render/egl: improve modifier support detection

Support for EXT_image_dma_buf_import_modifiers doesn't necessarily
indicate support for modifiers. For instance, Mesa will advertise
EXT_image_dma_buf_import_modifiers for all drivers. This is a trick
to allow EGL clients to enumerate supported formats (something
EXT_image_dma_buf_import is missing). For more information, see [1].

Add a new wlr_egl.has_modifiers flag which indicates whether
modifiers are supported. It's set to true if any
eglQueryDmaBufModifiersEXT query returned a non-empty list.

Use that flag to figure out whether the buffer modifier should be
passed to the EGL implementation on import.

[1]: https://github.com/KhronosGroup/EGL-Registry/issues/142

include/wlr/render/egl.h

@@ -65,6 +65,7 @@ struct wlr_egl {
 		PFNEGLQUERYDEVICESEXTPROC eglQueryDevicesEXT;
 	} procs;
 
+	bool has_modifiers;
 	struct wlr_drm_format_set dmabuf_texture_formats;
 	struct wlr_drm_format_set dmabuf_render_formats;
 };

render/egl.c

@@ -160,6 +160,8 @@ static void init_dmabuf_formats(struct wlr_egl *egl) {
 		has_modifiers ? "supported" : "unsupported");
 	free(str_formats);
 
+	egl->has_modifiers = has_modifiers;
+
 out:
 	free(formats);
 }
@@ -644,19 +646,11 @@ EGLImageKHR wlr_egl_create_image_from_dmabuf(struct wlr_egl *egl,
 		return NULL;
 	}
 
-	bool has_modifier = false;
-
-	// we assume the same way we assumed formats without the import_modifiers
-	// extension that mod_linear is supported. The special mod mod_invalid
-	// is sometimes used to signal modifier unawareness which is what we
-	// have here
 	if (attributes->modifier != DRM_FORMAT_MOD_INVALID &&
-			attributes->modifier != DRM_FORMAT_MOD_LINEAR) {
-		if (!egl->exts.EXT_image_dma_buf_import_modifiers) {
-			wlr_log(WLR_ERROR, "dmabuf modifiers extension not present");
-			return NULL;
-		}
-		has_modifier = true;
+			attributes->modifier != DRM_FORMAT_MOD_LINEAR &&
+			!egl->has_modifiers) {
+		wlr_log(WLR_ERROR, "EGL implementation doesn't support modifiers");
+		return NULL;
 	}
 
 	unsigned int atti = 0;
@@ -702,14 +696,15 @@ EGLImageKHR wlr_egl_create_image_from_dmabuf(struct wlr_egl *egl,
 		}
 	};
 
-	for (int i=0; i < attributes->n_planes; i++) {
+	for (int i = 0; i < attributes->n_planes; i++) {
 		attribs[atti++] = attr_names[i].fd;
 		attribs[atti++] = attributes->fd[i];
 		attribs[atti++] = attr_names[i].offset;
 		attribs[atti++] = attributes->offset[i];
 		attribs[atti++] = attr_names[i].pitch;
 		attribs[atti++] = attributes->stride[i];
-		if (has_modifier) {
+		if (egl->has_modifiers &&
+				attributes->modifier != DRM_FORMAT_MOD_INVALID) {
 			attribs[atti++] = attr_names[i].mod_lo;
 			attribs[atti++] = attributes->modifier & 0xFFFFFFFF;
 			attribs[atti++] = attr_names[i].mod_hi;