docs: Fix a few typos

There are small typos in:
- doc/source/how_to_use.rst
- doc/source/region_of_interest.rst
- examples/ViewBox.py
- pyqtgraph/flowchart/Node.py
- pyqtgraph/graphicsItems/AxisItem.py
- pyqtgraph/graphicsItems/PColorMeshItem.py
- pyqtgraph/graphicsItems/PlotDataItem.py
- pyqtgraph/graphicsItems/TargetItem.py
- pyqtgraph/graphicsItems/ViewBox/ViewBox.py
- pyqtgraph/widgets/RawImageWidget.py

Fixes:
- Should read `mapped` rather than `maped`.
- Should read `vector` rather than `vetctor`.
- Should read `value` rather than `vaule`.
- Should read `preferable` rather than `preferrable`.
- Should read `output` rather than `ouptut`.
- Should read `information` rather than `inforation`.
- Should read `information` rather than `infomation`.
- Should read `exempt` rather than `excempt`.
- Should read `emphasizing` rather than `emphacizing`.
- Should read `construction` rather than `constrution`.

doc/source/how_to_use.rst

@@ -101,7 +101,7 @@ Embedding PyQtGraph as a sub-package of a larger project
 
 When writing applications or python packages that make use of pyqtgraph, it is most common to install pyqtgraph system-wide (or within a virtualenv) and simply call `import pyqtgraph` from within your application. The main benefit to this is that pyqtgraph is configured independently of your application and thus you (or your users) are free to install newer versions of pyqtgraph without changing anything in your application. This is standard practice when developing with python.
 
-Occasionally, a specific program needs to be kept in working order for an extended amount of time after development has been completed. This is often the case for single-purpose scientific applications. If we want to ensure that the software will still work ten years later, then it is preferrable to tie it to a very specific version of pyqtgraph and *avoid* importing the system-installed version, which may be much newer and potentially incompatible. This is especially true when the application requires site-specific modifications to the pyqtgraph package. 
+Occasionally, a specific program needs to be kept in working order for an extended amount of time after development has been completed. This is often the case for single-purpose scientific applications. If we want to ensure that the software will still work ten years later, then it is preferable to tie it to a very specific version of pyqtgraph and *avoid* importing the system-installed version, which may be much newer and potentially incompatible. This is especially true when the application requires site-specific modifications to the pyqtgraph package. 
 
 To support such a separate local installation, all internal import statements in pyqtgraph are relative. That means that pyqtgraph never refers to itself internally as 'pyqtgraph'. This allows the package to be renamed or used as a sub-package without any naming conflicts with other versions of pyqtgraph on the system.
 

doc/source/region_of_interest.rst

@@ -16,7 +16,7 @@ To select a 2D region from an image, pyqtgraph uses the :class:`ROI <pyqtgraph.R
 
 To automatically extract a region of image data using an ROI and an ImageItem, use :func:`ROI.getArrayRegion <pyqtgraph.ROI.getArrayRegion>`. ROI classes use the :func:`affineSlice <pyqtgraph.affineSlice>` function to perform this extraction.
 
-ROI can also be used as a control for moving/rotating/scaling items in a scene similar to most vetctor graphics editing applications.
+ROI can also be used as a control for moving/rotating/scaling items in a scene similar to most vector graphics editing applications.
 
 See the ROITypes example for more information.
 

examples/ViewBox.py

@@ -4,7 +4,7 @@
 ViewBox is the general-purpose graphical container that allows the user to 
 zoom / pan to inspect any area of a 2D coordinate system. 
 
-This unimaginative example demonstrates the constrution of a ViewBox-based
+This unimaginative example demonstrates the construction of a ViewBox-based
 plot area with axes, very similar to the way PlotItem is built.
 """
 

pyqtgraph/flowchart/Node.py

@@ -17,7 +17,7 @@ class Node(QtCore.QObject):
     Node represents the basic processing unit of a flowchart. 
     A Node subclass implements at least:
     
-    1) A list of input / ouptut terminals and their properties
+    1) A list of input / output terminals and their properties
     2) a process() function which takes the names of input terminals as keyword arguments and returns a dict with the names of output terminals as keys.
 
     A flowchart thus consists of multiple instances of Node subclasses, each of which is connected

pyqtgraph/graphicsItems/AxisItem.py

@@ -157,7 +157,7 @@ class AxisItem(GraphicsWidget):
         tickAlpha           (float or int or None) If None, pyqtgraph will draw the
                             ticks with the alpha it deems appropriate.  Otherwise, 
                             the alpha will be fixed at the value passed.  With int, 
-                            accepted values are [0..255].  With vaule of type
+                            accepted values are [0..255].  With value of type
                             float, accepted values are from [0..1].
         =================== =======================================================
 

pyqtgraph/graphicsItems/PColorMeshItem.py

@@ -35,7 +35,7 @@ class PColorMeshItem(GraphicsObject):
         x, y : np.ndarray, optional, default None
             2D array containing the coordinates of the polygons
         z : np.ndarray
-            2D array containing the value which will be maped into the polygons
+            2D array containing the value which will be mapped into the polygons
             colors.
             If x and y is None, the polygons will be displaced on a grid
             otherwise x and y will be used as polygons vertices coordinates as::
@@ -140,7 +140,7 @@ class PColorMeshItem(GraphicsObject):
         x, y : np.ndarray, optional, default None
             2D array containing the coordinates of the polygons
         z : np.ndarray
-            2D array containing the value which will be maped into the polygons
+            2D array containing the value which will be mapped into the polygons
             colors.
             If x and y is None, the polygons will be displaced on a grid
             otherwise x and y will be used as polygons vertices coordinates as::

pyqtgraph/graphicsItems/PlotDataItem.py

@@ -319,7 +319,7 @@ class PlotDataItem(GraphicsObject):
     def setShadowPen(self, *args, **kargs):
         """
         | Sets the shadow pen used to draw lines between points (this is for enhancing contrast or
-          emphacizing data).
+          emphasizing data).
         | This line is drawn behind the primary pen (see :func:`setPen() <pyqtgraph.PlotDataItem.setPen>`)
           and should generally be assigned greater width than the primary pen.
         | *pen* can be a QPen or any argument accepted by :func:`pyqtgraph.mkPen() <pyqtgraph.mkPen>`

pyqtgraph/graphicsItems/TargetItem.py

@@ -379,7 +379,7 @@ class TargetLabel(TextItem):
         the target in pixels, by default it is (20, 0).
     anchor : tuple, list, QPointF or QPoint
         Position to rotate the TargetLabel about, and position to set the
-        offset value to see :class:`~pyqtgraph.TextItem` for more inforation.
+        offset value to see :class:`~pyqtgraph.TextItem` for more information.
     kwargs : dict of arguments that are passed on to
         :class:`~pyqtgraph.TextItem` constructor, excluding text parameter
     """

pyqtgraph/graphicsItems/ViewBox/ViewBox.py

@@ -50,7 +50,7 @@ class ChildGroup(ItemGroup):
         #         mechanism, but this causes a different PySide crash.
         self.itemsChangedListeners = WeakList()
 
-        # excempt from telling view when transform changes
+        # exempt from telling view when transform changes
         self._GraphicsObject__inform_view_on_change = False
 
     def itemChange(self, change, value):

pyqtgraph/widgets/RawImageWidget.py

@@ -2,7 +2,7 @@
 """
 RawImageWidget.py
 Copyright 2010-2016 Luke Campagnola
-Distributed under MIT/X11 license. See license.txt for more infomation.
+Distributed under MIT/X11 license. See license.txt for more information.
 """
 
 from .. import getConfigOption, functions as fn, getCupy