[PATCH v5 0/1] MR4912: winex11.drv: Fix wglSwapBuffers() with NULL current context with child window rendering.

[Paul Gofman (＠gofman)]

After wglMakeCurrent(NULL, NULL); wglSwapBuffers(HDC) actually swaps buffers for the device context. That works on Windows and basically with Wine glx (as glxSwapBuffers also works on drawable and doesn't need GLX context). But that doesn't work for child window rendering: first because of NULL ctx dereference (checked for NULL elsewhere) and next because of GLX_OML_sync_control path.

Fixes Black Desert Online launcher being black screen. The launcher does the following for drawing a frame (while drawing on the child window):
```
wglMakeCurrent(hdc, valid context);
<gl drawing>
wglMakeCurrent(NULL, NULL);
wglSwapBuffers(hdc);
```

--
  v5: winex11.drv: Fix wglSwapBuffers() with NULL current context with child window rendering.

https://gitlab.winehq.org/wine/wine/-/merge_requests/4912

[PATCH v5 1/1] winex11.drv: Fix wglSwapBuffers() with NULL current context with child window rendering.

[Paul Gofman]

From: Paul Gofman

---
 dlls/opengl32/tests/opengl.c | 52 ++++++++++++++++++++++++++++++++++++
 dlls/winex11.drv/opengl.c    | 10 +++----
 2 files changed, 57 insertions(+), 5 deletions(-)

diff --git a/dlls/opengl32/tests/opengl.c b/dlls/opengl32/tests/opengl.c
index e3ca82a9b03..74aff6b4bbd 100644
--- a/dlls/opengl32/tests/opengl.c
+++ b/dlls/opengl32/tests/opengl.c
@@ -2006,6 +2006,55 @@ static void test_copy_context(HDC hdc)
     ok(ret, "wglMakeCurrent failed, last error %#lx.\n", GetLastError());
 }

+static void test_child_window(HWND hwnd, PIXELFORMATDESCRIPTOR *pfd)
+{
+    int pixel_format;
+    DWORD t1, t;
+    HGLRC hglrc;
+    HWND child;
+    HDC hdc;
+    int res;
+
+    child = CreateWindowA("static", "Title", WS_CHILDWINDOW | WS_VISIBLE, 50, 50, 100, 100, hwnd, NULL, NULL, NULL);
+    ok(!!child, "got error %lu.\n", GetLastError());
+
+    hdc = GetDC(child);
+    pixel_format = ChoosePixelFormat(hdc, pfd);
+    res = SetPixelFormat(hdc, pixel_format, pfd);
+    ok(res, "got error %lu.\n", GetLastError());
+
+    hglrc = wglCreateContext(hdc);
+    ok(!!hglrc, "got error %lu.\n", GetLastError());
+
+    /* Test SwapBuffers with NULL context. */
+
+    glDrawBuffer(GL_BACK);
+
+    /* Currently blit happening for child window in winex11 may not be updated with the latest GL frame
+     * even on glXWaitForSbcOML() path. So simulate continuous present for the test purpose. */
+    trace("Child window rectangle should turn from red to green now.\n");
+    t1 = GetTickCount();
+    while ((t = GetTickCount()) - t1 < 3000)
+    {
+        res = wglMakeCurrent(hdc, hglrc);
+        ok(res, "got error %lu.\n", GetLastError());
+        if (t - t1 > 1500)
+            glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
+        else
+            glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+        glClear(GL_COLOR_BUFFER_BIT);
+        res = wglMakeCurrent(NULL, NULL);
+        ok(res, "got error %lu.\n", GetLastError());
+        SwapBuffers(hdc);
+    }
+
+    res = wglDeleteContext(hglrc);
+    ok(res, "got error %lu.\n", GetLastError());
+
+    ReleaseDC(child, hdc);
+    DestroyWindow(child);
+}
+
 START_TEST(opengl)
 {
     HWND hwnd;
@@ -2138,6 +2187,9 @@ START_TEST(opengl)
         else
             skip("WGL_EXT_swap_control not supported, skipping test\n");

+        if (winetest_interactive)
+            test_child_window(hwnd, &pfd);
+
 cleanup:
         ReleaseDC(hwnd, hdc);
         DestroyWindow(hwnd);
diff --git a/dlls/winex11.drv/opengl.c b/dlls/winex11.drv/opengl.c
index bb8f13f78b9..d70f1928655 100644
--- a/dlls/winex11.drv/opengl.c
+++ b/dlls/winex11.drv/opengl.c
@@ -3378,7 +3378,7 @@ static BOOL glxdrv_wglSwapBuffers( HDC hdc )
     case DC_GL_PIXMAP_WIN:
         if (ctx) sync_context( ctx );
         escape.gl_drawable = gl->pixmap;
-        if (pglXCopySubBufferMESA) {
+        if (ctx && pglXCopySubBufferMESA) {
             /* (glX)SwapBuffers has an implicit glFlush effect, however
              * GLX_MESA_copy_sub_buffer doesn't. Make sure GL is flushed before
              * copying */
@@ -3387,7 +3387,7 @@ static BOOL glxdrv_wglSwapBuffers( HDC hdc )
                                    gl->pixmap_size.cx, gl->pixmap_size.cy );
             break;
         }
-        if (pglXSwapBuffersMscOML)
+        if (ctx && pglXSwapBuffersMscOML)
         {
             pglFlush();
             target_sbc = pglXSwapBuffersMscOML( gdi_display, gl->drawable, 0, 0, 0 );
@@ -3401,7 +3401,7 @@ static BOOL glxdrv_wglSwapBuffers( HDC hdc )
         if (gl->type == DC_GL_CHILD_WIN) escape.gl_drawable = gl->window;
         /* fall through */
     default:
-        if (escape.gl_drawable && pglXSwapBuffersMscOML)
+        if (ctx && escape.gl_drawable && pglXSwapBuffersMscOML)
         {
             pglFlush();
             target_sbc = pglXSwapBuffersMscOML( gdi_display, gl->drawable, 0, 0, 0 );
@@ -3411,13 +3411,13 @@ static BOOL glxdrv_wglSwapBuffers( HDC hdc )
         break;
     }

-    if (escape.gl_drawable && pglXWaitForSbcOML)
+    if (ctx && escape.gl_drawable && pglXWaitForSbcOML)
         pglXWaitForSbcOML( gdi_display, gl->drawable, target_sbc, &ust, &msc, &sbc );

release_gl_drawable( gl );

if (escape.gl_drawable)
-        NtGdiExtEscape( ctx->hdc, NULL, 0, X11DRV_ESCAPE, sizeof(escape), (LPSTR)&escape, 0, NULL );
+        NtGdiExtEscape( ctx ? ctx->hdc : hdc, NULL, 0, X11DRV_ESCAPE, sizeof(escape), (LPSTR)&escape, 0, NULL );
     return TRUE;
 }

[Paul Gofman (＠gofman)]

v3:
 - added interactive test.

[PATCH v5 0/1] MR4912: winex11.drv: Fix wglSwapBuffers() with NULL current context with child window rendering. - approved

[Matteo Bruni (＠Mystral)]

This merge request was approved by Matteo Bruni.