patch 8.1.1714: cannot preview a file in a popup window

Problem:    Cannot preview a file in a popup window.
Solution:   Add the 'previewpopup' option.

Author: brammool

runtime/doc/options.txt

@@ -5627,7 +5627,16 @@ A jump table for the options with a short description can be found at |Q_op|.
 			{not available when compiled without the |+windows| or
 			|+quickfix| features}
 	Default height for a preview window.  Used for |:ptag| and associated
-	commands.  Used for |CTRL-W_}| when no count is given.
+	commands.  Used for |CTRL-W_}| when no count is given.  Not used when
+	'previewpopup' is set.
+
+					*'previewpopup'* *'pvp'*
+'previewpopup' 'pvp'	string (default empty)
+			global
+			{not available when compiled without the |+windows|,
+			|+textprop| or |+quickfix| feature}
+	When not empty a popup window is used for commands that would open a
+	preview window.  See |preview-popup|.
 
 					*'previewwindow'* *'nopreviewwindow'*
 					*'pvw'* *'nopvw'* *E590*

runtime/doc/windows.txt

@@ -864,7 +864,15 @@ height of the preview window when it's opened.  The 'previewwindow' option is
 set in the preview window to be able to recognize it.  The 'winfixheight'
 option is set to have it keep the same height when opening/closing other
 windows.
-
+						*preview-popup*
+Alternatively, a popup window can be used by setting the 'previewpopup'
+option.  When set, it overrules the 'previewwindow' and 'previewheight'
+settings.  The option is a comma separated list of values:
+	height		maximum height of the popup
+	width		maximu width of the popup
+Example: >
+	:set previewpopup=height:10,width:60
+<
 						*:pta* *:ptag*
 :pta[g][!] [tagname]
 		Does ":tag[!] [tagname]" and shows the found tag in a

src/ex_cmds.c

@@ -6270,28 +6270,42 @@ prepare_tagpreview(
      */
     if (!curwin->w_p_pvw)
     {
-	FOR_ALL_WINDOWS(wp)
-	    if (wp->w_p_pvw)
-		break;
+# ifdef FEAT_TEXT_PROP
+	if (*p_pvp != NUL)
+	{
+	    wp = popup_find_preview_window();
+	    if (wp != NULL)
+		popup_set_wantpos(wp);
+	}
+	else
+# endif
+	{
+	    FOR_ALL_WINDOWS(wp)
+		if (wp->w_p_pvw)
+		    break;
+	}
 	if (wp != NULL)
 	    win_enter(wp, undo_sync);
 	else
 	{
 	    /*
 	     * There is no preview window open yet.  Create one.
 	     */
-	    if (win_split(g_do_tagpreview > 0 ? g_do_tagpreview : 0, 0)
-								      == FAIL)
+# ifdef FEAT_TEXT_PROP
+	    if (*p_pvp != NUL)
+		return popup_create_preview_window();
+# endif
+	    if (win_split(g_do_tagpreview > 0 ? g_do_tagpreview : 0, 0) == FAIL)
 		return FALSE;
 	    curwin->w_p_pvw = TRUE;
 	    curwin->w_p_wfh = TRUE;
-	    RESET_BINDING(curwin);	    /* don't take over 'scrollbind'
-					       and 'cursorbind' */
+	    RESET_BINDING(curwin);	    // don't take over 'scrollbind'
+	    // and 'cursorbind'
 # ifdef FEAT_DIFF
-	    curwin->w_p_diff = FALSE;	    /* no 'diff' */
+	    curwin->w_p_diff = FALSE;	    // no 'diff'
 # endif
 # ifdef FEAT_FOLDING
-	    curwin->w_p_fdc = 0;	    /* no 'foldcolumn' */
+	    curwin->w_p_fdc = 0;	    // no 'foldcolumn'
 # endif
 	    return TRUE;
 	}

src/ex_docmd.c

@@ -5893,12 +5893,17 @@ ex_pclose(exarg_T *eap)
 {
     win_T	*win;
 
+    // First close any normal window.
     FOR_ALL_WINDOWS(win)
 	if (win->w_p_pvw)
 	{
 	    ex_win_close(eap->forceit, win, NULL);
-	    break;
+	    return;
 	}
+# ifdef FEAT_TEXT_PROP
+    // Also when 'previewpopup' is empty, it might have been cleared.
+    popup_close_preview();
+# endif
 }
 #endif
 

src/option.c

@@ -2079,6 +2079,15 @@ static struct vimoption options[] =
 			    (char_u *)NULL, PV_NONE,
 #endif
 			    {(char_u *)12L, (char_u *)0L} SCTX_INIT},
+    {"previewpopup", "pvp", P_STRING|P_VI_DEF|P_COMMA|P_NODUP,
+#ifdef FEAT_TEXT_PROP
+			    (char_u *)&p_pvp, PV_NONE,
+			    {(char_u *)"", (char_u *)0L}
+#else
+			    (char_u *)NULL, PV_NONE,
+			    {(char_u *)NULL, (char_u *)0L}
+#endif
+			    SCTX_INIT},
     {"previewwindow", "pvw", P_BOOL|P_VI_DEF|P_RSTAT|P_NOGLOB,
 #if defined(FEAT_QUICKFIX)
 			    (char_u *)VAR_WIN, PV_PVW,
@@ -7831,6 +7840,15 @@ did_set_string_option(
     }
 #endif
 
+#ifdef FEAT_TEXT_PROP
+    // 'previewpopup'
+    else if (varp == &p_pvp)
+    {
+	if (parse_previewpopup(NULL) == FAIL)
+	    errmsg = e_invarg;
+    }
+#endif
+
     /* Options that are a list of flags. */
     else
     {

src/option.h

@@ -499,6 +499,9 @@ EXTERN char_u	*p_fp;		/* 'formatprg' */
 EXTERN int	p_fs;		/* 'fsync' */
 #endif
 EXTERN int	p_gd;		/* 'gdefault' */
+#ifdef FEAT_TEXT_PROP
+EXTERN char_u	*p_pvp;		// 'previewpopup'
+#endif
 #ifdef FEAT_PRINTER
 EXTERN char_u	*p_pdev;	/* 'printdevice' */
 # ifdef FEAT_POSTSCRIPT