patch 9.0.1991: no cmdline completion for setting the font

Problem:  no cmdline completion for setting the font
Solution: enable it on Win32 and GTK builds

Add guifont cmdline completion (for Windows and GTK)

For Windows, auto-complete will only suggest monospace fonts as that's
the only types allowed. Will also suggest font options after the colon,
including suggesting the current font size for convenience, and misc
charset and quality options like `cANSI` and `qCLEARTYPE`.

For GTK, auto-complete will suggest only monospace fonts for `guifont`
but will include all fonts for `guifontwide`. The completion code
doesn't currently suggest the current font size, as the GTK guifont
format does not have a clear delimiter (':' for other platforms).

closes: #13264

Signed-off-by: Christian Brabandt <[email protected]>
Co-authored-by: Yee Cheng Chin <[email protected]>

Author: ychin

src/gui_gtk_x11.c

@@ -5315,6 +5315,62 @@ gui_mch_free_font(GuiFont font)
 	pango_font_description_free(font);
 }
 
+/*
+ * Cmdline expansion for setting 'guifont' / 'guifontwide'. Will enumerate
+ * through all fonts for completion. When setting 'guifont' it will only show
+ * monospace fonts as it's unlikely other fonts would be useful.
+ */
+    void
+gui_mch_expand_font(optexpand_T *args, void *param, int (*add_match)(char_u *val))
+{
+    PangoFontFamily	**font_families = NULL;
+    int			n_families = 0;
+    int			wide = *(int *)param;
+
+    if (args->oe_include_orig_val && *args->oe_opt_value == NUL && !wide)
+    {
+	// If guifont is empty, and we want to fill in the orig value, suggest
+	// the default so the user can modify it.
+	if (add_match((char_u *)DEFAULT_FONT) != OK)
+	    return;
+    }
+
+    pango_context_list_families(
+	    gui.text_context,
+	    &font_families,
+	    &n_families);
+
+    for (int i = 0; i < n_families; i++)
+    {
+	if (!wide && !pango_font_family_is_monospace(font_families[i]))
+	    continue;
+
+	const char* fam_name = pango_font_family_get_name(font_families[i]);
+	if (input_conv.vc_type != CONV_NONE)
+	{
+	    char_u *buf = string_convert(&input_conv, (char_u*)fam_name, NULL);
+	    if (buf != NULL)
+	    {
+		if (add_match(buf) != OK)
+		{
+		    vim_free(buf);
+		    break;
+		}
+		vim_free(buf);
+	    }
+	    else
+		break;
+	}
+	else
+	{
+	    if (add_match((char_u *)fam_name) != OK)
+		break;
+	}
+    }
+
+    g_free(font_families);
+}
+
 /*
  * Return the Pixel value (color) for the given color name.
  *

src/optiondefs.h

@@ -1164,9 +1164,13 @@ static struct vimoption options[] =
 			    {(char_u *)NULL, (char_u *)0L}
 #endif
 			    SCTX_INIT},
-    {"guifont",	    "gfn",  P_STRING|P_VI_DEF|P_RCLR|P_ONECOMMA|P_NODUP,
+    {"guifont",	    "gfn",  P_STRING|P_VI_DEF|P_RCLR|P_ONECOMMA|P_NODUP
+#if !defined(FEAT_GUI_GTK)
+				|P_COLON
+#endif
+				,
 #ifdef FEAT_GUI
-			    (char_u *)&p_guifont, PV_NONE, did_set_guifont, NULL,
+			    (char_u *)&p_guifont, PV_NONE, did_set_guifont, expand_set_guifont,
 			    {(char_u *)"", (char_u *)0L}
 #else
 			    (char_u *)NULL, PV_NONE, NULL, NULL,
@@ -1183,10 +1187,14 @@ static struct vimoption options[] =
 			    {(char_u *)NULL, (char_u *)0L}
 #endif
 			    SCTX_INIT},
-    {"guifontwide", "gfw",  P_STRING|P_VI_DEF|P_RCLR|P_ONECOMMA|P_NODUP,
+    {"guifontwide", "gfw",  P_STRING|P_VI_DEF|P_RCLR|P_ONECOMMA|P_NODUP
+#if !defined(FEAT_GUI_GTK)
+				|P_COLON
+#endif
+				,
 #if defined(FEAT_GUI)
 			    (char_u *)&p_guifontwide, PV_NONE,
-			    did_set_guifontwide, NULL,
+			    did_set_guifontwide, expand_set_guifont,
 			    {(char_u *)"", (char_u *)0L}
 #else
 			    (char_u *)NULL, PV_NONE, NULL, NULL,

src/optionstr.c

@@ -731,7 +731,8 @@ did_set_option_listflag(char_u *val, char_u *flags, char *errbuf)
 }
 
 /*
- * Expand an option that accepts a list of string values.
+ * Expand an option that accepts a list of fixed string values with known
+ * number of items.
  */
     static int
 expand_set_opt_string(
@@ -801,10 +802,11 @@ static char_u *set_opt_callback_orig_option = NULL;
 static char_u *((*set_opt_callback_func)(expand_T *, int));
 
 /*
- * Callback used by expand_set_opt_generic to also include the original value.
+ * Callback used by expand_set_opt_generic to also include the original value
+ * as the first item.
  */
     static char_u *
-expand_set_opt_callback(expand_T *xp, int idx)
+expand_set_opt_generic_cb(expand_T *xp, int idx)
 {
     if (idx == 0)
     {
@@ -817,7 +819,8 @@ expand_set_opt_callback(expand_T *xp, int idx)
 }
 
 /*
- * Expand an option with a callback that iterates through a list of possible names.
+ * Expand an option with a callback that iterates through a list of possible
+ * names using an index.
  */
     static int
 expand_set_opt_generic(
@@ -838,14 +841,103 @@ expand_set_opt_generic(
 	    args->oe_regmatch,
 	    matches,
 	    numMatches,
-	    expand_set_opt_callback,
+	    expand_set_opt_generic_cb,
 	    FALSE);
 
     set_opt_callback_orig_option = NULL;
     set_opt_callback_func = NULL;
     return ret;
 }
 
+static garray_T *expand_cb_ga;
+static optexpand_T *expand_cb_args;
+
+/*
+ * Callback provided to a function in expand_set_opt_callback. Will perform
+ * regex matching against the value and add to the list.
+ *
+ * Returns OK usually. Returns FAIL if it failed to allocate memory, and the
+ * caller should terminate the enumeration.
+ */
+    static int
+expand_set_opt_callback_cb(char_u *val)
+{
+    regmatch_T	*regmatch = expand_cb_args->oe_regmatch;
+    expand_T	*xp = expand_cb_args->oe_xp;
+    garray_T	*ga = expand_cb_ga;
+    char_u	*str;
+
+    if (val == NULL || *val == NUL)
+	return OK;
+
+    if (xp->xp_pattern[0] != NUL &&
+	    !vim_regexec(regmatch, val, (colnr_T)0))
+	return OK;
+
+    str = vim_strsave_escaped(val, (char_u *)" \t\\");
+
+    if (str == NULL)
+	return FAIL;
+
+    if (ga_grow(ga, 1) == FAIL)
+    {
+	vim_free(str);
+	return FAIL;
+    }
+
+    ((char_u **)ga->ga_data)[ga->ga_len] = str;
+    ++ga->ga_len;
+    return OK;
+}
+
+/*
+ * Expand an option with a provided function that takes a callback. The
+ * function will enumerate through all options and call the callback to add it
+ * to the list.
+ *
+ * "func" is the enumerator function that will generate the list of options.
+ * "func_params" is a single parameter that will be passed to func.
+ */
+    static int
+expand_set_opt_callback(
+	optexpand_T *args,
+	void (*func)(optexpand_T *, void* params, int (*cb)(char_u *val)),
+	void *func_params,
+	int *numMatches,
+	char_u ***matches)
+{
+    garray_T	ga;
+    int		include_orig_val = args->oe_include_orig_val;
+    char_u	*option_val = args->oe_opt_value;
+
+    ga_init2(&ga, sizeof(char *), 30);
+
+    if (include_orig_val && *option_val != NUL)
+    {
+	char_u *p = vim_strsave(option_val);
+	if (p == NULL)
+	    return FAIL;
+	if (ga_grow(&ga, 1) == FAIL)
+	{
+	    vim_free(p);
+	    return FAIL;
+	}
+	((char_u **)ga.ga_data)[ga.ga_len] = p;
+	++ga.ga_len;
+    }
+
+    expand_cb_ga = &ga;
+    expand_cb_args = args;
+
+    func(args, func_params, expand_set_opt_callback_cb);
+
+    expand_cb_ga = NULL;
+    expand_cb_args = NULL;
+
+    *matches = ga.ga_data;
+    *numMatches = ga.ga_len;
+    return OK;
+}
 
 /*
  * Expand an option which is a list of flags.
@@ -2237,6 +2329,27 @@ did_set_guifont(optset_T *args UNUSED)
     return errmsg;
 }
 
+/*
+ * Expand the 'guifont' option. Only when GUI is being used. Each platform has
+ * specific behaviors.
+ */
+    int
+expand_set_guifont(optexpand_T *args, int *numMatches, char_u ***matches)
+{
+    if (!gui.in_use)
+	return FAIL;
+
+# if defined(FEAT_GUI_MSWIN) || defined(FEAT_GUI_GTK)
+    char_u **varp = (char_u **)args->oe_varp;
+    int wide = (varp == &p_guifontwide);
+
+    return expand_set_opt_callback(
+	    args, gui_mch_expand_font, &wide, numMatches, matches);
+# else
+    return FAIL;
+# endif
+}
+
 # if defined(FEAT_XFONTSET) || defined(PROTO)
 /*
  * The 'guifontset' option is changed.