vo_opengl: angle: dynamically load ANGLE

ANGLE is _really_ annoying to build. (Requires special toolchain and a
recent MSVC version.) This results in various issues with people
having trouble to build mpv against ANGLE (apparently linking it
against a prebuilt binary doesn't count, or using binaries from
potentially untrusted sources is not wanted).

Dynamically loading ANGLE is going to be a huge convenience. This commit
implements this, with special focus on keeping it source compatible to
a normal build with ANGLE linked at build-time.

7 files changed, 135 insertions, 3 deletions

diff --git a/video/out/opengl/angle_dynamic.c b/video/out/opengl/angle_dynamic.c
new file mode 100644
index 0000000000..f4540c473a
--- /dev/null
+++ b/video/out/opengl/angle_dynamic.c
@@ -0,0 +1,33 @@
+#include <pthread.h>
+#include <windows.h>
+
+#define ANGLE_NO_ALIASES
+#include "angle_dynamic.h"
+
+#include "common/common.h"
+
+#define ANGLE_DECL(NAME, VAR) \
+    VAR;
+ANGLE_FNS(ANGLE_DECL)
+
+static bool angle_loaded;
+static pthread_once_t angle_load_once = PTHREAD_ONCE_INIT;
+
+static void angle_do_load(void)
+{
+    // Note: we let this handle "leak", as the functions remain valid forever.
+    HANDLE angle_dll = LoadLibraryW(L"LIBEGL.DLL");
+    if (!angle_dll)
+        return;
+#define ANGLE_LOAD_ENTRY(NAME, VAR) \
+    MP_CONCAT(PFN_, NAME) = (void *)GetProcAddress(angle_dll, #NAME); \
+    if (!MP_CONCAT(PFN_, NAME)) return;
+    ANGLE_FNS(ANGLE_LOAD_ENTRY)
+    angle_loaded = true;
+}
+
+bool angle_load(void)
+{
+    pthread_once(&angle_load_once, angle_do_load);
+    return angle_loaded;
+}
diff --git a/video/out/opengl/angle_dynamic.h b/video/out/opengl/angle_dynamic.h
new file mode 100644
index 0000000000..87ad85c268
--- /dev/null
+++ b/video/out/opengl/angle_dynamic.h
@@ -0,0 +1,82 @@
+// Based on Khronos headers, thus MIT licensed.
+
+#ifndef MP_ANGLE_DYNAMIC_H
+#define MP_ANGLE_DYNAMIC_H
+
+#include <stdbool.h>
+
+#include <EGL/egl.h>
+#include <EGL/eglext.h>
+
+#define ANGLE_FNS(FN) \
+    FN(eglBindAPI, EGLBoolean (*EGLAPIENTRY PFN_eglBindAPI)(EGLenum)) \
+    FN(eglBindTexImage, EGLBoolean (*EGLAPIENTRY PFN_eglBindTexImage) \
+        (EGLDisplay, EGLSurface, EGLint)) \
+    FN(eglChooseConfig, EGLBoolean (*EGLAPIENTRY PFN_eglChooseConfig) \
+        (EGLDisplay, const EGLint *, EGLConfig *, EGLint, EGLint *)) \
+    FN(eglCreateContext, EGLContext (*EGLAPIENTRY PFN_eglCreateContext) \
+        (EGLDisplay, EGLConfig, EGLContext, const EGLint *)) \
+    FN(eglCreatePbufferFromClientBuffer, EGLSurface (*EGLAPIENTRY \
+        PFN_eglCreatePbufferFromClientBuffer)(EGLDisplay, EGLenum, \
+        EGLClientBuffer, EGLConfig, const EGLint *)) \
+    FN(eglCreateWindowSurface, EGLSurface (*EGLAPIENTRY \
+        PFN_eglCreateWindowSurface)(EGLDisplay, EGLConfig, \
+        EGLNativeWindowType, const EGLint *)) \
+    FN(eglDestroyContext, EGLBoolean (*EGLAPIENTRY PFN_eglDestroyContext) \
+        (EGLDisplay, EGLContext)) \
+    FN(eglDestroySurface, EGLBoolean (*EGLAPIENTRY PFN_eglDestroySurface) \
+        (EGLDisplay, EGLSurface)) \
+    FN(eglGetConfigAttrib, EGLBoolean (*EGLAPIENTRY PFN_eglGetConfigAttrib) \
+        (EGLDisplay, EGLConfig, EGLint, EGLint *)) \
+    FN(eglGetCurrentContext, EGLContext (*EGLAPIENTRY \
+        PFN_eglGetCurrentContext)(void)) \
+    FN(eglGetCurrentDisplay, EGLDisplay (*EGLAPIENTRY \
+        PFN_eglGetCurrentDisplay)(void)) \
+    FN(eglGetDisplay, EGLDisplay (*EGLAPIENTRY PFN_eglGetDisplay) \
+        (EGLNativeDisplayType)) \
+    FN(eglGetError, EGLint (*EGLAPIENTRY PFN_eglGetError)(void)) \
+    FN(eglGetProcAddress, void *(*EGLAPIENTRY \
+        PFN_eglGetProcAddress)(const char *)) \
+    FN(eglInitialize, EGLBoolean (*EGLAPIENTRY PFN_eglInitialize) \
+        (EGLDisplay, EGLint *, EGLint *)) \
+    FN(eglMakeCurrent, EGLBoolean (*EGLAPIENTRY PFN_eglMakeCurrent) \
+        (EGLDisplay, EGLSurface, EGLSurface, EGLContext)) \
+    FN(eglQueryString, const char *(*EGLAPIENTRY PFN_eglQueryString) \
+        (EGLDisplay, EGLint)) \
+    FN(eglSwapBuffers, EGLBoolean (*EGLAPIENTRY PFN_eglSwapBuffers) \
+        (EGLDisplay, EGLSurface)) \
+    FN(eglReleaseTexImage, EGLBoolean (*EGLAPIENTRY PFN_eglReleaseTexImage) \
+        (EGLDisplay, EGLSurface, EGLint)) \
+    FN(eglTerminate, EGLBoolean (*EGLAPIENTRY PFN_eglTerminate)(EGLDisplay))
+
+#define ANGLE_EXT_DECL(NAME, VAR) \
+    extern VAR;
+ANGLE_FNS(ANGLE_EXT_DECL)
+
+bool angle_load(void);
+
+// Source compatibility to statically linked ANGLE.
+#ifndef ANGLE_NO_ALIASES
+#define eglBindAPI                      PFN_eglBindAPI
+#define eglBindTexImage                 PFN_eglBindTexImage
+#define eglChooseConfig                 PFN_eglChooseConfig
+#define eglCreateContext                PFN_eglCreateContext
+#define eglCreatePbufferFromClientBuffer PFN_eglCreatePbufferFromClientBuffer
+#define eglCreateWindowSurface          PFN_eglCreateWindowSurface
+#define eglDestroyContext               PFN_eglDestroyContext
+#define eglDestroySurface               PFN_eglDestroySurface
+#define eglGetConfigAttrib              PFN_eglGetConfigAttrib
+#define eglGetCurrentContext            PFN_eglGetCurrentContext
+#define eglGetCurrentDisplay            PFN_eglGetCurrentDisplay
+#define eglGetDisplay                   PFN_eglGetDisplay
+#define eglGetError                     PFN_eglGetError
+#define eglGetProcAddress               PFN_eglGetProcAddress
+#define eglInitialize                   PFN_eglInitialize
+#define eglMakeCurrent                  PFN_eglMakeCurrent
+#define eglQueryString                  PFN_eglQueryString
+#define eglReleaseTexImage              PFN_eglReleaseTexImage
+#define eglSwapBuffers                  PFN_eglSwapBuffers
+#define eglTerminate                    PFN_eglTerminate
+#endif
+
+#endif
diff --git a/video/out/opengl/context_angle.c b/video/out/opengl/context_angle.c
index fb2fb4b888..ef498f27eb 100644
--- a/video/out/opengl/context_angle.c
+++ b/video/out/opengl/context_angle.c
@@ -19,6 +19,8 @@
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
 
+#include "angle_dynamic.h"
+
 #include "common/common.h"
 #include "video/out/w32_common.h"
 #include "context.h"
@@ -109,6 +111,11 @@ static int angle_init(struct MPGLContext *ctx, int flags)
     struct priv *p = ctx->priv;
     struct vo *vo = ctx->vo;
 
+    if (!angle_load()) {
+        MP_VERBOSE(vo, "Failed to load LIBEGL.DLL\n");
+        goto fail;
+    }
+
     if (!vo_w32_init(vo))
         goto fail;
 
diff --git a/video/out/opengl/hwdec_d3d11egl.c b/video/out/opengl/hwdec_d3d11egl.c
index 28c5f27bf6..c78d9e9b0d 100644
--- a/video/out/opengl/hwdec_d3d11egl.c
+++ b/video/out/opengl/hwdec_d3d11egl.c
@@ -23,6 +23,8 @@
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
 
+#include "angle_dynamic.h"
+
 #include "common/common.h"
 #include "osdep/timer.h"
 #include "osdep/windows_utils.h"
@@ -147,6 +149,9 @@ static void destroy(struct gl_hwdec *hw)
 
 static int create(struct gl_hwdec *hw)
 {
+    if (!angle_load())
+        return -1;
+
     EGLDisplay egl_display = eglGetCurrentDisplay();
     if (!egl_display)
         return -1;
diff --git a/video/out/opengl/hwdec_dxva2egl.c b/video/out/opengl/hwdec_dxva2egl.c
index 3a4ee6089f..be4c4d78ea 100644
--- a/video/out/opengl/hwdec_dxva2egl.c
+++ b/video/out/opengl/hwdec_dxva2egl.c
@@ -22,6 +22,8 @@
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
 
+#include "angle_dynamic.h"
+
 #include "common/common.h"
 #include "osdep/timer.h"
 #include "osdep/windows_utils.h"
@@ -95,6 +97,9 @@ static void destroy(struct gl_hwdec *hw)
 
 static int create(struct gl_hwdec *hw)
 {
+    if (!angle_load())
+        return -1;
+
     EGLDisplay egl_display = eglGetCurrentDisplay();
     if (!egl_display)
         return -1;
diff --git a/wscript b/wscript
index d4f84e13b4..0a031aac81 100644
--- a/wscript
+++ b/wscript
@@ -699,9 +699,8 @@ video_output_features = [
         'desc': 'OpenGL Win32 ANGLE Backend',
         'deps_any': [ 'os-win32', 'os-cygwin' ],
         'groups': [ 'gl' ],
-        'func': check_statement(['EGL/egl.h'],
-                                'eglCreateWindowSurface(0, 0, 0, 0)',
-                                lib='EGL')
+        'func': check_statement(['EGL/egl.h', 'EGL/eglext.h'],
+                                'int x = EGL_D3D_TEXTURE_2D_SHARE_HANDLE_ANGLE')
     } , {
         'name': '--vdpau',
         'desc': 'VDPAU acceleration',
diff --git a/wscript_build.py b/wscript_build.py
index 15637826ea..66f733a182 100644
--- a/wscript_build.py
+++ b/wscript_build.py
@@ -329,6 +329,7 @@ def build(ctx):
         ( "video/out/cocoa_common.m",            "cocoa" ),
         ( "video/out/dither.c" ),
         ( "video/out/filter_kernels.c" ),
+        ( "video/out/opengl/angle_dynamic.c",    "egl-angle" ),
         ( "video/out/opengl/common.c",           "gl" ),
         ( "video/out/opengl/context.c",          "gl" ),
         ( "video/out/opengl/context_angle.c",    "egl-angle" ),