sdl_fb: implement rudimentary sdl fb backend

This uses a simple fixed 640x480 windowed mode (for now).

The SDL2 Renderer & Texture API is used for vsync-synchronized presents.
There's probably excessive copying going on because the rototiller fb
code manages pages and flips but SDL2 doesn't really expose low-level
control of such things.

This backend is quite useful for development purposes, allowing quick
iteration in a windowed environment.

Note this is just the backend implementation, it's dormant code but
trivially activated.

1 files changed, 155 insertions, 0 deletions

diff --git a/src/sdl_fb.c b/src/sdl_fb.c
new file mode 100644
index 0000000..7047f4a
--- /dev/null
+++ b/src/sdl_fb.c
@@ -0,0 +1,155 @@
+#include <SDL.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include "fb.h"
+#include "settings.h"
+
+
+/* sdl fb backend, everything sdl-specific in rototiller resides here. */
+
+typedef struct sdl_fb_t {
+	SDL_Window	*window;
+	SDL_Renderer	*renderer;
+	SDL_Texture	*texture;
+} sdl_fb_t;
+
+typedef struct sdl_fb_page_t sdl_fb_page_t;
+
+struct sdl_fb_page_t {
+	SDL_Surface	*surface;
+};
+
+
+int sdl_fb_setup(settings_t *settings, setting_desc_t **next_setting)
+{
+	/* TODO: window size? fullscreen? vsync? etc. */
+	return 0;
+}
+
+
+void * sdl_fb_init(settings_t *settings)
+{
+	sdl_fb_t	*c;
+
+	c = calloc(1, sizeof(sdl_fb_t));
+	if (!c)
+		return NULL;
+
+	if (SDL_Init(SDL_INIT_VIDEO) < 0) {
+		free(c);
+		return NULL;
+	}
+
+	return c;
+}
+
+
+void sdl_fb_shutdown(void *context)
+{
+	sdl_fb_t	*c = context;
+
+	SDL_Quit();
+	free(c);
+}
+
+
+static int sdl_fb_acquire(void *context, void *page)
+{
+	sdl_fb_t	*c = context;
+	sdl_fb_page_t	*p = page;
+
+	c->window = SDL_CreateWindow("rototiller", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);
+	if (!c->window)
+		return -1;
+
+	c->renderer = SDL_CreateRenderer(c->window, -1, SDL_RENDERER_PRESENTVSYNC);
+	if (!c->renderer)
+		return -1;
+
+	c->texture = SDL_CreateTexture(c->renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_STREAMING, 640, 480);
+	if (!c->texture)
+		return -1;
+
+	return 0;
+}
+
+
+static void sdl_fb_release(void *context)
+{
+	sdl_fb_t	*c = context;
+
+	SDL_DestroyTexture(c->texture);
+	SDL_DestroyRenderer(c->renderer);
+	SDL_DestroyWindow(c->window);
+}
+
+
+static void * sdl_fb_page_alloc(void *context, fb_page_t *res_page)
+{
+	sdl_fb_t	*c = context;
+	sdl_fb_page_t	*p;
+
+	p = calloc(1, sizeof(sdl_fb_page_t));
+	if (!p)
+		return NULL;
+
+
+	p->surface = SDL_CreateRGBSurfaceWithFormat(0, 640, 480, 32, SDL_PIXELFORMAT_RGB888);
+
+	res_page->fragment.buf = p->surface->pixels;
+	res_page->fragment.width = 640;
+	res_page->fragment.frame_width = 640;
+	res_page->fragment.height = 480;
+	res_page->fragment.frame_height = 480;
+	res_page->fragment.stride = p->surface->pitch - (640 * 4);
+
+	return p;
+}
+
+
+static int sdl_fb_page_free(void *context, void *page)
+{
+	sdl_fb_t	*c = context;
+	sdl_fb_page_t	*p = page;
+
+	SDL_FreeSurface(p->surface);
+	free(p);
+
+	return 0;
+}
+
+
+static int sdl_fb_page_flip(void *context, void *page)
+{
+	sdl_fb_t	*c = context;
+	sdl_fb_page_t	*p = page;
+
+	if (SDL_UpdateTexture(c->texture, NULL, p->surface->pixels, p->surface->pitch) < 0)
+		return -1;
+
+	if (SDL_RenderClear(c->renderer) < 0)
+		return -1;
+
+	if (SDL_RenderCopy(c->renderer, c->texture, NULL, NULL) < 0)
+		return -1;
+
+	SDL_RenderPresent(c->renderer);
+
+	if (SDL_QuitRequested())
+		return -EPIPE;
+
+	return 0;
+}
+
+
+fb_ops_t sdl_fb_ops = {
+	.setup = sdl_fb_setup,
+	.init = sdl_fb_init,
+	.shutdown = sdl_fb_shutdown,
+	.acquire = sdl_fb_acquire,
+	.release = sdl_fb_release,
+	.page_alloc = sdl_fb_page_alloc,
+	.page_free = sdl_fb_page_free,
+	.page_flip = sdl_fb_page_flip
+};