Change font size on pinch

src/pyj/read_book/iframe.pyj

@@ -120,6 +120,8 @@ class IframeBoss:
     def handle_gesture(self, gesture):
         if gesture.type is 'show-chrome':
             self.send_message('show_chrome')
+        elif gesture.type is 'pinch':
+            self.send_message('bump_font_size', increase=gesture.direction is 'out')
         else:
             self._handle_gesture(gesture)
 

src/pyj/read_book/prefs/font_size.pyj

@@ -34,6 +34,13 @@ def set_custom_size(ev):
     sz = int(element(CONTAINER, 'input').value)
     change_font_size(sz)
 
+def change_font_size_by(amt):
+    sd = get_session_data()
+    sz = sd.get('base_font_size')
+    nsz = sz + amt
+    nsz = max(8, min(nsz, 40))
+    change_font_size(nsz)
+
 def show_custom_size(ev):
     c = element(CONTAINER)
     for child in c.childNodes:

src/pyj/read_book/view.pyj

@@ -10,6 +10,7 @@ from read_book.globals import messenger, iframe_id
 from read_book.resources import load_resources
 from read_book.overlay import Overlay
 from read_book.prefs.colors import resolve_color_scheme
+from read_book.prefs.font_size import change_font_size_by
 from read_book.touch import set_left_margin_handler, set_right_margin_handler
 from book_list.theme import get_color
 from utils import parse_url_params, username_key
@@ -83,6 +84,7 @@ class View:
             'update_cfi': self.on_update_cfi,
             'content_loaded': self.on_content_loaded,
             'show_chrome': self.show_chrome,
+            'bump_font_size': self.bump_font_size,
         }
         self.currently_showing = {}
 
@@ -108,6 +110,10 @@ class View:
     def forward_gesture(self, gesture):
         self.send_message('gesture_from_margin', gesture=gesture)
 
+    def bump_font_size(self, data):
+        delta = 2 if data.increase else -2
+        change_font_size_by(delta)
+
     def show_chrome(self):
         self.overlay.show()