dpi: first commit to implement measurement parsing directly in NumericProperty + dpi in Window/EventLoop

kivy/base.py

@@ -19,6 +19,7 @@ from kivy.config import Config
 from kivy.logger import Logger
 from kivy.clock import Clock
 from kivy.event import EventDispatcher
+from kivy.utils import platform
 
 # private vars
 EventLoop = None
@@ -85,6 +86,7 @@ class EventLoopBase(EventDispatcher):
 
     def __init__(self):
         super(EventLoopBase, self).__init__()
+        self._dpi = None
         self.quit = False
         self.input_events = []
         self.postproc_modules = []
@@ -103,6 +105,22 @@ class EventLoopBase(EventDispatcher):
         '''
         return self.me_list
 
+    @property
+    def dpi(self):
+        '''Return the DPI of the screen.
+
+        .. versionadded:: 1.4.0
+        '''
+        if self._dpi is None:
+            # first call, resolve the dpi
+            plat = platform()
+            if plat == 'android':
+                self._dpi = self.get_dpi()
+            else:
+                self.ensure_window()
+                self._dpi = self.window.get_dpi()
+        return self._dpi
+
     def ensure_window(self):
         '''Ensure that we have an window
         '''

kivy/core/window/__init__.py

@@ -804,6 +804,12 @@ class WindowBase(EventDispatcher):
         '''
         pass
 
+    def get_dpi(self):
+        '''Return the DPI of the screen. If the implementation doesn't support
+        any DPI lookup, it will just return 75.
+        '''
+        return 75.
+
     def configure_keyboards(self):
         # Configure how to provide keyboards (virtual or not)
 

kivy/properties.pxd

@@ -15,7 +15,8 @@ cdef class Property:
     cpdef dispatch(self, obj)
 
 cdef class NumericProperty(Property):
-    pass
+    cdef float parse_str(self, value)
+    cdef float parse_list(self, value, ext)
 
 cdef class StringProperty(Property):
     pass

kivy/properties.pyx

@@ -153,6 +153,9 @@ __all__ = ('Property',
 
 from weakref import ref
 
+EventLoop = None
+
+
 cdef class Property:
     '''Base class for building more complex properties.
 
@@ -349,6 +352,44 @@ cdef class NumericProperty(Property):
                 obj.__class__.__name__,
                 self.name))
 
+    cdef convert(self, obj, x):
+        tp = type(x)
+        if tp is int or tp is float:
+            return x
+        if tp is tuple or tp is list:
+            if len(x) != 2:
+                raise ValueError('%s.%s must have 2 components' % (
+                    obj.__class__.__name__,
+                    self.name))
+            return self.parse_list(x[0], x[1])
+        elif tp is str:
+            return self.parse_str(x)
+        else:
+            raise ValueError('%s.%s have an invalid format' % (
+                obj.__class__.__name__,
+                self.name))
+
+    cdef float parse_str(self, value):
+        return self.parse_list(value[:-2], value[-2:])
+
+    cdef float parse_list(self, value, ext):
+        # 1in = 2.54cm = 25.4mm = 72pt = 12pc
+        global EventLoop
+        if EventLoop is None:
+            from kivy.base import EventLoop
+        cdef float rv = float(value)
+        cdef float dpi = EventLoop.dpi
+        if ext == 'in':
+            return rv * dpi
+        elif ext == 'px':
+            return rv
+        elif ext == 'pt':
+            return rv * dpi / 72.
+        elif ext == 'cm':
+            return rv * dpi / 2.54
+        elif ext == 'mm':
+            return rv * dpi / 25.4
+
 
 cdef class StringProperty(Property):
     '''Property that represents a string value.