client API: deprecate opengl-cb API and introduce a replacement API

The purpose of the new API is to make it useable with other APIs than
OpenGL, especially D3D11 and vulkan. In theory it's now possible to
support other vo_gpu backends, as well as backends that don't use the
vo_gpu code at all.

This also aims to get rid of the dumb mpv_get_sub_api() function. The
life cycle of the new mpv_render_context is a bit different from
mpv_opengl_cb_context, and you explicitly create/destroy the new
context, instead of calling init/uninit on an object returned by
mpv_get_sub_api().

In other to make the render API generic, it's annoyingly EGL style, and
requires you to pass in API-specific objects to generic functions. This
is to avoid explicit objects like the internal ra API has, because that
sounds more complicated and annoying for an API that's supposed to never
change.

The opengl_cb API will continue to exist for a bit longer, but
internally there are already a few tradeoffs, like reduced
thread-safety.

Mostly untested. Seems to work fine with mpc-qt.

1 files changed, 155 insertions, 0 deletions

diff --git a/libmpv/render_gl.h b/libmpv/render_gl.h
new file mode 100644
index 0000000000..01c09e80df
--- /dev/null
+++ b/libmpv/render_gl.h
@@ -0,0 +1,155 @@
+/* Copyright (C) 2018 the mpv developers
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef MPV_CLIENT_API_RENDER_GL_H_
+#define MPV_CLIENT_API_RENDER_GL_H_
+
+#include "render.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * OpenGL backend
+ * --------------
+ *
+ * This header contains definitions for using OpenGL with the render.h API.
+ *
+ * OpenGL interop
+ * --------------
+ *
+ * The OpenGL backend has some special rules, because OpenGL itself uses
+ * implicit per-thread contexts, which causes additional API problems.
+ *
+ * This assumes the OpenGL context lives on a certain thread controlled by the
+ * API user. All mpv_render_* APIs have to be assumed to implicitly use the
+ * OpenGL context if you pass a mpv_render_context using the OpenGL backend,
+ * unless specified otherwise.
+ *
+ * The OpenGL context is indirectly accessed through the OpenGL function
+ * pointers returned by the get_proc_address callback in mpv_opengl_init_params.
+ * Generally, mpv will not load the system OpenGL library when using this API.
+ *
+ * OpenGL state
+ * ------------
+ *
+ * OpenGL has a large amount of implicit state. All the mpv functions mentioned
+ * above expect that the OpenGL state is reasonably set to OpenGL standard
+ * defaults. Likewise, mpv will attempt to leave the OpenGL context with
+ * standard defaults. The following state is excluded from this:
+ *
+ *      - the glViewport state
+ *      - the glScissor state (but GL_SCISSOR_TEST is in its default value)
+ *      - glBlendFuncSeparate() state (but GL_BLEND is in its default value)
+ *      - glClearColor() state
+ *      - mpv may overwrite the callback set with glDebugMessageCallback()
+ *      - mpv always disables GL_DITHER at init
+ *
+ * Messing with the state could be avoided by creating shared OpenGL contexts,
+ * but this is avoided for the sake of compatibility and interoperability.
+ *
+ * On OpenGL 2.1, mpv will strictly call functions like glGenTextures() to
+ * create OpenGL objects. You will have to do the same. This ensures that
+ * objects created by mpv and the API users don't clash. Also, legacy state
+ * must be either in its defaults, or not interfere with core state.
+ *
+ * API use
+ * -------
+ *
+ * The mpv_render_* API is used. That API supports multiple backends, and this
+ * section documents specifics for the OpenGL backend.
+ *
+ * Use mpv_render_context_create() with MPV_RENDER_PARAM_API_TYPE set to
+ * MPV_RENDER_API_TYPE_OPENGL, and MPV_RENDER_PARAM_OPENGL_INIT_PARAMS provided.
+ *
+ * Call mpv_render_context_render() with MPV_RENDER_PARAM_OPENGL_FBO to render
+ * the video frame to an FBO.
+ *
+ * Hardware decoding
+ * -----------------
+ *
+ * Hardware decoding via this API is fully supported, but requires some
+ * additional setup. (At least if direct hardware decoding modes are wanted,
+ * instead of copying back surface data from GPU to CPU RAM.)
+ *
+ * There may be certain requirements on the OpenGL implementation:
+ *
+ * - Windows: ANGLE is required (although in theory GL/DX interop could be used)
+ * - Intel/Linux: EGL is required, and also a glMPGetNativeDisplay() callback
+ *                must be provided (see sections below)
+ * - nVidia/Linux: Both GLX and EGL should work (GLX is required if vdpau is
+ *                 used, e.g. due to old drivers.)
+ * - OSX: CGL is required (CGLGetCurrentContext() returning non-NULL)
+ * - iOS: EAGL is required (EAGLContext.currentContext returning non-nil)
+ *
+ * Once these things are setup, hardware decoding can be enabled/disabled at
+ * any time by setting the "hwdec" property.
+ */
+
+/**
+ * For initializing the mpv OpenGL state via MPV_RENDER_PARAM_OPENGL_INIT_PARAMS.
+ */
+typedef struct mpv_opengl_init_params {
+    /**
+     * This retrieves OpenGL function pointers, and will use them in subsequent
+     * operation.
+     * Usually, GL context APIs do this for you (e.g. with glXGetProcAddressARB
+     * or wglGetProcAddress), but some APIs do not always return pointers for
+     * all standard functions (even if present); in this case you have to
+     * compensate by looking up these functions yourself and returning them
+     * from this callback.
+     */
+    void *(*get_proc_address)(void *ctx, const char *name);
+    /**
+     * Value passed as ctx parameter to get_proc_address().
+     */
+    void *get_proc_address_ctx;
+    /**
+     * This should not be used. The main purpose is signaling support for
+     * "GL_MP_MPGetNativeDisplay", which is needed for compatibility with the
+     * opengl_cb API only. Thus it's deprecated and will be removed or ignored
+     * when the opengl_cb API is removed.
+     */
+    const char *extra_exts;
+} mpv_opengl_init_params;
+
+/**
+ * For MPV_RENDER_PARAM_OPENGL_FBO.
+ */
+typedef struct mpv_opengl_fbo {
+    /**
+     * Framebuffer object name. This must be either a valid FBO generated by
+     * glGenFramebuffers() that is complete and color-renderable, or 0. If the
+     * value is 0, this refers to the OpenGL default framebuffer.
+     */
+    int fbo;
+    /**
+     * Valid dimensions. This must refer to the size of the framebuffer. This
+     * must always be set.
+     */
+    int w, h;
+    /**
+     * Underlying texture internal format (e.g. GL_RGBA8), or 0 if unknown. If
+     * this is the default framebuffer, this can be an equivalent.
+     */
+    int internal_format;
+} mpv_opengl_fbo;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif