hotfix

If you want the pos to be rounded, blit's old job, you can call integer_blit.
Converting to pure-floats is useless, since nothing checks, so subpixel_blit is made an alias of absolute_blit which uses the good type.
The base behavior is to take elements of pos as style and transform properties do : as positions.

renpy/common/00compat.rpy

@@ -268,6 +268,7 @@ init -1100 python:
             config.history_current_dialogue = False
             config.scry_extend = False
             config.fadeout_audio = 0.0
+            config.int_render_blit = True
 
             if version > (6, 99, 5):
                 config.search_prefixes.append("images/")

renpy/config.py

@@ -1373,6 +1373,9 @@ check_translate_none = True
 # Like developer, but available at the end of python early blocks.
 early_developer = False
 
+# Does Render.blit round down its pos parameter ?
+int_render_blit = False
+
 
 del os
 del collections

renpy/display/render.pyx

@@ -786,7 +786,8 @@ cdef class Render:
         If `focus` is true, then focuses are added from the child to the
         parent.
 
-        This will only blit on integer pixel boundaries.
+        The elements of `pos` are interpreted as a ``position`` :
+        int and absolute are numbers of pixels, pure-float is relative to the size of this render.
         """
 
         if source is self:
@@ -798,8 +799,15 @@ cdef class Render:
 
         (xo, yo) = pos
 
-        xo = int(xo)
-        yo = int(yo)
+        if renpy.config.int_render_blit:
+            xo = int(xo)
+            yo = int(yo)
+        else:
+            if type(xo) is float:
+                xo *= self.width
+            if type(yo) is float:
+                yo *= self.height
+            # no need to convert to absolute
 
         if index is None:
             self.children.append((source, xo, yo, focus, main))
@@ -812,73 +820,19 @@ cdef class Render:
 
         return 0
 
-    cpdef int subpixel_blit(Render self, source, tuple pos, object focus=True, object main=True, object index=None):
+    cpdef int absolute_blit(Render self, source, tuple pos, *args, **kwargs):
         """
-        Blits `source` (a Render, Surface, or GL2Model) to this Render, offset by
-        xo and yo.
-
-        If `focus` is true, then focuses are added from the child to the
-        parent.
-
-        This blits at fractional pixel boundaries.
+        An proxy for blit that blits at fractional pixel boundaries.
         """
 
-        if source is self:
-            raise Exception("Blitting to self.")
-
-        if models:
-            if isinstance(source, pygame.Surface):
-                source = renpy.display.draw.load_texture(source)
-
-        (xo, yo) = pos
-
-        xo = float(xo)
-        yo = float(yo)
-
-        if index is None:
-            self.children.append((source, xo, yo, focus, main))
-        else:
-            self.children.insert(index, (source, xo, yo, focus, main))
-
-        if isinstance(source, Render):
-            self.depends_on_list.append(source)
-            source.parents.add(self)
-
-        return 0
-
-    cpdef int absolute_blit(Render self, source, tuple pos, object focus=True, object main=True, object index=None):
-        """
-        Blits `source` (a Render or Surface) to this Render, offset by
-        xo and yo.
-
-        If `focus` is true, then focuses are added from the child to the
-        parent.
-
-        This blits at fractional pixel boundaries.
-        """
-
-        if source is self:
-            raise Exception("Blitting to self.")
-
-        if models:
-            if isinstance(source, pygame.Surface):
-                source = renpy.display.draw.load_texture(source)
-
         (xo, yo) = pos
 
         xo = renpy.display.core.absolute(xo)
         yo = renpy.display.core.absolute(yo)
 
-        if index is None:
-            self.children.append((source, xo, yo, focus, main))
-        else:
-            self.children.insert(index, (source, xo, yo, focus, main))
+        return self.blit(source, (xo, yo), *args, **kwargs)
 
-        if isinstance(source, Render):
-            self.depends_on_list.append(source)
-            source.parents.add(self)
-
-        return 0
+    subpixel_blit = absolute_blit # legacy
 
 
     def get_size(self):

sphinx/source/cdd.rst

@@ -257,9 +257,11 @@ the implicit `self` parameter.
             The render object to draw.
 
         `pos`
-            The location to draw into. This is an (x, y) tuple
-            with the coordinates being pixels relative to the
-            upper-left corner of the target render.
+            The location to draw into. This is an (x, y) tuple of
+            :ref:`positions <style-property-values>` : integers and
+            ``absolute``\ s are a number of pixels relative to the upper-left
+            corner of the target render, and floats are interpreted as a
+            fraction of the width or height of the target render.
 
         `main`
             A keyword-only parameter. If true, `source` will be displayed

sphinx/source/changelog.rst

@@ -465,6 +465,10 @@ safer to use.
 When Ren'Py used to normalize every whitespaces into standard spaces, it now
 supports non-standard spaces such as \\u3000, the full-width ideographic space.
 
+:meth:`renpy.Render.blit` now takes :ref:`positions <style-property-values>`
+for its `pos` parameter, allowing one to pass values relative to the size of
+the Render.
+
 
 .. _renpy-7.5.3:
 .. _renpy-8.0.3:

sphinx/source/incompatible.rst

@@ -139,6 +139,11 @@ Alternatively, you can determine new default volumes for :var:`config.default_mu
 :var:`config.default_sfx_volume`, and :var:`config.default_voice_volume` variables. If any
 of these is 0.0 or 1.0, it can be left unchanged.
 
+**Render.blit** : this method now takes :ref:`positions <style-property-values>` as `pos` values,
+and will not round them down to integers. To revert to the old behavior::
+
+    define config.int_render_blit = True
+
 
 .. _incompatible-8.0.2:
 .. _incompatible-7.5.2:

sphinx/source/style_properties.rst

@@ -94,6 +94,8 @@ text.::
          selected_color "#ff0"
 
 
+.. _style-property-values:
+
 Style Property Values
 =====================