[Mesa-dev] [PATCH] loader_dri3/glx/egl: Reinstate the loader_dri3_vtable get_dri_screen callback

[Thomas Hellstrom]

Removing this callback caused rendering corruption in some multi-screen cases,
so it is reinstated but without the drawable argument which was never used
by implementations and was confusing since the drawable could have been
created with another screen.

Cc: "17.3" mesa-stable at lists.freedesktop.org
Fixes: 5198e48a0d (loader_dri3/glx/egl: Remove the loader_dri3_vtable get_dri_screen callback)
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105013
Reported-by: Daniel van Vugt <daniel.van.vugt at canonical.com>
Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
---
 src/egl/drivers/dri2/platform_x11_dri3.c | 12 ++++++++++++
 src/glx/dri3_glx.c                       | 11 +++++++++++
 src/loader/loader_dri3_helper.c          | 12 +++++++++++-
 src/loader/loader_dri3_helper.h          |  1 +
 4 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/egl/drivers/dri2/platform_x11_dri3.c b/src/egl/drivers/dri2/platform_x11_dri3.c
index 6e40eaa596..060b5f83a3 100644
--- a/src/egl/drivers/dri2/platform_x11_dri3.c
+++ b/src/egl/drivers/dri2/platform_x11_dri3.c
@@ -75,6 +75,17 @@ egl_dri3_get_dri_context(struct loader_dri3_drawable *draw)
    return dri2_ctx->dri_context;
 }
 
+static __DRIscreen *
+egl_dri3_get_dri_screen(void)
+{
+   _EGLContext *ctx = _eglGetCurrentContext();
+   struct dri2_egl_context *dri2_ctx;
+   if (!ctx)
+      return NULL;
+   dri2_ctx = dri2_egl_context(ctx);
+   return dri2_egl_display(dri2_ctx->base.Resource.Display)->dri_screen;
+}
+
 static void
 egl_dri3_flush_drawable(struct loader_dri3_drawable *draw, unsigned flags)
 {
@@ -88,6 +99,7 @@ static const struct loader_dri3_vtable egl_dri3_vtable = {
    .set_drawable_size = egl_dri3_set_drawable_size,
    .in_current_context = egl_dri3_in_current_context,
    .get_dri_context = egl_dri3_get_dri_context,
+   .get_dri_screen = egl_dri3_get_dri_screen,
    .flush_drawable = egl_dri3_flush_drawable,
    .show_fps = NULL,
 };
diff --git a/src/glx/dri3_glx.c b/src/glx/dri3_glx.c
index f280a8cef7..016f91b196 100644
--- a/src/glx/dri3_glx.c
+++ b/src/glx/dri3_glx.c
@@ -116,6 +116,16 @@ glx_dri3_get_dri_context(struct loader_dri3_drawable *draw)
    return (gc != &dummyContext) ? dri3Ctx->driContext : NULL;
 }
 
+static __DRIscreen *
+glx_dri3_get_dri_screen(void)
+{
+   struct glx_context *gc = __glXGetCurrentContext();
+   struct dri3_context *pcp = (struct dri3_context *) gc;
+   struct dri3_screen *psc = (struct dri3_screen *) pcp->base.psc;
+
+   return (gc != &dummyContext && psc) ? psc->driScreen : NULL;
+}
+
 static void
 glx_dri3_flush_drawable(struct loader_dri3_drawable *draw, unsigned flags)
 {
@@ -150,6 +160,7 @@ static const struct loader_dri3_vtable glx_dri3_vtable = {
    .set_drawable_size = glx_dri3_set_drawable_size,
    .in_current_context = glx_dri3_in_current_context,
    .get_dri_context = glx_dri3_get_dri_context,
+   .get_dri_screen = glx_dri3_get_dri_screen,
    .flush_drawable = glx_dri3_flush_drawable,
    .show_fps = glx_dri3_show_fps,
 };
diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c
index fbda3d635c..2e3b6c619e 100644
--- a/src/loader/loader_dri3_helper.c
+++ b/src/loader/loader_dri3_helper.c
@@ -1311,6 +1311,7 @@ dri3_get_pixmap_buffer(__DRIdrawable *driDrawable, unsigned int format,
    xcb_sync_fence_t                     sync_fence;
    struct xshmfence                     *shm_fence;
    int                                  fence_fd;
+   __DRIscreen                          *cur_screen;
 
    if (buffer)
       return buffer;
@@ -1341,8 +1342,17 @@ dri3_get_pixmap_buffer(__DRIdrawable *driDrawable, unsigned int format,
    if (!bp_reply)
       goto no_image;
 
+   /* Get the currently-bound screen or revert to using the drawable's screen if
+    * no contexts are currently bound. The latter case is at least necessary for
+    * obs-studio, when using Window Capture (Xcomposite) as a Source.
+    */
+   cur_screen = draw->vtable->get_dri_screen();
+   if (!cur_screen) {
+       cur_screen = draw->dri_screen;
+   }
+
    buffer->image = loader_dri3_create_image(draw->conn, bp_reply, format,
-                                            draw->dri_screen, draw->ext->image,
+                                            cur_screen, draw->ext->image,
                                             buffer);
    if (!buffer->image)
       goto no_image;
diff --git a/src/loader/loader_dri3_helper.h b/src/loader/loader_dri3_helper.h
index 4ce98b8c59..839cba30df 100644
--- a/src/loader/loader_dri3_helper.h
+++ b/src/loader/loader_dri3_helper.h
@@ -99,6 +99,7 @@ struct loader_dri3_vtable {
    void (*set_drawable_size)(struct loader_dri3_drawable *, int, int);
    bool (*in_current_context)(struct loader_dri3_drawable *);
    __DRIcontext *(*get_dri_context)(struct loader_dri3_drawable *);
+   __DRIscreen *(*get_dri_screen)(void);
    void (*flush_drawable)(struct loader_dri3_drawable *, unsigned);
    void (*show_fps)(struct loader_dri3_drawable *, uint64_t);
 };
-- 
2.14.3