Evas GL: support surfaceless make current

Summary:
Evas GL now supports surfaceless make current, where
evas_gl_make_current can be called with sfc parameter NULL.
This closely resembles EGL_KHR_surfaceless_context extension,
where applications that only want to render to client API targets
can make current to NULL surface instead of creating a dummy egl surface.
@feature

3 files changed, 14 insertions, 5 deletions

diff --git a/src/lib/evas/canvas/evas_gl.c b/src/lib/evas/canvas/evas_gl.c
index d7ec99e530..1552e5919e 100644
--- a/src/lib/evas/canvas/evas_gl.c
+++ b/src/lib/evas/canvas/evas_gl.c
@@ -424,6 +424,8 @@ evas_gl_make_current(Evas_GL *evas_gl, Evas_GL_Surface *surf, Evas_GL_Context *c
      ret = (Eina_Bool)evas_gl->evas->engine.func->gl_make_current(evas_gl->evas->engine.data.output, surf->data, ctx->data);
    else if ((!surf) && (!ctx))
      ret = (Eina_Bool)evas_gl->evas->engine.func->gl_make_current(evas_gl->evas->engine.data.output, NULL, NULL);
+   else if ((!surf) && (ctx)) // surfaceless make current
+     ret = (Eina_Bool)evas_gl->evas->engine.func->gl_make_current(evas_gl->evas->engine.data.output, NULL, ctx->data);
    else
      {
         ERR("Bad match between surface: %p and context: %p", surf, ctx);
diff --git a/src/modules/evas/engines/gl_common/evas_gl_core.c b/src/modules/evas/engines/gl_common/evas_gl_core.c
index e9f9bb194f..f3743019f9 100644
--- a/src/modules/evas/engines/gl_common/evas_gl_core.c
+++ b/src/modules/evas/engines/gl_common/evas_gl_core.c
@@ -2222,7 +2222,6 @@ evgl_make_current(void *eng_data, EVGL_Surface *sfc, EVGL_Context *ctx)
 
    // Check the input validity. If either sfc or ctx is NULL, it's also error.
    if ( (!evgl_engine) ||
-        ((!sfc) && ctx) ||
         (sfc && (!ctx)) )
      {
         ERR("Invalid Inputs. Engine: %p  Surface: %p   Context: %p!", evgl_engine, sfc, ctx);
@@ -2295,7 +2294,6 @@ evgl_make_current(void *eng_data, EVGL_Surface *sfc, EVGL_Context *ctx)
         evas_gl_common_error_set(eng_data, EVAS_GL_BAD_CONTEXT);
         return 0;
      }
-   sfc->current_ctx = ctx;
    rsc->current_ctx = ctx;
    rsc->current_eng = eng_data;
 
@@ -2318,6 +2316,16 @@ evgl_make_current(void *eng_data, EVGL_Surface *sfc, EVGL_Context *ctx)
           }
      }
 
+   if (sfc) sfc->current_ctx = ctx;
+   else
+     {
+        DBG("Performing surfaceless make current");
+        glViewport(0, 0, 0, 0);
+        glScissor(0, 0, 0, 0);
+        rsc->direct.rendered = 0;
+        goto finish;
+     }
+
    if (!sfc->buffers_skip_allocate)
      {
         if (!sfc->color_buf && !_surface_buffers_create(sfc))
@@ -2539,9 +2547,8 @@ evgl_make_current(void *eng_data, EVGL_Surface *sfc, EVGL_Context *ctx)
           }
      }
 
+finish:
    ctx->current_sfc = sfc;
-   rsc->current_ctx = ctx;
-   rsc->current_eng = eng_data;
 
    _surface_context_list_print();
 
diff --git a/src/modules/evas/engines/gl_generic/evas_engine.c b/src/modules/evas/engines/gl_generic/evas_engine.c
index 9012ba18e2..4b181a80be 100644
--- a/src/modules/evas/engines/gl_generic/evas_engine.c
+++ b/src/modules/evas/engines/gl_generic/evas_engine.c
@@ -1434,7 +1434,7 @@ eng_gl_make_current(void *data, void *surface, void *context)
    // TODO: Add check for main thread before flush
 
    EVGLINIT(data, 0);
-   if ((sfc) && (ctx))
+   if (ctx)
      {
         Evas_Engine_GL_Context *gl_context;