st/wgl: flush with ST_FLUSH_WAIT before releasing shared contexts

Before releasing a shared context, flush the context
with ST_FLUSH_WAIT to make sure all commands are executed.
This ensures that rendering to any shared resources is completed
before they will be referenced by another context.

Fixes an intermittent flickering with Photoshop. (VMware bug# 1779340)

Reviewed-by: Brian Paul <brianp@vmware.com>

src/gallium/state_trackers/wgl/stw_context.c

@@ -104,8 +104,11 @@ DrvShareLists(DHGLRC dhglrc1, DHGLRC dhglrc2)
    ctx1 = stw_lookup_context_locked( dhglrc1 );
    ctx2 = stw_lookup_context_locked( dhglrc2 );
 
-   if (ctx1 && ctx2 && ctx2->st->share)
+   if (ctx1 && ctx2 && ctx2->st->share) {
       ret = ctx2->st->share(ctx2->st, ctx1->st);
+      ctx1->shared = TRUE;
+      ctx2->shared = TRUE;
+   }
 
    stw_unlock_contexts(stw_dev);
 
@@ -175,6 +178,7 @@ stw_create_context_attribs(HDC hdc, INT iLayerPlane, DHGLRC hShareContext,
    if (hShareContext != 0) {
       stw_lock_contexts(stw_dev);
       shareCtx = stw_lookup_context_locked( hShareContext );
+      shareCtx->shared = TRUE;
       stw_unlock_contexts(stw_dev);
    }
 
@@ -184,6 +188,7 @@ stw_create_context_attribs(HDC hdc, INT iLayerPlane, DHGLRC hShareContext,
 
    ctx->hdc = hdc;
    ctx->iPixelFormat = iPixelFormat;
+   ctx->shared = shareCtx != NULL;
 
    memset(&attribs, 0, sizeof(attribs));
    attribs.visual = pfi->stvis;
@@ -403,7 +408,14 @@ stw_make_current(HDC hdc, DHGLRC dhglrc)
             return TRUE;
          }
       } else {
-         old_ctx->st->flush(old_ctx->st, ST_FLUSH_FRONT, NULL);
+         if (old_ctx->shared) {
+            struct pipe_fence_handle *fence = NULL;
+            old_ctx->st->flush(old_ctx->st,
+                               ST_FLUSH_FRONT | ST_FLUSH_WAIT, &fence);
+         }
+         else {
+            old_ctx->st->flush(old_ctx->st, ST_FLUSH_FRONT, NULL);
+         }
       }
    }
 

src/gallium/state_trackers/wgl/stw_context.h

@@ -40,6 +40,7 @@ struct stw_context
    DHGLRC dhglrc;
    int iPixelFormat;
    HDC hdc;
+   BOOL shared;
 
    struct stw_framebuffer *current_framebuffer;