wayland: release unused buffers after buffer swap

When the surface attaches to a buffer, all other buffers are available.
Export the function used to release a buffer, track the buffer used by
the surface, and release unused buffers when a new buffer is attached.

wayland/buffer.c

@@ -14,16 +14,11 @@
 
 #include "wayland.h"
 
-static int commit_buffer_resize(struct ufkbd_wl_buffer *ctx);
-
 static void on_buffer_release(void *data, struct wl_buffer *buf)
 {
 	struct ufkbd_wl_buffer *ctx = data;
 
-	if (ctx->resize)
+	ufkbd_wl_buffer_release(ctx);
-		commit_buffer_resize(ctx);
-
-	ctx->avail = true;
 }
 
 static const struct wl_buffer_listener buf_listener = {
@@ -140,6 +135,14 @@ int ufkbd_wl_buffer_resize(struct ufkbd_wl_buffer *ctx,
 	return 0;
 }
 
+void ufkbd_wl_buffer_release(struct ufkbd_wl_buffer *ctx)
+{
+	if (ctx->resize)
+		commit_buffer_resize(ctx);
+
+	ctx->avail = true;
+}
+
 int ufkbd_wl_buffer_init(struct ufkbd_wl_buffer *ctx,
 				 struct ufkbd_input_wayland *ufkbd_wl,
 				 unsigned int id)

wayland/driver.c

@@ -150,8 +150,6 @@ static int ufkbd_wayland_draw_begin(void *data, size_t *stride, void **ptr)
 		return ret;
 	}
 
-	wl_surface_attach(ctx->surface->wl, buf, 0, 0);
-
 	// NOPUSH
 	*stride = (size_t) ctx->surface->bufs[0].width * 4;
 
@@ -170,6 +168,7 @@ static void ufkbd_wayland_draw_end(void *data)
 	struct ufkbd_input_wayland *ctx = data;
 
 	wl_surface_commit(ctx->surface->wl);
+	ufkbd_wl_surface_release_unused(ctx->surface);
 }
 
 static void *ufkbd_wayland_init(struct ufkbd_ctx *ufkbd)

wayland/surface.c

@@ -163,16 +163,22 @@ static void on_global_viewporter(void *data,
 int ufkbd_wl_surface_consume_buffer(struct ufkbd_wl_surface *ctx,
 				    struct wl_buffer **buf, void **ptr)
 {
-	int ret;
+	int ret, i;
 
 	if (buf == NULL || ptr == NULL)
 		return -EINVAL;
 
-	ret = ufkbd_wl_buffer_consume(&ctx->bufs[0], buf, ptr);
+	for (i = 0; i < 2; i++) {
-	if (ret != -EBUSY)
+		ret = ufkbd_wl_buffer_consume(&ctx->bufs[i], buf, ptr);
-		return ret;
+		if (!ret) {
+			wl_surface_attach(ctx->wl, *buf, 0, 0);
+			ctx->used_buf = i;
+			break;
+		}
 
-	ret = ufkbd_wl_buffer_consume(&ctx->bufs[1], buf, ptr);
+		if (ret != -EBUSY)
+			break;
+	}
 
 	return ret;
 }
@@ -195,6 +201,16 @@ static int ufkbd_wl_surface_resize_buffers(struct ufkbd_wl_surface *ctx,
 				      height * ctx->scale);
 }
 
+void ufkbd_wl_surface_release_unused(struct ufkbd_wl_surface *ctx)
+{
+	int i;
+
+	for (i = 0; i < 2; i++) {
+		if (i != ctx->used_buf)
+			ufkbd_wl_buffer_release(&ctx->bufs[i]);
+	}
+}
+
 int ufkbd_wl_surface_init(struct ufkbd_input_wayland *ufkbd_wl,
 			  struct ufkbd_wl_surface **out)
 {
@@ -207,6 +223,7 @@ int ufkbd_wl_surface_init(struct ufkbd_input_wayland *ufkbd_wl,
 
 	ctx->ufkbd_wl = ufkbd_wl;
 	ctx->scale = 1;
+	ctx->used_buf = -1;
 
 	ret = ufkbd_wl_buffer_init(&ctx->bufs[0], ufkbd_wl, 0);
 	if (ret)

wayland/wayland.h

@@ -105,6 +105,7 @@ struct ufkbd_wl_surface {
 	unsigned int scale;
 	size_t stride;
 
+	int used_buf;
 	struct ufkbd_wl_buffer bufs[2];
 };
 
@@ -126,6 +127,7 @@ int ufkbd_wl_buffer_consume(struct ufkbd_wl_buffer *ctx,
 				    struct wl_buffer **buf, void **ptr);
 int ufkbd_wl_buffer_resize(struct ufkbd_wl_buffer *ctx,
 				   uint32_t width, uint32_t height);
+void ufkbd_wl_buffer_release(struct ufkbd_wl_buffer *ctx);
 int ufkbd_wl_buffer_init(struct ufkbd_wl_buffer *ctx,
 				 struct ufkbd_input_wayland *ufkbd_wl,
 				 unsigned int id);
@@ -133,6 +135,7 @@ void ufkbd_wl_buffer_uninit(struct ufkbd_wl_buffer *ctx);
 
 int ufkbd_wl_surface_consume_buffer(struct ufkbd_wl_surface *ctx,
 				    struct wl_buffer **buf, void **ptr);
+void ufkbd_wl_surface_release_unused(struct ufkbd_wl_surface *ctx);
 int ufkbd_wl_surface_init(struct ufkbd_input_wayland *ufkbd_wl,
 			  struct ufkbd_wl_surface **out);
 void ufkbd_wl_surface_uninit(struct ufkbd_wl_surface *ctx);