From 90c8619f426170b820f968b7633ee312b19b77ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <mail@baedert.org>
Date: Wed, 14 Mar 2018 12:23:38 +0100
Subject: [PATCH] gl renderer: Properly draw gl textures from a different
 context

Temporarily switch to the texture's gl context, download the texture and
create a new one in our context for it.
---
 gsk/gl/gskgldriver.c   | 35 +++++++++++++++++++++++++++--------
 gsk/gl/gskglrenderer.c | 31 ++++++++-----------------------
 2 files changed, 35 insertions(+), 31 deletions(-)

diff --git a/gsk/gl/gskgldriver.c b/gsk/gl/gskgldriver.c
index a7a62a49e1..21e1a5a1ee 100644
--- a/gsk/gl/gskgldriver.c
+++ b/gsk/gl/gskgldriver.c
@@ -372,14 +372,34 @@ gsk_gl_driver_get_texture_for_texture (GskGLDriver *driver,
   cairo_surface_t *surface;
 
   if (GDK_IS_GL_TEXTURE (texture))
-    return gdk_gl_texture_get_id (GDK_GL_TEXTURE (texture));
-
-  t = gdk_texture_get_render_data (texture, driver);
-
-  if (t)
     {
-      if (t->min_filter == min_filter && t->mag_filter == mag_filter)
-        return t->texture_id;
+      GdkGLContext *texture_context = gdk_gl_texture_get_context ((GdkGLTexture *)texture);
+
+      if (texture_context != driver->gl_context)
+        {
+          /* In this case, we have to temporarily make the texture's context the current one,
+           * download its data into our context and then create a texture from it. */
+          gdk_gl_context_make_current (texture_context);
+          surface = gdk_texture_download_surface (texture);
+          gdk_gl_context_make_current (driver->gl_context);
+        }
+      else
+        {
+          /* A GL texture from the same GL context is a simple task... */
+          return gdk_gl_texture_get_id (GDK_GL_TEXTURE (texture));
+        }
+    }
+  else
+    {
+      t = gdk_texture_get_render_data (texture, driver);
+
+      if (t)
+        {
+          if (t->min_filter == min_filter && t->mag_filter == mag_filter)
+            return t->texture_id;
+        }
+
+      surface = gdk_texture_download_surface (texture);
     }
 
   t = create_texture (driver, gdk_texture_get_width (texture), gdk_texture_get_height (texture));
@@ -387,7 +407,6 @@ gsk_gl_driver_get_texture_for_texture (GskGLDriver *driver,
   if (gdk_texture_set_render_data (texture, driver, t, gsk_gl_driver_release_texture))
     t->user = texture;
 
-  surface = gdk_texture_download_surface (texture);
   gsk_gl_driver_bind_source_texture (driver, t->texture_id);
   gsk_gl_driver_init_texture_with_surface (driver,
                                            t->texture_id,
diff --git a/gsk/gl/gskglrenderer.c b/gsk/gl/gskglrenderer.c
index ca8fe4a30e..8a4aa9393b 100644
--- a/gsk/gl/gskglrenderer.c
+++ b/gsk/gl/gskglrenderer.c
@@ -643,30 +643,15 @@ render_texture_node (GskGLRenderer   *self,
       ty2 = 1;
     }
 
-  if (GDK_IS_GL_TEXTURE (texture))
-    {
-      ops_draw (builder, (GskQuadVertex[GL_N_VERTICES]) {
-        { { min_x, min_y }, { tx1, ty2 }, },
-        { { min_x, max_y }, { tx1, ty1 }, },
-        { { max_x, min_y }, { tx2, ty2 }, },
+  ops_draw (builder, (GskQuadVertex[GL_N_VERTICES]) {
+    { { min_x, min_y }, { tx1, ty1 }, },
+    { { min_x, max_y }, { tx1, ty2 }, },
+    { { max_x, min_y }, { tx2, ty1 }, },
 
-        { { max_x, max_y }, { tx2, ty1 }, },
-        { { min_x, max_y }, { tx1, ty1 }, },
-        { { max_x, min_y }, { tx2, ty2 }, },
-      });
-    }
-  else
-    {
-      ops_draw (builder, (GskQuadVertex[GL_N_VERTICES]) {
-        { { min_x, min_y }, { tx1, ty1 }, },
-        { { min_x, max_y }, { tx1, ty2 }, },
-        { { max_x, min_y }, { tx2, ty1 }, },
-
-        { { max_x, max_y }, { tx2, ty2 }, },
-        { { min_x, max_y }, { tx1, ty2 }, },
-        { { max_x, min_y }, { tx2, ty1 }, },
-      });
-    }
+    { { max_x, max_y }, { tx2, ty2 }, },
+    { { min_x, max_y }, { tx1, ty2 }, },
+    { { max_x, min_y }, { tx2, ty1 }, },
+  });
 }
 
 static inline void