Re: "Fix" sag scaling for hidpi

[Alan Third <alan@idiocy.org>]

[-- Attachment #1: Type: text/plain, Size: 911 bytes --]

On Thu, Feb 11, 2021 at 08:18:41PM +0000, Alan Third wrote:
> On Thu, Feb 11, 2021 at 12:34:50PM -0500, Yuan Fu wrote:
> > Actually, :pixel-ratio probably isn’t a good idea. I guess we should
> > just let the user decide what they want when inserting an image, and
> > automatically add :scale in image-mode.
> 
> Yes, I agree. That's really what I was struggling with, getting
> image-mode to load the image at physical pixel size. I don't do much
> lisp coding, so I'm quite slow to get to understand it.
> 
> I'll keep looking, though.

OK, I've got something that works here. It seemed a bit too easy given
how much code there is in image-mode.el to do with scaling, but as I
said, it seems good to me.

(And I've just realised when attaching this that the commit name is
nonsense, but I imagine it will require a NEWS entry that I've not
written, so this won't be the final patch anyway.)
-- 
Alan Third

[-- Attachment #2: 0001-Scale-SVGs-to-match-frame-s-scale-factor.patch --]
[-- Type: text/plain, Size: 6368 bytes --]

From 62cbe4ed2376deeb3a6fc5315b938018cb71ef78 Mon Sep 17 00:00:00 2001
From: Alan Third <alan@idiocy.org>
Date: Wed, 10 Feb 2021 22:12:16 +0000
Subject: [PATCH] Scale SVGs to match frame's scale factor

* lisp/image-mode.el (image-vector-type): New variable.
(image-default-scale): New function.
(image-toggle-display-image): Use image-default-scale.
* src/image.c (FRAME_SCALE_FACTOR): New #define for getting frame
scale factor.
(image_set_transform):
(svg_load_image): Use FRAME_SCALE_FACTOR.
(Fframe_scale_factor): Returns the frame's scale factor.
* src/nsterm.m (ns_frame_scale_factor): Get the scale factor for an NS
frame.
---
 lisp/image-mode.el | 19 +++++++++++++++++--
 src/image.c        | 35 +++++++++++++++++++++++++++++++----
 src/nsterm.h       |  1 +
 src/nsterm.m       | 11 +++++++++++
 4 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/lisp/image-mode.el b/lisp/image-mode.el
index 9ed295e2aa..4b5e282328 100644
--- a/lisp/image-mode.el
+++ b/lisp/image-mode.el
@@ -100,6 +100,11 @@ image-transform-right-angle-fudge
 There's no deep theory behind the default value, it should just
 be somewhat larger than ImageMagick's MagickEpsilon.")
 
+(defvar image-vector-type '(svg)
+  "List of types that won't be rescaled by the frame's scale factor.
+Vector image types should not be scaled down to match the
+screen's physical pixel dimensions.")
+
 (defun image-mode-winprops (&optional window cleanup)
   "Return winprops of WINDOW.
 A winprops object has the shape (WINDOW . ALIST).
@@ -435,6 +440,14 @@ image-mode-fit-frame
 				     (cons width height)
 				     window-configuration)))))))
 
+(defun image-default-scale (type)
+  "Return the default scale amount for image type TYPE.
+Should be 1 / frame-scale-factor for all image types except
+vector image types listed in `image-vector-type' that don't
+require rescaling."
+    (if (member type image-vector-type) 1.0
+      (/ 1 (frame-scale-factor))))
+
 ;;; Image Mode setup
 
 (defvar-local image-type nil
@@ -868,9 +881,11 @@ image-toggle-display-image
     ;; :scale 1: If we do not set this, create-image will apply
     ;; default scaling based on font size.
     (setq image (if (not edges)
-		    (create-image file-or-data type data-p :scale 1
+		    (create-image file-or-data type data-p
+                                  :scale (image-default-scale type)
                                   :format (and filename data-p))
-		  (create-image file-or-data type data-p :scale 1
+		  (create-image file-or-data type data-p
+                                :scale (image-default-scale type)
 				:max-width max-width
 				:max-height max-height
                                 ;; Type hint.
diff --git a/src/image.c b/src/image.c
index a124cf91ba..3f06860794 100644
--- a/src/image.c
+++ b/src/image.c
@@ -135,6 +135,12 @@ #define PIX_MASK_DRAW	1
 # define COLOR_TABLE_SUPPORT 1
 #endif
 
+#ifdef HAVE_NS
+# define FRAME_SCALE_FACTOR(f) ns_frame_scale_factor (f)
+#else
+# define FRAME_SCALE_FACTOR(f) 1;
+#endif
+
 static void image_disable_image (struct frame *, struct image *);
 static void image_edge_detection (struct frame *, struct image *, Lisp_Object,
                                   Lisp_Object);
@@ -2207,8 +2213,8 @@ image_set_transform (struct frame *f, struct image *img)
   /* SVGs are pre-scaled to the correct size.  */
   if (EQ (image_spec_value (img->spec, QCtype, NULL), Qsvg))
     {
-      width = img->width;
-      height = img->height;
+      width = img->width / FRAME_SCALE_FACTOR (f);
+      height = img->height / FRAME_SCALE_FACTOR (f);
     }
   else
 #endif
@@ -10008,6 +10014,9 @@ svg_load_image (struct frame *f, struct image *img, char *contents,
   compute_image_size (viewbox_width, viewbox_height, img->spec,
                       &width, &height);
 
+  width *= FRAME_SCALE_FACTOR (f);
+  height *= FRAME_SCALE_FACTOR (f);
+
   if (! check_image_size (f, width, height))
     {
       image_size_error ();
@@ -10499,9 +10508,8 @@ DEFUN ("lookup-image", Flookup_image, Slookup_image, 1, 1, 0,
 
 #endif /* GLYPH_DEBUG */
 
-
 /***********************************************************************
-			    Initialization
+			    Image Scaling
  ***********************************************************************/
 
 DEFUN ("image-transforms-p", Fimage_transforms_p, Simage_transforms_p, 0, 1, 0,
@@ -10538,6 +10546,24 @@ DEFUN ("image-transforms-p", Fimage_transforms_p, Simage_transforms_p, 0, 1, 0,
   return Qnil;
 }
 
+DEFUN ("frame-scale-factor", Fframe_scale_factor, Sframe_scale_factor, 0, 1, 0,
+       doc: /* Return the image scale factor for FRAME.  */)
+       (Lisp_Object frame)
+{
+  struct frame *f = decode_live_frame (frame);
+  if (FRAME_WINDOW_P (f))
+    {
+      return make_float (FRAME_SCALE_FACTOR (f));
+    }
+
+  return make_float (1);
+}
+
+
+/***********************************************************************
+			    Initialization
+ ***********************************************************************/
+
 DEFUN ("init-image-library", Finit_image_library, Sinit_image_library, 1, 1, 0,
        doc: /* Initialize image library implementing image type TYPE.
 Return t if TYPE is a supported image type.
@@ -10820,6 +10846,7 @@ syms_of_image (void)
 #endif
 
   defsubr (&Simage_transforms_p);
+  defsubr (&Sframe_scale_factor);
 
   DEFVAR_BOOL ("cross-disabled-images", cross_disabled_images,
     doc: /* Non-nil means always draw a cross over disabled images.
diff --git a/src/nsterm.h b/src/nsterm.h
index eae1d0725e..017c2394ef 100644
--- a/src/nsterm.h
+++ b/src/nsterm.h
@@ -1252,6 +1252,7 @@ #define NSAPP_DATA2_RUNFILEDIALOG 11
 extern void ns_init_events (struct input_event *);
 extern void ns_finish_events (void);
 
+extern double ns_frame_scale_factor (struct frame *);
 
 #ifdef NS_IMPL_GNUSTEP
 extern char gnustep_base_version[];  /* version tracking */
diff --git a/src/nsterm.m b/src/nsterm.m
index 3aba76ff5e..c095212d3a 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -857,6 +857,17 @@ Free a pool and temporary objects it refers to (callable from C)
 }
 
 
+double
+ns_frame_scale_factor (struct frame *f)
+{
+#ifdef NS_IMPL_COCOA
+  return [[FRAME_NS_VIEW (f) window] backingScaleFactor];
+#else
+  return 1;
+#endif
+}
+
+
 /* ==========================================================================
 
     Focus (clipping) and screen update
-- 
2.29.2