simple-dmabuf-egl: Allow QueryDmaBufModifiers to report no modifiers

Some drivers expose the extension so they can expose
eglQueryDmaBufFormatsEXT, but don't support any modifiers. Treat this the
same as if the extension wasn't present.

clients/simple-dmabuf-egl.c

@@ -1232,26 +1232,32 @@ display_update_supported_modifiers_for_egl(struct display *d)
 	int num_egl_modifiers = 0;
 	EGLBoolean ret;
 	int i;
+	bool try_modifiers = d->egl.has_dma_buf_import_modifiers;
+
+	if (try_modifiers) {
+		ret = d->egl.query_dma_buf_modifiers(d->egl.display,
+						     BUFFER_FORMAT,
+						     0,    /* max_modifiers */
+						     NULL, /* modifiers */
+						     NULL, /* external_only */
+						     &num_egl_modifiers);
+		if (ret == EGL_FALSE) {
+			fprintf(stderr, "Failed to query num EGL modifiers for format\n");
+			goto error;
+		}
+	}
+
+	if (!num_egl_modifiers)
+		try_modifiers = false;
 
 	/* If EGL doesn't support modifiers, don't use them at all. */
-	if (!d->egl.has_dma_buf_import_modifiers) {
+	if (!try_modifiers) {
 		d->modifiers_count = 0;
 		free(d->modifiers);
 		d->modifiers = NULL;
 		return true;
 	}
 
-	ret = d->egl.query_dma_buf_modifiers(d->egl.display,
-				             BUFFER_FORMAT,
-				             0,    /* max_modifiers */
-				             NULL, /* modifiers */
-				             NULL, /* external_only */
-				             &num_egl_modifiers);
-	if (ret == EGL_FALSE || num_egl_modifiers == 0) {
-		fprintf(stderr, "Failed to query num EGL modifiers for format\n");
-		goto error;
-	}
-
 	egl_modifiers = zalloc(num_egl_modifiers * sizeof(*egl_modifiers));
 
 	ret = d->egl.query_dma_buf_modifiers(d->egl.display,