build: make vo_gpu + infrastructure non-optional

Also readd the the error message for when no GL backends are found (why
was this removed?).

options/options.c

@@ -57,9 +57,7 @@
 #include "video/out/drm_common.h"
 #endif
 
-#if HAVE_GPU
 #include "video/out/gpu/hwdec.h"
-#endif
 
 static void print_version(struct mp_log *log)
 {
@@ -181,11 +179,9 @@ static const m_option_t mp_vo_opt_list[] = {
                         0, drm_validate_connector_opt),
     OPT_INT("drm-mode", drm_mode_id, 0),
 #endif
-#if HAVE_GL
     OPT_STRING_VALIDATE("opengl-hwdec-interop", gl_hwdec_interop, 0,
                         ra_hwdec_validate_opt),
     OPT_REPLACED("hwdec-preload", "opengl-hwdec-interop"),
-#endif
     {0}
 };
 
@@ -688,9 +684,7 @@ const m_option_t mp_opts[] = {
     OPT_SUBSTRUCT("", vo, vo_sub_opts, 0),
     OPT_SUBSTRUCT("", demux_opts, demux_conf, 0),
 
-#if HAVE_GPU
     OPT_SUBSTRUCT("", gl_video_opts, gl_video_conf, 0),
-#endif
 
 #if HAVE_GL
     OPT_SUBSTRUCT("", opengl_opts, opengl_conf, 0),

video/out/vo.c

@@ -70,9 +70,7 @@ const struct vo_driver *const video_out_drivers[] =
 #if HAVE_RPI
     &video_out_rpi,
 #endif
-#if HAVE_GPU
     &video_out_gpu,
-#endif
 #if HAVE_VDPAU
     &video_out_vdpau,
 #endif

wscript

@@ -788,15 +788,10 @@ video_output_features = [
                  + 'gl-win32 || gl-wayland || rpi || mali-fbdev || '
                  + 'plain-gl',
         'func': check_true,
-    }, {
-        'name': '--gpu',
-        'desc': 'GPU-accelerated video output support',
-        'deps': 'gl',
-        'func': check_true,
         'req': True,
-        'fmsg': "No GPU context found or enabled. Aborting. " +
-                "If you really mean to compile without support for " +
-                "`--vo=gpu`, then use --disable-gpu."
+        'fmsg': "No OpenGL video output found or enabled. " +
+                "Aborting. If you really mean to compile without OpenGL " +
+                "video outputs use --disable-gl.",
     }, {
         'name': 'egl-helpers',
         'desc': 'EGL helper functions',

wscript_build.py

@@ -385,16 +385,16 @@ def build(ctx):
         ( "video/out/dither.c" ),
         ( "video/out/filter_kernels.c" ),
         ( "video/out/opengl/angle_dynamic.c",    "egl-angle" ),
-        ( "video/out/gpu/context.c",             "gpu" ),
-        ( "video/out/gpu/hwdec.c",               "gpu" ),
-        ( "video/out/gpu/lcms.c",                "gpu" ),
-        ( "video/out/gpu/osd.c",                 "gpu" ),
-        ( "video/out/gpu/ra.c",                  "gpu" ),
-        ( "video/out/gpu/shader_cache.c",        "gpu" ),
-        ( "video/out/gpu/user_shaders.c",        "gpu" ),
-        ( "video/out/gpu/utils.c",               "gpu" ),
-        ( "video/out/gpu/video.c",               "gpu" ),
-        ( "video/out/gpu/video_shaders.c",       "gpu" ),
+        ( "video/out/gpu/context.c" ),
+        ( "video/out/gpu/hwdec.c" ),
+        ( "video/out/gpu/lcms.c" ),
+        ( "video/out/gpu/osd.c" ),
+        ( "video/out/gpu/ra.c" ),
+        ( "video/out/gpu/shader_cache.c" ),
+        ( "video/out/gpu/user_shaders.c" ),
+        ( "video/out/gpu/utils.c" ),
+        ( "video/out/gpu/video.c" ),
+        ( "video/out/gpu/video_shaders.c" ),
         ( "video/out/opengl/common.c",           "gl" ),
         ( "video/out/opengl/formats.c",          "gl" ),
         ( "video/out/opengl/utils.c",            "gl" ),
@@ -433,7 +433,7 @@ def build(ctx):
         ( "video/out/vo_lavc.c",                 "encoding" ),
         ( "video/out/vo_rpi.c",                  "rpi" ),
         ( "video/out/vo_null.c" ),
-        ( "video/out/vo_gpu.c",                  "gpu" ),
+        ( "video/out/vo_gpu.c" ),
         ( "video/out/vo_opengl_cb.c",            "gl" ),
         ( "video/out/vo_sdl.c",                  "sdl2" ),
         ( "video/out/vo_tct.c" ),