Edit book: Apply the same workaround for use of 100% instead of 100vh in full screen SVG images as is used in the viewer. This should give the same rendering as in the viewer, leading to less confusion.

I of course dont like implementing this kind of hackery, but...

src/pyj/editor.pyj

@@ -4,6 +4,7 @@ from __python__ import bound_methods, hash_literals
 
 from elementmaker import E
 
+from fs_images import fix_fullscreen_svg_images
 from live_css import get_matched_css, get_sourceline_address
 from qt import from_python, to_python
 
@@ -172,3 +173,5 @@ document.documentElement.appendChild(E.style(
     type='text/css',
     '[data-in-split-mode="1"] [data-is-block="1"]:hover { cursor: pointer !important; border-top: solid 5px green !important }'
 ))
+
+fix_fullscreen_svg_images()

src/pyj/fs_images.pyj

@@ -0,0 +1,33 @@
+# vim:fileencoding=utf-8
+# License: GPL v3 Copyright: 2019, Kovid Goyal <kovid at kovidgoyal.net>
+from __python__ import bound_methods, hash_literals
+
+
+def fix_fullscreen_svg_images():
+    # Full screen images using SVG no longer render correctly
+    # webengine. This is because it sets the width to the
+    # viewport width and simply adjusts the height accordingly
+    # So we replace 100% with 100vw and 100vh to get the desired
+    # rendering
+    child_names = v'[]'
+    for node in document.body.childNodes:
+        if node.tagName:
+            name = node.tagName.toLowerCase()
+            if name is not 'style' and name is not 'script':
+                child_names.push(name)
+            if child_names.length > 1:
+                break
+    if child_names.length is 1 and child_names[0] is 'div':
+        names = []
+        svg = None
+        for node in document.body.querySelectorAll('*'):
+            if node.tagName:
+                name = node.tagName.toLowerCase()
+                if name is not 'style' and name is not 'script':
+                    names.push(name)
+                    if name is 'svg':
+                        svg = node
+        if names == ['div', 'svg', 'image'] or names == ['svg', 'image']:
+            if svg.getAttribute('width') is '100%' and svg.getAttribute('height') is '100%':
+                svg.setAttribute('width', '100vw')
+                svg.setAttribute('height', '100vh')

src/pyj/read_book/iframe.pyj

@@ -5,6 +5,7 @@ from __python__ import bound_methods, hash_literals
 import traceback
 from gettext import gettext as _
 
+from fs_images import fix_fullscreen_svg_images
 from iframe_comm import IframeClient
 from read_book.cfi import scroll_to as scroll_to_cfi
 from read_book.extract import get_elements
@@ -228,35 +229,6 @@ class IframeBoss:
             opts.color_scheme = data.color_scheme
             apply_colors()
 
-    def fix_fullscreen_svg_images(self):
-        # Full screen images using SVG no longer render correctly
-        # webengine. This is because it sets the width to the
-        # viewport width and simply adjusts the height accordingly
-        # So we replace 100% with 100vw and 100vh to get the desired
-        # rendering
-        child_names = v'[]'
-        for node in document.body.childNodes:
-            if node.tagName:
-                name = node.tagName.toLowerCase()
-                if name is not 'style' and name is not 'script':
-                    child_names.push(name)
-                if child_names.length > 1:
-                    break
-        if child_names.length is 1 and child_names[0] is 'div':
-            names = []
-            svg = None
-            for node in document.body.querySelectorAll('*'):
-                if node.tagName:
-                    name = node.tagName.toLowerCase()
-                    if name is not 'style' and name is not 'script':
-                        names.push(name)
-                        if name is 'svg':
-                            svg = node
-            if names == ['div', 'svg', 'image'] or names == ['svg', 'image']:
-                if svg.getAttribute('width') is '100%' and svg.getAttribute('height') is '100%':
-                    svg.setAttribute('width', '100vw')
-                    svg.setAttribute('height', '100vh')
-
     def content_loaded(self):
         document.documentElement.style.overflow = 'hidden'
         if self.is_titlepage and not opts.cover_preserve_aspect_ratio:
@@ -264,7 +236,7 @@ class IframeBoss:
         document.body.classList.add(f'calibre-viewer-{layout_style()}')
         self.last_window_width, self.last_window_height = scroll_viewport.width(), scroll_viewport.height()
         apply_settings()
-        self.fix_fullscreen_svg_images()
+        fix_fullscreen_svg_images()
         self.do_layout(self.is_titlepage)
         if self.mathjax:
             return apply_mathjax(self.mathjax, self.book.manifest.link_uid, self.content_loaded_stage2)