ios: add method for calculating DPI and read UIscreen scale

src/ios/ios.pyx

@@ -14,6 +14,8 @@ cdef extern from "ios_wrapper.h":
     int ios_send_email(char *subject, char *text, char *mimetype, char
             *filename, char *filename_alias, ios_send_email_cb cb, void *userdata)
     void ios_open_url(char *url)
+    float ios_uiscreen_get_scale()
+    int ios_uiscreen_get_dpi()
 
 cdef void _send_email_done(char *status, void *data):
     cdef object callback = <object>data
@@ -159,3 +161,13 @@ def send_email(subject, text, mimetype=None, filename=None, filename_alias=None,
         return 0
 
     return 1
+
+def get_scale():
+    '''Return the UIScreen scale (1 on iPad, 2 on iPad 3)
+    '''
+    return ios_uiscreen_get_scale()
+
+def get_dpi():
+    '''Return the approximate DPI of the screen
+    '''
+    return ios_uiscreen_get_dpi()

src/ios/ios_mail.m

@@ -109,3 +109,22 @@ int ios_send_email(char *subject, char *text, char *mimetype, char *filename,
 	return 1;
 }
 
+
+float ios_uiscreen_get_scale() {
+	float scale = 1.0;
+	if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
+		scale = [[UIScreen mainScreen] scale];
+	};
+	return scale;
+}
+
+int ios_uiscreen_get_dpi() {
+	float scale = ios_uiscreen_get_scale();
+	float dpi = 160 * scale;
+	if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
+		dpi = 132 * scale;
+	} else if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
+		dpi = 163 * scale;
+	}
+	return dpi;
+}

src/ios/ios_wrapper.h

@@ -1,6 +1,8 @@
 #ifndef __IOS_WRAPPER
 #define __IOS_WRAPPER
 
+float ios_uiscreen_get_scale(void);
+int ios_uiscreen_get_dpi(void);
 void ios_open_url(char *url);
 
 typedef void (*ios_send_email_cb)(char *, void *);