse_press', xdata=100, ydata=100)
+    do_event(viewer, 'move', xdata=110, ydata=110)
+    do_event(viewer, 'mouse_release')
+
     assert_equal(tool.overlay[tool.overlay == 2].size, 761)
 
     tool.label = 5
-    start = create_mouse_event(viewer.ax, xdata=20, ydata=20)
-    tool.on_mouse_press(start)
-    move = create_mouse_event(viewer.ax, xdata=40, ydata=40)
-    tool.on_move(move)
-    tool.on_mouse_release(move)
+    do_event(viewer, 'mouse_press', xdata=20, ydata=20)
+    do_event(viewer, 'move', xdata=40, ydata=40)
+    do_event(viewer, 'mouse_release')
+
     assert_equal(tool.overlay[tool.overlay == 5].size, 881)
     assert_equal(tool.overlay[tool.overlay == 2].size, 761)
 
-    enter = create_mouse_event(viewer.ax, key='enter')
-    tool.on_mouse_press(enter)
+    do_event(viewer, 'key_press', key='enter')
 
     tool.overlay = tool.overlay * 0
     assert_equal(tool.overlay.sum(), 0)
@@ -195,15 +186,14 @@ def test_base_tool():
     img = data.moon()
     viewer = ImageViewer(img)
 
-    tool = CanvasToolBase(viewer.ax)
+    tool = CanvasToolBase(viewer)
     tool.set_visible(False)
     tool.set_visible(True)
 
-    enter = create_mouse_event(viewer.ax, key='enter')
-    tool._on_key_press(enter)
+    do_event(viewer, 'key_press', key='enter')
 
     tool.redraw()
     tool.remove()
 
-    tool = CanvasToolBase(viewer.ax, useblit=False)
+    tool = CanvasToolBase(viewer, useblit=False)
     tool.redraw()
diff --git a/skimage/viewer/tests/test_utils.py b/skimage/viewer/tests/test_utils.py
index 3f9ec396..77f30299 100644
--- a/skimage/viewer/tests/test_utils.py
+++ b/skimage/viewer/tests/test_utils.py
@@ -28,7 +28,7 @@ def test_format_filename():
 def test_open_file_dialog():
     utils.init_qtapp()
     timer = QtCore.QTimer()
-    timer.singleShot(10, QtGui.QApplication.quit)
+    timer.singleShot(100, lambda: QtGui.QApplication.quit())
     filename = dialogs.open_file_dialog()
     assert filename is None
 
@@ -37,6 +37,6 @@ def test_open_file_dialog():
 def test_save_file_dialog():
     utils.init_qtapp()
     timer = QtCore.QTimer()
-    timer.singleShot(10, QtGui.QApplication.quit)
+    timer.singleShot(100, lambda: QtGui.QApplication.quit())
     filename = dialogs.save_file_dialog()
     assert filename is None
diff --git a/skimage/viewer/tests/test_widgets.py b/skimage/viewer/tests/test_widgets.py
index ef3cb83c..ee4c91fb 100644
--- a/skimage/viewer/tests/test_widgets.py
+++ b/skimage/viewer/tests/test_widgets.py
@@ -77,11 +77,11 @@ def test_save_buttons():
     viewer.plugins[0] += sv
 
     import tempfile
-    _, filename = tempfile.mkstemp(suffix='.png')
-    os.remove(filename)
+    fid, filename = tempfile.mkstemp(suffix='.png')
+    os.close(fid)
 
     timer = QtCore.QTimer()
-    timer.singleShot(100, lambda: QtGui.QApplication.quit())
+    timer.singleShot(100, QtGui.QApplication.quit)
 
     sv.save_to_stack()
     sv.save_to_file(filename)
@@ -92,6 +92,8 @@ def test_save_buttons():
     img = io.pop()
     assert_almost_equal(img, viewer.image)
 
+    os.remove(filename)
+
 
 @skipif(not viewer_available)
 def test_ok_buttons():
diff --git a/skimage/viewer/viewers/core.py b/skimage/viewer/viewers/core.py
index f1e541a1..00902112 100644
--- a/skimage/viewer/viewers/core.py
+++ b/skimage/viewer/viewers/core.py
@@ -60,6 +60,14 @@ class BlitManager(object):
         self.background = None
         self.artists = []
 
+    def add_artists(self, artists):
+        self.artists.extend(artists)
+        self.redraw()
+
+    def remove_artists(self, artists):
+        for artist in artists:
+            self.artist.remove(artist)
+
     def on_draw_event(self, event=None):
         self.background = self.canvas.copy_from_bbox(self.ax.bbox)
         self.draw_artists()
@@ -95,6 +103,13 @@ class EventManager(object):
         self.tools.append(tool)
         self.active_tool = tool
 
+    def detach(self, tool):
+        self.tools.remove(tool)
+        if self.tools:
+            self.active_tool = self.tools[-1]
+        else:
+            self.active_tool = None
+
     def on_mouse_press(self, event):
         for tool in self.tools:
             if not tool.ignore(event) and tool.hit_test(event):
@@ -375,10 +390,16 @@ class ImageViewer(QtGui.QMainWindow):
 
     def add_tool(self, tool):
         if self.useblit:
-            self._blit_manager.artists.extend(tool.artists)
+            self._blit_manager.add_artists(tool.artists)
         self._tools.append(tool)
         self._event_manager.attach(tool)
 
+    def remove_tool(self, tool):
+        if self.useblit:
+            self._blit_manager.remove_artists(tool.artists)
+        self._tools.remove(tool)
+        self._event_manager.detach(tool)
+
     def _format_coord(self, x, y):
         # callback function to format coordinate display in status bar
         x = int(x + 0.5)