Re: [AUCTeX-devel] Asking help for preview-latex

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>>>>> David Kastrup <[email protected]> writes:
>>> The test would be something like
>> 
>>> /GS_PDF_ProcSet where { pop [put old code here] } if
>> 
>> Do you mean that the patch listed below should work?

> No.  The brackets in [put old code here] were part of the description,
> not of the code.

Thanks, but the code without those brackets as listed below still gives
the same error for me.
I'm now working on a slightly different approach attached with this
message.  The option `preview-pdf-color-adjust-method' determines the
way how preview-latex works:

(1) New method using DELAYBIND
    Good for gs > 9.27
    Fail with gs <= 9.27
(2) Traditional method
    Good for gs < 9.27
    Fail with gs >= 9.27 if foreground color isn't trivial
(3) Fixed "black on white" appearance
    Fallback for gs 9.27 with non-trivial foreground color

Regards,
Ikumi Keita

----- failed patch --------------------------------------------------
diff --git a/preview.el.in b/preview.el.in
index 30bf45bf..cbfeaf11 100644
--- a/preview.el.in
+++ b/preview.el.in
@@ -750,10 +750,12 @@ to Ghostscript floats."
   (let ((fg (aref colors 1)))
     (if fg
 	(concat
+	 "/GS_PDF_ProcSet where { pop "
 	 "/GS_PDF_ProcSet GS_PDF_ProcSet dup maxlength dict copy dup begin\
 /graphicsbeginpage{//graphicsbeginpage exec "
 	 (mapconcat #'preview-gs-color-value fg " ")
-	 " 3 copy rg RG}bind store end readonly store "))))
+	 " 3 copy rg RG}bind store end readonly store "
+	 "} if "))))
 
 (defun preview-gs-color-string (colors)
   "Return a string setting up colors"

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diff --git a/preview.el.in b/preview.el.in
index 30bf45bf..7d043d1e 100644
--- a/preview.el.in
+++ b/preview.el.in
@@ -602,6 +602,34 @@ tag in the mode line."
       (setq preview-error-condition nil
 	    compilation-in-progress (delq process compilation-in-progress)))))
 
+(defcustom preview-pdf-color-adjust-method 'compatible
+  "Method to adjust colors of images generated from PDF.
+It is not consulted when the latex command produces DVI files.
+
+The valid values are:
+t: preview-latex transfers FG and BG colors of Emacs to the
+generated image.  This option requires that Ghostscript has
+working DELAYBIND feature, thus is invalid with gs 9.27 (and
+possibly < 9.27).
+
+compatible: preview-latex uses another mothod to transfer colors.
+This option is provided for compatibility with gs =< 9.27, but
+fail with gs 9.27 if `preview-reference-face' or the `default'
+face has non-trivial foreground color, including cases of
+customized themes.
+
+nil: no adjustment is done and \"black on white\" image is
+generated regardless of Emacs color.  This is for gs 9.27 users
+with customized foreground color.
+
+The default value will be changed to t after Ghostscript 9.28 is
+released."
+  :group 'preview-appearance
+  :type '(choice :tag "Method"
+		 (const :tag "Adjust to Emacs color (gs > 9.27)" t)
+		 (const :tag "Compatibility for gs =< 9.27" compatible)
+		 (const :tag "No adjustment (B/W, for gs 9.27)" nil)))
+
 (defun preview-gs-sentinel (process string)
   "Sentinel function for rendering process.
 Gets the default PROCESS and STRING arguments
@@ -732,7 +760,19 @@ null eq{pop{pop}bind}if def\
 {pop}{setpagedevice}{ifelse exec}\
 stopped{handleerror quit}if \
 .preview-ST aload pop restore}bind def "
-		  (preview-gs-color-string preview-colors)))
+		  (preview-gs-color-string
+		   preview-colors
+		   ;; Compatibility for gs 9.27 with non-trivial
+		   ;; foreground color.
+		   ;; Suppress color adjustment with PDF backend
+		   ;; when `preview-pdf-color-adjust-method' is nil.
+		   (and (not preview-pdf-color-adjust-method)
+			;; The switch `preview-parsed-pdfoutput' isn't
+			;; set before parsing the latex output, so use
+			;; heuristic here.
+			(with-current-buffer TeX-command-buffer
+			  (and TeX-PDF-mode
+			       (not TeX-PDF-from-DVI)))))))
     (preview-gs-queue-empty)
     (preview-parse-messages (or setup #'preview-gs-dvips-process-setup))))
 
@@ -744,21 +784,43 @@ to Ghostscript floats."
 
 (defun preview-pdf-color-string (colors)
   "Return a string that patches PDF foreground color to work properly."
-  ;; Actually, this is rather brutal.  It will only be invoked in
-  ;; cases, however, where previously it was not expected that
-  ;; anything readable turned up, anyway.
   (let ((fg (aref colors 1)))
     (if fg
-	(concat
-	 "/GS_PDF_ProcSet GS_PDF_ProcSet dup maxlength dict copy dup begin\
+	(cond (;; New code for gs > 9.27.
+	       ;; This assumes DELAYBIND feature, which is known to be
+	       ;; broken in gs 9.27 (and possibly, < 9.27).
+	       ;; <URL:https://lists.gnu.org/archive/html/auctex-devel/2019-07/msg00000.html>
+	       (eq preview-pdf-color-adjust-method t)
+	       (concat
+		"/initgraphics {
+  //initgraphics
+  /RG where {
+    pop "
+		(mapconcat #'preview-gs-color-value fg " ")
+		" 3 copy rg RG
+  } if
+} bind def "))
+	      (;; Traditional code for gs < 9.27.
+	       ;; Works with gs 9.27 as well if the foreground color
+	       ;; is trivial.
+	       (eq preview-pdf-color-adjust-method 'compatible)
+	       (concat
+		"/GS_PDF_ProcSet GS_PDF_ProcSet dup maxlength dict copy dup begin\
 /graphicsbeginpage{//graphicsbeginpage exec "
-	 (mapconcat #'preview-gs-color-value fg " ")
-	 " 3 copy rg RG}bind store end readonly store "))))
-
-(defun preview-gs-color-string (colors)
-  "Return a string setting up colors"
-  (let ((bg (aref colors 0))
-	(fg (aref colors 1))
+		(mapconcat #'preview-gs-color-value fg " ")
+		" 3 copy rg RG}bind store end readonly store "))
+	      (;; Do nothing otherwise.
+	       t
+	       "")))))
+
+(defun preview-gs-color-string (colors &optional suppress-fgbg)
+  "Return a string setting up COLORS.
+If optional argument SUPPRESS-FGBG is non-nil, behave as if FG/BG
+colors were just the default value."
+  (let ((bg (and (not suppress-fgbg)
+		 (aref colors 0)))
+	(fg (and (not suppress-fgbg)
+		 (aref colors 1)))
 	(mask (aref colors 2))
 	(border (aref colors 3)))
     (concat
@@ -910,9 +972,15 @@ The usual PROCESS and COMMAND arguments for
 	(cond ((eq status 'exit)
 	       (delete-process process)
 	       (setq TeX-sentinel-function nil)
+	       (if (eq preview-pdf-color-adjust-method t)
+		   (setq preview-gs-command-line (append
+						  preview-gs-command-line
+						  '("-dDELAYBIND"))))
 	       (setq preview-gs-init-string
 		     (concat preview-gs-init-string
-			     (preview-pdf-color-string preview-colors)))
+			     (preview-pdf-color-string preview-colors)
+			     (if (eq preview-pdf-color-adjust-method t)
+				 ".bindnow")))
 	       (preview-prepare-fast-conversion)
 	       (when gsstart
 		 (if preview-gs-queue

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