sagemathgh-38339: Add sage.misc.latex.pdf to save the image of object…

…s to pdf

    
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Hence
```sage
sage: from sage.misc.latex import pdf
sage: pdf(pi, 'test.pdf')
```
works. This is a companion to the existing `sage.misc.latex.png`, which
saves png image of objects. Of course, pdf image is scalable and hence
more suitable for inclusion into latex documents.

Also we fix it that `view()` sporadically fails on mac because the
temporary file is removed before the viewer opens the file. For example,
```sage
sage: view(pi)  # show pi
```
Thus after this PR, the temporary file is removed when the viewer
(`Preview` app on mac, not the window showing the image) closes. This
behavior is consistent with that on linux.

### 📝 Checklist

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- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

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URL: sagemath#38339
Reported by: Kwankyu Lee
Reviewer(s): Dima Pasechnik

src/sage/misc/latex.py

@@ -1683,7 +1683,9 @@ def _latex_file_(objects, title='SAGE', debug=False,
     s = LATEX_HEADER + '\n' + MACROS + s + '\n\\end{document}'
 
     if debug:
+        print('----')
         print(s)
+        print('----')
 
     return s
 
@@ -1827,7 +1829,6 @@ def view(objects, title='Sage', debug=False, sep='', tiny=False,
         ...
         ValueError: Unsupported LaTeX engine.
     """
-
     if tightpage:
         if margin is None:
             margin_str = ""
@@ -1870,16 +1871,16 @@ def view(objects, title='Sage', debug=False, sep='', tiny=False,
         tmp.cleanup()
         return
     output_file = os.path.join(tmp.name, "sage." + suffix)
-    # this should get changed if we switch the stuff in misc.viewer to
-    # producing lists
+
     if debug:
-        print('viewer: "{}"'.format(viewer))
+        print(f'temporary file: "{output_file}"')
+        print(f'viewer: "{viewer}"')
 
     # Return immediately but only clean up the temporary file after
     # the viewer has closed. This function is synchronous and waits
     # for the process to complete...
     def run_viewer():
-        run([viewer, output_file], capture_output=True)
+        run([*viewer.split(), output_file], capture_output=True)
         tmp.cleanup()
 
     # ...but we execute it asynchronously so that view() completes
@@ -1890,7 +1891,78 @@ def run_viewer():
     t.daemon = True
     t.start()
 
-    return
+
+def pdf(x, filename, tiny=False, tightpage=True, margin=None, engine=None, debug=False):
+    """
+    Create an image from the latex representation of ``x`` and save it as a pdf
+    file with the given filename.
+
+    INPUT:
+
+    - ``x`` -- a Sage object
+
+    - ``filename`` -- the filename with which to save the image
+
+    - ``tiny`` -- boolean (default: ``False``); if ``True``, use a tiny font
+
+    - ``tightpage`` -- boolean (default: ``True``); use the LaTeX package
+      ``preview`` with the 'tightpage' option
+
+    - ``margin`` -- float (default: no margin); width of border, only effective
+      with 'tight page'
+
+    - ``engine`` -- (default: ``None``) ``'latex'``, ``'pdflatex'``,
+      ``'xelatex'`` or ``'lualatex'``; if ``None``, the value defined in the
+      LaTeX global preferences ``latex.engine()`` is used
+
+    - ``debug`` -- boolean (default: ``False``); if ``True``, print verbose output
+
+    EXAMPLES::
+
+        sage: # optional - latex
+        sage: from sage.misc.latex import pdf
+        sage: import tempfile
+        sage: with tempfile.NamedTemporaryFile(suffix=".pdf") as f:  # random
+        ....:     pdf(ZZ[x], f.name)
+    """
+    from sage.plot.graphics import Graphics
+    if isinstance(x, Graphics):
+        x.save(filename)
+        return
+
+    if tightpage:
+        if margin is None:
+            margin_str = ""
+        else:
+            margin_str = '\n\\setlength\\PreviewBorder{%fmm}' % margin
+        latex_options = {'extra_preamble':
+                         '\\usepackage[tightpage,active]{preview}\n' +
+                         '\\PreviewEnvironment{page}%s' % margin_str,
+                         'math_left': '\\begin{page}$',
+                         'math_right': '$\\end{page}'}
+    else:
+        latex_options = {}
+
+    # create a string of latex code to write in a file
+    s = _latex_file_([x], title='', tiny=tiny, debug=debug, **latex_options)
+    if engine is None:
+        engine = _Latex_prefs._option["engine"]
+    # path name for permanent pdf output
+    abs_path_to_pdf = os.path.abspath(filename)
+    # temporary directory to store stuff
+    with TemporaryDirectory() as tmp:
+        tex_file = os.path.join(tmp, "sage.tex")
+        pdf_file = os.path.join(tmp, "sage.pdf")
+        # write latex string to file
+        with open(tex_file, 'w') as file:
+            file.write(s)
+        # run latex on the file
+        e = _run_latex_(tex_file, debug=debug, engine=engine)
+        if e == 'pdf':
+            # if no errors, copy pdf_file to the appropriate place
+            shutil.copy(pdf_file, abs_path_to_pdf)
+        else:
+            print("Latex error or no pdf was generated.")
 
 
 def png(x, filename, density=150, debug=False,

src/sage/misc/viewer.py

@@ -69,7 +69,7 @@ def default_viewer(viewer=None):
     elif os.uname()[0] == 'Darwin':
         # Simple on OS X, since there is an open command that opens
         # anything, using the user's preferences.
-        BROWSER = 'open'
+        BROWSER = 'open -W'
         DVI_VIEWER = BROWSER
         PDF_VIEWER = BROWSER
         PNG_VIEWER = BROWSER