vo_opengl: some option changes

Doing "mpv --vo=opengl:lscale=help" now lists possible scalers and
exits. The "backend" suboption behaves similar. Make the "stereo"
suboption a choice, instead of using magic integer values.

DOCS/man/en/vo.rst

@@ -235,31 +235,6 @@ Available video output drivers are:
     (or if the necessary extensions are available).
 
     ``lscale=<filter>``
-        Set the scaling filter. Possible choices:
-            bilinear
-            bicubic_fast
-            sharpen3
-            sharpen5
-            hanning
-            hamming
-            hermite
-            quadric
-            bicubic
-            kaiser
-            catmull_rom
-            mitchell
-            spline16
-            spline36
-            gaussian
-            sinc2
-            sinc3
-            sinc4
-            lanczos2
-            lanczos3
-            lanczos4
-            blackman2
-            blackman3
-            blackman4
 
         ``bilinear``
             Bilinear hardware texture filtering (fastest, mid-quality).
@@ -288,6 +263,10 @@ Available video output drivers are:
             Mitchell-Netravali. The ``b`` and ``c`` parameters can be set with
             ``lparam1`` and ``lparam2``. Both are set to 1/3 by default.
 
+
+        There are some more filters. For a complete list, pass ``help`` as
+        value, e.g.: ``mpv --vo=opengl:lscale=help``
+
     ``lparam1=<value>``
         Set filter parameters. Ignored if the filter is not tunable. These are
         unset by default, and use the filter specific default if applicable.
@@ -307,13 +286,13 @@ Available video output drivers are:
         Select a method for stereo display. You may have to use ``--aspect`` to
         fix the aspect value. Experimental, do not expect too much from it.
 
-        0
+        no
             Normal 2D display
-        1
+        red-cyan
             Convert side by side input to full-color red-cyan stereo.
-        2
+        green-magenta
             Convert side by side input to full-color green-magenta stereo.
-        3
+        quadbuffer
             Convert side by side input to quadbuffered stereo. Only supported
             by very few OpenGL cards.
 
@@ -406,6 +385,10 @@ Available video output drivers are:
         Continue even if a software renderer is detected.
 
     ``backend=<sys>``
+        The value ``auto`` (the default) selects the windowing backend. You
+        can also pass ``help`` to get a complete list of compiled in backends
+        (sorted by autoprobe order).
+
         auto
             auto-select (default)
         cocoa

video/out/gl_common.c

@@ -43,6 +43,7 @@
 #include "talloc.h"
 #include "gl_common.h"
 #include "core/options.h"
+#include "core/m_option.h"
 #include "sub/sub.h"
 #include "bitmap_packer.h"
 
@@ -879,6 +880,13 @@ int mpgl_find_backend(const char *name)
 int mpgl_validate_backend_opt(const struct m_option *opt, struct bstr name,
                               struct bstr param)
 {
+    if (bstr_equals0(param, "help")) {
+        mp_msg(MSGT_VO, MSGL_INFO, "OpenGL windowing backends:\n");
+        mp_msg(MSGT_VO, MSGL_INFO, "    auto (autodetect)\n");
+        for (const struct backend *entry = backends; entry->name; entry++)
+            mp_msg(MSGT_VO, MSGL_INFO, "    %s\n", entry->name);
+        return M_OPT_EXIT - 1;
+    }
     char s[20];
     snprintf(s, sizeof(s), "%.*s", BSTR_P(param));
     return mpgl_find_backend(s) >= -1 ? 1 : M_OPT_INVALID;

video/out/gl_video.c

@@ -283,7 +283,11 @@ const struct m_sub_options gl_video_conf = {
         OPT_FLAG("srgb", srgb, 0),
         OPT_FLAG("npot", npot, 0),
         OPT_FLAG("pbo", pbo, 0),
-        OPT_INT("stereo", stereo_mode, 0),
+        OPT_CHOICE("stereo", stereo_mode, 0,
+                   ({"no", 0},
+                    {"red-cyan",        GL_3D_RED_CYAN},
+                    {"green-magenta",   GL_3D_GREEN_MAGENTA},
+                    {"quadbuffer",      GL_3D_QUADBUFFER})),
         OPT_STRING_VALIDATE("lscale", scalers[0], 0, validate_scaler_opt),
         OPT_STRING_VALIDATE("cscale", scalers[1], 0, validate_scaler_opt),
         OPT_FLOAT("lparam1", scaler_params[0], 0),
@@ -2059,6 +2063,14 @@ bool gl_video_get_equalizer(struct gl_video *p, const char *name, int *val)
 static int validate_scaler_opt(const m_option_t *opt, struct bstr name,
                                struct bstr param)
 {
+    if (bstr_equals0(param, "help")) {
+        mp_msg(MSGT_VO, MSGL_INFO, "Available scalers:\n");
+        for (const char **filter = fixed_scale_filters; *filter; filter++)
+            mp_msg(MSGT_VO, MSGL_INFO, "    %s\n", *filter);
+        for (int n = 0; mp_filter_kernels[n].name; n++)
+            mp_msg(MSGT_VO, MSGL_INFO, "    %s\n", mp_filter_kernels[n].name);
+        return M_OPT_EXIT - 1;
+    }
     char s[20];
     snprintf(s, sizeof(s), "%.*s", BSTR_P(param));
     return handle_scaler_opt(s) ? 1 : M_OPT_INVALID;