Evas filters: fix black squares with the GL engine

If a text object changes regularily, there might be cases where
the object will be rendered as a simple black rectangle for just
one frame.

It seems that the previous output buffer is deleted before being
actually rendered on screen. This patch will delay the deletion
of the previous buffer until the current one has been rendered
to the target surface.

And again, thanks zmike for reporting.

@fix

Signed-off-by: Jean-Philippe Andre <jp.andre@samsung.com>

src/lib/evas/canvas/evas_object_text.c

@@ -2217,7 +2217,7 @@ evas_object_text_render(Evas_Object *eo_obj EINA_UNUSED,
         // Proxies
         evas_filter_context_proxy_render_all(filter, eo_obj, EINA_FALSE);
 
-        // Context: FIXME it should be a sw context only
+        // Draw Context
         filter_ctx = ENFN->context_new(ENDT);
         ENFN->context_color_set(ENDT, filter_ctx, 255, 255, 255, 255);
 

src/lib/evas/filters/evas_filter.c

@@ -681,7 +681,8 @@ evas_filter_buffer_backing_release(Evas_Filter_Context *ctx, void *stolen_buffer
    if (ctx->async)
      evas_unref_queue_image_put(ctx->evas, ie);
    else if (ctx->gl_engine)
-     ENFN->image_free(ENDT, stolen_buffer);
+     ctx->post_run.buffers_to_free =
+       eina_list_append(ctx->post_run.buffers_to_free, stolen_buffer);
    else
      _backing_free(ctx, ie);
 
@@ -1691,7 +1692,17 @@ static void
 _filter_thread_run_cb(void *data)
 {
    Evas_Filter_Context *ctx = data;
+   void *buffer;
+
+   // TODO: Add return value check and call error cb
    _filter_chain_run(ctx);
+
+   EINA_LIST_FREE(ctx->post_run.buffers_to_free, buffer)
+     {
+        if (ctx->gl_engine)
+          ENFN->image_free(ENDT, buffer);
+     }
+
    if (ctx->post_run.cb)
      ctx->post_run.cb(ctx, ctx->post_run.data);
 }

src/lib/evas/filters/evas_filter_private.h

@@ -55,6 +55,7 @@ struct _Evas_Filter_Context
       /** Post-processing callback. The context can be safely destroyed here. */
       Evas_Filter_Cb cb;
       void *data;
+      Eina_List *buffers_to_free; // Some buffers should be queued for deletion
    } post_run;
 
    struct