gl_common: add some sort of locking API

Some OpenGL implementations on some platforms require that a context
is current only on one thread. For this reason, mpgl_lock() and
mpgl_unlock() take care of this as well for convenience.

Each backend that needs thread safety should provide it's own locking strategy
inside of `set_current`.

2 files changed, 35 insertions, 0 deletions

diff --git a/video/out/gl_common.c b/video/out/gl_common.c
index 685258406a..39fb592df4 100644
--- a/video/out/gl_common.c
+++ b/video/out/gl_common.c
@@ -940,6 +940,33 @@ void mpgl_uninit(MPGLContext *ctx)
     talloc_free(ctx);
 }
 
+void mpgl_set_context(MPGLContext *ctx)
+{
+    if (ctx->set_current)
+        ctx->set_current(ctx, true);
+}
+
+void mpgl_unset_context(MPGLContext *ctx)
+{
+    if (ctx->set_current)
+        ctx->set_current(ctx, false);
+}
+
+void mpgl_lock(MPGLContext *ctx)
+{
+    mpgl_set_context(ctx);
+}
+
+void mpgl_unlock(MPGLContext *ctx)
+{
+    mpgl_unset_context(ctx);
+}
+
+bool mpgl_is_thread_safe(MPGLContext *ctx)
+{
+    return !!ctx->set_current;
+}
+
 void mp_log_source(int mod, int lev, const char *src)
 {
     int line = 1;
diff --git a/video/out/gl_common.h b/video/out/gl_common.h
index 1f28d87855..18d1cf8879 100644
--- a/video/out/gl_common.h
+++ b/video/out/gl_common.h
@@ -26,6 +26,7 @@
 
 #include <stdio.h>
 #include <stdint.h>
+#include <stdbool.h>
 
 #include "config.h"
 #include "core/mp_msg.h"
@@ -111,6 +112,7 @@ typedef struct MPGLContext {
     int (*vo_init)(struct vo *vo);
     void (*vo_uninit)(struct vo *vo);
     void (*releaseGlContext)(struct MPGLContext *);
+    void (*set_current)(struct MPGLContext *, bool current);
 
     // Resize the window, or create a new window if there isn't one yet.
     // On the first call, it creates a GL context according to what's specified
@@ -136,6 +138,12 @@ typedef struct MPGLContext {
 MPGLContext *mpgl_init(struct vo *vo, const char *backend_name);
 void mpgl_uninit(MPGLContext *ctx);
 
+void mpgl_lock(MPGLContext *ctx);
+void mpgl_unlock(MPGLContext *ctx);
+void mpgl_set_context(MPGLContext *ctx);
+void mpgl_unset_context(MPGLContext *ctx);
+bool mpgl_is_thread_safe(MPGLContext *ctx);
+
 // Create a VO window and create a GL context on it.
 // (Calls config_window_gl3 or config_window+setGlWindow.)
 // gl_caps: bitfield of MPGL_CAP_* (required GL version and feature set)