dwrite: Add helper object for blending operation

For easy integration with a new text rendering baseclass

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5121>

subprojects/gst-plugins-bad/sys/dwrite/gstdwriteoverlayobject.h

@@ -0,0 +1,112 @@
+/* GStreamer
+ * Copyright (C) 2023 Seungha Yang <seungha@centricular.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+#include <gst/d3d11/gstd3d11.h>
+#include <gst/video/video.h>
+#include <gst/base/base.h>
+#include "gstdwrite-utils.h"
+#include "gstdwrite-enums.h"
+
+G_BEGIN_DECLS
+
+enum class GstDWriteBlendMode
+{
+  NOT_SUPPORTED,
+
+  /* attach meta with d3d11 texture buffer. */
+  ATTACH_TEXTURE,
+
+  /* attach meta with bitmap buffer */
+  ATTACH_BITMAP,
+
+  /* software blending */
+  SW_BLEND,
+
+  /* 1) renders text on BGRA
+   * 2) blends */
+  BLEND,
+
+  /* 1) convert texture to BGRA
+   * 2) render text on another BGRA texture
+   * 3) blends two textures
+   * 3) converts back to original format */
+  CONVERT,
+
+  /* 1) converts texture to RGBA64_LE
+   * 2) renders text on BGRA texture
+   * 3) blends two textures
+   * 3) converts back original format */
+  CONVERT_64,
+};
+
+#define GST_TYPE_DWRITE_OVERLAY_OBJECT (gst_dwrite_overlay_object_get_type())
+G_DECLARE_FINAL_TYPE (GstDWriteOverlayObject,
+    gst_dwrite_overlay_object, GST, DWRITE_OVERLAY_OBJECT, GstObject);
+
+GstDWriteOverlayObject * gst_dwrite_overlay_object_new (void);
+
+gboolean  gst_dwrite_overlay_object_start (GstDWriteOverlayObject * object,
+                                           IDWriteFactory * dwrite_factory);
+
+gboolean  gst_dwrite_overlay_object_stop  (GstDWriteOverlayObject * object);
+
+void      gst_dwrite_overlay_object_set_context (GstDWriteOverlayObject * object,
+                                                 GstElement * elem,
+                                                 GstContext * context);
+
+gboolean  gst_dwrite_overlay_object_handle_query (GstDWriteOverlayObject * object,
+                                                  GstElement * elem,
+                                                  GstQuery * query);
+
+gboolean  gst_dwrite_overlay_object_decide_allocation (GstDWriteOverlayObject * object,
+                                                       GstElement * elem,
+                                                       GstQuery * query);
+
+gboolean  gst_dwrite_overlay_object_propose_allocation (GstDWriteOverlayObject * object,
+                                                        GstElement * elem,
+                                                        GstQuery * query);
+
+gboolean  gst_dwrite_overlay_object_set_caps (GstDWriteOverlayObject * object,
+                                              GstElement * elem,
+                                              GstCaps * in_caps,
+                                              GstCaps * out_caps,
+                                              GstVideoInfo * info,
+                                              GstDWriteBlendMode * selected_mode);
+
+gboolean  gst_dwrite_overlay_object_update_device (GstDWriteOverlayObject * object,
+                                                   GstBuffer * buffer);
+
+GstFlowReturn gst_dwrite_overlay_object_prepare_output (GstDWriteOverlayObject * object,
+                                                        GstBaseTransform * trans,
+                                                        gpointer trans_class,
+                                                        GstBuffer * inbuf,
+                                                        GstBuffer ** outbuf);
+
+gboolean  gst_dwrite_overlay_object_draw (GstDWriteOverlayObject * object,
+                                          GstBuffer * buffer,
+                                          IDWriteTextLayout * layout,
+                                          D2D1_COLOR_F background_color,
+                                          D2D1_RECT_F background_padding,
+                                          gboolean enable_color_font,
+                                          gint x,
+                                          gint y);
+
+G_END_DECLS

subprojects/gst-plugins-bad/sys/dwrite/meson.build

@@ -7,6 +7,7 @@ dwrite_sources = [
   'gstdwritebitmapmemory.cpp',
   'gstdwritebitmappool.cpp',
   'gstdwriteclockoverlay.cpp',
+  'gstdwriteoverlayobject.cpp',
   'gstdwritesubtitlemux.cpp',
   'gstdwritesubtitleoverlay.cpp',
   'gstdwritetextoverlay.cpp',