[PATCH 2/3] system/vl.c: Expand OpenGL related errors

[Peter Maydell]

Expand the OpenGL related error messages we produce for various
"OpenGL not present/not supported" cases, to hopefully guide the
user towards how to fix things.

Now if the user tries to enable GL on a backend that doesn't
support it the error message is a bit more precise:

$ qemu-system-aarch64 -M virt -device virtio-gpu-gl -display curses,gl=on
qemu-system-aarch64: OpenGL is not supported by display backend 'curses'

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 system/vl.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/system/vl.c b/system/vl.c
index 9e8f16f1551..213ee6a6a92 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -1973,9 +1973,10 @@ static void qemu_create_early_backends(void)
 
     if (dpy.has_gl && dpy.gl != DISPLAYGL_MODE_OFF && display_opengl == 0) {
 #if defined(CONFIG_OPENGL)
-        error_report("OpenGL is not supported by the display");
+        error_report("OpenGL is not supported by display backend '%s'",
+                     DisplayType_str(dpy.type));
 #else
-        error_report("OpenGL support is disabled");
+        error_report("OpenGL support was disabled when QEMU was compiled");
 #endif
         exit(1);
     }
-- 
2.34.1