mem_fb: introduce --video=mem; a dummy in-memory video backend

The immediate impetus for adding this is to enable running
rototiller even on headless machines just for the sake of getting
some FPS measurements.

It'd be nice to get a sense for what FPS rototiller would
experience on larger modern machines like big EPYC or
Threadripper systems.  But it seems most of those I can get
access to via others running them on work hardware or the like
can at most just run it over ssh without any display or risk of
disrupting the physical console.

But this is probably also useful for testing/debugging purposes,
especially since it doesn't bother to synchronize flips on
anything not even a timer.  So a bunch of display complexity is
removed running with video=mem as well as letting the framerate
run unbounded.

Having said that, it might be nice to add an fps=N setting where
mem_fb uses a plain timer for scheduling the flips.

Currently the only setting is size=WxH identical to the sdl_fb
size= setting, defaulting to 640x480.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/main.c b/src/main.c
index 68ff1da..c22eb3c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -34,6 +34,7 @@
 #endif
 
 extern til_fb_ops_t	drm_fb_ops;
+extern til_fb_ops_t	mem_fb_ops;
 extern til_fb_ops_t	sdl_fb_ops;
 static til_fb_ops_t	*fb_ops;
 
@@ -74,6 +75,7 @@ static int setup_video(til_settings_t *settings, til_setting_t **res_setting, co
 #ifdef HAVE_DRM
 						"drm",
 #endif
+						"mem",
 #ifdef HAVE_SDL
 						"sdl",
 #endif
@@ -106,6 +108,11 @@ static int setup_video(til_settings_t *settings, til_setting_t **res_setting, co
 		return drm_fb_ops.setup(settings, res_setting, res_desc, res_setup);
 	}
 #endif
+	if (!strcasecmp(video, "mem")) {
+		fb_ops = &mem_fb_ops;
+
+		return mem_fb_ops.setup(settings, res_setting, res_desc, res_setup);
+	}
 #ifdef HAVE_SDL
 	if (!strcasecmp(video, "sdl")) {
 		fb_ops = &sdl_fb_ops;