new command: Capabilities

For some changes in fvwm3, it is often preferable to have something
which can run side-by-side with the original, so that compatibility
isn't broken whilst the feature is in development.

To handle this, create a new command 'Capabilities' which works very
similar to the 'BugOpts' command, but isn't for bugs.

doc/fvwm3_manpage_source.adoc

@@ -2925,6 +2925,16 @@ the newcomer.
 
 === Miscellaneous Commands
 
+*Capabilities* [_option_ [_bool_]], ...::
+	This command enables features which are still experimental.
++
+_FvwmStyleV3_ activates enhanced style matching whereby different aspects of
+styles can be matched, for example:
++
+....
+Style (Class=XTerm, Name=mc) Sticky
+....
+
 *BugOpts* [_option_ [_bool_]], ...::
 	This command controls several workarounds for bugs in third party
 	programs. The individual options are separated by commas. The optional

fvwm/builtins.c

@@ -3360,6 +3360,52 @@ void CMD_UnsetEnv(F_CMD_ARGS)
 	return;
 }
 
+void CMD_Capabilities(F_CMD_ARGS)
+{
+	char *opt;
+	int toggle;
+	char *optstring;
+
+	while (action && *action && *action != '\n')
+	{
+		action = GetNextFullOption(action, &optstring);
+		if (!optstring)
+		{
+			/* no more options */
+			return;
+		}
+		toggle = ParseToggleArgument(
+			SkipNTokens(optstring,1), NULL, 2, False);
+		opt = PeekToken(optstring, NULL);
+		free(optstring);
+
+		if (!opt)
+		{
+			return;
+		}
+
+		if (StrEquals(opt, "FvwmStyleV3"))
+		{
+			switch (toggle)
+			{
+			case -1:
+				Scr.cap.fvwm_style_v3 ^= 1;
+				break;
+			case 0:
+			case 1:
+				Scr.cap.fvwm_style_v3 = toggle;
+				break;
+			default:
+				Scr.cap.fvwm_style_v3 = 0;
+				break;
+			}
+		} else {
+			fvwm_debug(__func__,
+				   "Unknown capability '%s'", opt);
+		}
+	}
+}
+
 void CMD_BugOpts(F_CMD_ARGS)
 {
 	char *opt;

fvwm/commands.h

@@ -29,6 +29,7 @@ enum
 	F_BUSY_CURSOR,
 	F_BUTTON_STATE,
 	F_BUTTON_STYLE,
+	F_CAPABILITIES,
 	F_CHANGE_MENUSTYLE,
 	F_CIRCULATE_DOWN,
 	F_CIRCULATE_UP,
@@ -215,6 +216,7 @@ void CMD_BugOpts(F_CMD_ARGS);
 void CMD_BusyCursor(F_CMD_ARGS);
 void CMD_ButtonState(F_CMD_ARGS);
 void CMD_ButtonStyle(F_CMD_ARGS);
+void CMD_Capabilities(F_CMD_ARGS);
 void CMD_ChangeDecor(F_CMD_ARGS);
 void CMD_ChangeMenuStyle(F_CMD_ARGS);
 void CMD_CleanupColorsets(F_CMD_ARGS);

fvwm/functable.c

@@ -113,6 +113,9 @@ const func_t func_table[] =
 		FUNC_DECOR, 0),
 	/* - Define a window button look (will be reworked) */
 
+	CMD_ENT("capabilities", CMD_Capabilities, F_CAPABILITIES, 0, 0),
+	/* - Define capabilities which can be changed at runtime */
+
 	CMD_ENT("changedecor", CMD_ChangeDecor, F_CHANGE_DECOR,
 		FUNC_NEEDS_WINDOW, CRS_SELECT),
 	/* - Attach decor to a window (will be obsolete) */

fvwm/screen.h

@@ -444,6 +444,10 @@ typedef struct ScreenInfo
 		unsigned do_debug_randr : 1;
 	} bo; /* bug workaround control options */
 	struct
+	{
+		unsigned fvwm_style_v3 : 1;
+	} cap; /* Capabilities. */
+	struct
 	{
 		unsigned do_emulate_mwm : 1;
 		unsigned do_emulate_win : 1;