wgl: do not disable error-dialogs by default

We don't know if an application developer wants error-dialog by default
or not, even when using a Mesa OpenGL driver.

So let's not assume this is a good thing, and instead make an option for
this behavior that we can enable for CI testing.

Reviewed-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15485>

docs/envvars.rst

@@ -235,6 +235,9 @@ on Windows.
 :envvar:`WGL_FORCE_MSAA`
    if set to a positive value, specifies the number of MSAA samples to
    force when choosing the display configuration.
+:envvar:`WGL_DISABLE_ERROR_DIALOGS`
+   if set to 1, true or yes, disables Win32 error dialogs. Useful for
+   automated test-runs.
 
 Intel driver environment variables
 ----------------------------------------------------

src/gallium/drivers/d3d12/ci/gitlab-ci.yml

@@ -12,6 +12,7 @@
   variables:
     GIT_STRATEGY: none # testing doesn't build anything from source
     GALLIUM_DRIVER: d3d12
+    WGL_DISABLE_ERROR_DIALOGS: "true"
 
 .d3d12-test-piglit:
   extends:

src/gallium/frontends/wgl/stw_device.c

@@ -28,6 +28,7 @@
 #include <windows.h>
 
 #include "glapi/glapi.h"
+#include "util/debug.h"
 #include "util/u_debug.h"
 #include "util/u_math.h"
 #include "util/u_memory.h"
@@ -120,7 +121,8 @@ stw_init(const struct stw_winsys *stw_winsys)
 {
    static struct stw_device stw_dev_storage;
 
-   debug_disable_win32_error_dialogs();
+   if (env_var_as_boolean("WGL_DISABLE_ERROR_DIALOGS", false))
+      debug_disable_win32_error_dialogs();
 
    assert(!stw_dev);