uterm: video: return buffer information on display_use()

uterm_display_use() now returns the current back-buffer index when called.
It returns <0 on error. Whether OpenGL is supported is returned via a new
parameter "opengl". Set it to NULL if you're not interested.

Note that a backend might support OpenGL _and_ memory-mapped buffer
access. But you shouldn't rely on uterm_display_use() to return the
correct buffer-index if uterm_display_get_buffers() is not supported. For
instance the DRM-3D backend always returns 0 as buffer index as it has no
way of detecting it, yet.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

src/kmscon_terminal.c

@@ -201,6 +201,7 @@ static int add_display(struct kmscon_terminal *term, struct uterm_display *disp)
 	unsigned int cols, rows;
 	struct kmscon_font_attr attr = { "", 0, 20, false, false, 0, 0 };
 	const char *be;
+	bool opengl;
 
 	attr.ppi = term->conf->font_ppi;
 	attr.points = term->conf->font_size;
@@ -242,10 +243,10 @@ static int add_display(struct kmscon_terminal *term, struct uterm_display *disp)
 		kmscon_font_ref(scr->bold_font);
 	}
 
-	ret = uterm_display_use(scr->disp);
+	ret = uterm_display_use(scr->disp, &opengl);
 	if (term->conf->render_engine)
 		be = term->conf->render_engine;
-	else if (!ret)
+	else if (ret >= 0 && opengl)
 		be = "gltex";
 	else
 		be = "bbulk";

src/text_gltex.c

@@ -147,6 +147,7 @@ static int gltex_set(struct kmscon_text *txt)
 	GLint s;
 	const char *ext;
 	struct uterm_mode *mode;
+	bool opengl;
 
 	memset(gt, 0, sizeof(*gt));
 	shl_dlist_init(&gt->atlases);
@@ -163,8 +164,8 @@ static int gltex_set(struct kmscon_text *txt)
 	if (ret)
 		goto err_htable;
 
-	ret = uterm_display_use(txt->disp);
+	ret = uterm_display_use(txt->disp, &opengl);
-	if (ret) {
+	if (ret < 0 || !opengl) {
 		if (ret == -EOPNOTSUPP)
 			log_error("display doesn't support hardware-acceleration");
 		goto err_bold_htable;
@@ -231,7 +232,7 @@ static void gltex_unset(struct kmscon_text *txt)
 	struct atlas *atlas;
 	bool gl = true;
 
-	ret = uterm_display_use(txt->disp);
+	ret = uterm_display_use(txt->disp, NULL);
 	if (ret) {
 		gl = false;
 		log_warning("cannot activate OpenGL-CTX during destruction");
@@ -526,7 +527,7 @@ static int gltex_prepare(struct kmscon_text *txt)
 	struct shl_dlist *iter;
 	int ret;
 
-	ret = uterm_display_use(txt->disp);
+	ret = uterm_display_use(txt->disp, NULL);
 	if (ret)
 		return ret;
 

src/uterm_fbdev_video.c

@@ -430,6 +430,19 @@ static int display_set_dpms(struct uterm_display *disp, int state)
 	return 0;
 }
 
+static int display_use(struct uterm_display *disp, bool *opengl)
+{
+	struct fbdev_display *dfb = disp->data;
+
+	if (opengl)
+		*opengl = false;
+
+	if (!(disp->flags & DISPLAY_DBUF))
+		return 0;
+
+	return dfb->bufid ^ 1;
+}
+
 static int display_get_buffers(struct uterm_display *disp,
 			       struct uterm_video_buffer *buffer,
 			       unsigned int formats)
@@ -499,7 +512,7 @@ static const struct display_ops fbdev_display_ops = {
 	.activate = display_activate,
 	.deactivate = display_deactivate,
 	.set_dpms = display_set_dpms,
-	.use = NULL,
+	.use = display_use,
 	.get_buffers = display_get_buffers,
 	.swap = display_swap,
 	.blit = uterm_fbdev_display_blit,

src/uterm_video.c

@@ -415,12 +415,12 @@ int uterm_display_get_dpms(const struct uterm_display *disp)
 	return disp->dpms;
 }
 
-int uterm_display_use(struct uterm_display *disp)
+int uterm_display_use(struct uterm_display *disp, bool *opengl)
 {
 	if (!disp || !display_is_online(disp))
 		return -EINVAL;
 
-	return VIDEO_CALL(disp->ops->use, -EOPNOTSUPP, disp);
+	return VIDEO_CALL(disp->ops->use, -EOPNOTSUPP, disp, opengl);
 }
 
 int uterm_display_get_buffers(struct uterm_display *disp,

src/uterm_video.h

@@ -164,7 +164,7 @@ void uterm_display_deactivate(struct uterm_display *disp);
 int uterm_display_set_dpms(struct uterm_display *disp, int state);
 int uterm_display_get_dpms(const struct uterm_display *disp);
 
-int uterm_display_use(struct uterm_display *disp);
+int uterm_display_use(struct uterm_display *disp, bool *opengl);
 int uterm_display_get_buffers(struct uterm_display *disp,
 			      struct uterm_video_buffer *buffer,
 			      unsigned int formats);

src/uterm_video_drm.c

@@ -305,7 +305,7 @@ static void display_deactivate(struct uterm_display *disp)
 	disp->current_mode = NULL;
 }
 
-static int display_use(struct uterm_display *disp)
+static int display_use(struct uterm_display *disp, bool *opengl)
 {
 	struct uterm_drm3d_display *d3d = uterm_drm_display_get_data(disp);
 	struct uterm_drm3d_video *v3d;
@@ -317,6 +317,10 @@ static int display_use(struct uterm_display *disp)
 		return -EFAULT;
 	}
 
+	if (opengl)
+		*opengl = true;
+
+	/* TODO: lets find a way how to retrieve the current front buffer */
 	return 0;
 }
 
@@ -461,7 +465,7 @@ static int display_blit(struct uterm_display *disp,
 		return -EINVAL;
 
 	v3d = uterm_drm_video_get_data(disp->video);
-	ret = display_use(disp);
+	ret = display_use(disp, NULL);
 	if (ret)
 		return ret;
 	ret = init_shaders(disp->video);
@@ -590,7 +594,7 @@ static int display_blend(struct uterm_display *disp,
 		return -EINVAL;
 
 	v3d = uterm_drm_video_get_data(disp->video);
-	ret = display_use(disp);
+	ret = display_use(disp, NULL);
 	if (ret)
 		return ret;
 	ret = init_shaders(disp->video);
@@ -748,7 +752,7 @@ static int display_fill(struct uterm_display *disp,
 	int ret;
 
 	v3d = uterm_drm_video_get_data(disp->video);
-	ret = display_use(disp);
+	ret = display_use(disp, NULL);
 	if (ret)
 		return ret;
 	ret = init_shaders(disp->video);
@@ -843,7 +847,7 @@ static void show_displays(struct uterm_video *video)
 		if (iter->dpms != UTERM_DPMS_ON)
 			continue;
 
-		ret = display_use(iter);
+		ret = display_use(iter, NULL);
 		if (ret)
 			continue;
 

src/uterm_video_dumb.c

@@ -240,6 +240,16 @@ static void display_deactivate(struct uterm_display *disp)
 	disp->current_mode = NULL;
 }
 
+static int display_use(struct uterm_display *disp, bool *opengl)
+{
+	struct uterm_drm2d_display *d2d = uterm_drm_display_get_data(disp);
+
+	if (opengl)
+		*opengl = false;
+
+	return d2d->current_rb ^ 1;
+}
+
 static int display_get_buffers(struct uterm_display *disp,
 			       struct uterm_video_buffer *buffer,
 			       unsigned int formats)
@@ -449,7 +459,7 @@ static const struct display_ops dumb_display_ops = {
 	.activate = display_activate,
 	.deactivate = display_deactivate,
 	.set_dpms = uterm_drm_display_set_dpms,
-	.use = NULL,
+	.use = display_use,
 	.get_buffers = display_get_buffers,
 	.swap = display_swap,
 	.blit = display_blit,

src/uterm_video_internal.h

@@ -53,7 +53,7 @@ struct display_ops {
 	int (*activate) (struct uterm_display *disp, struct uterm_mode *mode);
 	void (*deactivate) (struct uterm_display *disp);
 	int (*set_dpms) (struct uterm_display *disp, int state);
-	int (*use) (struct uterm_display *disp);
+	int (*use) (struct uterm_display *disp, bool *opengl);
 	int (*get_buffers) (struct uterm_display *disp,
 			    struct uterm_video_buffer *buffer,
 			    unsigned int formats);