backend: add interfaces for readiness reporting

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/backend/backend.h

@@ -5,8 +5,8 @@
 
 #include <stdbool.h>
 
-#include "driver.h"
 #include "compiler.h"
+#include "driver.h"
 #include "kernel.h"
 #include "region.h"
 #include "x.h"
@@ -14,15 +14,22 @@
 typedef struct session session_t;
 struct managed_win;
 
+struct ev_loop;
 struct backend_operations;
 
 typedef struct backend_base {
 	struct backend_operations *ops;
 	xcb_connection_t *c;
 	xcb_window_t root;
+	struct ev_loop *loop;
+
+	/// Whether the backend can accept new render request at the moment
+	bool busy;
 	// ...
 } backend_t;
 
+typedef void (*backend_ready_callback_t)(void *);
+
 enum image_operations {
 	// Invert the color of the entire image, `reg_op` ignored
 	IMAGE_OP_INVERT_COLOR_ALL,
@@ -177,6 +184,9 @@ struct backend_operations {
 
 	// ===========         Hooks        ============
 	/// Let the backend hook into the event handling queue
+	void (*set_ready_callback)(backend_t *, backend_ready_callback_t cb);
+	/// Called right after compton has handled its events.
+	void (*handle_events)(backend_t *);
 	// ===========         Misc         ============
 	/// Return the driver that is been used by the backend
 	enum driver (*detect_driver)(backend_t *backend_data);

src/backend/backend_common.c

@@ -279,3 +279,11 @@ default_backend_render_shadow(backend_t *backend_data, int width, int height,
 	xcb_render_free_picture(backend_data->c, pict);
 	return ret;
 }
+
+void init_backend_base(struct backend_base *base, session_t *ps) {
+	base->c = ps->c;
+	base->loop = ps->loop;
+	base->root = ps->root;
+	base->busy = false;
+	base->ops = NULL;
+}

src/backend/backend_common.h

@@ -13,6 +13,7 @@ typedef struct session session_t;
 typedef struct win win;
 typedef struct conv conv;
 typedef struct backend_base backend_t;
+struct backend_operations;
 
 bool build_shadow(xcb_connection_t *, xcb_drawable_t, double opacity, int width,
                   int height, const conv *kernel, xcb_render_picture_t shadow_pixel,
@@ -35,3 +36,5 @@ bool default_is_frame_transparent(void *, win *, void *);
 void *
 default_backend_render_shadow(backend_t *backend_data, int width, int height,
                               const conv *kernel, double r, double g, double b, double a);
+
+void init_backend_base(struct backend_base *base, session_t *ps);

src/backend/gl/glx.c

@@ -218,8 +218,8 @@ static backend_t *glx_init(session_t *ps) {
 	bool success = false;
 	glxext_init(ps->dpy, ps->scr);
 	auto gd = ccalloc(1, struct _glx_data);
-	gd->gl.base.c = ps->c;
+	init_backend_base(&gd->gl.base, ps);
-	gd->gl.base.root = ps->root;
+
 	gd->display = ps->dpy;
 	gd->screen = ps->scr;
 	gd->target_win = ps->overlay != XCB_NONE ? ps->overlay : ps->root;

src/backend/xrender/xrender.c

@@ -474,9 +474,7 @@ static void *copy(backend_t *base, const void *image, const region_t *reg) {
 
 backend_t *backend_xrender_init(session_t *ps) {
 	auto xd = ccalloc(1, struct _xrender_data);
-
+	init_backend_base(&xd->base, ps);
-	xd->base.c = ps->c;
-	xd->base.root = ps->root;
 
 	for (int i = 0; i < 256; ++i) {
 		double o = (double)i / 255.0;